Weird physics question

Diopos · 11-16-10, 11:04 AM

Quote:

Originally Posted by Gargamel

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An object already going light speed, could in theory stay at that speed if they don't encounter any drag. In that same theory, objects could go faster than the speed of light, IF they began that way. But where would such objects come from?

The future ?

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tater · 11-16-10, 11:34 AM

For a vibration in the string, the speed depends on the mass and tension on the string (it's a transverse wave). It will be less than c.

For a pull, the string will stretch, and then the wave propagates like sound (longitudinal wave) and will move at the speed of sound in the media.

BTW, doesn't matter if you replace the string with a neutronium rod. Still takes time (more than light) to propagate.

the_tyrant · 11-16-10, 11:35 AM

Quote:

Originally Posted by tater

For a vibration in the string, the speed depends on the mass and tension on the string (it's a transverse wave). It will be less than c.

For a pull, the string will stretch, and then the wave propagates like sound (longitudinal wave) and will move at the speed of sound in the media.

thanks

Gargamel · 11-16-10, 09:29 PM

Quote:

Originally Posted by tater

BTW, doesn't matter if you replace the string with a neutronium rod. Still takes time (more than light) to propagate.

But thats not the point, the hypothetical string has no stretch and is completely static. A stick with infinite length, no stretch, and no flex, the moment one end is moved, the other moves too.

Diopos · 11-16-10, 09:48 PM

Quote:

Originally Posted by Gargamel

But thats not the point, the hypothetical string has no stretch and is completely static. A stick with infinite length, no stretch, and no flex, the moment one end is moved, the other moves too.

Relativistic length contraction: Link
Or to put simple, in the end, light always wins!

Until the next theory is discovered ...

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Gargamel · 11-16-10, 09:58 PM

Quote:

Originally Posted by Diopos

Relativistic length contraction: Link
Or to put simple, in the end, light always wins!

Until the next theory is discovered ...

,

From your Link:

Quote:

This contraction (more formally called Lorentz contraction or Lorentz–Fitzgerald contraction) is usually only noticeable at a substantial fraction of the speed of light;...........At a speed of 13,400,000 m/s (30 million mph), the length is 99.9% of the length at rest; at a speed of 42,300,000 m/s (95 million mph), the length is still 99%

Since we are dealing with speeds of no more than that of pushing a pencil, lengthwise, across a table, this theory has no application in this scenario.

Diopos · 11-17-10, 05:09 AM

Quote:

Originally Posted by Gargamel

From your Link:

Since we are dealing with speeds of no more than that of pushing a pencil, lengthwise, across a table, this theory has no application in this scenario.

In the link, paragraph "Paradoxes" as regard to the concept of rigid bodies.

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TarJak · 11-17-10, 05:43 AM

I may be wrong, but the string in the OP exists at both points a and b at the same time. Depending on the relativity of the observer, the light will either arrive before, after or at exactly the same time as the string movement is felt. It's all relative.

Gargamel · 11-17-10, 06:13 PM

Quote:

Originally Posted by Diopos

In the link, paragraph "Paradoxes" as regard to the concept of rigid bodies.

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All of the paradox's refer to objects that are undergoing length contractions. Our 'stick' is not moving fast enough to undergo this phenomenon.

TLAM Strike · 11-16-10, 01:12 PM

Quote:

Originally Posted by Diopos

The future ?

.

Actually you are right. As I understand it Tachyons travel back in time as they travel faster than c.

Diopos · 11-16-10, 01:41 PM

Quote:

Originally Posted by TLAM Strike

Actually you are right. As I understand it Tachyons travel back in time as they travel faster than c.

I know. I was born in 2055. !

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Aramike · 11-16-10, 07:01 PM

It should be noted that tachyons themselves are highly speculative, theorized particles.

Raptor1 · 11-16-10, 07:06 PM

Quote:

Originally Posted by Aramike

It should be noted that tachyons themselves are highly speculative, theorized particles.

Of course, but I think the point was that relativity doesn't actually forbid something from going over the speed of light, you just can't accelerate anything to the speed of light in the first place.

Aramike · 11-16-10, 10:46 PM

Quote:

Originally Posted by Raptor1

Of course, but I think the point was that relativity doesn't actually forbid something from going over the speed of light, you just can't accelerate anything to the speed of light in the first place.

That's true for anything with information or mass. However, we can routinely violate c regarding massless particles and radiation.

Raptor1 · 11-17-10, 06:28 AM

Quote:

Originally Posted by Aramike

That's true for anything with information or mass. However, we can routinely violate c regarding massless particles and radiation.

Ordinary massless particles can routinly go faster than light in a vacuum?

11-16-10, 11:34 AM	#2
tater Navy Seal Join Date: Mar 2007 Location: New Mexico, USA Posts: 9,023 Downloads: 8 Uploads: 2	For a vibration in the string, the speed depends on the mass and tension on the string (it's a transverse wave). It will be less than c. For a pull, the string will stretch, and then the wave propagates like sound (longitudinal wave) and will move at the speed of sound in the media. BTW, doesn't matter if you replace the string with a neutronium rod. Still takes time (more than light) to propagate.

11-17-10, 05:43 AM	#8
TarJak Fleet Admiral Join Date: Jul 2006 Location: Sydney, Australia Posts: 17,052 Downloads: 150 Uploads: 8	I may be wrong, but the string in the OP exists at both points a and b at the same time. Depending on the relativity of the observer, the light will either arrive before, after or at exactly the same time as the string movement is felt. It's all relative.

11-16-10, 07:01 PM	#12
Aramike Ocean Warrior Best of SUBSIM Chairman Join Date: Dec 2008 Location: Milwaukee, WI Posts: 3,207 Downloads: 59 Uploads: 0	It should be noted that tachyons themselves are highly speculative, theorized particles.