**Ask a monkey a physics question thread**

[MadMojoMonkey]

what did you think of the movie primer? i've been obsessing about it and it still mindfucks me trying to figure everything out. and if you haven't seen it, wtfbbq dl that shit now.

I watched it last night and it's a pretty good film. There is a lot of subtle stuff going on at first impression, so I'll have to watch it again to try to unravel it all.

Main question: Why are there 4 characters at the beginning? The whole thing is based on 2 guys and their "time machine" and them recursively undermining each other's plans. I kept saying to myself, they introduced those characters, they must be somehow manipulating things. But no.

Also, I call BS on 4 guys working from a garage who wear button down shirts with ties and belts every day.

Oh, since this is the physics thread:
They actually state in dialogue that there is nothing but thermodynamics going on in "the box". While the "thermodynamic arrow of time" (which explains why we can remember the past but not the future) is an idea, it's not well grounded physics. It's based on entropy, which might not exist. Entropy is probably is just a statistical summary of quantum energy exchanges which are too numerous to identify independently.

[Pascal]

If you like times about time travel etc, check out - Timecrimes (2007) - IMDb . I really enjoyed it.

Will check out Primer, ty GMML.

[chemist]

If you like times about time travel etc, check out - Timecrimes (2007) - IMDb . I really enjoyed it.

Will check out Primer, ty GMML.

Not sure if I've seen that, probably have but don't remember it.

My first thought was that is was something else which I do remember very clearly.

Chloë Annett is so beautiful.

Crime Traveller (1997) TV Series

Shame they didn't carry on making them.


MojoMonkey probably doesn't approve of this fictitious physics.

(didn't know how to spell fictishous, but now I know it is 'fic' 'tit' 'ious' will probably be able to remember).

[MadMojoMonkey]

I wouldn't say I'm a fan of time travel movies, just that this one was suggested in the thread. So I watched it and answered the question.

Wait, wait, wait...

Back to the Future trilogy, Bill and Ted 1 & 2, the Terminator series, 12 Monkeys, Army of Darkness, Time Bandits, the Final Countdown, Groundhog Day, Austin Powers films, a few of the Star Trek movies...

I guess I do like time travel movies, now that I think about it.

MojoMonkey probably doesn't approve of this fictitious physics.

What I approve of and what fits the discussion in this thread are 2 different things. I do have willing suspension of disbelief when I watch a movie that is intended to be fantastical. It's when the movie is trying so hard to be 'real world' and they screw it up that I disapprove.

Apparently in Hollywood, a car can explode if you ... well just about anything. Have you ever seen a car explode in the real world? I've seen a car fire where the gas tank caught, but no explosion. BECAUSE THE GAS TANK IS VENTED SO NO PRESSURE CAN BUILD UP.

Also, when someone gets shot and the blood spatters on the wall behind them, but there is no bullet hole in the wall.... that gets me a bit irate. DUCY

[MadMojoMonkey]

If you like times about time travel etc, check out - Timecrimes (2007) - IMDb . I really enjoyed it.

Will check out Primer, ty GMML.

Is Timecrimes in English? I hate reading a movie.

Fun list of all the laws of classical physics: These 13 laws describe nearly everything about the world you directly experience. These are the shortest possible descriptions I can think of, and I left out all the equations.

MOVEMENT
Newton's First Law: In an inertial reference frame, an object that is at rest will remain at rest, or an object that is moving will continue to move in a straight line with constant speed, if and only if the net force acting on the object is zero.
Newton's Second Law: The vector sum of all forces acting on an object will result in a change in the objects momentum.
Newton's Third Law: For every action, there is an equal and opposite reaction.
Newton's Law of gravitation:Gravity is an attractive, long-range force between any two objects.

HEAT AND WORK
Zeroth Law of Thermodynamics: If two systems are in thermal equilibrium with a third system, they are also in thermal equilibrium with each other.
First Law of Thermodynamics: In all cases in which work is produced by the agency of heat, a quantity of heat is consumed which is proportional to the work done; and conversely, by the expenditure of an equal quantity of work an equal quantity of heat is produced.
Second Law of Thermodynamics: No process is possible whose sole result is the transfer of heat from a body of lower temperature to a body of higher temperature.
Third Law of Thermodynamics: It is impossible for any procedure to bring a system to a temperature of absolute zero in a finite number of steps.

ELECTRICITY AND MAGNETISM
Gauss’s Law: Charged particles create an electric field.
Faraday’s Law: An electric field can also be created by a changing magnetic field.
Gauss’s Law for Magnetism: There are no magnetic monopoles.
Ampère-Maxwell Law: Moving charges create magnetic fields (Ampère). Changing electric fields also create magnetic fields (Maxwell).
Lorentz Force Law: The general force equation, which describes how matter responds to electromagnetic fields.

[Pascal]

It's in Spanish with subtitles, get the feeling I watched an English dubbed version somewhere but not 100% (I've seen it a few times)

[DoubleJ]

Zeroth Law

????

you're making this up now, surely?

just put a word-search in or something...no-one will read this far

[Ash256]

I look down at my hand. It's made of skin, flesh and bone. I look at my house, it's made of bricks.

But what, at the most fundamental level, is everything made out of?

[MadMojoMonkey]

????

you're making this up now, surely?

just put a word-search in or something...no-one will read this far

I'm not making it up. And stop calling me Shirley.

It's the real deal. Google it.
The other 3 laws were worked out first, before someone realized that they didn't have any law that said "thermometers... they work".

The zeroth law basically states exactly that. A thermometer works by exchanging heat with the thing it's measuring until they are the same temp. The 2 objects are then in thermodynamic equilibrium. The thermometer has some scale and readout, so by knowing the temp of the thermometer, you know the temp of the thing you are measuring. If you then measure another thing and it measures the same temp on the thermometer, then it is the same temp as the first thing. LDO.

It was just so obvious that it was taken for granted.

[surviva316]

It was just so obvious that it was taken for granted.

Could I publish a paper with an equally obvious conclusion? I didn't see any laws listed there that say that if two objects are moving the same speed as a third object, then the two objects are moving the same speed as each other.

I'll be taking my Nobel Peace Prize now.

[MadMojoMonkey]

I look down at my hand. It's made of skin, flesh and bone. I look at my house, it's made of bricks.

But what, at the most fundamental level, is everything made out of?

Short answer: Everything is made of QUARKS, LEPTONS and BOSONS.

Your hand is made of organs, which are made of tissues, which are made of cells, which are made of molecules, which are made of atoms.
Bricks are far less complicated, but still made of atoms.

All that stuff is made of Up quarks, Down quarks and Electrons, which are the building blocks of atoms.

Atoms (from the Greek a tomos, "no cut" or "indivisible") were originally thought to be fundamental particles. To a chemist, in a way, they are, since there is no smaller bit that retains the chemical properties. However, this is a physics thread, not a chemistry thread, so let's break it all the way down.

Definition: A fundamental particle is a particle which does not have any constituent parts.

Atoms are made of protons, neutrons and electrons. Protons and neutrons are made of quarks. Electrons are leptons, which are fundamental particles. Electrons are fundamental particles.

There are 6 quarks (plus their anti-particles, making 12). They are called: Up, Down, Charm, Strange, Top, Bottom
For the anti-particles, just add the prefix anti- to these 6 names.
Note that an anti-Up quark is not a Down quark.

A proton is made of 2 Up quarks and 1 Down quark.
A neutron is made of 1 Up quark and 2 Down quarks.

(Yes, DoubleJ, there are such things as Strange quarks and Charm quarks. They were named by the hippie physicists at Cal-Tech who first discovered them. Top and Bottom were almost named Truth and Beauty. True story. Also, and this is my favorite law of physics, there is a Law of Conservation of Strangeness.)

There are 6 leptons (plus their anti-particles, making 12). They are called: electron, muon, tau, electron neutrino, muon neutrino, tau neutrino.
For the anti-particles, just add the prefix anti- to these 6 names.
Note that an anti-electron is commonly called a positron, but either name is fine.

There are 4 fundamental bosons (maybe 5 if the Higgs boson is a fundamental boson). They are called: photon, gluon, Z boson, W boson
Note that bosons do not have anti- versions. Bosons are the force mediators between particles. For example, like charges repel each other and unlike charges attract each other by emitting and absorbing photons.

[MadMojoMonkey]

Could I publish a paper with an equally obvious conclusion? I didn't see any laws listed there that say that if two objects are moving the same speed as a third object, then the two objects are moving the same speed as each other.

I'll be taking my Nobel Peace Prize now.

Actually, that's covered in Newton's First Law.

But don't let that stop you from thinking. There is a huge, enormous, gigantic hell of a lot that is left to figure out in physics, and someday, people will look back and think, LDO.

Oh, and there's a Nobel Prize for Physics and another for Literature (and others), so you got at least 3 chances to win!

[Ash256]

Short answer: Everything is made of QUARKS, LEPTONS and BOSONS.

Your hand is made of organs, which are made of tissues, which are made of cells, which are made of molecules, which are made of atoms.
Bricks are far less complicated, but still made of atoms.

All that stuff is made of Up quarks, Down quarks and Electrons, which are the building blocks of atoms.

Atoms (from the Greek a tomos, "no cut" or "indivisible") were originally thought to be fundamental particles. To a chemist, in a way, they are, since there is no smaller bit that retains the chemical properties. However, this is a physics thread, not a chemistry thread, so let's break it all the way down.

Definition: A fundamental particle is a particle which does not have any constituent parts.

Atoms are made of protons, neutrons and electrons. Protons and neutrons are made of quarks. Electrons are leptons, which are fundamental particles. Electrons are fundamental particles.

There are 6 quarks (plus their anti-particles, making 12). They are called: Up, Down, Charm, Strange, Top, Bottom
For the anti-particles, just add the prefix anti- to these 6 names.
Note that an anti-Up quark is not a Down quark.

A proton is made of 2 Up quarks and 1 Down quark.
A neutron is made of 1 Up quark and 2 Down quarks.

(Yes, DoubleJ, there are such things as Strange quarks and Charm quarks. They were named by the hippie physicists at Cal-Tech who first discovered them. Top and Bottom were almost named Truth and Beauty. True story. Also, and this is my favorite law of physics, there is a Law of Conservation of Strangeness.)

There are 6 leptons (plus their anti-particles, making 12). They are called: electron, muon, tau, electron neutrino, muon neutrino, tau neutrino.
For the anti-particles, just add the prefix anti- to these 6 names.
Note that an anti-electron is commonly called a positron, but either name is fine.

There are 4 fundamental bosons (maybe 5 if the Higgs boson is a fundamental boson). They are called: photon, gluon, Z boson, W boson
Note that bosons do not have anti- versions. Bosons are the force mediators between particles. For example, like charges repel each other and unlike charges attract each other by emitting and absorbing photons.

Thank you sir!

[CoccoBill]

Science <3

[chemist]

(Short answer: Everything is made of QUARKS, LEPTONS and BOSONS.
Your hand is made of organs, which are made of tissues, which are made of cells, which are made of molecules, which are made of atoms).

What is it about the same quantity and configuration of quarks, leptons and bosons, that makes the difference between living tissue and non living tissue?

[MadMojoMonkey]

I don't think there is any clear answer to that. I don't even know whether it will eventually be explained by physics. If so, we're a long, long way from it.

Maybe the configuration is not (exactly) the same.

I have nothing intelligent to add.

[CoccoBill]

I might be completely wrong, having no formal education regarding this, but my understanding is there's no fundamental difference. Quarks, leptons and bosons form atoms, which in turn form molecules. Molecules have enough complexity to "do" various things, such as replication:

https://en.wikipedia.org/wiki/DNA_replication

There's also nothing fundamentally different about living and non-living tissue, or organic and inorganic matter, we just call all matter that is found in carbon-based lifeforms organic.

https://en.wikipedia.org/wiki/Organic_matter
https://en.wikipedia.org/wiki/Organic_compound

[MadMojoMonkey]

There's also nothing fundamentally different about living and non-living tissue.

... except that one is alive and one is not. That seems to be a strikingly fundamental difference. Is there a biologist in the house?

Also, given the inability to measure all qualities of even a single particle (e.g. the position and momentum) simultaneously to arbitrary precision, I don't think the statement that the living and dead tissue are identical is meaningful. At least, it's not a meaningful question to a physicist.

Stephen Colbert: In 10 words or less, why is there something instead of nothing?
Neil DeGrasse Tyson: Words that make questions might not be questions at all.

[a500lbgorilla]

(Short answer: Everything is made of QUARKS, LEPTONS and BOSONS.
Your hand is made of organs, which are made of tissues, which are made of cells, which are made of molecules, which are made of atoms).

What is it about the same quantity and configuration of quarks, leptons and bosons, that makes the difference between living tissue and non living tissue?

So the question is what is the difference between a pile of carbon dancing around as people have been known to do, and a pile of carbon, set some life on fire, just a pile of ashes?

What is the difference between you right now and you 10 minutes after you die?

That is an awesome question.

[a500lbgorilla]

Also, no field theory explanation of matter?

[CoccoBill]

... except that one is alive and one is not. That seems to be a strikingly fundamental difference.

That was sort my point exactly, any distinction we can muster up for organic vs inorganic compounds is largely arbitrary. A cell that can multiply is where "life" starts and you could say the rest, up to human intelligence, is just extra features that make replicating more effective. We don't know how life and non-life differ fundamentally or if they do at all, maybe it's more up to our perspective and lack of objectivity regarding the issue, our need to think we surely must be a lot more special than a rock.

[MadMojoMonkey]

That was sort my point exactly, any distinction we can muster up for organic vs inorganic compounds is largely arbitrary. A cell that can multiply is where "life" starts and you could say the rest, up to human intelligence, is just extra features that make replicating more effective. We don't know how life and non-life differ fundamentally or if they do at all, maybe it's more up to our perspective and lack of objectivity regarding the issue, our need to think we surely must be a lot more special than a rock.

For whom are you speaking? I formally exclude myself from that group.

It seems your deeper point is that there are questions that physics can't answer. As I have already stated such multiple times in this thread, I certainly agree. Physics is ill-equipped to answer questions with non-measurable answers.

If you show me how to measure "life" then I can tell you if something has it and how much. Maybe a biologist could clear this up a bit. Until then, it's up to psychology, religion, and philosophy to debate.

Please feel free to start your own thread or PM me if you wish to "make a point" about something you read here. Please help me keep this thread a Q & A with a minimal amount of opinion based content. Thanks!

[MadMojoMonkey]

That is an awesome question.

It is an awesome question. Awesome in a original sense of the word.

[MadMojoMonkey]

Also, no field theory explanation of matter?

There is no field theory explanation of matter in classical physics, no. There were field theories for energy at least, and understanding vibrations and waves was the major interest in physics just before Planck, Einstein, Bohr, Schroedinger, Heisenberg, etc. revolutionized the field. Wave equations are solved for fields.

When it was discovered that particle and wave are synonymous, suddenly matter fields were introduced. It was a hard pill to swallow for established physicists, as were many revolutionary concepts in the early 1900's.

[a500lbgorilla]

There is no field theory explanation of matter in classical physics, no. There were field theories for energy at least, and understanding vibrations and waves was the major interest in physics just before Planck, Einstein, Bohr, Schroedinger, Heisenberg, etc. revolutionized the field. Wave equations are solved for fields.

When it was discovered that particle and wave are synonymous, suddenly matter fields were introduced. It was a hard pill to swallow for established physicists, as were many revolutionary concepts in the early 1900's.

Pardon my ignorance but I was the believe the Higgs Boson was proposed on the basis of field theory.

Rolling from memory, field theory is the most basic mathematic description of stuff. Fields are everywhere and have value where there is stuff, that stuff represents discrete jumps in specific fields. All fields interact with each other in different ways. The Higgs field exists and is everywhere nonzero, making it unique. Its interaction with the other fields yield mass.

So, the other natural question is how indivisible are the Lepton, Boson and Quark?

[Icanhastreebet]

That's all quite intuitive. What isn't however, is that wouldn't even a slight change in velocity, even the tiniest bit of acceleration or deceleration cause the planet to either get loose or crash? How come this doesn't happen? What creates this universal (ha!) tendency for all objects to just play nice and circle each other at exactly the right speed?

Dunno if this was answered, if an object speeds up it just moves into a larger orbit(this is happening to the moon as we speak). If it slows down it goes into a smaller orbit. This happens with ~meter sized objects in the asteroid belt so their is literally almost no meter sized objects in the belt. Basically as if the object rotates the same way it goes in revolution it'll be pushed out because the object is the warmest on the rear side(This works like a mini rocket). If it rotates the opposite way of it's orbit it slows down and falls toward the sun.

So basically everything is going at "exactly" the right speed because if it was going any slower/faster it would be in a different orbit where it would be exactly the right speed.

Also no one mentioned the earth formed within 100k years after the sun and the whole solar system was VERY stable after the first few 100k years maybe even sooner. That's the best guess anyway from my understanding.

[MadMojoMonkey]

Pardon my ignorance but I was the believe the Higgs Boson was proposed on the basis of field theory.

Yes. I see the confusion. Classical physics excludes Einstein's Relativity and Quantum Mechanics, which were developed in the early 1900's. Field theories were known for a while, as the Electromagnetic fields were well understood no later than 1873. As modern physics has developed, it has relied heavily on the use of fields. Fields are just a useful tool to keep track of things.

Rolling from memory, field theory is the most basic mathematic description of stuff. Fields are everywhere and have value where there is stuff, that stuff represents discrete jumps in specific fields. All fields interact with each other in different ways. The Higgs field exists and is everywhere nonzero, making it unique. Its interaction with the other fields yield mass.

A field exists everywhere in space, and is not discreet in this sense. There is no point in space where the field does not have a value. A discrete field would have a value at some points but not others. Like the integers are a discrete set of numbers on a continuous number line.

Some fields represent discrete quantities, but some represent continuous quantities.

Stuff is discrete in a sense. As in, "There's one electron in the ground state of that Hydrogen atom". But the field represents something like the position of the electron, which is not discrete. The properties of a particle are represented by probability functions. The position is smeared out over a volume, with high probability density regions and low probability density regions. Ultimately the position/momentum field for any particle is non-zero at all points in space.

Not all fields interact with each other. Electromagnetic fields do not interact with non-charged particles.

The explanation of mass is the unique property of the Higgs mechanism.

So, the other natural question is how indivisible are the Lepton, Boson and Quark?

That's another good question. I am quite curious myself. I'll get back to you on this.

[MadMojoMonkey]

Ultimately the position/momentum field for any particle is non-zero at all points in space.

This is poorly worded. I meant to say that the position field for any particle is non-zero over any volume. There are, in fact, sometimes, surfaces which have a zero probability of the particle being there, but no volumes.

The corresponding momentum field has positive, negative or zero values based on the orientation of the reference frame relative to the average velocity of the particle.

That's another good question. I am quite curious myself. I'll get back to you on this.

working... working...
I have found the experiments that showed that protons and neutrons have internal structure (quarks and gluons). I have not found the reason why it is believed that the quarks and gluons do not have internal structure.

The thing that is daunting: Science is no good at proving a negative.

[MadMojoMonkey]

According to the Standard Model, quarks and leptons are fundamental particles (bosons are the force carriers). The Standard Model is the theory that explains the most and makes verifiable predictions, which have been repeatedly observed.

As I understand it, the particle accelerator which would have the required power to probe the substructure of a quark would need to be the size of Pluto's orbit. Needless to say, we're a long way from building anything of that scale, if ever.

In other theories, quarks and leptons are not fundamental particles. In string theory, strings are fundamental and quarks and leptons are different vibrations of the strings. The reason string theory hasn't been adopted is that it makes no predictions that can be verified which are not explained by the Standard Model.

[a500lbgorilla]

How do force carriers physically work?

Use Gravity and orbits as an example. If I'm the ISS how am I exchanging force carriers with the Earth and vice versa?

[MadMojoMonkey]

How do force carriers physically work?

Use Gravity and orbits as an example. If I'm the ISS how am I exchanging force carriers with the Earth and vice versa?

Gravity is not explained in terms of force carriers. The hypothetical force carrier for mass is called the graviton. It is hypothetical because no graviton has ever been observed. The link between Quantum Mechanics and General Relativity is still not understood.

Gravitation is the motions of large bodies
Gravity is the force which causes said motion
A Graviton is the force carrier of mass which imparts gravity interactions and causes gravitation.

I can do this for anything BUT gravity and orbits. The problem with gravity and orbits is that the hypothetical graviton has never been observed. There is reason to suspect that there might be another explanation for the way gravitation is caused. Recall that Einstein's General Relativity states what appear to be ellipses are really straight lines in curved space-time.

If you had a trampoline, and you took some point on the mat (call it the center) and pulled it down, the mat would have a curved surface similar to the bell on a tuba. (I have no idea if these curves are similar mathematically, but they look so visually). Now put a marble on the mat and push it in any direction except for directly toward or away from the center. If the push was less than the "escape velocity" and somehow there is no friction and the mat is large enough to contain the entire path, then the marble will roll in an elliptical "orbit" forever.

Now imagine that what appears to be empty space is, in fact, curved like that mat. Instead of a plane that is warped out of form into a third dimension, space-time is a volume (really, it's 4-dimensional, so volume is still not the right word) that is warped out of form into some higher dimension(s).

This visualization illustrates the description offered by General Relativity. The problem is that it really fails. In the example, there is an external force (gravity) acting on the marble, and in space-time the curvature is enough. This really bothers me, but I don't have a better analogy.

Next post: Virtual Particles and the exchange of forces.

Here is a link to a great FAQ about this topic. I will probably say much the same in my next post.

[MadMojoMonkey]

OK, so I haven't forgotten about this question. I have a job now, so I have far less time to devote to this search and I'm pretty exhausted when I do have time. It's just taking longer than I expected.

Major issue: Virtual Particles are unobserved. Yeah. I said that. It seems that virtual particles are unobserved, but their effects are observed. Also, if a virtual particle is made to exist in a way that it CAN BE observed, it is no longer a virtual particle, it's a particle.

It turns out that what I thought I understood about these was actually just a rude hand-waving explanation given to an under-grad.

Virtual particles are a way of summarizing the effects of an infinite number of integrals using a trick in Quantum Mechanics called Perturbation Theory. This trick, while successful in some equations, is not comprehensive.

Perturbation Theory requires the use of math that is not at a layman's level. I am trying to find a way to explain it without getting into wave functions and Fourier Transforms... into probability theory and calculus... into a whole can of worms that could not be easily explained in a forum.

[MadMojoMonkey]

I'm laid off for at least a week, so:

A prelude to virtual particles:

When considering the interactions on the length scale of a photon's wavelength, things get tricky. A photon can have any wavelength, you remind me. Yes, the long wavelengths have low energy; the short wavelengths have high energy. So the issue isn't the length scale, really, it's the energy you have to put into the system to probe it. At some energy, the photon that has a short enough wavelength to probe the system has so much energy that it disturbs system being observed.

A digression about quantum uncertainty:
In order to see (observe) some object, a photon (or whatever particle) has to interact with the object, then reach my eye (or whatever detector).
Consider a low energy photon as a balloon, and a high energy photon as a bullet. If I bounce the balloon off of some object, the balloon reacts to that object's momentum in a dramatic way, but it is so big that the position of the object is unclear. If I bounce a bullet off that object, it is small enough to more clearly pinpoint the location of the object, but it barely reacts to the object's momentum. There is an inherent trade-off between what knowledge can be obtained.
*note: even a mass-less photon carries momentum proportional to its energy, (inversely proportional to its wavelength). Also, what amounts to a balloon or a bullet depends on what is being observed.

[JKDS]

Was Schrodinger a dog person?

[MadMojoMonkey]

What really made me take my time on this topic is that virtual particles arise in a trick of math. The equations of Quantum Mechanics are disgustingly complicated. So much so, that the only atom that is solved for explicitly is Hydrogen, which has only 2 particles (1 proton, 1 electron). Even Helium (6 particles: 2 protons, 2 neutrons, 2 electrons) is only solved approximately. It takes some tricky mathematics to get a solution to any practical application.

... here goes ...

The energy density in the volume "between" charged particles is greater than other volumes. If the particles are sufficiently close together, the energy density becomes great enough that there is uncertainty in the number of particles in the volume. This uncertainty means that particles can exist, so long as the product of their energy uncertainty and lifespan (time) uncertainty is beneath some threshold.

So why do these particles not repel all charged objects? Why do unlike charges attract each other? How can particles spontaneously existing and darting off for some short distance, perhaps colliding with one of the particles, cause a "pull"?

There is just no simple way to explain this without probability theory, complex numbers and partial differential equations... at least... I can't think of any way to explain it without using the "condensed" terms in these fields of math. Quite frankly, I don't understand how a particle's position can be described using imaginary numbers, either, but I trust the math that makes Quantum Mechanics so successful a theory.

There is a trick called Perturbation Theory that is used to approximate solutions for a certain class of equations in quantum interactions. It is in the intermediate steps of applying Perturbation Theory that virtual particles arise.

With virtual particles, the momentum is uncertain, so it could be going in any direction. The position is uncertain, so it might not even be between the particles, even though that is from where it borrowed the energy. Except that there are other factors which influence the location and momentum of the virtual particles. Among them is the charge of the objects, which displaces the position/momentum probability density function such that virtual photons cause electromagnetic interactions that are... well, what they are. Like charges repel; unlike charges attract.

Complete fail?

[MadMojoMonkey]

Was Schrodinger a dog person?

I wouldn't trust him near any animal, personally. Also, I wouldn't go into any empty room before him.

The Schroedinger's Cat thought experiment is idiotic, anyway. It explains nothing, is full of obvious holes, and is needlessly murderous of a cat.

[chemist]

(I think it fits better here than the joke thread, I hope MMM likes it).


Two atoms walking down the road bump in to each other.
One says "I think I've just been ionised".
The other asks "are you ok, that was quite a bump"?
First atom says: "I don't think I am, I think I've lost an electron".
Second atom says: "Oh dear, are you sure"?
First atom says: "Yes I'm positive".

[jackvance]

Old. (seriously, lol)

[MadMojoMonkey]

Seriously old. Tweak it for a physicist and make the atoms Hydrogen. You can make it a mugging, too.

Officer, I've been mugged!
What did they take?
They stole my electron!
Are you sure?
Yes... I am positive!


It's nice to see the thread bumped. I've give it a quick scan and see if I can ask myself a question.

[oskar]

When you stir an espresso and tap the cup, the frequency of the tapping drops significantly while the coffee is agitated and rises back up when it settles down. This works with expresso and some foamy instant coffees, does not work with filter coffee or generally non-foamy liquids. Why is that?

[surviva316]

If you drop 5 ice cubes into an 8 oz drink and 1 ice cube into another 8 oz drink at the same temperature, obviously the one with 5 cubes will water down more eventually, but after 30 seconds, which is watered down more?

I (and other non-science/math people I've asked) intuitively feel that the one with 5 cubes will adjust the temperature of the drink so much quicker that it will melt more slowly so that in spite of having 5x's as much surface area, it will water down more slowly. Not only does this seem unlikely when taking into account how much more surface area this is, but even if this is the case, then surely if you drop 5 ice cubes 100s of miles apart in the ocean, then the ocean will water down more quickly with 5 cubes rather than 1 regardless of what part of the time axis you're looking at, so at the very very least, the drink will only water down more slowly up to a certain drink size.

Don't give me any of this "I would have to study it" shit either.

EDIT: I'm also skeptical about this "it will get cold so fast that it won't melt as quickly" hypothesis because that heat is going somewhere, and presumably that "somewhere" is the ice cubes, so a drink cooling down more quickly should be indicative of the fact that a larger area of ice is reaching melting point.

Of course, maybe there is a margin between the ice's temp at t=0 and its melting point (say, the ice cube is initially 25 degrees F), so that when the heat loss of the drink is dispersed over a larger area, less ice actually melts initially. Latent heat would also possibly cause this, so that energy is being spent on too many places at once which is causing the melting process of any one molecule to slow.

Actually, though I started this edit as a skeptic, unraveling starts to make more sense so that maybe adding more ice cubes does make it melt less efficiently (ie: make your drink stay water down less while cooling off more, at least initially).

[surviva316]

Also, I would very much enjoy a thread devoted entirely to coffee/espresso/tea.

[jackvance]

While this effect is there, I still think the 5 ice cubes will melt faster overall. Just instinctively.

But I would have to study it.

[MadMojoMonkey]

When you stir an espresso and tap the cup, the frequency of the tapping drops significantly while the coffee is agitated and rises back up when it settles down. This works with expresso and some foamy instant coffees, does not work with filter coffee or generally non-foamy liquids. Why is that?

WTF? Really?

Umm... Got any links to this phenomenon? It's the first I've heard of it.

It's quite counter-intuitive that the frequency would DROP when the carrier fluid has more energy. Well, the heat energy is so vastly prevalent over the rotational energy of stirring the drink, that I guess it's probably a red herring.

OK, so it's the characteristic lengths being altered by the motion of the foam that makes a difference. The bubbles in the foam might have a different average spacing when it's stirred. Or even it could be that bubbles in the foam are slightly larger or smaller when the stirring alters their base-line interactions.

Either way, I'm going to guess that it's altering the average lengths between fluid/air boundaries within the foam with a net effect of increasing either bubble size or bubble spacing or possibly both. This is because lower frequencies have longer wavelengths, and would resonate in larger spaces, than higher frequencies.

Hmmm...
Bernoullii's Principle states that flowing fluid has a lower pressure than fluid that is standing still, so the reduced pressure of the stirred fluid could cause the foam's bubbles to increase ever so slightly in size.

(This is pure speculation if you haven't gathered from the tone.)

[MadMojoMonkey]

Ice cubes:

This is really a simple one. The amount of energy it takes to melt ice into water is constant. Well, it's constant by mass (at a given temp. and pressure), expressed in J/kg. The geometry of the ice "cubes" could allow for faster melting of the single "cube" over the 5 "cubes". However, the quantity of ice turned to water requires a given amount of energy. The watered-downedness is directly linked to the temperature change.

Thermodynamic work is being done. Assuming the beverages were the same liquid, perfectly insulated from any other temperature-altering effects, started at the same temperature, and were under identical pressure conditions...
Assuming that... then the one with more volume of ice turned into water will be the cooler drink.


Which one is more watered down?
Short answer: The colder one.


It is also interesting to note that the ice can't cool a drink below 0 C. When the drink cools to that temp, the rate of melting slows to maintain that temp against losses to the environment. In the hypothetical situation where the drink is perfectly insulated, the ice would stop melting entirely.

[MadMojoMonkey]

Of course, maybe there is a margin between the ice's temp at t=0 and its melting point (say, the ice cube is initially 25 degrees F), so that when the heat loss of the drink is dispersed over a larger area, less ice actually melts initially. Latent heat would also possibly cause this, so that energy is being spent on too many places at once which is causing the melting process of any one molecule to slow.

I missed this part about the ice starting at a temperature below the melting point. You are correct that the temp change of the ice up to the melting point would cool the drink without causing melting of the ice. As long as we start with identical ice cubes for both beverages, though, the answer I gave still holds.

[oskar]

yah it has something to do with bubbles
TL/DN
#explainlike5 pls
http://www2.eng.cam.ac.uk/~hemh/coffeecup/coffeecup.htm

This is much more noticeable with espresso - the drop is ridiculous.

[MadMojoMonkey]

yah it has something to do with bubbles
TL/DN
#explainlike5 pls
http://www2.eng.cam.ac.uk/~hemh/coffeecup/coffeecup.htm

This is much more noticeable with espresso - the drop is ridiculous.

OK, now that's a really cool link, but it's not what I thought you were describing. I thought what you were saying is that if you stir the espresso, the tone drops when it is stirred, then rises as it stills. I thought you were saying this is wholly repeatable, in that you could then re-stir the same espresso and tap it again and hear the same phenomenon.

In your link, they're describing the change in the liquid's Bulk Modulus caused by nucleation. In other words... The liquid becomes less "springy" as the bubbles form. Then it returns to its normal "springiness" as the bubbles rise to the surface and pop. Since the liquid is carrying the vibrations, the springiness will affect how quickly they travel through the liquid, which in turn affects the frequency of the vibration.

However, this phenomenon would not be repeatable. Once the bubbles have worked their way out of the fluid, the fluid would need to be "recharged" with more trapped gasses to recreate the initial results.

If the notion of gasses trapped in a liquid seems odd, think of a fish tank with an air pump keeping a constant stream of bubbles in the tank. This is to re-supply the water with oxygen that is not trapped as molecular water (H2O) for the fish to "breath". Think about this while sipping a beer and notice the bubbles nucleate from the liquid as it trickles down your throat.

[eugmac]

when you pee into a normal toilet, not urinal but the type with some reservoir of water to excrete excrement into, and you get some splashback onto your foot/pant leg/etc.

what % of that splashback is pee, and what part is original toilet water? in other words how diluted does the pee get before it bounces back out onto your naked foot making you go ewww splashback?

[eugmac]

OK, now that's a really cool link, but it's not what I thought you were describing. I thought what you were saying is that if you stir the espresso, the tone drops when it is stirred, then rises as it stills. I thought you were saying this is wholly repeatable, in that you could then re-stir the same espresso and tap it again and hear the same phenomenon.

In your link, they're describing the change in the liquid's Bulk Modulus caused by nucleation. In other words... The liquid becomes less "springy" as the bubbles form. Then it returns to its normal "springiness" as the bubbles rise to the surface and pop. Since the liquid is carrying the vibrations, the springiness will affect how quickly they travel through the liquid, which in turn affects the frequency of the vibration.

However, this phenomenon would not be repeatable. Once the bubbles have worked their way out of the fluid, the fluid would need to be "recharged" with more trapped gasses to recreate the initial results.

If the notion of gasses trapped in a liquid seems odd, think of a fish tank with an air pump keeping a constant stream of bubbles in the tank. This is to re-supply the water with oxygen that is not trapped as molecular water (H2O) for the fish to "breath". Think about this while sipping a beer and notice the bubbles nucleate from the liquid as it trickles down your throat.

btw, air pumps aerate aquariums far less from the bubbles in the water than the breaking of surface tension at the water surface when the bubbles pop. in fact a filter which has a water outlet pointed near the surface which causes lots of waves is a far more effective aerator than an air pump.

[eugmac]

i've never had air pumps in my aquariums. in fact my filter doesn't do much aerating either 'cause i have shitloads of plants that love the co2, which in turn of course produce o2.

[MadMojoMonkey]

btw, air pumps aerate aquariums far less from the bubbles in the water than the breaking of surface tension at the water surface when the bubbles pop. in fact a filter which has a water outlet pointed near the surface which causes lots of waves is a far more effective aerator than an air pump.

That is quite interesting. I've never kept a fish tank, myself (well, I once had a Beta for a couple of months, but no aeration required for Beta).
Thanks for the clarification.

On the pee-splash question: I am intrigued, but have no idea where to begin with this. Nonetheless, I will begin. I'll keep you posted on my progress.

[MadMojoMonkey]

Looks like with a droplet, the majority of the drop is rebounded, carrying a small amount of the reservoir water with it.

But this is not a stream, and the stream would not be uniform, so I'm still looking.

[Renton]

Do you think there will ever be a computer so sophisticated that it can collect all the data of all of the particles in the immediate vicinity of Earth (lets say the just including the Solar System) and the trajectories/velocities/temperatures etc of those particles, and thus can predict the future? Like, couldn't you theoretically know exactly what was going to happen, even mundane events on a small scale (i.e. will I masturbate today or will I be too lazy), just by knowing how all the particles are interacting, and how and when they will bounce against others?

[rong]

This may be a dumb question as I know nothing on this subject whatsoever. But is there any evidence to suggest our universe is not the inside of a black hole. I mean the big bang sounds like a star imploding/exploding/whatever we call the creation of a black hole and the universe expanding sounds like it fits the theory of a black hole sucking stuff in as it grows. Is this not the most obvious theory of our universe? Does anything prove/imply/suggest that this isn't the case?

I may have asked this before, I've asked it before somewhere and don't remember getting a satisfactory answer.

[MadMojoMonkey]

Do you think there will ever be a computer so sophisticated that it can collect all the data of all of the particles in the immediate vicinity of Earth (lets say the just including the Solar System) and the trajectories/velocities/temperatures etc of those particles, and thus can predict the future? Like, couldn't you theoretically know exactly what was going to happen, even mundane events on a small scale (i.e. will I masturbate today or will I be too lazy), just by knowing how all the particles are interacting, and how and when they will bounce against others?

In a way, all of physics is the pursuit of exactly that. The goal of physics is to answer the category of questions which start, "What happens if..." and which have measurable answers. So rest assured that however close we can get to this, we are rushing towards it.

This is impossible in the sense that you mean, though. Recall that at a particle scale, position and momentum are linked properties. They are linked by Fourier Transform, creating a Fourier Transform Pair. Generally, a bell-curve, or Gaussian function, is used to describe the position or momentum, but whatever function, the pairing holds. The standard deviation (uncertainty) of one of these defines the minimum standard deviation in the other, with the uncertainties being inversely proportional. This means that the thinner one bell curve is, the wider the other is. More generally, the smaller the uncertainty in one, the greater the uncertainty in the other.

LET:
delta_x be the standard deviation of a Gaussian describing position
delta_p be the standard deviation of a Gaussian describing momentum
h_bar be the reduced Planck Constant

Heisenberg Uncertainty Principle (HUP):
(delta_x)(delta_p) = h_bar

which can be re-written
delta_p = h_bar / delta_x

The smaller delta_x, the larger delta_p.


The HUP tells us the absolute minimum uncertainty that is the product of 2 linked properties. That's a very tiny amount, indeed, but it is non-zero. So even with perfect measuring instruments, there is still uncertainty in some properties of a particle... most notably would be the position and momentum. Since both position and momentum are needed to define a trajectory, no exact particle trajectory can be known.


(Hey, sorry if this seems phoned-in. A browser crash just deleted a much longer, more thorough explanation, which I haven't fully re-created.)

[MadMojoMonkey]

I may have asked this before, I've asked it before somewhere and don't remember getting a satisfactory answer.

In post #20, you asked:

Are we inside a black hole?
This seems to me to be the most obvious explanation of our universe.
Is there any evidence to suggest we aren't?

In post #30, my response:

Physics answer: could be
Nothing can be observed beyond an event horizon, and therefore it is outside the purview of physics. We don't know what happens inside black holes, so it is impossible to rule out that the entire universe is, in fact, inside a black hole.

As stated, there can be no physical evidence for or against this claim.

[MadMojoMonkey]

I mean the big bang sounds like a star imploding/exploding/whatever we call the creation of a black hole

... except that the Big Bang involves ALL of the stars, black holes and everything in the universe (even all the space and time) existing in a volume smaller than a single proton. There really is no comparison to any other kind of explosion or expansion.

A Black Hole is a region of space-time in which the gravitational energy well is too deep for anything to escape, even photons. Generally, they are formed by the core collapse of a massive star. Sometimes, 2 objects can collide to create a black hole. Also, an object that is nearly massive enough to be a black hole can become a black hole by accretion, the gradual gathering of mass from a nearby object.
There is also some evidence for primordial black holes, or black holes that formed in the early universe and were kind of the planted seeds for galaxies and eventually star formation.

So far, every galaxy observed (lol only 1, the Milky Way) has a super-massive black hole at its center.

and the universe expanding sounds like it fits the theory of a black hole sucking stuff in as it grows.

Black holes do not "suck stuff in as they grow"... except when they do, of course.

General Relativity tells us that mass curves space-time creating the illusion of a gravitational force. The force is an illusion, because objects move in straight lines at a constant velocity through curved space-time. Since only an object which is not being acted on by a force will move at a constant velocity in a straight line (Newton's 2nd), the "force" of gravity is an illusion cause by a human limitation in "seeing" the curvature of space-time.

E.g. if the sun were instaneously replaced with a black hole of equal mass, the planetary orbits would be unaffected.

All of that is to say, it is the mass of the object, and not its composition, that defines how much it sucks.

ALSO: Black Holes radiate profusely, by Hawking Radiation, which makes them not-so-black after all. It means they slowly shrink over time.
In other words, it really sucks to be inside them, and it kind of blows to be near them.

IF a black hole collides with a star or other massive object, then obviously, the resulting object is more massive than the original black hole, so it would have a "growth spurt" (I made that up). So, technically, they do "suck stuff in" and "grow" but it's not like they're the Hoovers of the universe.

Another point is that the black hole would be expanding because of "stuff" "coming in" from the "outside". Whereas, the universe is expanding because "space" is "spontaneously expanding" "everywhere".

This may be a dumb question as I know nothing on this subject whatsoever. But is there any evidence to suggest our universe is not the inside of a black hole. [...] Is this not the most obvious theory of our universe? Does anything prove/imply/suggest that this isn't the case?

There is just no basis for a physicist to answer this. Physics answers questions about observable things, and the inside of a black hole can not be observed by definition. So physics is simply not equipped to answer this as of now.

I mean... the way to answer it would be:
What are the implications/predictions of your theory?
Can any of those be measured?
If yes: Well, go on and measure that and see if the data support or refute your theory.
In no: Sorry, this is not science.

[Savy]

There is just no basis for a physicist to answer this. Physics answers questions about observable things, and the inside of a black hole can not be observed by definition. So physics is simply not equipped to answer this as of now.

I mean... the way to answer it would be:
What are the implications/predictions of your theory?
Can any of those be measured?
If yes: Well, go on and measure that and see if the data support or refute your theory.
In no: Sorry, this is not science.

There are definitely lots of top physicists trying to answer questions like this right now. Although they probably won't have any of their work verified in their life time. Always used to annoy me how people would just disregard the question "what was there before the big bang" because what we know as time didn't exist before the big bang, but that's not really what the question is asking and there are a few hypotheses about exactly this.

The question that used to piss me off was we'd get told "matter can't be created or destroyed", which leaves to the obvious question where did it come from then? Which I never really had answered by a teacher, when in reality this isn't the case and it's just a simplified theory of what is really happening which when I found out I didn't really understand why it couldn't be explained to a 14 year old.

[rong]

Haha knew I'd asked that to someone once. Clearly learning from this thread.

[MadMojoMonkey]

Always used to annoy me how people would just disregard the question "what was there before the big bang" because what we know as time didn't exist before the big bang, but that's not really what the question is asking and there are a few hypotheses about exactly this.

The question, "What is beyond space-time?" is not a physics question... yet. Physics is interested in observable things, and since that kind of question is about something not-yet-observed, there is just no evidence to back any claims.

Still, there is good reason to ask the question and to postulate what might be, and follow through to see what the implications are.

The question that used to piss me off was we'd get told "matter can't be created or destroyed", which leaves to the obvious question where did it come from then? Which I never really had answered by a teacher, when in reality this isn't the case and it's just a simplified theory of what is really happening which when I found out I didn't really understand why it couldn't be explained to a 14 year old.

Well, Einstein explained that matter and energy are basically 2 sides of the same coin. Until then, the smartest people in the world believed that the Law of Conservation of Mass was correct. Most people even today don't have any clue what Einstein was talking about, so you can hardly blame your teachers... unless they were physics teachers.

The Law of Conservation of Energy still holds, though, once you accept that mass is a form of energy. The thing is that there is positive and negative energy, you see. The whole equation is really
E^2 = p^2c^2 + m^2c^4
where E is the energy, p is the vector momentum, c is the speed of light in vacuum, and m is the mass of the object.
This reduces to the familiar E = mc^2 when p=0.

Since p is the vector momentum, it can be positive or negative. E.g. 2 objects of identical mass moving away from a central point at the same speed have a net energy of 0.

So long as all the conservation laws are followed, all kinds of particles can pop into existence where there was "nothing" before. This is exactly what a particle accelerator experiment does. It smashes 2 protons into each other, annihilating them and producing a whole mess of particles that spray out. Two protons go in... hundreds or thousands of particles come out.

Check out this Encyclopedia Britannica article about Pair Production for a relatively simple explanation of 1 process by which energy becomes matter.

[NightGizmo]

From what I understand, at the quantum level, the location of particles are a probability wave until they are observed. What is the definition of "observation" of a particle? Why does the act of observation cause the probability wave to collapse, and what is the bare minimum that meets the criteria of "observation" to cause the wave to collapse? Is there anything that a layperson would expect to count as "observation", but doesn't?

[Keith]

IF a black hole collides with a star or other massive object, then obviously, the resulting object is more massive than the original black hole, so it would have a "growth spurt" (I made that up). So, technically, they do "suck stuff in" and "grow" but it's not like they're the Hoovers of the universe.

So far, every galaxy observed (lol only 1, the Milky Way) has a super-massive black hole at its center.

what would happen if two galaxies collided, would the super massive black holes collide at such high force combined with all the material circling them to also then get sucked in cause the big bang. or would the mass that is circling the original black holes help to influence the resulting spread of matter in the explosion

[MadMojoMonkey]

From what I understand, at the quantum level, the location of particles are a probability wave until they are observed.

Yes. Even after they are observed, their positions (among other qualities) are still described by probability distributions, which evolve as waves, as described by the Schroedinger Equation.

What is the definition of "observation" of a particle?

Any interaction that carries information about a state of the particle can be considered an "observation". The notion of whether a human saw it is not relevant.

This is a subtly different use than "Physics is concerned with what can be observed", which means observed (in the broadest sense) by a human, or human created device. This type of observation hinges on someone besides the original claimant being able to reproduce the observation.

Why does the act of observation cause the probability wave to collapse, and what is the bare minimum that meets the criteria of "observation" to cause the wave to collapse?

Wave function collapse is an instantaneous event in which the state of a particle (shape of the wave function) is altered. A probability wave function will either gradually evolve (as illustrated by the Schroedinger Equation) or suddenly change due to a collapse.

Observation causes collapse because observation is an interaction which carries information about the state. This interaction is always an exchange of sorts, equal and opposite (sounds like Newton's 3rd, but is the result of numerous conservation laws).

In order to get something, you have to give something.

When the particle is observed, the interaction causes a sudden change in the wave function, as opposed to the gradual change expected of a wave. E.g. in order to see something, a photon has to bounce off of it, and to my eye. That bouncing imparts a change in the thing.

Is there anything that a layperson would expect to count as "observation", but doesn't?

Probably more the opposite. Since the use of the word "information" in Quantum Mechanics is a bit misleading, I'd guess that far more stuff counts as observation that no non-physicist would agree with.
Such as: particles inside the core of a star observe each other because they interact with each other... even though no human instrument can see past the outermost layer of a star.

[MadMojoMonkey]

what would happen if two galaxies collided, would the super massive black holes collide at such high force combined with all the material circling them to also then get sucked in cause the big bang. or would the mass that is circling the original black holes help to influence the resulting spread of matter in the explosion

Galaxies are mostly empty space. The sun's nearest neighbor star is over 4 light years away. When galaxies collide, they largely pass right through each other, with a surprisingly small amount of mixing and stuff thrown away in all directions.

But that's not your question.

You want to know what happens when 2 super massive black holes collide. They spin around each other more and more quickly as they fall toward each other, like a twirling ice skater pulling in their arms. This does really crazy stuff to space-time, causing geodesic lines which are so relativistic that a particle can actually run into itself from behind, essentially existing on the entire orbit everywhere at once. Madness.

After that, the super massive black holes would merge into an even more super massive black hole. The combined gravity would likely "suck in" the nearest stars and nebulae in an accretion disk, and would have a long reaching effect as the "gravity ripples" spread through the surrounding galaxy.

No Big Bang, though, sorry. It's really quite a different beast than anything else.

Some cool NASA computer simulations of merging black holes

[oskar]

So how do you handle it? When you constantly look at things at a very large scale and a very small scale and then look back at yourself and try to find your place in it?

[MadMojoMonkey]

Well, "my place in it" is the perception that I'm most familiar with. The other descriptions came much later. In addition to acquiring a degree in physics, I have studied philosophy and music. I feel that each subject offers specific insight into 1) the environment (universe) I live in 2) modes of human explanation and 3) a personal need for expression and identity.

Reconciling the Quantum Mechanics with my human experiences is actually part of the course-work. There is a practice of taking any discovery of QM and putting it to the limit of large numbers of particles. The Laws of Quantum Mechanics all look like classical laws when taking many particles and applying statistical analysis.

I am far less competent with General Relativity than QM. The same idea applies, though. The laws of GR all look like classical laws when the masses and velocities are reduced.

So the whole thing is just 1 picture that exists across many orders of magnitude in scale.

As an aside, the first time I witnessed falling snow after I understood vector fields was one of the most awe-inspiring events of my life. Physics truly makes the world a far more beautiful place. There is so much more to notice and appreciate.

[a500lbgorilla]

Always used to annoy me how people would just disregard the question "what was there before the big bang" because what we know as time didn't exist before the big bang, but that's not really what the question is asking and there are a few hypotheses about exactly this.

What you should remember is that we're in the present, and we can only observe so far into the past. That limit is troublesome to the question you're looking to have answered. Stephen Hawking had a clever brush-away answer that he gave and people have always liked to shove at those who are getting ahead of themselves.

MMM, do you have a book/textbook suggestion for learning QM?

I tried getting into Feynmanns book, but I can't find any answer manual to go with his problem sets, so, it's a difficult time knowing I'm doing the math(s) right.

[Savy]

Quantum by Jim Al-Kahalili
http://www.amazon.co.uk/Quantum-Guid.../dp/1780223951

Meant to be quite good, more of a general overview though I think.

If you are looking to actually get your teeth sunk into it, "Principles Of Quantum Mechanics" by Shankar is a great book.

[MadMojoMonkey]

The textbook from which I learned is:

Introduction to Quantum Mechanics by David J Griffiths

I'm sure you can find it for free online or for cheap as a used book.

I caution you that you simply must do the math if you want to understand QM. It's almost all algebra, but some basic trig. and calc. is used from time to time. I have a .pdf of the solutions manual for this book, which will be invaluable to you if you intend to learn.


I also recommend buying a nice, thick, full color physics textbook for yourself. What you want is one that has a section on modern physics. This section is the important one, but everything else will be nice to have on reference as you're thinking through QM.

[MadMojoMonkey]

Interesting that you mentioned Jim Al-Khalili.

I was just looking for a good video to introduce the Double Slit Experiment, and this was what I found.

I encourage everyone reading the thread who is curious about Quantum Mechanics to watch this video and bring me your questions.

[MadMojoMonkey]

If you're interested in physics, there's a few MIT courses that are on youtube. Dr. Walter Lewin is an amazing professor and every lecture has a demonstration to show you what he's describing. These lectures were an essential companion to my own education during freshman year.

For classical mechanics:
Lec 1 | 8.01 Physics I: Classical Mechanics, Fall 1999

For Electricity and Magnetism:
Lec 1 | MIT 8.02 Electricity and Magnetism, Spring 2002

For Vibrations and Waves (an essential primer if you wish to understand Quantum Mechanics):
Lec 1 | MIT 8.03 Vibrations and Waves, Fall 2004


EDIT: I can just about promise you that this will not be boring. However, my own bias is clear. I think Dr. Lewin presents things in such a way as to bring fascination to the student, and even students who once thought physics was boring come away with a real appreciation of how much fun it can be.

[ChipEaterMan]

If spacetime is not a material substance, how can it make MASSIVE objects, which tend not to accelerate due to their inertia, move?
2 - If gravity is not a force, why does an object put in rest relative to the earth accelerate toward it?
3 - If the earth mass curved ONLY space, than an object put at rest relative to the earth would continue at rest relative to it. But this is not what happens, so the earth mass also curves TIME. How does this curved time make things to accelerate?
4 - What did you find more difficult, to answer these general relativity questions or playing heads up against me in Stars?
Thanks

[kingnat]

The textbook from which I learned is:

Introduction to Quantum Mechanics by David J Griffiths

ah, griffiths' quantum. so nice.

[jackvance]

Do galaxies form around black holes only?