**Ask a monkey a physics question thread**

[OngBonga]

That stuff about quark tension is cool.

Light always travels at c

So we're back to the problem of the entire life of the EW universe happening before light can travel even a tiny distance. That really does bend my head. Certainly, I feel like our concept of time is redundant in this world. I mean, the best I can imagine is that the universe is so dense, that even though a photon only travels a tiny distance in during the entire EW epoch, it still interacts with a truly massive amount of energy. I keep thinking of particles colliding, but I know we're at a much more quantum level than that. Still, it's a reasonable metaphor for what I can't understand going on, so forgive me if I persist with it. When we talk of time, we have to think of space, too. I think a light cone (actually a sphere) one light second in diameter would be a fair spacial representation of a second in time. This is the range of causality. A light cone with a diameter of 10^-43 light seconds is practically a singularity, yet an enormous amount of stuff must be happening in this region. From a tiny universe in a fraction of a second came the hugest and most complex of systems. It really does make you wonder what the fuck time really is.

Time doesn't flow backwards, as far as we can observe. It flows at different rates for different observers, but always in the same direction. That reminds me of the second law of thermodynamics. Is time just the flow of entropy? Nature's eternal quest for equlibrium?

[MadMojoMonkey]

Time doesn't flow backwards, as far as we can observe. It flows at different rates for different observers, but always in the same direction. That reminds me of the second law of thermodynamics. Is time just the flow of entropy? Nature's eternal quest for equlibrium?

The "thermodynamic arrow of time" is directly related to the 2nd Law of Thermo.

[OngBonga]

The "thermodynamic arrow of time" is directly related to the 2nd Law of Thermo.

Something I was watching about entropy yesterday seemed to suggest that it's the result of probability. This confused me, because they kept saying heat NEVER spontaneously moves from cold region to warm. Surely if probability governs this, then we should expet to see it happen rarely?

[MadMojoMonkey]

Something I was watching about entropy yesterday seemed to suggest that it's the result of probability. This confused me, because they kept saying heat NEVER spontaneously moves from cold region to warm. Surely if probability governs this, then we should expet to see it happen rarely?

Thermodynamics describes systems with large numbers (greater than Avogadro's number) of particles.
The statements of thermodynamics came about to explain and understand experimental results prior to the quantum description of nature.
The statistical statement that heat never flows spontaneously from cold to hot is experimentally verified for systems of particles.
Statistically speaking, the "never" is an overstatement, but not a terrible one. The equipartition theorem states, broadly, that systems of particles tend toward thermal equilibrium, and not toward isolated regions of high and low temperatures. "Tend toward" is a statistical statement, and we generally look at the large ensemble of particles as a dynamic equilibrium.

A moving pendulum is in dynamic equilibrium. At any given time, it's total energy is constant, but whether that energy is kinetic or potential varies.
This is similar for temperature. At any given time, the individual atoms of a molecule can have dramatically different thermal energy, but the overall energy of the molecule remains relatively constant and in thermal equilibrium with its environment.


However, Quantum Mechanically, there is no such thing as entropy. All QM processes are time-reversible. I.e. any process that is observed to happen forward in time is also observed to happen in another experiment, but in the opposite order, and with particles and anti-particles swapped.

So entropy is a breaking of symmetry at some scale of particle interactions?

[MadMojoMonkey]

Dwell on the fact that there was (from memory) ~ a billion times more stuff in the universe back then. Matter and anti-matter were believed to be in near equilibrium for a brief while there. The exact mechanism for why only 1 kind of matter dominates the universe isn't known, but there are strong beliefs held by string theorists that there is a weak reaction which annihilates 10^-9 less matter than anti-matter... meaning that of all the mass in the early universe, only ~1 billionth remains.

How that is not a singularity is not remotely known or credibly speculated.

[OngBonga]

I think the matter vs antimatter thing is really a simple question of probability. If we flip a coin 100 trillion trillion times, are we to expect there to be exactly 50 trillion trillion heads? The probability of that happening is actually very slim indeed. It's extremely likely that one side will very slightly dominate over 100 trillion trillion flips. The same happened with antimatter vs matter. There was perhaps 0.1% more matter, so it won. It actually seems fairly simple to me. The scary thing about this hypothesis though is that basically god was rolling dice when he made the universe, and a double six would've meant exactly 50-50 ratio, total annihilation, and no universe*.

* as we know it

[MadMojoMonkey]

I think the matter vs antimatter thing is really a simple question of probability. If we flip a coin 100 trillion trillion times, are we to expect there to be exactly 50 trillion trillion heads? The probability of that happening is actually very slim indeed. It's extremely likely that one side will very slightly dominate over 100 trillion trillion flips. The same happened with antimatter vs matter. There was perhaps 0.1% more matter, so it won. It actually seems fairly simple to me. The scary thing about this hypothesis though is that basically god was rolling dice when he made the universe, and a double six would've meant exactly 50-50 ratio, total annihilation, and no universe*.

* as we know it

Whether or not and how often an interaction or reaction takes place is probabilistic in nature.
Conservation laws are not probability based.

With virtual particles, the conservation laws are bent by unobservable events, but all observable events follow conservation laws.

[OngBonga]

Dwell on the fact that there was (from memory) ~ a billion times more stuff in the universe back then.

meaning that of all the mass in the early universe, only ~1 billionth remains.

But the energy still exists. It must do. What happened to that energy? The energy content of the universe is exctly the same today as it was 10^-43 seconds after big bang. And since energy is mass... well that "stuff" just changed, it didn't disappear.

[OngBonga]

How that is not a singularity is not remotely known or credibly speculated.

Seems obvious. A positive number minus a smaller positive number equals a number greater than zero, and a volume greater than zero is not a singularity.

[MadMojoMonkey]

Seems obvious. A positive number minus a smaller positive number equals a number greater than zero, and a volume greater than zero is not a singularity.

The radius of the universe was smaller than the Swarzchild radius for that mass.

Why was it expanding, and not collapsing under the curvature of spacetime caused by that much mass-energy in that small a volume?

[OngBonga]

Why was it expanding, and not collapsing under the curvature of spacetime caused by that much mass-energy in that small a volume?

Umm... because it was rotating at an incomprehensible rate, and therefore inertial forces were of the order required to do battle with gravity? That's my best guess.

It has been transformed predominantly into heat and the gravitational potential energy stored in the curvature of spacetime.

Right, so the energy still exists. The "annhiliation" of the matter and antimatter isn't annihilation in the context of "obliteration", it's to "convert to radiation". So all that matter and antimatter that was annihilating each other in the very early universe, it still contributes to the mass of the universe, because its energy remains part of the system. It's still "stuff".

[MadMojoMonkey]

Umm... because it was rotating at an incomprehensible rate, and therefore inertial forces were of the order required to do battle with gravity? That's my best guess.

My only critique is that IF the universe started as an idealized point mass (not even sure how absurd that is), then the notion that it was rotating is absurd. A thing with no measurable length dimension cannot be said to be rotating in any meaningful way.


***
Just to be clear, this is a separate topic, which we are discussing at the same time.

Right, so the energy still exists. The "annhiliation" of the matter and antimatter isn't annihilation in the context of "obliteration", it's to "convert to radiation". So all that matter and antimatter that was annihilating each other in the very early universe, it still contributes to the mass of the universe, because its energy remains part of the system. It's still "stuff".

Which is true, but doesn't address, "Why, of all the stuff that's left, is there ANY matter, and not just energy?"

"So all that matter and antimatter that was annihilating each other in the very early universe"

Ahem: most of that matter and all of that antimatter

[MadMojoMonkey]

But the energy still exists. It must do. What happened to that energy? The energy content of the universe is exactly the same today as it was 10^-43 seconds after big bang. And since energy is mass... well that "stuff" just changed, it didn't disappear.

Yes. The mass-energy is conserved.

It has been transformed predominantly into heat and the gravitational potential energy stored in the curvature of spacetime.

The point is that matter and anti-matter annihilate each other in pairs by all known observed interactions. There are only hypothetical and unobserved interactions in which matter and anti-matter annihilate at a rate other than 1:1.

[OngBonga]

My only critique is that IF the universe started as an idealized point mass (not even sure how absurd that is), then the notion that it was rotating is absurd. A thing with no measurable length dimension cannot be said to be rotating in any meaningful way.

I suppose it could be rotating at infinity rps. Meaningful? Well no, not to us, but I'm thinking of an ice skater spinning and stretching her arms out... as the universe expands, the rotation slows... during the EW epoch, the universe was tiny, but not a singularity... rotation can be meaningful in this world, and therefore so too can intertial forces. Before then, who knows? I expect the universe to be rotating faster and faster as we go closer and closer to the big bang. That is, of course, assuming that the torus model, which I particularly like, is incorrect. In this model, the big bang is merely the centre of the universe, which is already rotating. Expansion is merely motion through the geometry of the universe, driven by outward pressure from the central singularity, and accelerated by inertial forces, which we call dark energy. I like this model more than the problematic ever-expanding model.

Which is true, but doesn't address, "Why, of all the stuff that's left, is there ANY matter, and not just energy?"

Did you not like the answer "probability"? I have another potential solution... initial conditions of matter vs antimatter were an odd number. If one particle of matter survives, along with all the energy that's left over, then we still have an interaction. There is a universe. Perhaps the universe as we know it "grew" from one solitary matter particle.

idk, but in a truly random world, it seems statistically unlikely that with such large numbers of particles, there would be an exact match. So perhaps the probability answer is the easiest to digest.

[MadMojoMonkey]

I suppose it could be rotating at infinity rps. Meaningful? Well no, not to us, but I'm thinking of an ice skater spinning and stretching her arms out... as the universe expands, the rotation slows... during the EW epoch, the universe was tiny, but not a singularity... rotation can be meaningful in this world, and therefore so too can intertial forces. Before then, who knows? I expect the universe to be rotating faster and faster as we go closer and closer to the big bang.

OK, what is rotation? Motion about an axis, yeah?
How can an object with no part of it lying off of any axis be said to be moving about said axis?
(Granted this is all predicated on my IF an idealized point mass... statement)

We're not talking EW epoch. We're talking quark-gluon plasma. EW epoch is post-inflation.

If the universe is rotating, then we should see effects of centrifugal forces in our non-inertial, rotating reference frame on some length scales in the universe. There would be a definite center of rotation, i.e. center of the universe.

[OngBonga]

If the universe is rotating, then we should see effects of centrifugal forces in our non-inertial, rotating reference frame on some length scales in the universe. There would be a definite center of rotation, i.e. center of the universe.

Well yeah. That centre is all around us in every direction... the past. We can't see where we're going, only calculate it. The further ahead we look, the further back in time we're seeing, and the bigger the light cone required to calculate where we're going. How long before that light cone becomes the observable universe? At that point we are utterly blind to our future.

Dark energy is why we're told the universe's expansion is accelerating. That there is an outward motion from the centre, so why does dark energy not hint at a rotating universe with a definite centre of rotation? Because we see the acceleration in all directions? Of course we do! We're looking at the past, not the future!

[MadMojoMonkey]

Well yeah. That centre is all around us in every direction... the past.

If everywhere is the center, then it wasn't rotating at the initial moment of the big bang (because this affirms the point-mass assumption).

We can't see where we're going, only calculate it.

This is called the "psychological arrow of time."
Rather the psychological arrow of time says we understand that time always flows in the same direction because we can remember the past, but not the future.

The further ahead we look, the further back in time we're seeing

The further away we look, the further back in time we're seeing.

, and the bigger the light cone required to calculate where we're going.

What?
What does the knowledge of the distant in both space and time have to do with...?

The vertex of a light cone is a spacetime event (in a 2-d plane, where one axis is distance and the other is time, so kind of a 1-D plane in time). The light cone describes that event's possible causal relationship with the rest of spacetime. The light cone is infinite in both directions, and contains all possible causal pasts in one direction and all possible causal futures in the other direction. Any spacetime coordinate not contained by the cone cannot have caused the event at the vertex or be affected by the event at the vertex, due to it being too far away in space and too close in time for the information from the event at the vertex to travel there at the speed of light.

How long before that light cone becomes the observable universe? At that point we are utterly blind to our future.

There will always be spacetime coordinates which are not causally related to other spacetime coordinates, based on the fact that the speed of light is finite.

Look at any straight line through the universe at a single moment in your spacetime frame. Pick any point on that line. It is not causally related to any other point on the line in that frozen instant, because it takes some time for a signal moving at finite speed to move away from it.

There is a unique light cone at every point in the universe which corresponds to that point in both space and time, which is the light cone's vertex.

If you're talking about the big bang's light cone, then it already encompasses everything we know, because we know we are causally linked to the big bang, so must be within its light cone, like the rest of the universe.

Dark energy is why we're told the universe's expansion is accelerating.

But it's a non-answer.

Why is the universe accelerating?
Dark energy.
What's dark energy?
It's what we're saying is making the universe accelerate in its expansion.
What is it beyond that, though?
Dunno.
Why are you even talking about it, then?
It's kind of a place-holder name while we look into it more.
... and it sounds cool.

That there is an outward motion from the centre, so why does dark energy not hint at a rotating universe with a definite centre of rotation? Because we see the acceleration in all directions? Of course we do! We're looking at the past, not the future!

SAME acceleration in all directions. Only a function of distance, not direction.

I don't understand your past/future argument, here.

[MadMojoMonkey]

Did you not like the answer "probability"?

As I explained, probability describes the rate of a process happening, not the outcome.

To determine the rate of a nuclear reaction or interaction, you first calculate the probability of the outcome happening per chance to happen, then multiply by the chances to happen.
Each observable outcome is a deterministic state, and the sum of probabilities of all observable outcomes is always 1.

Probability describes whether or not a thing happened, it doesn't alter the outcomes of the thing happening.

I have another potential solution... initial conditions of matter vs antimatter were an odd number. If one particle of matter survives, along with all the energy that's left over, then we still have an interaction. There is a universe. Perhaps the universe as we know it "grew" from one solitary matter particle.

That explains the existence of 1 piece of matter in the universe, not the 10^big other particles out there with no anti-particle partner to annihilate with.

[OngBonga]

So entropy is a breaking of symmetry at some scale of particle interactions?

It's really hard to get the concept of symmetry in the context of physics, but I think I'm getting there.

[MadMojoMonkey]

It's really hard to get the concept of symmetry in the context of physics, but I think I'm getting there.

Jury's out. I'm still not confident and posing a question, there.

[OngBonga]

I don't understand your past/future argument, here.

We see expansion in every direction. But we're looking at the past, so what we're observing is past expansion, not present expansion.

SAME acceleration in all directions. Only a function of distance, not direction.

In a 3D model, sure. But this is 4-dimensional expansion. We're talking about spacetime, not space. The same acceleration in all directions is because we're always looking in the same direction... the past.

If we're seeing expansion at the very edge of the observable universe, then we're witnessing the expansion of the early universe, not the now universe. We know that was insane expansion. I mean, if we're seeing an acceleration of expansion, then surely what's actually happening is expansion is slowing down, because we're witnessing faster acceleration in the distant past to what we observe locally.

I'm just confusing myself here. I'm sure that made sense before I read it back.

[MadMojoMonkey]

We see expansion in every direction. But we're looking at the past, so what we're observing is past expansion, not present expansion.

This is one reason why we know how much the universe was expanding in the past compared to now.
This is one piece of evidence that the expansion is accelerating.

We're looking into the past, but the closest things to see (which are, admittedly, pretty far out there) are still relatively not that far in the past compared to the CMBR. So we have a long record of what the expansion was over a wide span of time.

Additionally, we've been watching the sky with decent instruments for a while now. We compare the past images to the present images with spectroscopy and we can see the red shift has changed.

In a 3D model, sure. But this is 4-dimensional expansion. We're talking about spacetime, not space. The same acceleration in all directions is because we're always looking in the same direction... the past.

If we're seeing expansion at the very edge of the observable universe, then we're witnessing the expansion of the early universe, not the now universe. We know that was insane expansion. I mean, if we're seeing an acceleration of expansion, then surely what's actually happening is expansion is slowing down, because we're witnessing faster acceleration in the distant past to what we observe locally.

I'm just confusing myself here. I'm sure that made sense before I read it back.

We're looking into the past, but it's still moving in chronological order.
The scientists working on this know the GR much better than you and I. I'm certain the many measurements of the Hubble constant and the cosmological constant haven't all accidentally made some mistakes that end up all getting the sign (+/-) of their estimate wrong.

[OngBonga]

Block holes don't trap light by slowing it down. They trap light by red-shifting it to the limit of infinite red shift, which has infinite wavelength, and therefore 0 energy.

So the Newtonian view of the event horizon representing the region where escape velocity is c is... a coincidence? Or is it the same kind of coincidence that inertial and gravitational mass are... ie different ways of measuring the same effect?

[OngBonga]

I'm still confused.

If the universe's expansion is accelerating, then why aren't nearby galaxies (more recent) drifting apart at a faster rate than distant ones (less recent)? Why is it the other way round? Why was expansion greater in the distant past than it was in the recent past?

What does the CMB tell us about the rate of expansion? Are we seeing an accelerated increase in wavelength? That would be pretty hard to explain without conceding the argument.

[MadMojoMonkey]

I'm still confused.

I have to take some responsibility. I'm confused by some of this, too.
My responses in this conversation are bound to have some of my misunderstandings woven in there as I work my way through some of this.
I've tried to use question marks where appropriate.

If the universe's expansion is accelerating, then why aren't nearby galaxies (more recent) drifting apart at a faster rate than distant ones (less recent)? Why is it the other way round? Why was expansion greater in the distant past than it was in the recent past?

The spacetime in between galactic clusters is expanding. Stuff with more spacetime in between us and it will be moving away from us more quickly 'cause there's more stuff expanding in between us.

What does the CMB tell us about the rate of expansion? Are we seeing an accelerated increase in wavelength? That would be pretty hard to explain without conceding the argument.

Well, the photons' wavelentghts in the CMB have red shifted significantly, and measuring that red shift tells us the age of the CMB.

IDK if we've measured a change in the red shift of the CMB.

[OngBonga]

Additionally, we've been watching the sky with decent instruments for a while now. We compare the past images to the present images with spectroscopy and we can see the red shift has changed.

I'm not arguing the universe isn't expanding. I still anticipate red shift.

[Savy]

I really enjoy reading this thread. I don't think MMM gets enough credit for not being a snobby ass when it comes to talking about this stuff with people. I know I tend to do that as do most people.

[OngBonga]

I really enjoy reading this thread. I don't think MMM gets enough credit for not being a snobby ass when it comes to talking about this stuff with people. I know I tend to do that as do most people.

I really love talking shit in this thread. Obviously I like to talk about this kind of stuff with my friends, but I'm not IRL friends with a physicist, so it's really something I appreciate to be able to bounce my stoned ideas off someone qualified to refute them.

[MadMojoMonkey]

I really enjoy reading this thread. I don't think MMM gets enough credit for not being a snobby ass when it comes to talking about this stuff with people. I know I tend to do that as do most people.

Thanks.

I strongly believe that if I can't explain something to someone who is trying to understand it, then I don't understand it.

It's not always true. There can be plenty of reasons to complicate this, but it serves me well most of the time.

[OngBonga]

I have to take some responsibility. I'm confused by some of this, too.

Yeah I think my confusion is based on my misunderstanding of what "expansion" actually is.

There is a feeling in me though that we're missing something simple, perhaps something as simple as an optical illusion. The fact we naturally think in three spacial dimensions is a hinderance to our intuition, imo. We're travelling through spacetime away from every direction we look in, and that isn't easy to imagine. Our motion is towards what we can't see, spactime that is yet to exist.

Perhaps that's where the expansion is. We're moving into expanded space, it expands as we move into it.

[MadMojoMonkey]

There is a feeling in me though that we're missing something simple, perhaps something as simple as an optical illusion. The fact we naturally think in three spacial dimensions is a hinderance to our intuition, imo. We're travelling through spacetime away from every direction we look in, and that isn't easy to imagine. Our motion is towards what we can't see, spactime that is yet to exist.

Perhaps that's where the expansion is. We're moving into expanded space, it expands as we move into it.

It bums me out a bit that someone with your interest and intelligence isn't more directly involved in the field.

I mean... if you spent a week or two studying a book on GR, you'd know more about it than I do, probably. Your background understanding of Newtonian concepts is competent for any undergrad. I'm sure the calculus and linear algebra will be painful to learn, but you'd be good at it. You may not love doing it, but you'd love knowing that you understand the inner workings of GR.

Plus, you're already familiar with light cones and other stuff that an undergrad has no knowledge of coming into the program.

***
I mean... its selfish of me to want you in my field, but damn if you don't have excellent scientific instincts.
Some scientific field would greatly benefit by you being in a building where they do stuff.

[OngBonga]

It bums me out a bit that someone with your interest and intelligence isn't more directly involved in the field.

Not sure if this post is a compliment or a moan! I think a bit of both!

Honestly, it bums me out that I was so smart at school but left with no qualifications. I'm not getting into why that was, other than to say it wasn't my fault.

Obviously I take responsibility for my actions (or rather, lack of) since becoming an adult, and certainly I could have studied better at college instead of drinking and smoking, but I was fresh out of an oppressive naughty-boys school regime and released into pure freedom, so it's no surprise I just did what I wanted to do... it was the first time in my life I had such freedom.

I dunno, I guess there's a part of me that wants to learn, and a part of me that just wants to carry on being free.

If I were going to study, I think it would have to be physics. I have an interest too in environmental sciences, but since I have controversial views about global warming, I think it's probably best I avoid that field! Physics isn't politically controversial, at least not to the same degree.

Will I ever study? Possibly. I mean I'm seriously looking to get the fuck out of my shitty town and into the countryside. Once I've done that, I'd like to think I'll have more motivation. Until then, I'll probably just carry on as I am... getting stoned and learning what I can be bothered to learn, while talking shit about what I'm learning and how I interpret it. That must be better than doing nothing! At least I'm well placed if I eventually decide to study formally.

[MadMojoMonkey]

Not sure if this post is a compliment or a moan! I think a bit of both!

How could it possibly not be both?

I dunno, I guess there's a part of me that wants to learn, and a part of me that just wants to carry on being free.

pffft.
Ignorance is a cage, man.
*cough cough*


***
Your controversial views about global warming are no reason to stay away if you're interested.

In the sciences, we welcome controversial views. If data can't refute your views, then they're are no less valid than more popular unrefuted views.

Einstein's relativity was controversial.
QM was controversial.
Simply defining "observe" is still a bit controversial in physics.

[OngBonga]

To give an example what I'd be like studying environmental science, when I studied psychology at college, it took me about a month before I started rejecting Freud and his ideas, arguing that he was applying his fucked up thoughts as a kid to everyone instead of acknowledging he was a wrong-un. I wanted to study Jung, and felt that were were learning the history of psychology, rather than psychology itself. Can you imagine what I'd be like when I'm being taught about climate change?

[MadMojoMonkey]

Can you imagine what I'd be like when I'm being taught about climate change?

I imagine you'd be, like, relieved that you're in a hard science rather than a soft science.
Your challenging questions will be answered with data or a nod that it's a good question. Not with hand-waving and conjecture.

I imagine you'd be, like, "What a relief that what counts as knowledge in this field isn't just whatever BS sounds good to my culture right now."


(Sorry, psychologists. My views on psychology can fall toward pretty rude at times. I don't think all psychology is misguided, but a lot of it is more a reflection of culture than of any hard, permanent truths about the mind.)

[OngBonga]

In the sciences, we welcome controversial views.

To a degree. The problem with disputing climate change is that you get treated the same as flat earthers, creationists, 9/11 truthers, holocaust deniers. You'd quickly be cast to the fringes.

I imagine you'd be, like, relieved that you're in a hard science rather than a soft science.

Climate change is way too politicised for me to consider it a hard science. There's too much external influence.

[Jack Sawyer]

To a degree. The problem with disputing climate change is that you get treated the same as flat earthers, creationists, 9/11 truthers, holocaust deniers. You'd quickly be cast to the fringes.



Climate change is way too politicised for me to consider it a hard science. There's too much external influence.

You bring forward your hypotheses and other scientists proceed to tear them to shreds. If they are bulletproof, they will withstand the intense scrutiny by other scientists, and if not, they will falter.

The scientific method is an ongoing process. This is why science has little bullshit. It's not based on faith nor feelings, rather objective testing and retesting and scrutiny. You cannot be cast to the fringes if your data holds. If it doesn't and still you claim such findings, then yes, you will be declared a loon.

[Savy]

This is why science has little bullshit. It's not based on faith nor feelings, rather objective testing and retesting and scrutiny. You cannot be cast to the fringes if your data holds.

Being a little idealistic there pal. Obviously the "right" side tends to pull through but this process can certainly take longer than a persons remaining life.

[CoccoBill]

I was going to ask about this but now feel I don't have to.

https://drivetribe.com/p/R5Q6z6jqSgG...Q8uVDBOg8SjjpA

If, though, you feel you can add something to it, pls do.

[MadMojoMonkey]

Torque is hard to understand. If anyone tells you otherwise, they're a liar and they want something from you.
Even physicists who totally get it now had a hard time learning it. It's tricky. It does unexpected things sometimes.

Fundamentally, a torque is the rotational equivalent of a force. A force causes an acceleration in a straight line, and a torque causes a spinning acceleration.

In physics, we describe a lot of things with vectors. Vectors have a magnitude and a direction. An arrow has a length and a direction. We readily use arrows as symbols for vectors, with the magnitude of the vector corresponding to the length of the arrow, and direction is same for both.

With force, if your butt pushes on the chair with your weight, we can describe that force with a vector located at your butt and pointing down. It's length would correspond to your weight. It's pretty straight forward. Your butt pushes down, so the arrow points down.

With torque it's trickier. A thing starts spinning. Part of it is moving in every direction (except the directions parallel to the axis of rotation). There's no unique direction which indicates what the torque is doing. The axis of rotation would be the ideal place to put the vector, but that exact point doesn't move at all.
So we make an executive decision.
We decide to point the torque vector along the axis of rotation. This isn't fully solving the problem, though. The axis goes both ways. I mean... there's a spinning thing, and the axis goes through it. So depending on which side we attach the torque arrow, it could be flipped 180 in direction.
Another executive decision.
We still need to link the direction of spinning to the arrow, too. It could be going clockwise or counterclockwise (from a defined coordinate perspective). We can link the direction of rotation with the 180 flip of the arrow and clean up both problems if we simply pick a standardized way to link the direction of the spinning to the direction of the arrow which describes the vector which describes the spinning.

We use the right hand rule.
I can get into this in more detail if you like. For now, it's enough to say
if I open my right palm with my thumb out,
then close my fingers, keeping my thumb out,
my thumb points in the direction of the vector which describes the spinning of my fingers.

(Notice that if you do this with your left hand, it's a mirror image, and flips the direction of the thumb relative to the rotation. We could have used this rule in our 2nd executive decision. Which we use isn't relevant, so long as all of our math and physics is consistent. The right hand rule comes up a lot, so just go with it... even if you're left-handed.)

Here's a somewhat more involved explanation of torque as pertains to not cars.

[MadMojoMonkey]

This is worth the extra ~4 minutes if the other video didn't bore you.


"None of this is intuitive. None of this is intuitive."

[CoccoBill]

Thanks for the replies, sorry took a while to comment. Yeah that's some weird stuff, I'm not sure I'm any closer to intuitive understanding of torque.

Another, completely unrelated, thing. Ever since years ago watching some documentary about the scale of atoms, the relative distance between electrons and the nuclei, I've been wondering about this but never been able to find any explanation that I could understand. If you exert enough outside pressure to the electrons to squeeze them into the nucleus you're breaking the electron degenerative pressure, and if you have enough mass together in practise this is what happens when a star collapses into a white dwarf, right? If then you keep applying more force, enough to force the electrons and protons to combine and create neutrons (the Chandrasekhar limit?), you're left with a neutron star? Still not satisfied, you keep exerting more force (and adding mass) to collapse the neutrons (the Tolman–Oppenheimer–Volkoff limit?) you end up with a black hole or something silly like a quark star?

[MadMojoMonkey]

Thanks for the replies, sorry took a while to comment. Yeah that's some weird stuff, I'm not sure I'm any closer to intuitive understanding of torque.

You just gotta keep on it. It's a classical phenomenon (unlike QM and GR), so as a general rule it will eventually be intuitive to you if you keep thinking about it.

Another, completely unrelated, thing. Ever since years ago watching some documentary about the scale of atoms, the relative distance between electrons and the nuclei, I've been wondering about this but never been able to find any explanation that I could understand.

Well, let's see...

If you exert enough outside pressure to the electrons to squeeze them into the nucleus you're breaking the electron degenerative pressure, and if you have enough mass together in practise this is what happens when a star collapses into a white dwarf, right?

Yes, that's right. Except "into the nucleus" is terribly misleading. Electrons already spend time inside the nucleus, just not much on average.

The degeneracy pressure is a consequence of squeezing electrons close to each other, not to a nucleus.

If then you keep applying more force, enough to force the electrons and protons to combine and create neutrons (the Chandrasekhar limit?), you're left with a neutron star?

Yes.

Be cautioned against thinking that a neutron is somehow a proton and an electron stuck together. That's not the case. The electron is annihilated in the process of changing the proton into a neutron. They aren't really "combined" in that sense.

Still not satisfied, you keep exerting more force (and adding mass) to collapse the neutrons (the Tolman–Oppenheimer–Volkoff limit?) you end up with a black hole or something silly like a quark star?

Yes again... but this one isn't really a question, now, is it?

[BananaStand]

What's the latest on the quantem enigma?

Is there any progress or viable theories on why matter behaves differently based on whether or not you're watching it?

[MadMojoMonkey]

What's the latest on the quantem enigma?

What's that?
(google search)
Oh... I'm pretty sure that's a misunderstanding of what physics says because it's being interpreted by non-physicists and the physicists didn't make it clear what their definitions are.

Is there any progress or viable theories on why matter behaves differently based on whether or not you're watching it?

I'm guessing the confusion stems from the typical quantum physicist's use of the word "observe" to be interchangeable with "interacts with."

The behavior of matter has nothing to do with whether a person or consciousness is watching it.

It simply states that when matter isn't interacting with anything, it behaves in one way, and when it is interacting with other stuff, it behaves in another way. Both patterns of behavior are well defined within the statistical limits of observation and theory.

[BananaStand]

What's that?

The behavior of matter has nothing to do with whether a person or consciousness is watching it.

Hmm, that's not how it was explained to me. Caution: Netflix-documentary style science ahead.

Imagine a solid wall. A few feet in front of it, you have another wall with two holes cut out of it. You stand in front of both walls and throw baseballs. Some of your baseballs will go through the holes in the outer wall, and hit the solid wall behind it. If we marked the points of contact, the solid wall in back would have two hole-shaped regions where it was struck by baseballs, and the rest of the wall would be untouched.

Now imagine instead of baseballs you launched something that travels in a wave, like sound, toward the walls. The sound waves would hit all over the outer wall, and some of the sound wave would make its way through the holes. Since there two holes, the sound wave is now emanating from two points on the outer wall and travelling toward the solid wall. Again, if you could mark the points of impact where the sound wave meets the solid wall, you'd have a completely different pattern than the baseball example.

So particles traveling through holes in the outer wall will only impact the solid wall in certain hole-shaped regions that align with the outer wall. Waves travelling through the holes will split up, emanate through two holes, and the two new waves will overlap each other somewhat before they hit the solid wall. And if you could mark their impacts with the solid wall, it would make a different pattern than the baseballs. Regions where the waves overlapped got double-impact, and places that only got hit by one wave had less impact. On the show it looked like vertical lines.

So what should light do?

It's not a wave, it's photons. Particles with a finite observable size and shape. Logic tells you that they should behave like the baseballs, and only make impact with the solid wall in the regions that align with the holes on the outer wall.

Except that's not what happens. Light hits the solid wall and makes a pattern as if it were a wave

So scientists saw this and said "What the fuck??" Let's slow this all down, and watch individual photons and see what they do.

So they built some kind of science-y apparatus that let's them see individual particles and they watched what happens when photons are fired through this outer wall with holes in it.

Well jiminy cricket.....when they watched the photons move through the holes, they impacted the solid wall in only specific regions. Just like baseballs.

Then they turned around and ran the experiment again, without watching, and found that the light acted like a wave again.

So they tried again, this time watching, and......baseball pattern

Close your eyes and try again......wave pattern

Now open them and do it one more time.....baseball pattern

What's up with that?

EDIT: This link explains it a little better than I did
https://motherboard.vice.com/en_us/a...ssical-world-2

[MadMojoMonkey]

So what should light do?

Weeee!

It's not a wave, it's photons.

Wave = particle = wave = particle
Observations to the contrary reveal a fault in human perception (which I share).
The experimental confirmation of wave-particle duality is ridiculously well established.

Just today, I demonstrated the photoelectric effect which shows the particle nature of photons. Tomorrow I'm demonstrating that exact double-slit experiment you described, showing the wave-nature of photons.

I have Geiger counters which detect Beta radiation (emitted electrons from nuclear decay) as individual particles. I also have a demonstration which shows electrons diffracting like waves when a beam of them is passed through a crystal.

I mean... none of this should really convince you, as it's all hearsay... on the internet, no less... but it's actually not very hard to do some experiments yourself. It takes some equipment and a DIY spirit, but you don't really need expensive stuff to tease out the physics.

photons. Particles with a finite observable size and shape.

Photons are hardly alone on the list of particles which have no known measurable size or shape.
As always with these kind of measurements, it's impossible to prove a 0. There is always measurement uncertainty. You can keep pushing down the maximum size, given that you keep measuring 0, but your resolution isn't infinite. There's always a cutoff where you have to admit that it could be there, but smaller than X.

Quantum particles have fuzzy edges... their positions and momenta are probability fields manifest in moving matter, which obey various uncertainty relations. Even for particles whose size and shape we can measure, e.g. protons and neutrons, these properties are described as probability density functions. I.e. there's a sphere which we call the proton radius, but it really represents some statistical percent chance of finding a proton in that volume, and not the size of a ball which is the proton occupying that volume.

Logic tells you that they should behave like the baseballs, and only make impact with the solid wall in the regions that align with the holes on the outer wall.

When flawless logic yields absurd results, then at least one of the "given" statements of the logic must be false.
Algebra is awesome!

In this case, it's the assumption that "particle" and "wave" are somehow not the same.
The difficult to accept reality is that they are the same, or at least, aspects of the same thing.

Except that's not what happens. Light hits the solid wall and makes a pattern as if it were a wave
So scientists saw this and said "What the fuck??" Let's slow this all down, and watch individual photons and see what they do.
So they built some kind of science-y apparatus that let's them see individual particles and they watched what happens when photons are fired through this outer wall with holes in it.
Well jiminy cricket.....when they watched the photons move through the holes, they impacted the solid wall in only specific regions. Just like baseballs.

"Watched" is in need of defining, here. I don't know what exact experiment you're referencing, but they are all similar in the important respects.

They setup some way to detect which hole the photons passed through. In so doing, the photons' superposition of passing through both holes collapses to a single hole, and it propagates accordingly thereafter.

The "watching" isn't being done by scientists... it's being done by whatever they setup as a detector. All detectors detect by interacting, so it's the detector watching the photons that matters, not the conscious minds which set it up.

Then they turned around and ran the experiment again, without watching, and found that the light acted like a wave again.
So they tried again, this time watching, and......baseball pattern
Close your eyes and try again......wave pattern
Now open them and do it one more time.....baseball pattern

What's up with that?

When the wave function approaches a hole or slit commensurate with its wavelength, weird things happen.
The photons don't technically have to pass through a hole, they just have to pass closer than their wavelength to something to diffract off of it.

The wave function diffracts off of the edges of the hole, and if the hole is small enough, the waves will diffract throughout its opening. However, the quantum weirdness is that no matter how the position wave function spreads out, we never observe the energy of the photon spread out. We only observe single bumps (quanta) of energy, equal to the energy corresponding to that wavelength of light.

It's weird. It defies intuitive understanding.

The diffracting causes the photon's wave function to exist as a superposition of more than one position/momentum pair.
Which means that until it interacts with something, it is spread out over many places, and its momentum is spread out to match how it got there.

If it interacts with the wall, then the wave function collapses will only be where the wave function is not completely destructively interfering with itself. The wave functions are collapsing at the wall, which captures the amalgam of many individual wave function collapses, and the probabilistic nature of their superposition manifests as wave interference they experience at the moment of their observation (by the wall).

If it interacts with something else, prior to the wall, then the spread-out wave function collapses at that interaction and it no longer exists in the particular superposition of states which was set up in passing through the hole.

EDIT: This link explains it a little better than I did
https://motherboard.vice.com/en_us/a...ssical-world-2

This experiment is a little different in that they discuss measuring the photons' positions just prior to one of the slits.
It raises the question of why does the photon which doesn't pass through the detector's slit still not behave as though it passes through both slits?

The answer is the same. Prior to being detected, the photon was in a superposition of states with a spread in it's position and momentum functions. Whether or not the photon was detected at the detector, certain portions of its wave function always passes through the detector. A lack of detection can still have caused a wave function collapse. The portions of the superposed wave function which describe the wave passing through the detector collapsed to nothing. The measurement was made. The photon wasn't there. The rest of that photon's wave function continues on, uncollapsed, and passing definitively through the undetected hole.

[OngBonga]

Thanks for the replies, sorry took a while to comment. Yeah that's some weird stuff, I'm not sure I'm any closer to intuitive understanding of torque.

Torque is the force applied to a wrench, multiplied by the length of the wrench (and the angle of force, but let's not think about changing that, just stick to a nice perpendicular 90 degrees). If you apply a force, the nut turns. If you increase the length of the wrench, but apply the same force, the nut turns quicker. Why? Because we're getting more work for the force... torque.

I guess it's easy to say this and accept it as fact, because we know it's easier to turn nuts with longer spanners, but it's not so easy to understand why we're getting more work for our force.

The easiest way to imagine torque that I can think of is to think of a scale. First, imagine it balanced. Now put a 2kg weight on one side, and a 1 kg weight on the other, but twice the distance from the centre as the 2kg weight is. The scales remain balanced. Why? Torque. The rotational force around the centre of balance applied by the 2kg weight equals the rotational force applied by the 1kg weight. Torque is the measure of rotational force, the torques are balanced in this example, and as such the scales are balanced.

Things on a scale appear "heavier" the further they are from the the centre of balance. If you apply this concept to a spanner and nut, then you're getting more "weight" from your work with a long spanner than you get with a smaller one.

[OngBonga]

I came here because I wanted to ask a question...

My computer room is approx 2x2x2 meters, and has no windows. During the recent good weather we had, the temperature in this room was getting up to 35 degrees, and was too hot for my computer, which would crash due to "thermal event". A fan pointing directly at the comp deals with this, but it's still uncomfortable sitting in 35 degrees. I can't afford a AC unit, so I'm left wondering how much I can cool this room using evaporation methods.

Are there any tables I can refer to that will tell me how much evaporation needs to take place for a set target in reduction in temperature? Obviously I know humidity is an important factor, I might be able to borrow a dehumidifier through the summer so that might be controllable despite the lack of ventilation. So... at 50% RH and 35 degrees celcius in 8 cubic meters of air, can I get a reduction of 10 degrees by evaporation alone?

[MadMojoMonkey]

It takes 40.66 kJ/mol of water to turn it from 100 degree water into 100 degree water vapor.
1 mol of H2O is (2*1g/mol + 1*16g/mol = ) 18 g/mol. Since 1 cc of water has a mass of 1 g, a mol of water is 18 cc.
So evaporating 18 cc of water will require the water to absorb 40.66 kJ of energy

The density of dry air is 1.225 kg/m^3.
Your 8 m^3 room has (8 m^3 * 1.225 kg/m^3 = ) 9.8 kg of air in it.

The specific heat of air is 1.005 kJ/kg*K.
You want to change the temperature of a 9.8 kg of air, so 1.005 kJ/kg*K * 9.8 kg = 9.849 kJ/K.

You want to lower the temperature by 10 C (which equals 10 K), so 9.849 kJ/K * 10 K = 98.49 kJ

This is a lottle more than double the energy required to evaporate 18cc of water, so evaporating a bit more than 36 cc, maybe 40 cc of water should do the trick.
This is a 1-time cost. Once you cool the room, you don't have to do so again... so long as there are no heat sources in the room, and it is perfectly insulated from heat transfer through the walls / doors.


In practice, you sitting there doing no exercise is close to ~75 - 100 Watts of power produced. Most of that power is heating the room.
That's another ~0.1 kJ per second that you need to dissipate. To do this, you need to evaporate another ~27 cc per minute.
Plus the computer is also a heat source.

[OngBonga]

It takes 40.66 kJ/mol of water...

Thanks for this analysis, I'll get back to you when the weather perks up again and I put this into action!

[MadMojoMonkey]

Thanks for this analysis, I'll get back to you when the weather perks up again and I put this into action!

Keep in mind that you don't want that evaporated water in the room. It bears the energy and keeping that energy out is kinda the point.

It's important that the water is evaporated by energy taken from the room. Adding an energy source to evaporate the water kinda eliminates the point.

Keep me posted. You'll want a cool room while you setup your pilot wave detector.

[CoccoBill]

I guess I more meant that the effects of applied torque can be unintuitive, not the force itself. Hm so in car specs, torque is the rotational force applied to the crankshaft, and horsepower is the amount of work, or transfer of energy, the engine can do in a set time?

And yeah on that atom squeezing stuff was I was more looking for a confirmation if I got it right, no question there if it was in the ballpark.

The degeneracy pressure is a consequence of squeezing electrons close to each other, not to a nucleus.

Alrighty then, not as simple as I expected, not surprisingly. In the visualizations it's always stressed how far the electrons actually are from the nucleus and how much empty space there is in between. If matter is mostly nothing, it just led me to think what would happen if you squeeze matter enough, and just picturing applying enough force to pack all of the atoms (or nuclei) together, with no empty space in between. I do realize it's not like electrons are just there spinning on perfect orbits around the nucleus like earth around the sun, but they're all over the place, even at the same time. That would have just been such a satisfactory intuitive explanation. So what does exactly happen when the force applied is nearing the Chandrasekhar limit, is the distance between the electrons and the nuclei being limited or how do they end up butting heads?

[MadMojoMonkey]

I guess I more meant that the effects of applied torque can be unintuitive, not the force itself. Hm so in car specs, torque is the rotational force applied to the crankshaft, and horsepower is the amount of work, or transfer of energy, the engine can do in a set time?

You gotta be careful with what the torque is referring to. The torque going into the transmission is not, in general, the same as the torque coming out of the transmission. A differential is a kind of gearbox, too, so it also changes torque from its input to output shafts, in general.

Torque coming out of the engine is not generally the same as torque coming out of the transmission, which is not generally the same as the torque applied to the wheels.

The power delivered in all cases is (nearly) the same, because of conservation of energy (but not exactly the same, 'cause friction and stuff).
Your definition of work is spot on.

Since energy is conserved in every split second, power is conserved, too. So the power into the transmission is roughly equal to the power coming out of the transmission.
Roughly equal because friction losses mean that the output of the transmission really includes heat and noise and other forms of dissipating energy.
This is true for all gearboxes.

A slowly spinning shaft with a high rotational force can be put through a gearbox to produce a faster spinning shaft capable of delivering less rotational force.
Also, the opposite is true. Gears are efficient tools for trading rotational force for rotational speed and back.

So the horsepower rating of the engine tells you how much constant brute force the engine is capable of producing.
The torque is a variable thing, depending on where you measure it.

[MadMojoMonkey]

Disclaimer: when talking about stellar evolution, physicists tend to talk about the core of the star. We go on about core collapse, and the effects thereof. This may clash with what you've heard about the sun's size expanding over the coming billion years to be larger than the orbit of Earth. The outer layers of a star expand as it ages, but the core collapses and becomes more dense as more "heavy" elements are fused.

It's something to bear in mind.

Also, I spent days creating this post, and I'm not sure where it's too heady and long-winded and where it's hard to follow and obtuse at this point.
Please follow up as needed.

***
lol... "Post Quick Reply" couldn't be less true.

Alrighty then, not as simple as I expected, not surprisingly. In the visualizations it's always stressed how far the electrons actually are from the nucleus and how much empty space there is in between.

Atoms are crazy little things [citation needed].

Just so that you don't think I'm saying that it's common for an electron to be inside a nucleus:
It is the case that electrons spend some time in the nucleus... that is... there is a non-0 chance of occasionally detecting an electron inside a nucleus.
It's not a very probable situation, but it is definitely part of the description of atoms.
The most probable place to find an atomic electron is definitely outside a nucleus.
A nucleus is generally ~(10)^-15 m in diameter.
An atomic diameter is generally ~(10)^-10 m.
So the atom (rather, its electron cloud) is 10,000 times as wide as its nucleus.

Like I mentioned before, the (10)^-15 m is misleading. It represents some probability of finding a nucleon inside that diameter. Just as electrons are sometimes inside of nuclei, nucleons are sometimes outside this nuclear size (it's ridiculously more rare, though). The forces acting on nucleons to hold them together are different than gravitational or electromagnetic forces, and nuclei therefore have a "hard shell." Meaning that finding a nucleon much beyond its parent nucleus means that it is no longer a part of that nucleus. I.e. you didn't find one of "that" atom's nucleons outside it's nucleus, you found a free nucleon, not bound to any nucleus.

If matter is mostly nothing, it just led me to think what would happen if you squeeze matter enough, and just picturing applying enough force to pack all of the atoms (or nuclei) together, with no empty space in between. I do realize it's not like electrons are just there spinning on perfect orbits around the nucleus like earth around the sun, but they're all over the place, even at the same time. That would have just been such a satisfactory intuitive explanation. So what does exactly happen when the force applied is nearing the Chandrasekhar limit, is the distance between the electrons and the nuclei being limited or how do they end up butting heads?

Keep in mind that what we're talking about now is not atoms, but plasma. Plasma is not made of atoms, per se.
An atom is some number of electrons bound to a nucleus with the same number of protons and any number of neutrons. If protons and electrons are not in equal numbers, it is not an atom, strictly speaking, but an ion.
Plasma consists of fully ionized nuclei (the nuclei have no electrons bound to them) going crazy, mad bonkers in a sea of electrons, also going crazy, mad bonkers.

The plasma forms from pre-stellar atoms when the thermal energy (created by increasing pressure due to gravitational collapse) overcomes the electron binding energy. In any collision (particle interaction), now, the average thermal energy delivers more energy to the electron (or nucleus, doesn't matter) than the energy binding it to the atom, and so the nucleus / electron(s) become(s) unbound.

Now what we have is a bunch of nucleons bound gravitationally and a bunch of electrons bound gravitationally. These 2 clouds are also coupled to each other. Each cloud acts to disperse itself, being composed entirely of like charges. However, the clouds are of opposite charge to each other, which means they attract each other. The net effect is that the 2 clouds remain interspersed through each other, shielding each other from the extreme dispersing forces of like-charge repulsion.

So what we have is a state of plasma. The core of collapsing star is basically a single quantum object, composed of unfathomably many entangled particles. We're talking about electron degeneracy pressure, so let's ignore the nucleons for a minute. Remember before when the thermal energy went past some threshold, it turned the atoms of the proto-star in to a plasma. This change happened because it was energetically favorable for the electrons to be unbound from their nuclei. I.e. it would have taken MORE energy to hold the atoms together than it did to create the plasma.

A similar thing is going to happen with the creation of a white dwarf star. The core of the star started to fuse Iron, which is always the end of that star. Iron fusion is endothermic, not exothermic. The outward pressure holding off the full gravitational collapse of the star is due to exothermic fusion reactions of elements lighter than Iron. Those exothermic reactions provide an outward force to balance the gravitational force. With Iron, the reaction not only doesn't provide any outward force, it contributes to the inward pull. For all stars, Iron fusion means supernova is imminent. (The iron in your blood was literally made by the death of a star.)

What I'm describing is a runaway reaction in which the pressure in the core of the star is increasing as the volume (of the core) decreases. That volume contains a mostly constant number of electrons. (There are nuclear decays going on which cause it to fluctuate, but it's fairly constant.)

Now it's gonna get ugly. There's no way to summarize what's going on any better than you understand without getting into quantized wave mechanics.
OK, oscillators.
If I have 2 masses, connected by springs, then they can move in 2 basic ways. Either they move together as a unit, where the spring does nothing, or they bounce back and forth, always moving in opposite directions to each other in the center of mass rest frame. No matter what movement you see them exhibit, it is always some additive combination of those 2 states.
If I have 3 masses, connected by springs, then they can move in 3 basic ways. As always, they can move together as one unit, where the springs do nothing. This is always the lowest energy state. They have an intermediate state, where the 2 "outer" masses move in opposite directions of each other, but the "middle" one sits still. The highest energy state is always one in which every mass is moving in the opposite direction as its adjacent neighbors.
With quantized systems, here, the number of masses is quantized, there is always a highest energy state... A maximum amount of energy that can be (nearly losslessly) stored in that system.

OK, it's well different with electron states, and we're talking about the state of a ridiculous number of particles in an ensemble, but the fact that there is a maximum energy that can be stored in the system still holds. As the volume decreases, the number of available states decreases. When the number of available states is equal to the number of fermions (particles that don't share states) in those states, then extreme physics is going on.

The increasing pressure can no longer compress the core of the star, because the core is effectively incompressable under the applied pressure. It can't reduce its volume with that number of electrons in there, and the electrons have nowhere to go. It will take a LOT more energy to make it energetically favorable for the electrons to undergo a process called electron capture. In electron capture, a proton and an electron interact, and a neutron and electron neutrino are left.

In fact, no free proton has ever been witnessed to spontaneously decay. Free neutrons do spontaneously decay into a proton, electron and anti-electron neutrino. This is because the combined rest-mass (energy) of the resulting particles is less than the rest mass of the neutron (and other conservation laws are followed).

In general, for small atoms, the lowest energy state for the nucleus is to have an equal number of protons and neutrons. As we look at larger atoms, we see more and more neutrons than protons. This is because protons have the same sign of electric charge and they're stupid close together. The repulsive forces they express on each other are stupendous. So protons in a nucleus have more energy than neutrons in the nucleus, because they experience a force that the neutrons (not having electric charge) do not.

Nonetheless, if you put a few neutrons together in a nucleus with no protons, at least one of them kinda immediately decays into a proton, because neutrons have the same wave mechanics constricting them in a specific volume as we talked about before. (protons, too). So if you got a bunch of neutrons, and no protons, then it's definitely lower in energy to take one of the highest energy neutrons in that volume and move it to the lowest energy available proton spot. That doesn't even count the bonus energy of a spontaneous decay.

The practical upshot is that in order to compress the electron degenerate matter to neutron degenerate matter, there is a steep cost in energy to pay. Those neutrons are higher in energy than protons, and still confined to a finite volume. If the infalling matter of the collapsing stellar core is does not create enough pressure to pay this cost, then it basically hits an immovable wall and rebounds in a supernova.

The same rebound happens when it collapses to a neutron star, and the neutron degeneracy pressure cannot be overcome.

When the neutron degeneracy pressure is overcome, it collapses into a black hole (or some theorized objects, not yet observed).

[BananaStand]

I don't know dude. That all really sounds like a lot of maybes and excuses.

Still sounds to me like doing the exact same experiment will yield two different results based on whether or not certain parts of that experiment are being observed.

That's spooky fucking shit!

[OngBonga]

Still sounds to me like doing the exact same experiment will yield two different results based on whether or not certain parts of that experiment are being observed.

observed = measured

The act of measuring changes the initial conditions. Of course there will yield two different results based on whether or not it was observed. That's not spooky, it's totally intuitive. How do you "meausre" the velocity and location of a particle? Or, more to the point, how do you do this accurately without altering its trajectory and thus changing the conditions? Hint - you can't, see "uncertainty prinicple".

The double slit experiment can be explained by pilot wave theory. I'm not sure what to make of it all, but the basic gist is every particle has an associated wave, and the wave essentially carves out a geomoetric path for the particle to follow. The trajectory of the particle is determined by its initial conditions, at least until we try to measure it, thus changing its trajectory.

[BananaStand]

The act of measuring changes the initial conditions. Of course there will yield two different results based on whether or not it was observed. That's not spooky, it's totally intuitive.

So I can change the temperature outside by walking outdoors with a thermometer? Sorry, I'm not buying it.

The fact that I can change the behavior of matter in a way that defies the rules of physics, merely by exercising my own consciousness, pretty much proves that I am God.

Or at least, a god

[MadMojoMonkey]

So I can change the temperature outside by walking outdoors with a thermometer?

Theoretically, yes... ish.
Your presence is definitely emitting ~75 Watts of heat when you're inactive. It can be as high as ~150 Watts under intense physical exertion, like any time your breathing is elevated for a sustained period.
This is going to trump the small amount of heat being absorbed or emitted by the thermometer as it comes into thermodynamic equilibrium.

Being able to measure and prove the heat a body emits in a well insulated room of any size is standard. In laboratories where temperature control is essential, there is generally a line of 100 W lamps in the room and whenever a researcher enters the lab, they turn off a light, and turn it back on when they leave. This helps maintain the heat being generated in the lab.

Proving this happens in the atmosphere with a thermometer is going to be impossible.

Conservation of Energy still holds that if you're emitting heat into the atmosphere, then the atmosphere is getting warmer. Whether or not you're inside is probably of minimal relevance. The air in your house is cycled with outside air more often than you may think, but it varies widely. It's just that the atmosphere is really big [citation needed] and the cumulative effect your body heat has on global climate is negligible.

Sorry, I'm not buying it.

There goes my retirement!

The fact that I can change the behavior of matter in a way that defies is explained by the rules of physics, merely by exercising my own consciousness, pretty much proves that I am God.

Or at least, a god

FYP, oh mighty god-brother.

[MadMojoMonkey]

observed = measured

In this context, yes.

The act of measuring changes the initial conditions. Of course there will yield two different results based on whether or not it was observed. That's not spooky, it's totally intuitive. How do you "meausre" the velocity and location of a particle? Or, more to the point, how do you do this accurately without altering its trajectory and thus changing the conditions? Hint - you can't, see "uncertainty prinicple".

This is measurement uncertainty and it is a separate problem than quantum uncertainty laid out in the uncertainty principle.

Measurement uncertainty is a common problem. Consider measuring your car's tire's pressure. By attaching the pressure gauge to the tire, you obtain a reading by releasing some of the pressure into the tire pressure gauge. You cannot measure the pressure with that gauge without altering the pressure you're trying to measure.

This applies to quantum particles, too, but it is NOT the uncertainty principle.

The uncertainty principle says that, even with "perfect" measurement devices, you still cannot simultaneously measure the position and momentum of something to arbitrarily high precision. Those properties DON'T SIMULTANEOUSLY EXIST IN THE UNIVERSE for any particle... because particles are waves, and waves have this property.

The double slit experiment can be explained by pilot wave theory. I'm not sure what to make of it all, but the basic gist is every particle has an associated wave, and the wave essentially carves out a geomoetric path for the particle to follow. The trajectory of the particle is determined by its initial conditions, at least until we try to measure it, thus changing its trajectory.

That pilot wave is the imaginary portion to the solutions of Schroedinger's Wave Equation. Particle wave functions are complex-valued. To determine probabilities of observing certain properties of a particle, you square the wave function and integrate over some domain. The squaring eliminates all negative and complex values from the result, making them neatly measurable predictions.

There is no known way to measure a complex-valued wave, and the pilot wave theory is predicated on these imaginary solutions directing the particles' apparently random motions in deterministic ways. It's a comfortable view, but not falsifiable by any known means, so not, strictly speaking, science.

[MadMojoMonkey]

I don't know dude. That all really sounds like a lot of maybes and excuses.

Still sounds to me like doing the exact same experiment will yield two different results based on whether or not certain parts of that experiment are being observed.

That's spooky fucking shit!

This is mostly spot on, actually.

I mean,there are no maybes* or excuses, but it does sound like I'm making stuff up.
Like I said: There's no reason you should believe hearsay on the internet, whether from me or colonel Sanders in spandex.

It is spooky. There are more spooky aspects to quantum, too.
Check out the EPR paradox.


*OK, saying that the position and momentum of all the things are actually best described by squaring a complex-valued probability density function, then integrating that over some domain - that sounds dangerously close to maybes... but it's really not. That probability density function is well-defined and repeated experiments continue to confirm its utility.

[BananaStand]

This is mostly spot on, actually.

I know. What about the subsequent post where we determine that I'm God? You on board with that too?

I mean,there are no maybes* or excuses, but it does sound like I'm making stuff up..

For what it's worth, it was better than Ong's explanation where photons shoot out of your eyeballs.

Like I said: There's no reason you should believe hearsay on the internet, whether from me or colonel Sanders in spandex

Let's be clear on one thing. This is the last time you badmouth the colonel.

It is spooky. There are more spooky aspects to quantum, too.
Check out the EPR paradox.

No shit it's spooky. So fuck your EPR paradox. I'm not interested in giving myself nightmares.

*OK, saying that the position and momentum of all the things are actually best described by [nerd talk]

I can sorta wrap my head around the idea of things being two places at once and all that. Like the electron passing through the double slit is both a particle and a wave. And it goes through both slits, and neither. Or just one. Or just the other. All at the same time. Fine.

What's not clear to me is how I can personally determine whether it's one thing or another just by my conscious decision to pay attention to it or not.

The idea that a thought is a physical thing that interacts with the environment around it is a pretty incredible thing to think about. Imagine the power that might be unleashed if a whole bunch of people all had the same thought at the same time!

[BananaStand]

It might seem kinda dubious to get your science lessons from Colonel Sanders in a super hero outfit, but this does a way better job of explaining what I was talking about.

[OngBonga]

Here's a visualisation of pilot wave theory...

[OngBonga]

So I can change the temperature outside by walking outdoors with a thermometer? Sorry, I'm not buying it.

Sure going outside changes the temperature. I'm assuming you're warmer than the atmosphere. You are therefore lsoing heat to the atmosphere. Just because the average increase in temperature of the atmopshere is a very slight fraction above zero, doesn't mean it is zero.

The fact that I can change the behavior of matter in a way that defies the rules of physics, merely by exercising my own consciousness, pretty much proves that I am God.

You're not defying phsyics, merely observing it.

[BananaStand]

You're not defying phsyics, merely observing it.

Wait but....

The behavior of matter has nothing to do with whether a person or consciousness is watching it

So which is it?

[OngBonga]

Also, the thermometer itself causes change. It cools the atmopshere, because the mercury has absorbed heat, causing it to expand.

The mercury moving is direct proof that you have changed the initial conditions that you were trying to measure.

Assuming you go from a warm place to a cold place with a thermometer, then you're warming the atmosphere, because the mercury contracts, losing heat to the atmosphere.

It's negligible, but >0, and therefore change.

[OngBonga]

I don't see the contradiction.

[OngBonga]

The behavior of matter has nothing to do with whether a person or consciousness is watching it

It's not the act of "watching" that changes behaviour... it's direct interaction. And everything (with mass) is interacting with everything else (with mass) because of gravity.

Matter behaves as it is insrtucted to based on the conditions in which it is exposed to. If you're standing outside with a thermometer, then you're taking heat from the atmopshere in order to measure the temperature of the atmosphere (assuming it's warmer outside than inside). It's changing because you're measuring it. The only way it wouldn't change is if the atmosphere was already exactly the same temperature as the thermometer. And even then, you'd be interacting with the atmosphere in other ways. You'd displaced air, and therefore changed the airflow of the atmopshere. Again, the most negligible effect one can imagine, but non-zero.

The idea you're "defying" physics is fundamentally flawed. One can't defy phsyics. If it appears you have done, then you've either discovered new laws of phsyics, or you took a bad measurement.

[OngBonga]

Even a case of a police officer firing a beam at a car to determine its speed... that's causing change. The photon hits the car, the car absorbs evergy, and the conditions have changed (albeit in an immeasureable way).

When you realise that in order to measure the velocity and trajectory of a partcle, or even a large physical object such as the moon, one needs to at the very least fire photons at it, then you can start to see that you're changing the conditions in which the object you're measuring was intitially subject to. Yes, in a tiny manner, and for all practical purposes on the macro scale, the change is zero. But it's not actually zero. When we get to the quantum level, well it becomes much less nelgigible.

[BananaStand]

When you realise that in order to measure the velocity and trajectory of a partcle, or even a large physical object such as the moon, one needs to at the very least fire photons at it

What?

Who's firing photons? We're just watching particles go through two slits, in two different ways, based upon which way the camera is pointing.

When you look at the moon, you aren't firing photons at it. It's the opposite. Your eyes are detecting photons that are coming from the moon.

[OngBonga]

I suppose the act of "watching" does actually cause change. Your posture is causing light to scatter in certain ways. If you have to move to view something, then you're changing the way in which light scatters, and therefore changing the amount of energy being absorbed by whatever it is you're observing. So yes, phsyically looking at something causes change. But that's the same interaction as firing a photon, measuring gravity, whatever.

The relationship between interaction is ludicrously complex, because there's probably over a googolplex of particles all simultaneously interacting with each other.

Our conciousness throws something into the mix... if we assume we have free will, then the universe is essentially shaped by the decisions that conscious beings make. So maybe there is a contradiction.

[OngBonga]

Your eyes are detecting photons that are coming from the moon.

Sure, but some of those photons hit you and deflect back to the moon. Some photons that didn't originate from the moon and wouldn't have gone there if you hadn't looked at it are now deflected in that direction. By looking at the moon, you're changing the initial conditions that existed before you looked at the moon. Just changing your posture changes your gravitational relationship with the moon. In fact standing perfectly still won't help, even if you could, because the moon is moving, so is the earth, so your gravitational relationship with the moon is constantly changing.

Observation is interaction, and interaction changes the initial conditions.

[OngBonga]

For what it's worth, it was better than Ong's explanation where photons shoot out of your eyeballs.

lol shooting photons out my eyeballs.

I would hope a physicist can explain phsyics better than me.

[OngBonga]

And it goes through both slits, and neither. Or just one. Or just the other. All at the same time. Fine.

Pilot wave theory says the wave goes through both slits, but the particle only goes through one, following a trajectory based on initial conditions (which determines the wave's propogation). Because we can't measure the initial conditions without changing them (uncertainty principle), we observe apparent randomness that correlates with interference, but the randomness only emerges because we can't measure the initial conditions accurately. If we could, we'd know where the particle would land.

I'm not saying this theory is correct because I obviously have no idea, but it makes more sense than the Copenhagen interpretation, which is basically what you're talking about here with one particle going through two slits until observed, or whatever fucking nonsense they're spouting.