General Relativity, Quantum Mechanics, The Speed of Light and More...

[Henry]

Everytime I read stuff like this, it just makes me want to play Aetherco's Continuum all the more.

 

[Umbran]

Of waves and particles
Einstien said light was a particle AND a wave.

Say what?

Light has the properties of both and so it must be both.

Technically, that isn't what is said at all. What is said is that light has the properties of both wave and particle. That doesn't say that light is both, merely that it can be described either way, depending upon the situation. In the end, the wave/particle nature of a thing is really a matter of mathematical convenience. Not so much a question of what the thing is, as what math you'll use to describe it.

So, you might venture to say that light is particle and wave, or that it is neither. The fact that light is not special might weigh into your choice. The coffee mug on your desk acts liek a wave, too. It just has so incredibly short a wavelength that for practical purposes you might as well call it a particle and be done with it.

Well, actually it isn't. My theory is that light is a wave, and only a wave, but it is a wave that doesn't entirely exist within the dimensions we sense.

The Ether Hypothesis was disproven by Michelson and Morley back in 1907. This may well impact your thoughts on the matter.

Wait, isn't time the 4th dimension
No. Time is a continuum, not a dimension. The difference is that a dimension can vary in value. Time is a constant, and proceeds at a set rate.

Mathematically speaking, quantum mechanics uses time as a dimension. And quantum mechanics makes the computer you posted with work, so you might want to be careful which parts of it you try to refute

Time is observably not a universal constant. Many times, we have verified that the passage of time varies depending upon the relative motion of the observers. And that's not he oly source of different time-flow. There's a whole lot of experimental data that says you're wrong here. Sorry.

Observances of time "speeding up" I believe can be borne as false due to transmissions. For instance, there is a variance of error in the GPS system since the satellites are moving so fast. It's micro and nano-seconds, but it's there. But this lag also must be from light's own travel and the atmosphere has a role as well.

No, it isn't just time lag in transmission. That's accounted for separately. And it isn't just that the satellites are moving so fast. It's also because the ground and the satellites are at different points in Earth's gravity well. Relative motion aside, simple altitude also has a measureable effect.

Light doesn't have a constant speed

Light has a constant speed within a given medium. The speed of light in vacuum is a bit faster than the speed of light in air, or water, yes. But in a given medium, the speed of light is observably constant.

- it has a constant maximum speed perhaps, but light slows down and refracts as it interacts with particles. This is observable, but it puzzles me why this isn't taken into account in any science journal I've read. Further, light seems to speed up again when the interference is removed. Again, why?

I don't think anything exists at the smallest level. If energy and matter are indeed one and the same as implied and later proved by E=mc² then how does this transition work.

Light can pass through glass. Occasionally there are collisions, but unless light exists extra-dimensionally it would be entirely stopped or changed into a particulate vibration of some sort like sound.

The subject of transparency and opacity is a matter of details of solid state physics. While I cannot think of a way to adequately explain it without math that makes even my head hurt, there's nothing very mysterious about it.

For an idaequate description - you must remember that matter is mostly empty space. It is not all all odd that a particle (or wave) of very small size should be able to pass through matter without encountering anything and being absorbed. There's really very little there to stop the light, you know.

Remember though that everything - and I do mean everything is in motion. Nothing truly stands still. If my ramblings are correct - coming to a complete stop relative to the origin of the universe is impossible.

There is truth and falseness here. Quantum mechanically - complete rest is in fact impossible, as it would violate the Uncertainty Principle. However best theory says that the "origin of the Universe" is not a place within the Universe that you can point, making that idea a bit hinkey.

 

[BryonD]

Time is observably not a universal constant. Many times, we have verified that the passage of time varies depending upon the relative motion of the observers. And that's not he oly source of different time-flow. There's a whole lot of experimental data that says you're wrong here. Sorry.

<SNIP>

Light has a constant speed within a given medium. The speed of light in vacuum is a bit faster than the speed of light in air, or water, yes. But in a given medium, the speed of light is observably constant.

correct

And these are directly related. The speed of light, relative to all observers, is constant in the same way that the length of a foot in inches is constant. Dilation of time "corrects" for a photon moving at the same speed relative to both a stationary observer and an observer moving at a significant fraction of c.

(allowing for some fast and loose language, of course)

 

[Steverooo]

Actually, there is a way to do science without paradox, or so I am told... An old theory, called DeBroglia Waves, is supposed to explain the particle-wave characteristics of light. This is similar to the right-hand/left-hand rule (depending upon how long ago you took physics) where the electric and magnetic charges are at right angles to each other AND the direction of travel. I have to admit, I really don't understand DeBroglia's theories...

Also, on dimensions, there are indeed supposed to be 11 (some in space, some in time), most of which work on a level too small for us to observe. Since we see only four of these dimensions, there is almost 2/3 of the Universe which is unobservable to us! This makes sense to me.



Supposedly, back in the 1960s, someone was doing some computer modelling of atoms, and noticed that, if they posited a fourth spatial dimension, and then rotated a particle through it, that it transformed the electric/magnetic charge into the other, thus explaining the electromagnetic effect. Everybody thought that that was cool, so they decided to try positing the existence of other spatial dimensions, and see if that explained other such phenomena...

What they found was that they could explain ALL of the observable phenomena by positing the existance of 22 dimension! Then, someone sat down and looked over the math, and saw a way to put several of these dimensions together... After working on it for a while, they realized that all they really needed was 11 dimensions.

String Theory posited some explanations, but had the problem (and still has it) of making no testable predictions. Worse, five competing string theories were developed! Finally, one mathemetician (whose name I have long forgotten) "unified his field" by showing that ALL FIVE THEORIES were applications of one single theory. Now, if they can just come up with a prediction that can be observationally tested!

Personally, I believe that Einstein had it right, and that The Universe is a finite, quasi-spherical region. Therefore; since space is limited, time must be, also.

I also believe that matter/energy will eventually be proven to be neither a particle nor a wave, but something else that we don't understand, yet. We'll see...

Now, whoever puts together String Theory, M Theory, and DeBroglia Waves...

 

[Umbran]

Actually, there is a way to do science without paradox, or so I am told... An old theory, called DeBroglia Waves is supposed to explain the particle-wave characteristics of light.

The name you're probably looking for is de Broglie (as in Count Louis de Broglie). It was he who first postulated that because photons have wave and particle characteristics, perhaps all forms of matter have wave as well as particle properties. When I said that the coffee mug on your desk has a wavelength, I was referring to it's de Broglie wavelength.

Note that this is not intended to explain the particle-wave characteristics of light. That was done by others. de Broglie's claim to fame was extending that to electrons, protons, and every other bit of matter in the Universe.

This is similar to the right-hand/left-hand rule (depending upon how long ago you took physics) where the electric and magnetic charges are at right angles to each other AND the direction of travel.

In electromagnetic waves, the electic and magnetic fields (not charges) are at right angles to each other, and at right angles to the direction of travel. But those right angles are all in our good old normal 3-space, and are what allow us to make use of polarized light. This is also a "classical" thing, as opposed to quantum mechanical.

De Broglie's waves and Maxwell's waves are similar, in that all waves are similar. But de Broglie's dont' have any real funky right or left handedness issues.

Now, if they can just come up with a prediction that can be observationally tested!

And this is a really big point. If a theory does not make predictions that can be tested, it is merely mathematical game-playing.

Personally, I believe that Einstein had it right, and that The Universe is a finite, quasi-spherical region. Therefore; since space is limited, time must be, also.

Well, the physical boundary of the Universe does not necessarily speak to it having a temporal boundary as well. One can set up a physically spherical Universe that is not "spherical" in time.

Specifically, the Big Bang Theory that comes out of Einstein's General Relativity posits that Time has a sort of beginning. For some solutions of the equations, Time has an end (the Big Crunch, where the Universe eventually falls back in on itself), and the physical universe is bounded. There are other solutions in which the universe is bounded in space, but not in time - it has a definite size, but never comes to the Big Crunch.

I also believe that matter/energy will eventually be proven to be neither a particle nor a wave, but something else that we don't understand, yet.

Again - the wave/particle thing, to physicists, is largely a matter of mathematical convenience. It is quite clear that a thing which has the characteristics of both particles and waves can't really be either.

 

[Zoatebix]

Specifically, the Big Bang Theory that comes out of Einstein's General Relativity posits that Time has a sort of beginning. For some solutions of the equations, Time has an end (the Big Crunch, where the Universe eventually falls back in on itself), and the physical universe is bounded. There are other solutions in which the universe is bounded in space, but not in time - it has a definite size, but never comes to the Big Crunch.

Nowadays these other solutions are mostly mathematical game playing, too, since we've measured the cosmic backround radiation with enough precision to know the age of our universe (to within +/-200 million years, which is pretty damn good), that we are indeed in a universe with flat geometry that is expanding and that the rate of expansion is increasing. No Big Crunch for the Universe - we get heat-death. And probably a few other things that I'm forgetting, too. Oh yeah! The approximate current contents of the Universe - 70% dark energy, 26% dark matter, 4% good ol' baryonic matter that we know, love, and interact with every day, and a pretty negligible 0.005% radition. Ah for the years when Radiation was the primary component...

Messing with other solutions to General Relativity is still cool though - because the most 'general' mathematical solutions don't yield universes anything like ours - an isotropic and heterogeneous universe is apparantly something special, if I'm to believe the really smart people who learned Riemann Geometry and stuff while I was studying literature.

So... I'm not sure what my point is. I guess the Golden Age of Cosmology is now - there so much to learn that's just now within our reach!

And after that burst of optimism, I go back to studying Candide.

 

[Numion]

Actually there's nothing Cthulhuish about realities with non-euclidean geometries. Our reality doesn't follow eaclidean geometry. For practical purposes it does seem to do that (for example, draw a triangle and the angles will add up to 180 degrees, as fas as you can measure).

But the truth is that mass defines geometry in space around it. Gravity of earth is not enough to make us see the difference with naked eye, but it is there.

Euclidean geometry is a mathematical model, with strong isomorphism towards reality. The isomorphism is not complete though, which makes it difficult to dispel. Nothing horrific about it though

 

[Umbran]

Nowadays these other solutions are mostly mathematical game playing, too, since we've measured the cosmic backround radiation with enough precision to know the age of our universe

Eh. the problem there is that the measurement does not tell you the age. The measurement, when plugged into a particular model, tells you the age - because the particular model determines initial temperature and rate of cooling. So errors as small as 200 million years need to be taken with a grain of salt.

... that we are indeed in a universe with flat geometry that is expanding and that the rate of expansion is increasing. No Big Crunch for the Universe - we get heat-death.

You got a citation on that? Because that sure isn't the position of the cosmologists I work with. Last I checked, the jury would still be out until someone managed to meld gravitation into quatum mechanics. And, as mentioned previously, none of the current theories make any testable predictions. Thus, there's no sure thing.

 

[Zoatebix]

I'm well aware that wikipedia isn't good enough, but paragraph 4 of this (http://en.wikipedia.org/wiki/Big_Crunch) will have to suffice until I can root through John Hawley or some other professor's (or multiple professors') web-pages and books.

Edit: Did some more reading and figured out that I'm silly and that I ook things a professor said as 'facts' instead of 'the facts according to our current best model.' Sorry!

Second Edit: Of course, no other observations -like the age of the oldest stars we can see (assuming our star-formation etc. theories are correct)- goes against the age of universe figure or any of the other CMB findings. Still - maybe I shouldn't have put so much faith in the seemingly consistent package (with, admittedly, plenty of unkowns) that Astronomy-minor level classes present to me.