**Ask a monkey a physics question thread**

[MadMojoMonkey]

Our motion through spacetime is always c. Our motion through space is not. So if we set c to 1, our motion through time is the reciprocal of our motion through space. If we move slower than c in space, we move faster than c in time, such that the product of the two is equal to 1 (c). I think this complicates matters.

Basically we move forwards in space and backwards in time. That is my Sunday morning hypothesis.

But moving faster than c is moving backwards in time (at least in some inertial frames).

[MadMojoMonkey]

If you were coming toward me, and accelerated through c...
Until you reached c, I'd see you approaching from a long, long way off.

Then the moment you matched c, I'd suddenly see you teleport to being right in front of me, and there'd now be 3 of you.
The current you immediately bifurcates into a you and a past you. The past you zips away along the path you came, moving backward in time... absorbing fuel into its rocket engines to accelerate in the direction of the exhaust (inhaust?). This continues as your distant ship is approaching in forward time. Eventually the 2 past yous will meet at some intermediate point and disappear, leaving only the current you in my timeline.

Fun

[MadMojoMonkey]

Just for kicks, I calculated the Planck length-second.

With h
~4.051(10)^-35 m s

With h_bar:
~1.616(10)^-35 m s

where m s is meters*seconds, not milliseconds.

[OngBonga]

With h_bar:
~1.616(10)^-35 m s

This is really really interesting. See how long it takes to figure out why.

[OngBonga]

I'm legit curious if your calculations are accurate here or if you've just made some kind of mistake.

I have no idea what the implications of that are if accurate, let's just say my mind would be utterly blown unless you can give a geometric explanation for it.

Let me know when the penny drops.

[MadMojoMonkey]

I can explain how I used the Buckingham Pi method to calculate it. I can't explain what it means, 'cause I never introduced any physics into my calculation.

Here's how it goes. It's a lot of very simple algebra, so don't be daunted by a wall of math.

We have 3 units we consider fundamental: [c] = m/s, [G] = m^3/(kg s^2), and [h_bar] = kg m^2/s.
I'm using square brackets to indicate the units only, w/o the magnitude.

We want something with units m s.

We'll find it by raising each of our fundamental units to some unknown exponent, then solve for those exponents.

[c]^x + [G]^y + [h_bar]^z = [m s]

From here on, it's going to help a bit to write out exponents in a certain way.
For m, I'll write m^1, and for 1/s, I'll write s^-1.
This will be clear in a bit.

[m^1 s^-1]^x + [m^3 kg^-1 s^-2]^y + [kg^1 m^2 s^-1]^z = [m^1 s^1]

That's ugly. But since it's all exponents, we actually get 3 equations in 1, and that is exactly what we need to solve for those 3 unknowns.

The m equation:
1*x + 3*y + 2*z = 1

The s equation
(-1)*x + (-2)*y + (-1)*z = 1

The kg equation
0*x + (-1)*y + 1*z = 0

From the last equation, we solve that y = z. Plug that into the other 2 equations and simplify.
x + 3y + 2y = 1
x + 5y = 1

-x - 2y - y = 1
-x - 3y = 1

Let's add the 2 equations to eliminate x
x + 5y = 1
-x - 3y = 1

0 + 2y = 2
y = 1

plug that into one of the above equations
x + 5 = 1
x = -4

And we're done
x = -4, y = 1, and z = 1


Also... I did find a mistake in my prior work, so this is not the result I posted earlier.
Never hurts to go over your own work.


Wrap it up:
[our new constant with units m s] = c^-4 * G * h_bar
= G h_bar / c^4

which, according to google is
8.714(10)^-79 m s

And it did tell me the units on my result, and they are my target units, so I'm prob. good this time.
Just type "G*hbar/c^4" into Google to see for yourself.

[MadMojoMonkey]

I'm legit curious if your calculations are accurate here or if you've just made some kind of mistake.

I did make a mistake in my initial calculation.

When I added the 2 equations, I accidentally said 1 + 1 = 0, which left we with the incorrect answer y = z = 1/2 instead of 1.

So the result I posted earlier was the SQRT of the better answer.

[OngBonga]

With h_bar:
~1.616(10)^-35 m s

What you don't seem to have realised yet is that here, your solution for h-bar is h.

[MadMojoMonkey]

What you don't seem to have realised yet is that here, your solution for h-bar is h.

It's not remotely the same.

h = 6.626(10)^-34 J s

[OngBonga]

Ok let me rephrase.

Your solution for h-bar is the Planck length

[MadMojoMonkey]

Ok let me rephrase.

Your solution for h-bar is the Planck length

The magnitude was the same, but the units were off.

Which means I made yet another error somewhere in my calculation.

L_Planck = SQRT(hbar G / c^3)

What I was trying to calculate was SQRT(hbar G) / c^2
which wouldn't have the same magnitude because of the exponent on c in the denominator.

I got the exponents wrong by a factor of 2. My revised answer is
G * hbar / c^4

[OngBonga]

Ok so I think I know why h-bar and not h

It's the uncertainty principle. It's the limit at which we can have certainty of the location of a particle. To locate it any further would give rise to potentially infinite momentum. h-bar seems to be the point at which this infinity is reached.

[MadMojoMonkey]

My point is that whichever you choose to use in the Buckingham Pi method is irrelevant.
The "unknown constant" that Buckingham Pi cannot solve for just absorbs or corrects for the divisor of 2pi.

If you can show me a derivation of the Planck Length that is based on physics, and not math, then maybe I'd have some hope of interpreting the meaning of that value. But w/o any physics attached to the derivation, any physical interpretation is speculative.

The notion that the Planck Length represents a lower limit in space beyond which our current models make no predictions seems sound, but I haven't actually seen a proof that it is so. Certainly nothing which resolves the h vs. hbar vs. some other unitless scalar multiplying the result in question. It's just sensible to note that our model has limits, and if that is one of them, then I can accept that.

[MadMojoMonkey]

Ok so I think I know why h-bar and not h

It's the uncertainty principle. It's the limit at which we can have certainty of the location of a particle. To locate it any further would give rise to potentially infinite momentum. h-bar seems to be the point at which this infinity is reached.

There's nothing wrong with reducing the uncertainty in either 1 of the terms on the LHS of the inequality, provided the uncertainty in the other value is of no concern to you.
This principle is what allows the LIGO to work. They're measuring length changes many orders of magnitude less than the diameter of a proton. Which can only be done if you don't care at all about the uncertainty in the momentum being arbitrarily large.

The universe tends to put a kibash on infinities. Conservation Laws are very effective at preventing any system or object from gaining infinite energy or momentum or a few other properties. The requirement to inject infinite X to the particle or system requires something else lost infinite X (provided X is conserved). The lack of an infinite to lose prevents the rise of anything else to infinite.

[MadMojoMonkey]

I learned some new stuff about climate change today that I think is interesting.


If we released *all* the carbon trapped in *all* the fossil fuels and put it into the air, well... That's technically where the Carbon came from in the first place. I.e. this isn't "new," geologically speaking.

The rise and fall of average temperatures on Earth is a well-catalogued "cycle". Cycle in quotes 'cause it's pretty random looking, but does go up and down quite a lot. Global temperatures have been much warmer than our projections in the past - while there was life on Earth doing dinosaur things and other things.

The troubling thing about the current trend of warming isn't that global temperatures haven't been that warm before (even in the worst case projections). It's that in the past, the temperature changes happened over centuries or millennia, not over decades. The rapid pace of change puts pressure on every economy, not just human economies, but ecological economies.


Sea levels could rise up to 230 ft if all the ice trapped in glaciers melts. Different coast lines wont matter all that much. The rapid changes don't allow biological evolution the time to catch up, though. This will lead to a large reduction in biodiversity.

The effects on the food chains will be unpredictable, but humans have pretty well secured our food chains by now. We may have to adapt what we grow where, but we do have all that figured out well enough to sustain huge populations, even on a warmer planet.

[OngBonga]

I hope that got deleted before anyone digested it.

[OngBonga]

I was blabbering how the math didn't check out, that we were three orders of magnitude short of ice.

My mistake was to not convert km to m when considering height of water, which accounts for the three orders of magnitude.

[OngBonga]

https://www.youtube.com/watch?v=qYSKEbd956M

Latest PBS... gravity is an entropic force! What does that mean? That gravity is not a force, or even a law of physics, it's just statistically likely, in the same way it's statistically likely, ridiculously so, though not an absolute certainty, that tea and milk mix together nicely when stirred.

I'll need to watch this again, because it's a bit much. There seems to be a deep connection between gravity and entropy.

[oskar]

My mistake was to not convert km to m when considering height of water, which accounts for the three orders of magnitude.

As it so often does.

https://www.youtube.com/watch?v=qYSKEbd956M

I should learn about Entropy. I have like a high-school understanding of Entropy, but it seems like a thing where you have to get into the math to really get it.

[OngBonga]

Entropy isn't really a math thing. I mean, obviously there's a fuck ton of math involved in thermodynamics, but you don't need to actually do the math to understand what thermodynamics is. You just have to trust the math.

[OngBonga]

Entropy is for the most part really badly explained in layman's terms. I think the "disorder" description fails to adequately describe it.

Entropy is better described imo as the tendency of useful energy to spread out. When you have a bunch of gas atoms with different velocities, all smashing into each other, they are exchanging energy in such a way that the velocity of each individual atom is approaching the average. The energy of each atom with different velocities is useful energy... the faster atom has done work on the slower atom, causing it to gain kinetic energy. In turn, the faster atom loses kinetic energy. As the atoms approach average velocity, the acceleration from collisions is lower, until the system reaches thermal equilibrium and each atom collides with equal velocity, meaning they just bounce without an exchange of energy. The amount of work each higher-velocity atom does when it collides is always getting lower, on average. That's basically the same as saying entropy is always increasing. It happens because useful energy is spreading out over the system. The total energy of the system of course remains constant.

How this relates to gravity is not something I even remotely understand.

[MadMojoMonkey]

The model does show that you can recreate Newtonian gravity from the physics of Entropy on the holographic boundary maximizing, but Newtonian gravity isn't our current model of gravity. So there's that.

If the model could recreate the observed consequences of Einstein's description of gravity, then I'd be more interested.

I'm not really comfortable with the phrase "Entropic Force" because the forces involved do not come "from" Entropy considerations, they come from other descriptions. Much like centrifugal force doesn't come "from" any physical interactions, but from rotation between system and observer. It's fine to talk about centrifugal force in a rotating frame of reference, because in that frame, there is an observed tendency of things to be pushed "outward." However, there is no "real" mechanism for centrifugal force. It's simply Newton's 1st Law acting on straight line motions in a rotating frame. Since there is no physical interaction that accounts for centrifugal force, and that force is absent in non-rotating frames, physicists tend to call it a "fictitious force" or "illusory force." I.e. it's not really there, but an artifact of the way a system is being observed.

BUT if you are willing to hold all of that in your mind, then talking about centrifugal forces in rotating frames is fine. If you google a picture of Lagrange Points, it's almost always shown in a rotating frame.



OK, so sometimes a description is "good" because it caters to our human perceptions, even when it's not a "good" description of physics.
In his example of the molecule being stretched out or coiled up, it's not some mysterious Entropy force that pushes the molecule, it's the molecule's internal bonds and the external air molecules bumping into it. Accounting for all those forces describes the behavior. There's no "missing" force we need to explain with entropy. Much like in the rotating frame, there's no "missing" force that pushes things outward, it's just their straight line inertial movement in a rotating frame.

OK, with all that as preamble, the equivalence of the force of gravity with an Entropic increase is fine. As long as 2 descriptions are mathematically equivalent, they are identical. The universe doesn't care what humans know of math or what particular description humans find more comfortable. Equal means equal.
If there is an equivalent description of gravity from Entropy, then great. But merely showing you can recreate Newton's Laws is not the trick. We already know Newton's laws are a crude approximation of Einstein's laws. We can only assume Einstein's laws will someday be shown to be a crude approximation of something deeper. Showing you can get to Newton is fine, and perhaps encouraging that a deeper link could be made between Entropy and Einstein's curved space-time, but the deeper link is still not shown.

[MadMojoMonkey]

Entropy isn't really a math thing. I mean, obviously there's a fuck ton of math involved in thermodynamics, but you don't need to actually do the math to understand what thermodynamics is. You just have to trust the math.

The math of thermodynamics is elementary school math for the most part. It's mostly bookkeeping and the math is addition and subtraction. In the rare case where you'd need to solve an integral, someone has already solved it, and you just look up the solutions. Typically, you'll have an extensive table of those integral solutions, and you're just looking up the values and plugging them into your equations to do some plus and minus on them.

[MadMojoMonkey]

Entropy is a fucky one to understand.

It's a statistical thing. It doesn't exist in individual quantum mechanics interactions between particles. It's emergent when you look at many interactions.

It's not a rigid law on the micro scales. The density of air in a box at thermodynamic equilibrium is not constant. Even after infinite time has passed, the particles will never reach 0 speed. The moving particles tend to be evenly distributed in the box, but they are not rigidly confined to always be so. Tiny fluctuations in the position of the particles will create local "hot spots" albeit briefly. The entropy of each particle is constant, but the entropy of each finite volume of space is not. The entropy in the finite volume fluctuates, both up and down.

I.e. on the microscale, the law of entropy only increasing in an isolated system doesn't really apply. I can imagine a finite volume over a finite time where nothing crosses the boundary of my imagined volume - it is isolated. Still, within that volume, there may be slightly more particles in 1 half of it than the other, however briefly. This "clumping" (exquisitely loosely stated) is antithetical to Entropy always increasing in isolated systems.

Things get even weirder when we just trust the math and start applying entropy concerns to isolate molecules or particles. The math tends to work out rather well. The math tends to hold up in some cases and the entropy concern makes a good prediction. We can predict the amounts of memory needed to compress data (like mp3's) using entropy concerns. The application of entropy to Information Theory is totally fuckey to me. Even when I get the math, I can't wrap my head around why there would be physical laws for intangible notions like "information." As humans, we have to re-imagine what that word even means to use it in this context, but in so doing, we get a wealth of "good" predictions.
I'm not entirely sure any human understands why that is the case.

[OngBonga]

If the model could recreate the observed consequences of Einstein's description of gravity, then I'd be more interested.

They say it's "compatible" with GR, but that's not the same as actually deriving the field equations.

I wasn't really comfortable with the phrase either "entropic force", not so much when it comes to certain "entropic" forces but where a stretched elastic band is concerned (an example they cite) that's standard EM and/or weak/strong force. No need to invoke a "new" force.

Centrifugal force might not be a "real" force but it certainly has real effects. With that in mind, clearly we need a term for this "force", it's just whether "force" is the right word to describe it. And we already caveat this "force" by saying it's an inertial force (a much better term for a fictitious force), which gravity can also be described as. That's a force that emerges only in non-inertial frames of reference... in an inertial frame of reference it's non-existent. So the problem isn't the word "centrifugal", it's "force".

[OngBonga]

It's a statistical thing. It doesn't exist in individual quantum mechanics interactions between particles. It's emergent when you look at many interactions.

At what point does entropy emerge? We can say with confidence that in a one-particle universe, there is no entropy. What about a two-particle universe? Given infinite time, will the two particles collide more than once? Will they collide an infinite number of times? Entropy seems to emerge when there are an infinite number of collisions over an infinite period of time, allowing energy to spread out evenly in the system. If gravity demands that the two particles will continue to interact and collide, then surely entropy exists in the two-particle universe. Maybe there's the link between gravity and entropy in its most basic form.

[MadMojoMonkey]

IDK where the line is. There's a field of physics called "meso-scale physics" that is trying to figure out questions like that.

With only 2 particles, entropy would never change. Leaving out that it's problematic to suggest there's a definite and constant number of particles in the universe, I mean.

1) For every interaction in quantum mechanics, you can calculate the probability of that interaction taking place.
2) For every interaction in quantum mechanics, the exact opposite interaction (as though you reversed time) happens (but in forward time).
3) The probability of every such pair of interactions is identical for both.

This is commonly shown by noting that the probability of any interaction in a Feynman diagram is calculated by examining the vertices in said diagram. Also that any diagram you can read with time flowing in any direction (usually just up or down, but whatever) has the same vertices, so the same calculation of probability.
Ergo, all quantum interactions are equally likely to happen in one way or the opposite way, so if either changes entropy, the other changes it back, and both have identical probability. Spoiler - neither ever changes the entropy.

Quantum Mechanically, Entropy kinda doesn't exist. All quantum interactions are "reversible" in that exact way that entropy makes it super duper hard to uncrack an egg.

[OngBonga]

Leaving out that it's problematic to suggest there's a definite and constant number of particles in the universe, I mean.

Well, it's also problematic to talk about an "ideal gas" but that doesn't stop the concept being useful when it comes to thermodynamics.

It's difficult to even begin to understand how an emergent property that "kinda doesn't exist" at the quantum scale can be so fundamental to the way our universe works.

[MadMojoMonkey]

It's difficult to even begin to understand how an emergent property that "kinda doesn't exist" at the quantum scale can be so fundamental to the way our universe works.

Unfortunately, the most common explanation out there is that statistically, the higher entropy states are more common, therefore more likely.

Like, if you have 100 people flip a coin 4 times, you can accurately guess that 6 or 7 of people will flip 4 heads. Likewise, 6 or 7 will flip 4 tails. Whereas, you can guess that about 38 people will flip 2 heads and 2 tails.

The number of states where things are "evenly distributed" is much higher than the number of states where everything is ordered or clumped.

This was an example with only 4 particles in 2 states. When you take the number of ways the air molecules can arrange themselves in a room, the vast majority of the states are near thermodynamic equilibrium, and a state such as "all the air is only in the left half of the room" is vanishingly unlikely.

This argument basically says, "given all the ways it could possibly happen, it tends to be the most likely ways that it happens." which is fine.
What I don't like is the assertion that improbable things don't happen. You can rigorously calculate the probability of those "uncommon macrostates" and show the probability is non-0.

The argument we pose is basically, "It definitely happens." and the conclusion we draw is, "So that's why it doesn't happen."
I can't even understand how an otherwise intelligent physicist can say this out loud in good faith, but I've heard that argument so many times.

[OngBonga]

What I don't like is the assertion that improbable things don't happen.

Well, they do, it's just that they happen so rarely, and for an exceedingly small amount of time. For all I know, all the air molecules in the room might well have just occupied a part of the room where I'm not sitting for a couple of Planck seconds, but I certainly wouldn't notice because I have more than enough oxygen in my lungs to survive that amount of time in a vacuum, and I doubt there exists a tool I could use to measure such an event. In fact, it's entirely possible that this event consistently happens hundreds or even thousands of times a second, it's just it's not happening 10^something times a second, so we don't and probably can't observe it.

[MadMojoMonkey]

Did you know?

There are more atoms of Hydrogen in a single molecule of water than there are stars in the entire solar system?

[OngBonga]

Did you know?

There are more atoms of Hydrogen in a single molecule of water than there are stars in the entire solar system?

I did not know this, but I can confirm it's true, having just counted all the hydrogen atoms in a molecule of water, and then all the stars in the solar system. There are in fact exactly twice as many hydrogen atoms as there are stars. Mind blown.

[OngBonga]

Another fun watery fact is that water weighs less than air.

[MadMojoMonkey]

I just wanted to put this first because it feels like a dick move to say "You're wrong." then to follow up with, "But all that I said is dubious at best."

A counterpoint to my own thoughts would be that a single molecule of water does not have ANY of the properties we'd associate with liquid water. A single molecule of anything does not behave like a liquid, so the phrase, "a molecule of water," is a bit of a clusterfuck. It has meaning only when used casually, but if we get pedantic about it, there is no such thing as an isolated H2O molecule that behaves like a liquid and not a gas.

Another fun watery fact is that water weighs less than air.

Correct-ish. Water vapor and steam (the gaseous forms of H2O) are less dense than air. For an equal volume of either compared with air, the water vapor or steam will weigh less than the air. Indeed, this is why clouds float in the sky.

Fun fact, the average weight of a rain cloud (cumulus cloud) is over 1 million pounds. Clouds are heavy AF, not because they're dense, but because they're huge.

However, in utter pedantry, water is the liquid form of an ensemble of molecules, and is about 1000 times as dense as its gas form, which has a different name. So saying water weighs less than air is literally incorrect and pedantically incorrect. It's just that, only the most utterly deranged pedagogue would waste time writing this out in a forum post.

[OngBonga]

Why would an isolated water molecule behave like a gas? Isn't that equally as absurd as calling it a liquid? Like a liquid, a gas is a fluid. If we're being pedantic, surely an isolated molecule isn't in any state of matter we can relate to, it's in its own state... we might as well just call this state "molecular".

And I knew my water "fact" was probably not accurate when I read it back. I figured "weighs" is probably the wrong word, but I couldn't be bothered to correct it to "is less massive".

[OngBonga]

Also, since we're being pedants, we can't actually be certain that the sun is the only star in the solar system. While there is no evidence of such things existing, there's also no way we can be certain that relic black holes do not exist... that is, black holes that are almost fully evaporated, but cannot evaporate further. This could be dark matter. Given our best understanding of black holes is that they are the end state of massive stars, I can argue that there could be a ludicrous number of "stars" in the solar system for all we know.

[MadMojoMonkey]

Why would an isolated water molecule behave like a gas? Isn't that equally as absurd as calling it a liquid? Like a liquid, a gas is a fluid. If we're being pedantic, surely an isolated molecule isn't in any state of matter we can relate to, it's in its own state... we might as well just call this state "molecular".

The problem is in the fact that a single molecule doesn't have any inter-molecular bonds to form with other identical molecules. It's those bonds that determine the phase of matter (solid, liquid, gas, plasma - noting that some materials have multiple, distinct solid phases). We can retreat to saying an isolated molecule acts like a gas because to first approximation, particles in a gas do not interact with each other (or do so infrequently compared to the time they spend not interacting).

In truth, gas particles do interact, but, as is often the case in physics, the approximation gives remarkably good results while still being relatively easy to calculate.

[MadMojoMonkey]

Also, since we're being pedants, we can't actually be certain that the sun is the only star in the solar system. While there is no evidence of such things existing, there's also no way we can be certain that relic black holes do not exist... that is, black holes that are almost fully evaporated, but cannot evaporate further. This could be dark matter. Given our best understanding of black holes is that they are the end state of massive stars, I can argue that there could be a ludicrous number of "stars" in the solar system for all we know.

There is some hypothesis that the sun may have a binary partner way out past the orbit of Pluto. It would be a very distant, cold, and dark object to have gone undetected for so many decades (centuries?) without being positively identified. It could be a Jupiter-sized planet, a slightly larger object called a "failed star" which is either just not quite big enough to start its own fusion, or is too rich in non-Hydrogen elements to achieve the pressure needed to fuse whatever it's made of. It could be a tiny black hole.

The evidence for "some" object being out there is slim, but not so slim as to ignore. It's just not 100% required for the data to be explained by a single errant object in the outer solar system. It could be, but it could also be a bunch of random events with smaller objects that statistically just happen to look like maybe there's 1 big thing out there causing it.

Good point, though, that we don't know for certain that there's only 1 star in the solar system.

[MadMojoMonkey]

There's a gap in physics when it comes to explaining how Super Massive Black Holes (SMBH) were formed.

In short, for black holes up to about 100 times the mass of the sun, we can understand with currently known physics the mechanisms by which those are formed.

However anything more massive than that, we just can't explain. The universe simply isn't old enough for them to have formed by the merging of smaller black holes.

The larger a black hole is, the further out its reach extends. The larger the black holes, the further apart they are when they start to orbit each other. The further apart they are, the less energy is dissipated by gravitational waves as the black holes spiral toward each other. The universe isn't old enough for those low energy gravity waves to have brought 2 black holes of masses larger than ~50 solar masses together.

There are other mechanisms by which black holes approach each other. One of them is by consuming each other's accretion disks. I.e. the black holes are basically experiencing friction as they move through each other's "atmosphere." (I'm using the word atmosphere purely metaphorically, here.)

Those other mechanisms don't have anywhere near enough energy in them to slow the black holes enough to make a difference at the mass scales I'm talking about.

These 1 million solar mass SMBH's seem to exist at the center of every galaxy.

***
So that's a long-known issue with the Standard Model.

New research has proposed that dark matter can interact with other dark matter and annihilate, releasing energy in the form of photons. We do not observe this annihilation today because that interaction is so improbable and the universe has expanded and spread out the dark matter so much that it doesn't have the density needed for this self-annihilation anymore.

But in the early universe, when it was hotter and denser, if the above hypothesis is true, then we'd have so-called dark stars. The gravitational center of the dark matter could attract a million solar masses of Hydrogen into a huge cloud. The annihilation photons racing out from the center would provide the equilibrium pressure to prevent the Hydrogen from forming a core dense enough to begin fusion.

These dark stars would be enormous, bloated objects.

Eventually, the universe expands and cools and the dark matter interactions are lessened and start to run out. Then you have a million solar masses of matter no longer supported from gravitational collapse.

Et viola. SMBH's with 1 million solar masses collapse without ever really being a star powered by fusion.

***
Data from the James Webb Space Telescope has produced 3 candidates for objects that might look like dark stars. They have the brightness, and seem to be point sources (as opposed to some cluster of other bright objects) and they exist long enough back in time.

This isn't confirmed physics, yet, but it's exciting that one of the big issues with understanding black holes and also dark matter may be culminating with some data to show an answer.

[oskar]

Could you surf a SMBH?

[MadMojoMonkey]

Could you surf a SMBH?

Kinda

[oskar]

*shudders*

This universe makes the Hellraiser dimension look like Disneyland.

[OngBonga]

Et viola. SMBH's with 1 million solar masses collapse without ever really being a star powered by fusion

I'm going to argue that they are, in fact, regular stars for a very brief period of time. The first thing that hydrogen is going to do as it collapses is fusion. It's just the pressure from this fusion isn't going to be near enough to hold back the enormous gravitational collapse of the cloud for more than the tiniest fraction of a second. But during this brief window of opportunity, it's a star!

[oskar]

...but enough about Tila Tequila!

[MadMojoMonkey]

I'm going to argue that they are, in fact, regular stars for a very brief period of time. The first thing that hydrogen is going to do as it collapses is fusion. It's just the pressure from this fusion isn't going to be near enough to hold back the enormous gravitational collapse of the cloud for more than the tiniest fraction of a second. But during this brief window of opportunity, it's a star!

I don't know the details of the collapse.

Of course, your version fits intuition, but if it happens inside the event horizon, then who's to say it happened at all?
Not that I have any guesses as to whether the collapse is so rapid that the growth of the event horizon outpaces the formation of a fusion-driven core.


I imagine the cessation of the dark matter annihilation would gradually decrease and not flip like a switch.
But that doesn't mean the collapse when it ends is gradual.

A supernova is the result of a gradual increase in the pressure in the core of a star until it starts fusing Nickel and Iron. The problem is that fusion of Nickel, Iron and heavier atoms is endothermic. So while the approach to that condition is gradual, once the condition is met, the collapse happens in no time.

But ... the ending of the dark matter annihilation wont be because of the start of an endothermic reaction. It's just the gradual depletion of fuel gradually reducing the outward pressure.


OK, you talked me into it. I'm rather on your side of this hypothesis.

[OngBonga]

I asked chat GDP to help me find something in the universe that there's more than a googol of, and the only thing I've found so far is Planck volumes. Apparently there's 2.68*10^184 of those, so there's room for more stuff. Any ideas?

Estimated potential chess positions (including illegal positions) was getting (kind of) close, which was similar in size to the number of quarks, in the order of 1*10^80. The radius of the observable universe in Planck lengths isn't close to these numbers (1*10^61), which seems crazy to me but that's what Chat GDP is telling me so it must be true.

[OngBonga]

Oh the age of the universe in Planck seconds is also around 1*10^80.

[OngBonga]

Strings in string theory between 1*10^80 and 1*10^90, so not all that many more than quarks. I'm not too confident in these calculations if I'm honest, though I'll accept it's a lot better than I could do with my pathetic human brain.

[OngBonga]

Electrons around 1*10^80

[OngBonga]

Go! That's more complex than chess, we're up to 1^10*170, so we're approaching Planck volumes.

There's nearly not enough room in the universe to ever theoretically solve Go, even assuming perfect technology. Surely we can only store one "bit" of information in a Planck volume. I'm making that assumption.

[OngBonga]

Actually I was playing "Chess on an infinite plane" for a while and even held the title (and might still do) of World Champion, seeing as we were the only people in the world playing that variant that we were aware of!

That's obviously infinitely complex in terms of theoretical potential.

But I want the biggest finite thing in the universe. Some variants of chess on finite boards will exceed Go, but chat GDP isn't giving numbers because there are too many variants. Just adding a new piece adds many orders of magnitude of complexity.

[OngBonga]

And off on a complete tangent... apparently you'd need 420 skyscrapers 100-floors high to fit the entire population of China onto the Isle of Wight while maintaining liveable conditions.

Chat GDP is great. It knows so much stuff.

[MadMojoMonkey]

Number of universes under the many worlds hypothesis.

Every interaction that causes the collapse of a wave function tied to probability creates all possible outcomes in a new universe that forked from that moment.
That happens in every newly created universe, too.

The rate of creation of universes just by particle interactions in our universe is insane. But every one of those universes is spawning new universes just as fast, each of the spawned universes spawning new universes... yada yada.

There's no possible way to count these universes, but a google doesn't even cover what happened in the first nothingth of a second.

[OngBonga]

*Googol

Don't let that corporate bastard fool you into thinking the number is spelled like the search engine!

If we're going into multiple universes, then everything I said is even bigger, because there's only one universe per universe. Unless there's less than one universe with quarks in per 1*10^80 universes (approximately), then there's more quarks than universes. Probably a lot more. If all universes have quarks, and ours is average, there's a fuck ton to the power of 80 more quarks than universes.

[OngBonga]

I'll entertain the many world theory for a post or two.

If we assume we have 1 interaction per Planck unit per Planck second, and that's the rate of universe generation, and the same happens in every new universe, with every possible outcome happening creating new universes, then that's more than a googol universes. A lot more.

We might be getting into Tree (3) territory here. Perhaps even Tree (4). Probably not Tree (5) though.

Tree (1) is equal to 1 and Tree (2) I think is equal to 3. To go from that to whatever the fuck Tree (3) is, which is a bigger number than we can fit into the universe (not kidding, not enough room to store the data), then each iteration from there is just getting into unholy territory, much like our universes.

Many worlds is bollocks anyway. At least Tree (3) is a thing.

[MadMojoMonkey]

*Googol

[MadMojoMonkey]

Many worlds is bollocks anyway. At least Tree (3) is a thing.

I tend to agree, but many people smarter than me about physics think it's probably more right than anything else we've come up with, yet.

Sean Carrol makes his arguments for Many Worlds in a way that is like... OK, you're not convincing me many worlds is right, but you are convincing me everything else is AS FLAWED as many worlds in the EXACT SAME WAYS, so really... all the interpretations are just hiding that they're secretly many worlds-ing behind the scenes.

[MadMojoMonkey]

So the dark matter hypothesis is basically ruled out at this point.
The JWST has data showing early galaxy formation, and can plot size/distance (age) and show that these things just didn't form in the time scales that the dark matter hypothesis predicted.

There are predictions which match the data, but ... there are lots of predictions from the various researchers who've hopped on the Modified Newtonian Dynamics (MOND) wagon, and while, yes, some of them have predictions that do match the data... others of them have predictions that don't.

So there's a sense of ... maybe that prediction is right, or maybe it's just a lucky coincidence that if you get a bunch of people guessing things, the more chance that one of them can guess something that looks good, whether or not it is good.

[CoccoBill]

I'm sure it's just a bug in our early version simulation. It'll be patched out.

[MadMojoMonkey]

Check out the pretty pics I got at work today.

https://imgur.com/a/5NdzR8v

It's a beam of electrons in a tube with thin Neon gas to show where the beam is.
I'm holding a magnet outside the tube to make the beam curl around and back on itself.
This is called the magnetic bottle effect.

If you've heard of the Van Allen Radiation Belts around the Earth, this effect is related to how those are formed and sustained by the Earth's magnetic field capturing charged particles from the solar wind.