Question about relativity theory

Hey, I was reading Einstein's relativity theory, but there's something that I read about lightspeed that seems to be, well, wrong.
The part where he says that the lightspeed is a constant, doesn't matter where it is, it will always be the same.
Look this hypothetical situation: if we could, somehow, put a light source to travel at 99% of the lightspeed, and them we could, somehow, watch this light while traveling at the same speed as the light source. Ok so far, according to Einstein, we would see the light at 300,000 km/s. But, at the same time, we have a person observing and measuring the speed of the light generated by the source traveling at 99% of the lightspeed, but he is standing still. There, he would see the source travelling at 99%, and, according to Einstein, the light generated by it would be at 100% the lightspeed. Well, that would be 1% for us who are watching at the same speed that the source. There, the lightspeed wouldn't be a constant.

I'm right with my thoughts? Share your opinions here please. Thanks.

In matters of physics it is never a good idea for someone to assume he is smarter than Einstein. If you won't trust Einstein, trust me. He got it right.

Instruments we have today have projected light to be a constant at 300,000 km/s. Light travels at that speed...so that is the constant..the speed of light. If you made something travel less than that speed it would not be travelling at the speed of light. And Einstein was a genius...he performed many experiments about Relativity and was pretty accurate in all of them, so I would not doubt him. Hope that clears it up.

Originally posted by Anyndur
The part where he says that the lightspeed is a constant, doesn't matter where it is, it will always be the same.

I think you missed the part where he said "in a vacum." In fact, light speed varies depending on the medium (which Einstein indicated.)

Look this hypothetical situation: if we could, somehow, put a light source to travel at 99% of the lightspeed, and them we could, somehow, watch this light while traveling at the same speed as the light source. Ok so far, according to Einstein, we would see the light at 300,000 km/s. But, at the same time, we have a person observing and measuring the speed of the light generated by the source traveling at 99% of the lightspeed, but he is standing still. There, he would see the source travelling at 99%, and, according to Einstein, the light generated by it would be at 100% the lightspeed. Well, that would be 1% for us who are watching at the same speed that the source. There, the lightspeed wouldn't be a constant.

Actually, Einstein had TWO theories of relativity; a General Theory of Relativity and a Special Theory of Relativity. I take it that you haven't yet got to the point where he mentions the distortions of time at that speed? What you seem to be talking about is sort of a Xeno's paradox... I think.

If so, that's addressed in the writings of Einstein and those who did other developmental work on it.

Remember, that the Theory of Relativity didn't just QUIT with Einstein. He started it out and there's been a whopping boatload of papers written about it since then. To see what current thought is, try the new google search engine at scholar.google.com... :
Here's what comes up for some of that


ask.yahoo.com...



Similar to Xeno's paradox, if I'm understanding you correctly.

However, Einstein's theory of relativity isn't

Originally posted by Chieftian Chaos
And Einstein was a genius...he performed many experiments about Relativity and was pretty accurate in all of them, so I would not doubt him. Hope that clears it up.

What experiments are you talking about here?

If I remember correclty he used deductive method, made up a theory and found evidence to support them. Only thing I can think of is the eclipse.

Surf

Remember, that while the speed of light is a constant, the "flow" of time changes the faster your relative speed is.



[edit on 18-11-2004 by HowardRoark]

Well, what's really odd is that it's experimentally correct... light's always travelling the same speed relative to an observer, so the light shall be travelling away from the observer who is travelling at 0.99c at a speed of c, but the person standing apparently stationary (from their reference point) will also see it travelling at c from them. How does it work?

Uh.... I'd attempt to explain if I didn't have a hang over, but I don't think it'd make sense from me. It seems it shouldn't work but does, hell, it doesn't even make sense. It's true though.

Science is far stranger than you realise, learn about Quantum Physics, it reads like a drunkard wrote the rules...

I had to read your question a few times to understand it: I think I understand it correctly now and as such I think you misunderstood what Einstein was really saying.

You see, light is made of particles called photons. These photons don't have any actual mass and as such they travel at the speed of light; if you were able to slow down a photon by adding mass, then my understanding would be it would no longer be a light wave.

Thus light as it's self cannot be slowed without adding mass, light may appear to travel slower, but that is only because photons travel from atom to atom, an atom can retain a photon for a period and then release it but at the it's orginating speed of 186,000 miles per second.

That is why the speed of light remains constant at least in my understanding and in laymen terms.

Recent experiments have slowed "light" to almost a stop. It is not a constant. Light has an "acceleration" component that we can not yet measure. That acceleration can and has been varied based on the medium light is passing through. The "constant" assigned to the speed of light makes our calculations simpler, thats all.

www.msnbc.com...

www.msnbc.com...

After reading the articles you posted it would appear as I stated light cannot be slowed down without adding mass.

And that's exactly what they did, they slowed down a photon by adding the mass of the atom, thus creating a new particle, a polariton. Hence it's no longer a photon or a light wave, once they release the pull of additional mass from the atom the polariton looks like it becomes a photon again and regains it's pace.

It's seems like either the author of the article just wanted to catch some attention or they didn't really understand what they were talking about. Some people just don't understand physics, others distort it, but it still seems as if Einstein was correct.

[edit on 19-11-2004 by hanburu_juuboku]

The simple fact that you can alter the mass of a light wave means there are different "states" of light and therefore the speed of "light" can not be constant. Visible light waves are a small segment of the electromagnetic spectim. Visible "white" light is made up of all specific "colors" of light. It disburses quickly because the "waves" bump into each other. The extention of this is that different "colored" light travels at different speeds. When we have "clocks" that are fast enough we will find different speeds.

Anyndur's question
The problem is that you're still using Galilean relativity. If I understand you correctly, you are saying this:

There are two observers, A and B. A sees B moving away from him with a speed of 0.99c. B emits a beam of light in the direction he is travelling in. According to relativity, both A and B see the light moving with c. However, because B is moving at 0.99c relative to A, A observes the relative speed between the light and B to be 0.01c. This means that for B the speed of light can't be c.

.

Let's start by saying that all of this happens in a vacuum. It is true that A observes the relative velocity between the light and B as 0.01c. However, this doesn't mean that for B the speed of light is 0.01c. There are two reference frames here, A and B.

In Galilean relativity, the relative velocities don't change when you change reference frames. If two cars move at the same speed next to eachother, their relative velocity s zero. A pedestrian would measure the same relative velocity.

In special relativity, velocities transform in a different way. The formula is different: If you add two velocities, v and w together you get u = (v + w)/(1 + v*w/c^2). John Baez explains the formula here. For this case, we get a subtraction of two velocities in A: c for the light and 0.99c for the speed of B. This gives us: (c - 0.99c)/(1 - 0.99c*c/c^2) = c.

How can you explain this result? Like some have said above, the rate of time is different for B. Both observe that the other has a slower rate of time.

On testing the theory
This formula follows automatically from the constant speed of light c. Therefore, you can't use it to prove that the theory is correct. You only prove that the theory is selfconsistent.

Special relativity had to verified in other ways. The evidence includes the famous Michelson-Morley experiment, relativistic mass change in fast-moving particles and time dilation in cosmic radiation. If special relativity didn't approximate reality to a larger degree, no particle accelerator would work.

On the speed of light in a medium
The group speed of light is slower in a medium. Although the actual photons still move at c, they are absorbed and emitted again all the time. This makes them move slower. In our macroscopic world, it seems like the light has become slower.

With very high refractive indices, you can slow the speed of light a lot, even freeze it. I think that this is was what the experiments that DrHoracid talks about have done. I don't really understand how the experiments that transmits pulses faster than light work, though.

[edit on 19-11-2004 by amantine]

the speed of light would travel the same always to the human eye for we have only limits of recieving capabilities.if light was surpressed like in a black hole then the speed might change due to the fact that light is pulled away from it source.well some parts of the universe where we dont understand dark matter yet or opposites in physics well we need more time to formulate.there is lots to still study.if we could use light to travel with mass we might have more info.

I read the above posts and I don't disagree with you.
I just look at things a little differently.
I studied physics and quantum mechanics back when I was like nine on through to my early twenties. The drawback is I have expanded on ideas far more unique and complex than anything I've come across. Unfortunately I abandoned almost everything for more than a decade so I admit that I may be out of touch with modern day ideals.
Not to mention the fact that my head literally throbs now when I try to make my brain explain and understand all the equations and reasonings of complexities I once knew.


Edited - I had to sit down and think about things; rather than double post I'm just going to edit this one.

First of all math is flawed so you cannot use traditional mathematics to truly understand higher dimensions.

At best we use 2 dimensional math to solve 3 dimensional problems, yet the known universe consists of perhaps 9 to 12 or more dimensions.

At best we can only struggle to understand these higher states of being in a primitve 2 dimensional math.

To best understand this; imagine that you are a 2 dimensional being and a 3rd dimensional being is trying to explain that the 3rd dimension consists of a finite amount of 2 dimensions stacked up one another. In such limited understanding how could you, a 2 dimensional being, understand the concept of why we an atom's placement can be predicted at any specific time, granted the fact that in 2 dimensional terms atoms would appear to constantly be stacked upon one another. Thus the concepts of a 3rd dimension may never truly be understood by a lesser dimensional being; thus this is why light "appears" to slow down but in reality it maintains it's constant.

Let me explain. Let's say time is a fourth dimension, now granted we permit a 3rd dimensional interaction with a fluidic flow to allow time travel. One would assume the river of time would flow backwards and fowards but in such cases paradoxes would run rampant. Now let's still consider that time is parallel to us, but still fluidic thus it still runs back and fourth, yet in being parallel let's say that time is a dimension we do not interact with. At best it is a reference. In such a case time would always flow foward for us thus eliminating paradoxes yet maintaining the concept of a multiverse - (granted that the multiverse is also flawed because if string theory holds true in dictating a sort of universal connection then appearantly there aren't any visible boundries, thus the multiverse is more like a unified verse.

Also before you start throwing hypercubes in my direction, consider that these cubes may only "appear" to connect on lower dimensional levels.)

Anyway stay with me, here's how it works:
When John Doe travels back in time, he only appears to travel back in time; in actuality he is in both the past and the future; this is possible on the quantum level. Thus whatever he does, he will never affect the future; because he doesn't not interact with the fourth dimension; he only references it as a specific point.

In the fourth dimension time flows foward and backward, but as a "safety feature," we only view foward time, even when it appears we are traversing backward in time.

As such regardless of the viewpoint from a 3rd dimensional being, the reality is that in a full four dimensional world and/or above, 3rd dimensional actions do not influence 4th dimensional outcomes.

Man's concept of time is purely egocentric, at best it's like the question of whether a tree will make a sound if it falls in the forest without any one around to hear it. A dumb question to say the least because the laws physics on every level dictate that is will, hence the laws of physics do not stop for any man. It's man's egocentrics that lead him to believe that they may.

So in conclusion light regardless of wavelength or color or viewpoint cannot be slowed. In the fourth dimesion it would travel at a constant speed. The only "thing" ever effected is the 3rd dimension, and that "thing" is only man's concept of time.

The mistake I see being made on this thread is the lack of understanding that time is not a variable in a problem, time is the solution of the problem, in an essence time is the solver of the problem.

Now granted this may be considered a "crackpot" theory, but in reality it makes sense to me.

If you think my theory is weird, there are scientist who do not accept any concept of time. I've read of scientist that believe time in it's self doesn't move, thus all points are infinte, hence they believe our conscious is our real vehicle of mobility.

So believe what you choose; I'm just stating what I think.


[edit on 20-11-2004 by hanburu_juuboku]

There is so much misinformation on this board about physics, it is really sad.

After browsing this forum for a couple of years and just now posting, I have seen an incredible amount of just plain wrong information about physics that I often wonder if some of you have ever had a class in newtonian physics, let alone even modern physics...

sorry for the rant....

To the main reason for this post:

The speed of light is constant.

You can send a pulse faster then light, just as you can make an electric and magnetic field propogate faster then the speed of light...this does not mean you can transfer information faster then the speed of light.

Originally posted by sre2f
You can send a pulse faster then light, just as you can make an electric and magnetic field propogate faster then the speed of light...this does not mean you can transfer information faster then the speed of light.

Yeah...

Good example is that if you would take laser pointer and swing it fast, at certain distance dot would move with bigger speed than c.
But you couldn't transfer any information with bigger speed than c because those photons forming laser's dot still move at lightspeed.

Originally posted by hanburu_juuboku
I may be out of touch with modern day ideals

Have you tried the new Google search engine? scholar.google.com...

.

First of all math is flawed so you cannot use traditional mathematics to truly understand higher dimensions.

WHICH math is flawed? The algebras (including the algebras involving infinities)? Quantum mechanics? How are they flawed?

At best we use 2 dimensional math to solve 3 dimensional problems, yet the known universe consists of perhaps 9 to 12 or more dimensions.

I think you may have missed out on some mathematical developments in the past decades. Mathemeticians don't use "2 dimensional maths to solve 3 dimensional problems." In fact, here's a link to a recent paper that discusses gravity theories in more than four dimensions:
adsabs.harvard.edu...

...and one of thousands of papers on n-dimensional topology:
portal.acm.org...


...and so on and so forth, ad nauseum.

To best understand this; imagine that you are a 2 dimensional being and a 3rd dimensional being is trying to explain that the 3rd dimension consists of a finite amount of 2 dimensions stacked up one another.

Ah, the old "Flatland" concept. A wonderful book, but of course mathematics had passed that point early on.

In such a case time would always flow foward for us thus eliminating paradoxes yet maintaining the concept of a multiverse - (granted that the multiverse is also flawed because if string theory holds true in dictating a sort of universal connection then appearantly there aren't any visible boundries, thus the multiverse is more like a unified verse.

String theory has been replaced by the Brane constructs. As you say, your reading may not be current. (for those not familiar with branes, they're sor of explained for the layman here: www.th.physik.uni-frankfurt.de... Don't kid yourself that the theory is as simplistic as the article explains or that the math is doable at a high school level.)

The mistake I see being made on this thread is the lack of understanding that time is not a variable in a problem, time is the solution of the problem, in an essence time is the solver of the problem.

I don't see that. From what I read, time could be a variable in any of the discussions. We just haven't gotten into the hard maths yet.

This is a good question; it's one of those mind-paradoxes that Einstein himself had to figure out how to resolve to make his theory consistent, so nice job asking.

amantine's answer is right: observer A sees the beam of light travelling @ c, so in one second FOR OBSERVER A the light's moved ahead 300,000 kms.

observer B sees the beam of light travelling 300,000 kms/sec relative to him, so in one second FOR OBSERVER B the light's moved ahead of him 300,000 km. The catch, of course, is that that one second for observer B has lasted quite a bit longer than that one second for observer A.

if you want a more precise answer, i'd suggest taking it over to www.physicsforums.com...; there's a lot of very knowledgable people on that site.

Originally posted by DrHoracid
The simple fact that you can alter the mass of a light wave means there are different "states" of light and therefore the speed of "light" can not be constant. Visible light waves are a small segment of the electromagnetic spectim. Visible "white" light is made up of all specific "colors" of light. It disburses quickly because the "waves" bump into each other. The extention of this is that different "colored" light travels at different speeds. When we have "clocks" that are fast enough we will find different speeds.

Congratulations... you got it all completely wrong.
They all proceed at same speed... whether or not they are visible light, X-rays, UV, gamma, IR or radiowaves.
It's frequency/wavelength what is different.

Let's imagine that you take army company and tell it to march.
If everyone takes equal steps then company marches nicely. (it's like laser, every photon takes steps with same length in same pace)
Now lets tell some of them to take different steps, the more there is individuals taking different steps, the better. After that tell them to start marching.
Wavelength is like length of step and frequency is pace.
Speed is always same, its just that photon has to take bigger amount of smaller steps in same time and vice versa.


Is the speed of light constant?
How do scientists slow light down?
Why doesn't gravity change the speed of light?
Can I communicate faster than light?
Is light of different colors affected differently by gravity?

The Theory of Relativity
Why can't relative velocities add up to more than the speed of light?

Originally posted by Anyndur
Hey, I was reading Einstein's relativity theory, but there's something that I read about lightspeed that seems to be, well, wrong.
The part where he says that the lightspeed is a constant, doesn't matter where it is, it will always be the same.
Look this hypothetical situation: if we could, somehow, put a light source to travel at 99% of the lightspeed, and them we could, somehow, watch this light while traveling at the same speed as the light source. Ok so far, according to Einstein, we would see the light at 300,000 km/s. But, at the same time, we have a person observing and measuring the speed of the light generated by the source traveling at 99% of the lightspeed, but he is standing still. There, he would see the source travelling at 99%, and, according to Einstein, the light generated by it would be at 100% the lightspeed. Well, that would be 1% for us who are watching at the same speed that the source. There, the lightspeed wouldn't be a constant.

I'm right with my thoughts? Share your opinions here please. Thanks.

Nope, you are wrong.

What Einstein actually said is that light is MEASURED 100% constant in different frames of reference. He did not say that light travels with constant speed.

So, if you are an observer standing still, watching a beam of light travelling at 99% of C, the images coming toward you, made of light, will travel with the speed of light.

In other words, you will watch the changes with the speed of light, but light will actually travel slower. So you will actually be able to see the light beam edge.

On the other hand, if you moved, let's say on the opposite direction, with speed C, you would not see anything, because light from the other beam would never catch you.

If you moved with speed less than C, let's say 95%, you would catch a glimse of the other beam, as if it was almost frozen in time, because light from the other beam would catch you slowly.

The tricky part lies in the concept of 'observing'. In order to observe something, a particle, let's say a photon, would have to travel from the source to you. When you observe a beam of light, you don't actually observe the beam of light, but the photon particles are accepted by your eye with a delay. These photon particles that got away from the light source travel at C, even if the light itself moves in less than C.