Can something move faster than light?

[ldsoftwaresteve]

Just an observation, one that has been made by every person who has ever thought about this.....
Since speed is relative, something has to be wrong with the following picture:
A and B are two black holes at the centers of two galaxies. Each black hole is ejecting matter precisely in the same line, one that colides head-on with the matter being ejected from the other, thereby giving us the case of particles traveling toward each other at well over the speed of light.
I'm assuming that such a case exists. I'm assuming that the matter is being ejected at or near the speed of light.
So how is it that theory says they don't? What theory is so powerful that it can overide such an obvious, or at least possibly obvious flaw?
If the theory is correct, then our simple perception of this situation is flawed. That also means that our perception of existence is fundamentally flawed.
Or, maybe it just means that mine is.
Perhaps the flaw is in thinking that straight lines exist. Or perhaps the limit is bogus.

[Qfwfq]

There's no need for remarks like:

Originally Posted by lindagarrette

This is a silly poll.

[Qfwfq]

Originally Posted by ldsoftwaresteve

Each black hole is ejecting matter precisely in the same line, one that colides head-on with the matter being ejected from the other, thereby giving us the case of particles traveling toward each other at well over the speed of light.
I'm assuming that such a case exists. I'm assuming that the matter is being ejected at or near the speed of light.
So how is it that theory says they don't? What theory is so powerful that it can overide such an obvious, or at least possibly obvious flaw?

According to SR, in the coordinates of each particle, the other is travelling at a slightly greater speed than in the coordinates of the black holes.

Such cases do exist. They are even created with particle accelerator facilities that can produce two beams and make them collide head on. Measurements are analysed according to Lorentz-covariant theories and things match up. No flaw.

[TheFaithfulStone]

Originally Posted by chendoh

'If man can break the speed of sound, then why can it not be done with light?'

Because the speed of sound is not a fundamental physical property of the universe.

It's an entirely different set of problems - it doesn't require brand new physics to go faster than sound, just brand new thrust.

That said, I like to believe it's possible. There are a few steps to breakthrough technologies like this.

1) Theoretically it's possible, but it would never happen.
2) Okay, we can make it happen with ungodly (but achievable) amounts of energy/technology/unobtanium.
3) Nature already does it.
4) We pull it off.

I'd say we're at step 1 with the whole FTL thing - see Alcubierre, Kip Thorne.

TFS

[CraigD]

Originally Posted by ldsoftwaresteve

A and B are two black holes at the centers of two galaxies. Each black hole is ejecting matter precisely in the same line, one that colides head-on with the matter being ejected from the other, thereby giving us the case of particles traveling toward each other at well over the speed of light.
..
So how is it that theory says they don't? What theory is so powerful that it can overide such an obvious, or at least possibly obvious flaw?

This is a very good question, and a commonly asked one, for which there’s a straightforward answer.

Special Relativity doesn’t forbid what ldsoftwaresteve describes. An observer can measure the distance between 2 objects approaching or receding from one another such that it (as the observer measures it) decreases or increases at a rate greater than the speed of light (c). That SR forbids is that an observer can measurement the distance between it and any other object as changing at a speed greater than c.

This isn’t hypothetical. The greatest observed redshifts for distant objects implies a relative speed greater than .5 c. Since there’s no evidence that we, as observers, are particularly central to the universe, an observer at one of these distant object would measure us as receeding at a speed greater than .5 c, and other distant object in the opposite direction also receeding at a speed greater than .5 c. We can also see this object, but do not see it receeding from us at greater than 1 c.

Here’s an example, with a crude asciiart sketch

<-(.60)-<A      B           C>-(.60)->
A               B>-(.60)->  C>-(.88)->

A>-(.60)->      B           <-(.60)-<C
A               B<-(.60)-<  <-(.88)-<C

As observed by B, A and C are moving away from one another in opposite directions at speed .6. As observed by A, B is moving away at .6 c, C at a little over .88 c. The second example shows the same, but with the object moving toward one another. Without SR, we’d expect A to see C moving away or toward it at 1.2 c.

The formula for “Relativistic speed addition” is V = (V1 +V2)/(1 +V1*V2), where V, V1, and V2 are in units of c. It can be derived using simple algebra without much difficulty from the SR’s equivalance principle, and is supported by experimental evidence to a very high precision.

[CraigD]

Originally Posted by TheFaithfulStone

Because the speed of sound is not a fundamental physical property of the universe.

It's an entirely different set of problems …[/quote]I agree, TFS.

- it doesn't require brand new physics to go faster than sound, just brand new thrust.

Actually, it doesn’t take any thrust to break the sound barrier, just gravity and streamlining.

I’ve long found in interesting, and surprisingly little known, that large manmade objects were made to exceed the speed of sound simply by being dropped from airplanes, in late 1944 by the US, and, rumor has it, earlier, by Germany. (see http://web.archive.org/web/200503081...housandMPH.htm – unfortunately, this is the only internet reference
I can find, and its graphics are missing) Projectiles, from small bullets to large artillery shells, had been breaking the speed of sound for many years before then, but were not as useful for testing the effects of supersonic flight as a nice, 8 foot-long missle dropped gently from a B-29 at 40,000 ft.

[mocnarf]

Question:

If an observer, could see three fixed points "A" "B" and "C" and these three points are aligned on a straight line with a fixed distance between "A" and "C", with point "B" in the middle between point "A" and point "C". Now, suppose a photon is shot at point "B" from both point "A" and "C" at the same time. The observer would see both photons travelling towards point "B" at the speed of light.
Question: At what speed would the observer see the distance between the photons shrink?

Does this not set up a conundrum? If the observer see's the distance shrinking between the two photons occurring at the speed of light, then the speed of the photon's travelling towards point "B" must be 1/2 the speed of light. Or, the distance between point "A" and point "C" must be increasing at 1/2 the speed of light, which would mean that there can be no fixed distance between two points.

Your thoughts.....?

[Zythryn]

As I recall, information is already able to break the speed of light. If someone has more information on the following please feel free to chime in.

I recall reading tests done with the quantum state of two particles. The two particles could be 'bound' at a quantum level. Then when the two particles were at a greater distance from each other, altering the quantum state of one would simultaneously alter the state of the other.

While this is not moving matter, it is moving information which I suggest qualifies as 'something'

Mark

[CraigD]

Originally Posted by mocnarf

If an observer, could see three fixed points "A" "B" and "C" and these three points are aligned on a straight line with a fixed distance between "A" and "C", with point "B" in the middle between point "A" and point "C". Now, suppose a photon is shot at point "B" from both point "A" and "C" at the same time. The observer would see both photons travelling towards point "B" at the speed of light.
Question: At what speed would the observer see the distance between the photons shrink?

The observer would see the distance between the 2 photons shrinking at 2 times the speed of light (c).

Does this not set up a conundrum?

No. There are some technical details necessary for an observer to “see a photon” – there must be at least a short pulse of many photons, and some sort of mechanism to send some photons toward the observer rather than toward C (such as a diffuse reflective cloud between A, B, and C), and the observer must account for the time it takes light to travel between the moving pulse and him – but these issues can be resolved with simple, non-relativitistic mechanics.

If the observer see's the distance shrinking between the two photons occurring at the speed of light, then the speed of the photon's travelling towards point "B" must be 1/2 the speed of light.

Since the observer sees the distance shrinking by 2 c, the speed of the photons remains the expected 1 c, and the conundrum is resolved.

Good questions, mocnarf!

[TheFaithfulStone]

Originally Posted by Zythryn

As I recall, information is already able to break the speed of light. If someone has more information on the following please feel free to chime in.

Nope - there is now way to send information in quantum entanglement. For one, as Will pointed out to me a while back in this thread it isn't nessecarily true that the wavefunction collapse is a causal effect. It's impossible at relativistic speeds to talk about who measured "first." so the casuality of the relationship is in question, anyway.

Let's say that we have two entangled particles, and I measure mine. The result is random. Now I know what the measurement on yours will be - before you measure it (in my frame) but you have no way of knowing what this is. When you measure yours you have no way of knowing whether you've collapsed the wavefunction, or whether I already have. Even if you could solve the program (say with an equidistant pulsar...) you'd not be able to communicate with this method.

In any case, there isn't any way I can control what answer I get - so If I measure the spin and get 2-1-2-0-1 - you'll know what the answer is, but it won't be meaningful to you, because it's impossible for me to encode any information in a bunch of random q-bits.

Not that that was particularly lucid, but there you are. People smarter than I can explain this better.

TFS