Physics question

[CountZero]

So physics is all about frame of reference right? As in there is no background frame on which to base everything (no ether as it were).

So if two vehicles are traveling at .75c constant velocity traveling towards each other wouldn't it appear from either vehicles perspective as if the other vehicle is traveling at 1.5c and wouldn't that violate some fundamental law of nature? Or would the other vehicle appear to be traveling at c since the information couldn't possibly reach you any faster than c thereby preserving the inability to travel faster than c?

 

[CSMR]

Originally posted by: CountZero
So physics is all about frame of reference right? As in there is no background frame on which to base everything (no ether as it were).

Special relativity is all about...

So if two vehicles are traveling at .75c constant velocity traveling towards each other wouldn't it appear from either vehicles perspective as if the other vehicle is traveling at 1.5c and wouldn't that violate some fundamental law of nature? Or would the other vehicle appear to be traveling at c since the information couldn't possibly reach you any faster than c thereby preserving the inability to travel faster than c?

A speed somewhere between .75c and c. Lorentz transformation to go between frames of reference.

Let c=1 for convenience. Changing speed by v at point 0 transforms coordinates (x,t) in space-time by the matrix
(1 -v) *1/sqrt(1-v^2)
(-v 1)
So when you change frame of reference by -.75 to follow one vehicle, the path of the other vehicle {(.75,1)} becomes {(.75+.75,.75^2+1)}, so the speed becomes 1.5/(1+9/16)=24/25. So each vehicle sees the other moving at 24/25c.

({x} denotes the line formed by the vector x.)

 

[Geniere]

Originally posted by: CountZero
So physics is all about frame of reference right? As in there is no background frame on which to base everything (no ether as it were).

So if two vehicles are traveling at .75c constant velocity traveling towards each other wouldn't it appear from either vehicles perspective as if the other vehicle is traveling at 1.5c and wouldn't that violate some fundamental law of nature? Or would the other vehicle appear to be traveling at c since the information couldn't possibly reach you any faster than c thereby preserving the inability to travel faster than c?

If you were moving at .75C and being approached by someone with a red light moving at .75C, you would not see the light as red, its color would be shifted to the green-blue-violet end of the spectrum. In other words the speed of light is not additive, it is always constant at C. Its kinetic energy does change resulting in you seeing the red light as a higher energy color such as blue. This is the basis by which Hubble found that far distant galaxies were moving away from us at high velocities, as their emitted light was ?red-shifted?.

In the 1800?s, physicists performed experiments, trying to discover the properties of the ?ether?. The experiments proved the ether did not exist; at least it does not exist in the classical sense. The (absolute) vacuum of space does have physical properties that can be measured such as its permeability and permittivity. It is these properties that determine the value of C since light has an electric and a magnetic field. In a letter to Lorentz of 17 June 1916, Einstein wrote: ? I agree with you that the general relativity theory admits of an ether hypothesis as does the special relativity theory?? This should not in any way be confused with a medium such as is necessary for the propagation of sound. It is merely a property of the vacuum.

 

[CountZero]

So is the Lorentz transformation due to the fact that space itself changes shape at speeds close to c?

 

[silverpig]

Originally posted by: CountZero
So is the Lorentz transformation due to the fact that space itself changes shape at speeds close to c?

Nope, it's due to the fact that time changes when you get close to c.

 

[CSMR]

Neither; space-time changes: it has different shapes at different frames of reference (that is, depending how one is moving). Both time and space coordinates are altered. You can't think of space coordinates or time coordinates changing by themselves - the Lorentz transformation acts on both of them together.

 

[JF0603]

face it the answer is no!!!:laugh:

 

[eLiu]

Originally posted by: CountZero
So physics is all about frame of reference right? As in there is no background frame on which to base everything (no ether as it were).

So if two vehicles are traveling at .75c constant velocity traveling towards each other wouldn't it appear from either vehicles perspective as if the other vehicle is traveling at 1.5c and wouldn't that violate some fundamental law of nature? Or would the other vehicle appear to be traveling at c since the information couldn't possibly reach you any faster than c thereby preserving the inability to travel faster than c?

Have to use the lorentz transformation...b/c close to c, time-changes become *very* noticeable. I mean, the time altercation is present when you walk from the comp to the bathroom, but it's so miniscule that it can be ignored.

This situation does "violate" Newtonian physics...if two trains traveling at 50mph approach each other, the engineer on train A will see B approach at 100mph (and vice versa). However netwonian physics are more a 'special case' of einstein's relativity-physics (uhm...is there a specific name for this..?). That is, our daily lives exist in a system where the lorentz transform is very nearly 1...so it can be disregarded, and the classic train problems from Algebra I work out intuitively.