increasing rate of universe's expansion

[HarryKeogh]

ok, i have some questions..just watched a program on the Science Discovery Channel on how it seems the universe is expanding at an ever increasing speed.

my question is i always thought the universe was expanding in all directions at or close to the speed of light. if that's the case how could it be expanding at an increasing speed since nothing can travel faster than light

do we have any ideas on exactly how fast the universe is expanding now and how fast it was expanding billions of years ago?

(if you could help i just ask you to keep answers at the laymen level, i've just started to get fascinated by this stuff and needless to say i get lost frequently):)

[CurtC]

Space is expanding. The more space two things have between them, the faster they will be moving apart. So your idea that it's expanding at a constant speed is where you went wrong.

[HarryKeogh]

Originally posted by CurtC
Space is expanding. The more space two things have between them, the faster they will be moving apart. So your idea that it's expanding at a constant speed is where you went wrong.

ok, so that's because of gravity's reduced pull between the two bodies right? and if that's the case the universe's expansion will continually pick up speed forever?

[CurtC]

Until just about five years ago, it was thought that the galaxies have a large speed because of the initial bang, but that they're slowing down because of their mutual gravity. As they get farther apart, the gravity pulls less, and the question was whether there was enough gravity to eventually slow down everything and start drawing it closer together.

But a few years ago, it was discovered that the galaxies are actually *accelerating* apart. I think the first person to explain that can book his flight to Sweden. There's speculation about "pressure" from the quantum creation/annihilation of particles that goes on in empty space, described by the uncertainty principle, but I don't think this is past the point of speculation.

[wollery]

ok, so that's because of gravity's reduced pull between the two bodies right? and if that's the case the universe's expansion will continually pick up speed forever?

NO! Sorry for the caps, but that's precisely not what's happening. You have to remember that light takes a finite time to travel from one place to another, so the further away something is the longer the light from it has taken to reach us. This means that the light from the furthest galaxies left them billions of years ago. The velocity with which they are moving away from us is the velocity that the universe was expanding with billions of years ago. This expansion is slowing due to gravity, so nearby galaxies (ie from later in the life of the Universe) are moving apart less quickly because gravity has had time to slow them down a lot.

For more info I suggest you visit the WMAP website, it's written in pretty plain English and laymans terms http://map.gsfc.nasa.gov

edited to correct crappy grammar and spelling!

[slimshady2357]

Originally posted by HarryKeogh


ok, so that's because of gravity's reduced pull between the two bodies right? and if that's the case the universe's expansion will continually pick up speed forever?

If you think about this, it just can't be right.

Say the gravitational pull between two bodies is reducing because they are getting farther apart, this cannot speed them up. It can will only decelerate them less and less.

If they are accelerating apart, it must be something else that is driving the acceleration.

Adam

[Dancing David]

as a science dufer, I think it is the mysterious cosmological consatand and that there is reason to believe that the rate of expansion is increasing, it is some deep stuu, so lets type
Bad Astronomer and
Dr. Stupid and see if they show up to resolve the issue.

(I don't think that the rate of expansion was considered highest right after the big bung for a while now)

[HarryKeogh]

Originally posted by slimshady2357


If you think about this, it just can't be right.

Say the gravitational pull between two bodies is reducing because they are getting farther apart, this cannot speed them up. It can will only decelerate them less and less.

If they are accelerating apart, it must be something else that is driving the acceleration.

Adam

i thought gravity was acting as a sort of brake, trying to slow down the acceleration but losing out to the cosmological constant.

ugh, who would have thought the origins of the universe would be so complicated.

[slimshady2357]

Originally posted by Dancing David
as a science dufer, I think it is the mysterious cosmological consatand and that there is reason to believe that the rate of expansion is increasing, it is some deep stuu, so lets type
Bad Astronomer and
Dr. Stupid and see if they show up to resolve the issue.

(I don't think that the rate of expansion was considered highest right after the big bung for a while now)

Have you been bady swapped with pillory? :D

And Harry, what I meant was that if gravity is like a brake and when it's acting less (bodies getting farther apart) the only way to speed up is to apply more gas (so to speak ;)). So in this case, what is providing the increase in speed?

The cosmological constant isn't a source of acceleration itself, now is it? ;)

But I'm no expert in cosmology, that's for sure! :)

Adam

[wollery]

Originally posted by slimshady2357

The cosmological constant isn't a source of acceleration itself, now is it? ;)


Actually that's exactly what it is, Einstein originally intended it as an acceleration that countered gravity, thus removing the need for the expansion/contraction that Relativity predicted and allowing for the static Universe that he preferred.

[slimshady2357]

Originally posted by wollery


Actually that's exactly what it is, Einstein originally intended it as an acceleration that countered gravity, thus removing the need for the expansion/contraction that Relativity predicted and allowing for the static Universe that he preferred.

Wow! A simple number is a source of acceleration! Cool ;)

Sorry, I was under the impression that the cosmological constant was just a name for a force of some kind that had not been explained yet.

I didn't realize the constant was a force itself.

Adam

[Dancing David]

Quit a compiment
compared to pillory I am

[Duncan]

What boggles my mind is this. If the universe is everything that exists, including the planets, stars, galaxies and all that they contain; the entire cosmos, then what exactly is the universe expanding into? More space? Wouldn't that space then be considered part of the universe, which would make the universe infinite, and if the universe was infinite, how could it expand?

Am I looking at this all wrong?

[TillEulenspiegel]

HarryK: "ok, i have some questions.."

O man.. questions huh? =) Well sir all your questions can be addressed ( not answered ) by taking Physics 101 through 409.
Jeeze where to start? A lot of this stuff is counter intuitive but most of has been proven experimentally of mathematically.

Ok the Hubble constant.
Edwin Hubble discovered that the universe is ever expanding at a rate of ~20,000 meters per sec per million light years.In other words a galaxy traveling away from us at the arbitrary distance of 1 million light years ( a light year being the distance light can travel in one year ), will be moving at 20,000 meters per second , if the distance is 2 million light years that speed increases to 40,000 meters per sec. The speed of light = 299 792 458 meters per second so you don't have to worry too much about the Milky Way exceeding the speed limit.

Einstein and relativity.
The classical model of the casual observer ( you stand by at a neutral spot where you are not involved in the action taking place) was disproved by Einstein, he basically showed that there is no such place, a place of absolute rest, that any spot that we can observe from IS involved and any motion taking place is happening relative to the observer. Back to those two galaxy's moving away from us , you observe the first one and relative to you it is traveling at 40, 000 MPS, the closer one is moving at 20,000 MPS, yet if you were in the middle galaxy the speed of the farthest one would be 20,000MPS and the Milkey Way would be moving away at 20,000 MPS RELATIVE to you!

Lightspeed and weird stuff.
Einstein also showed that nothing can travel FTL (faster then light). All kinds of weird ( and predictable ) stuff occurs as you approach the speed of light. Time slows, things stretch in the direction of travel, the faster you go the more pronounced the effect. None of this is essential ( I don't think ) to understand your question, except the effect it has on objects speeding away from us. The important one being Doppler effect or redshift. As that galaxy speeds away from us the light shifts towards the red end of the spectrum, like a train as it approaches the whistle is pitched higher and higher as it rushes away it is lower and lower. Light shifts also with speed coming towards us it is blue shifted , traveling away redshifted. This matters because we can observe the light and measure the shift which gives us the speed of travel. ( away or towards us )

The Nexus.
Actually you are addressing two issues when it comes to gravity and the "acceleration" of expansion.
The gravity one touches on so many topics it would take books to understand it properly, but as to the major point..... gravitational attraction as a break...This is a much a problem as the expansion question...it's called the missing mass problem.The galaxy's behave in a way that requires more mass the we can see . they stay together and circulate in a way that requires as much as 75% more matter to be the way they are. With the existent laws ( good ole' Newton applies here )and observable matter they should fly apart. .. so we come up with things like dark matter , matter we cant see like black holes and more exotic stuff, theories ( some which sound more like a sound imagination rather then a grasp of reality ). And the answer IS>>> we don't know.

The accelerating Hubble constant is a relatively (hehe) new arrival, Einstein ( that name again?!) actually accounted for it as a "negative pressure" and called it "quintessence", he also called it " the greatest mistake in his life". O my God Einstien wrong??? EVERYONE in cosmology is working overtime on this one Tez (on this board ) Hawking,Thorne EtAl. The consensus in the majority is to reexamine the classical interpretation of Einstien ( as he accounted for it, even if he discarded it ), with the minority trying to invest in new strategies to explain it. And the answer IS>>> we don't know

The downside to both of these observed phenomon is it looks like we have a flat, open universe that will keep expanding forever.....so bring a book , it's gonna be a long night.

As for the question someone asked about space expanding..
The expansion of spacetime is self-inclusional...in other words your trying to set a "boundary" for the universe, but there is no boundry, the only "thing" that exists is the universe, but it is getting bigger. Your mind is trying to see whats outside..but there is no outside. Told ya some of this stuff is counter-intutive .
:wink8:

Hope that cleared it all up for ya . I hope I didn't sound condisending , I was trying to remain simple. If I got any major parts wrong , experts are invited to smack me.

[Samus]

Originally posted by Duncan
What boggles my mind is this. If the universe is everything that exists, including the planets, stars, galaxies and all that they contain; the entire cosmos, then what exactly is the universe expanding into? More space? Wouldn't that space then be considered part of the universe, which would make the universe infinite, and if the universe was infinite, how could it expand? I used to bug my college physics teacher with questions like this. From what I understand (someone correct me if I'm wrong), what is just on the other side of the edge of the universe is, by definition, nothing.

That said, I'm not sure if the universe truly is expanding, and if it is, what is is expanding into. Franko's omniverse? :) I don't think anyone knows with any degree of certainty.

Of course, the fundamental problem with cosmology is that it's all ancient history. The things we observe now happened very far in the past (as has been mentioned). We won't have accurate observations for what is going on at the edges of the universe for billions of years. That's a shame, because I bet it's really interesting.

[Michael Redman]

Maybe the universe isn't expanding. Maybe everything is just shrinking.

[HarryKeogh]

Originally posted by TillEulenspiegel
[BHope that cleared it all up for ya . I hope I didn't sound condisending , I was trying to remain simple. If I got any major parts wrong , experts are invited to smack me. [/B]

thanks alot. very helpful!

[SquishyDave]

I am an astronomy buff, but no expert, so I too should be smacked down if wrong, but this is how I understand the situation.

Einstein's theory ended up showing that the universe could not be static, and so he said, "NOOOOOOOO that's not right, I screwed up, I'll just add in a little constant here so that the universe doesn't have to move."

Of course looking at the evidence later he realised, "NOOOOOOO the universe is NOT static, it is expanding, my orginal theories all worked, I have to take out my little constant, I just made it up anyway so it's no big deal to remove. How could I have been so stupid?"

The question then became, would gravity pull all matter back together again, or would it not be enough and leave the universe constantly expanding? At this stage everyone KNEW that the universe was slowing down as it expanded, I mean it had to be, there was a huge push at the start from the big bang, then gravity was slowing everything down. SO either the universe started falling back to itself like a ball thrown in the air, or just kept going coz it got too far for gravity to pull back.

THEN came the big upset, through observation they noticed the universes expansion wasn't slowing down, hell it wasn't even staying the same, it was ACCELERATING!! Now at this point they said "Scientfically speaking, that aint right" How can something accelerate when it only had an initial push, and then gravity should have been slowing it down? And now we are here, today, everyone is scratching their heads and looking at each other for ideas.

There's some whacky ideas too at the moment, I don't pretend to understand some of them. Multidimensions have been mentioned.

The only thing that seems clear is that SOMETHING is pushing the universe further apart, but no one on this planet knows what it is. We will have to wait for the those astronomers and physicists to figure it out for us.

Hows that? :)

[CurtC]

G'day SquishyDave. I am also an armchair astronomer (I view Astronomy Picture of the Day (http://antwrp.gsfc.nasa.gov/apod/astropix.html) every day), and your explanation conveys my understanding perfectly.

I'd just add the small detail that the big upset, where they found the galaxies were accelerating away from each other, was *really* recently, like four or five years ago.

[SquishyDave]

Excellent point Curt. That's part of the reason why there are so many theories at the moment.

[peptoabysmal]

The part I still don't get about the Hubble Constant is, don't we need some sort of absolute speed that we are travelling at to measure the speed of other objects accurately? And if so, how do you measure that speed?

Abstract example:
What if we are actually travelling at Light Speed minus 50,000 MPS (I'm not saying we are, I would imagine we would start noticing things like blue stars on one horizon and red stars on the other at that speed)? If another galaxy would then accelerate to 50,000 MPS relative to us, would it disappear from our perspective because it reached light speed? (Of course, we woudn't know about it right away)

I'm a programmer, not a Cosmologist, so be gentle with me :)

[peptoabysmal]

Originally posted by Duncan
What boggles my mind is this. If the universe is everything that exists, including the planets, stars, galaxies and all that they contain; the entire cosmos, then what exactly is the universe expanding into? More space? Wouldn't that space then be considered part of the universe, which would make the universe infinite, and if the universe was infinite, how could it expand?

Am I looking at this all wrong?

To me, it makes logical sense that outside of the Universe exists absolute vacuum, absolute nothing, 0 dimensions. Not even 2D. In that way, nothing can continue on forever, because it goes actually nowhere, it has 0 dimensions. Our universe, in this scenario would have at least four dimensions and what we percieve as movement actually only takes place in perhaps the fourth dimension, thereby preserving the relationship to the outside vacuum which has 0 dimensions and from that vacuum's perspective every point in our universe is the same point.

But, like I said, I'm a programmer, not a Cosmologist, so I'm probably all wet on this one.

[wollery]

Originally posted by peptoabysmal
The part I still don't get about the Hubble Constant is, don't we need some sort of absolute speed that we are travelling at to measure the speed of other objects accurately? And if so, how do you measure that speed?

Abstract example:
What if we are actually travelling at Light Speed minus 50,000 MPS (I'm not saying we are, I would imagine we would start noticing things like blue stars on one horizon and red stars on the other at that speed)? If another galaxy would then accelerate to 50,000 MPS relative to us, would it disappear from our perspective because it reached light speed? (Of course, we woudn't know about it right away)

I'm a programmer, not a Cosmologist, so be gentle with me :)

Okay, I'll try to be gentle, unfortunately you're going to have to let go of any reliance you have on 3-dimensional Newtonian Mechanics.
The fundamental underlying principles of General Relativity are;
1. there is no absolute frame of reference,
2. what an observer sees can only be measured relative to their frame of reference.

This means that in your example it doesn't matter how fast we are travelling, if another galaxy is travelling at 50,000mps relative to us then we will see it travelling at 50,000mps. All velocities are relative, and no relative velocity can exceed the speed of light. Most importantly in our relativistic Universe you can't just add our velocity relative to galaxy A and our velocity relative to galaxy B to get the relative velocity between galaxies A & B. There are equations called the Lorentz Transforms which can be used to calculate this, but the relative velocity of A & B will be less than the speed of light!

OK now to your second post, when people say that there is nothing outside the Universe it doesn't mean that there is a boundary outside of which is some sort of Not Universe which contains nothing, it means that there is no such thing as outside of the Universe. The Universe defines it's own size and `boundaries' which don't include an edge or end. As noted earlier in the thread, the Universe does not exist in just 3 dimensions (or even just 4 for that matter) so thinking in 3-d terms such as inside and outside just isn't applicable.

Err, hope that helps a bit! :)

[davefoc]

A quibble:
TillEulenspiegel said:Einstein also showed that nothing can travel FTL (faster then light).

Einstein derived his special theory of relativity from the experimentally determined fact that the speed of light was constant in whatever frame of reference one was in. He did not show that nothing can travel faster than light.

It was the Michelson-Morley experiment that first experimentally determined the constancy of the speed of light.

The speed of light can be determined theoretically from Maxwell's equations based on certain statically determined parameters. Einstein might have been the first to argue that if the speed of light wasn't constant in all frames that the electrical laws that form the basis of Maxwell's equations would not be invariant with respect to the frame of reference.

[sorgoth]

Okay, just one question: Does light have momentum?

Lets say your on something that's moving at 40000 KM/H, and then you turn on a flashlight to make the light go in the same direction that the thing is going. Would light still go c, or c+40000?

[CurtC]

That's pretty much the essence of relativity. Physicists pretty much suspected in the 1800s that even if you're already going 40000 km/hr, when you turn on your flashlight, you'll see the beam going away at c. And a "stationary" observer would see the beam moving at c. The obvious question is "how can that be?". Einstein was the one who figured out how to combine the speeds into a framework that it consistent.

[davefoc]

Sorgoth asked:
Okay, just one question: Does light have momentum?

CurtC answered the second question.

The answer to the first question is yes. A photon of light has momentum which is proportional to its energy, which is proportional to its frequency.

Hence when a photon of light strikes something it imparts a force. This is the basis of the idea behind solar sails which were discussed in this thread:
http://www.randi.org/vbulletin/showthread.php?s=&threadid=24298&highlight=solar+sail

[TillEulenspiegel]

Answer to a quibble

Einstein derived his special theory of relativity from the experimentally determined fact that the speed of light was constant in whatever frame of reference one was in. He did not show that nothing can travel faster than light
You are approximately correct, Bradley determined the speed of light in 1779 based on the work of Ole Roemer in !676 . ( NASA has a good record of the Methology ) STR arose from both MMX's null outcome and Einstiens own intuition , his theories were not derived from any particular source but synthesized from expiremental data . MMX was designed to be a proof of the idea of a background field, force, wind that effected all objects traveling through it like a submarine being disposed to the vagaries of deep ocean currents when submerged. It was called the Aether. The MMX did not catalog any such phenomenon. ( some blame the fact that they only included the light travel time in two dementions or that the equipment they used was crude on the null results in light of recent re-conciderations to be the cause), being as that may , MMX had nothing to do with the absolute speed of light (as far as the constraints of the experiments purpose ) , but did give impetus to the idea of the lack of a plane of zero motion/reference. Einstein is SOLELY responsible for that intellectual jump he took even if it was based on the work of others.
The second part of the paragraph is patently wrong. Einstein and he alone showed the equivelentcy of matter and energy. He showed that the motion of particles at near relativistic speeds manifested strange properties of time and spacial dilation and did prove by that most famous equation that it would take infinite energy and infinity of time to reach that state.
If you ask a physicists what is the mass of a particle he will answer in terms of energy ( charge) a direct aspect of that equivelentcy.
Maxwell's view of the expression of his ( and Lorentz's) electromagnetic equations also have disparities that were addresses by Einstien and others in the field of electrodynamics which in turn saw the birth of quantum mechanics. And thus arose a most profound battle of Quantum Electrodynamics and classical relatively.

Gendlin's mid 80's critique of relitivity and localasation is a good starting point.

[davefoc]

deleted because I was confused when I wrote it. I think I understand better what TillEulenspiegel was saying now.

[davefoc]

TillEulenspiegel,
I believe that this is the statement that you said was patently wrong:

He did not show that nothing can travel faster than light.

Hmm, I think I disagree with you a bit here, although I stand to be corrected. Einstein started with the premise that the speed of light was a constant to an observer regardless of his frame of reference.

We are agreed that based on this assumption he derived his famous equation E=MC^2.

But how had he proved that the premise that was the basis for his theorizing was correct? We are in agreement that later experiments provided evidence that the predictions of his theories were correct, but what in his theories at the time he published them showed that nothing can travel faster than light?

On a slightly different subject you mentioned his role with regards to the beginning of quantum mechanics. Did this have to do mostly with his work on the photoelectric effect? Did the relativity theories have much to do with the beginnings of quantum mechanics?

Lastly, you mentioned Lorentz. How does he fit in? It seems like his transformations were a major step forward in the development of the special theory of relativity. Why doesn't he get more credit for that role?

[Earthborn]

Maybe...

The Big Bang was actually an implosion in reverse. Maybe it was actually the Big Crunch, but time is going backwards.

Or maybe...

The Universe is rotating in some weird multidimensional way, and this increase in expansion is actually a centrifugal force.

Oh, well, what do I know? :p

[BillyJoe]

It is not correct to say that the universe is expanding into empty space because there is actually nothing outside the universe not even empty space.
It is also not correct to say that there is nothing outside the universe because, as we know nothing is full of quantum fluctuations.
It is more correct to say that the universe is all there is and that when we say it expands we mean that the existing space of the universe is expanding.

BillyJoe
(Yeah, jump on me if I'm wrong as well)

[wollery]

Originally posted by Earthborn
Maybe...

The Big Bang was actually an implosion in reverse. Maybe it was actually the Big Crunch, but time is going backwards.

Or maybe...

The Universe is rotating in some weird multidimensional way, and this increase in expansion is actually a centrifugal force.

Oh, well, what do I know? :p
Interestingly, a few years ago myself and a couple of my fellow PhD students, after a particularly long stressful day and a couple of beers (it's hard being a student:D ) we decided that Einstein et al. were wrong and came up with what we described as the `Rotating Universe Splat Model'. Surprisingly the idea never really caught on! :roll:

[BPSCG]

Originally posted by CurtC
But a few years ago, it was discovered that the galaxies are actually *accelerating* apart. I think the first person to explain that can book his flight to Sweden. There's speculation about "pressure" from the quantum creation/annihilation of particles that goes on in empty space, described by the uncertainty principle, but I don't think this is past the point of speculation.
Okay, help me here, 'cuz me very confused. I remember from HS physics that F=MA, i.e., force = mass x acceleration.

Which my physics teacher used to demonstrate that if force = zero, then acceleration = zero.

But if the universe's expansion is accelerating, then either mass is decreasing or there is a force greater than zero pushing the mass around.

So what is it? Is the mass of the universe decreasing, in which case Einstein is wrong? Or is the mass of the universe remaining the same and there's some undetected force Out There somewhere? :confused:

[Dancing David]

Actually,
the space that the universe is composed of and the energy which reside in could have little to no effect on wether that space expands.

For one, it is not expanding because there was a big band, the big band plays the tune but it is not the reason for the expansion.

It could be that the universe is expanding despite the aggregate of matter and energy within it. It could be that space expands because it has to, imagine that really all the galaxies are relativly motionless, what is happening is that the space in between them is actualy expanding.

(If I get the smack down thats fine!)

PS There is also the Violent Barf secnario where the other universe had too much to drink and vomited out our universe, which led to the Big Splat.

[TillEulenspiegel]

Davefoc:
There has to be two caveats here. One is that ten, twelve or so years ago there wouldn't have much second thought about what were discussing here, with recent discoveries however we find the scientific community is re-examining proofs and theories over a hundred years old. There is a question "Was Einstein wrong?" that would have been considered heresy. The second is that much of the information we discuss here, in order to be expertly critical require the understanding of special mathematics of which I do not enjoy.In fact GRT proof consists of 10 complex, coupled, nonlinear partial differential equations that as far as I know remain unsolved ( to any complex degree)
So I guess we'll just muddle thru with topical semantics and metaphor


"But how had he proved that the premise that was the basis for his theorizing was correct? We are in agreement that later experiments provided evidence that the predictions of his theories were correct, but what in his theories at the time he published them showed that nothing can travel faster than light?"

By showing the equivalence of mass and energy SRT shows that the faster a particle travels the more mass (charge) it acquires approaching infinity at 0.9999999% SOL also the time dilation at that speed is extremely pronounced , the "fact" is not only cannot a mass travel at FTL it cannot travel at SOL. There are all kinds of gimme's here tho..massless particles , virtual particles, Inflationary theory that includes Variable SOL, that states that the original SOL was closer to 270,00 MPS in the first inflationary phase after the big bang but we're talking about the original time of publishing yes?

"On a slightly different subject you mentioned his role with regards to the beginning of quantum mechanics. Did this have to do mostly with his work on the photoelectric effect? Did the relativity theories have much to do with the beginnings of quantum mechanics?"

His role was a antagonistic ( A.E. "God does not play dice...God is not malicious"..N.Bohr " Who is Einstien to tell God what to do?" ) but not only did he argue with the idea , he incorporated much of the same basis for QFT in his work as well. The Photoelectric effect was a quantum explanation of the photon as a discrete entity , won him. a Nobel prize, but he rejected the probibilistic and wavelike nature of QFT in general. It was others who gave impetus to the idea of QM, Plank, Bohr, in fact N.Bohr's best contribution seems to be the rather then interpretation of Maxwell's equations that predicts the shedding of EMR from an electron because of motion, he explained that there were discrete levels or orbits of the electron , which later understanding changed to a "cloud of probability", depending on energy levels. His Copenhagen interpretation, coelested a group of like minded folks and fired the rise of QFT

Maxwells field equations did not account for motion , that was the difference between Lorentz and A.E.'s respective approaches. That difference gave rise to A.E.'s take on inertial frames of reference. I.E. no plane of absolute rest. They are roughly equivelent in nature , but A.E.'s approch was considered more ontologically correct


"Lastly, you mentioned Lorentz. How does he fit in? It seems like his transformations were a major step forward in the development of the special theory of relativity."

Lorentz arrived at basically the same place that Einstien did ( also based on Maxwell's Field equations), but his flaw (?) was he embraced the discredited solid ether continuum idea. Which as I stated previously must be rethought in light of recent events...even tho the majority seem to think if the aether does exist , it must be a dynamic medium. Where that leaves Lorentz remains to be seen.

hope that muddies things conciderably =)

[davefoc]

TillEulenspiegel,
Perhaps I am pursuing this beyond the point of usefulness, but the distinction is important an important one I believe.

I would suggest this by way of analogy:

Newton created a formula for gravitational force based on observation and supposition. From that formula and some mathematics that he invented he predicted the orbits of the planets.

Is it correct to say that he proved his gravitational force formula. I don't think so. He used it to make some predictions about the orbits of the planets which were verified to be correct. The validity of his predictions gave credence to the notion that his formula was correct, but he did not prove it correct.

In similar way, Einstein created the theory of relativity based on the observation of others that the speed of light seemed to be constant. Based on his assumption that those observations were correct he made a number of predictions that eventually led to his theory about the equivalence of mass and energy. Subsequently these predictions have been verified, thus leading credence to his theories and the basis of those theories, in particular the constancy of the speed of light.

But no place in Einstein's theories is there any proof that the speed of light is constant or what makes it so. Although I can understand that you might reasonably disagree wtih this, I continue to believe that my statement that "he (Einstein) did not show that nothing can travel faster than light" is correct.

[TillEulenspiegel]

Well I suspect we're doing a semantical dance here and ,if that's the case, then you are correct. A.E. did not PROVE the inability of mass to travel FTL. He did prove that mass at relativistic speeds act in a way that if it followed the trend at observable speeds would wind up at a point where it would require infinite energy and infinite time. Leaving aside the time dilation effect, that would mean on the energy side, the force required would require all the energy available ( both in the forms of energy and mass) in the universe to accomplish. I cannot guess such a mechanism that could do that as it would ultimately require that itself be added to the store of energy to accomplish its task . ( a regression that seems logically unallowable )Besides that condition would preclude an observer as we would also be added to the energy stockpile. So Prove, no, show, indicate, exemplify by inference, Yes. Guess that's why it's still called theory