Relativity

[AV1611VET]

A red car, going 30 mph, approaches a blue car approaching the red car, going 40 mph.

1. What is the relative speed of the blue car from the red car's perspective?
2. What is the relative speed of the red car from the blue car's perspective?

 

[Freodin]

1. 70 mph
2. 70 mph

 

[BarryDesborough]

A red car, going 30 mph, approaches a blue car approaching the red car, going 40 mph.

1. What is the relative speed of the blue car from the red car's perspective?
2. What is the relative speed of the red car from the blue car's perspective?

Almost, but not quite exactly, 70mph. (If they are approaching one another head on.)

 

[BarryDesborough]

1. 70 mph
2. 70 mph

You must allow for tiny relativistic effects.

 

[AV1611VET]

Okay, this one is much easier:

Observing a binary star on the same plane as the earth, true or false?

Relatively speaking, the light from the star moving toward the earth is faster than the light from the star moving away from the earth.

 

[sfs]

69.999993 mph for each (assuming they're approaching head on).

 

[AV1611VET]

69.999993 mph for each (assuming they're approaching head on).

Minus that Lorentz stuff.

Let's keep this simple.

 

[Freodin]

Okay, this one is much easier:

Observing a binary star on the same plane as the earth, true or false?

Relatively speaking, the light from the star moving toward the earth is faster than the light from the star moving away from the earth.

Nope, it is the same speed.

 

[GrowingSmaller]

Blue and red shift for the stars light moving towards and away form Earth. I know that (I think).

 

[Loudmouth]

Okay, this one is much easier:

Observing a binary star on the same plane as the earth, true or false?

Relatively speaking, the light from the star moving toward the earth is faster than the light from the star moving away from the earth.

False. Light always moves at the same speed in a vacuum. If you are travelling in a car travelling at 99% of the speed of light and you turn on the headlights all observers, both in and outside the car, will measure the same speed for the light coming from the headlights. However, observers in different frames of reference will measure different wavelengths for that light.

 

[AV1611VET]

However, observers in different frames of reference will measure different wavelengths for that light.

Is that what they call the Doppler effect?

 

[Loudmouth]

Is that what they call the Doppler effect?

Yes. This effect is actually used in some radar technologies to measure the speed of distant objects.

 

[Michael]

Is that what they call the Doppler effect?

Be careful my friend about getting a blatant bait and switch routine. The Doppler effect is *specifically* (only) related to the *movement of objects*. The changing frequency of a train whistle, or a car horn as it moves toward and away from you is an example of Doppler shift.

This is *not* what the mainstream is claiming. They are not claiming that galaxies are actually physically moving, they are making *supernatural* claims about 'space' (undefined in GR theory by the way) doing some sort of mythical expansion trick in the most remote places of the universe.

They're going to try to claim that Doppler shift supports their claims, but it does not. Ask him if the galaxies are actually moving faster than the speed of light at a Z>10 redshift?

 

[Loudmouth]

Be careful my friend about getting a blatant bait and switch routine. The Doppler effect is *specifically* (only) related to the *movement of objects*. The changing frequency of a train whistle, or a car horn as it moves toward and away from you is an example of Doppler shift.

This is *not* what the mainstream is claiming.

For the car experiment that I described, it is what the mainstream is claiming. Your windmill has no place in this thread. This thread is not about your obsession with plasma cosmology.

 

[AV1611VET]

Loudmouth, are the galaxies actually moving faster than the speed of light at a Z>10 redshift?

 

[Loudmouth]

Loudmouth, are the galaxies actually moving faster than the speed of light at a Z>10 redshift?

According to the consensus theory in astrophysics, the cumulative expansion of the space between us and distant galaxies can be greater than the speed of light. The galaxies themselves are not moving through space. It is the space itself that is expanding. It can result in a universe with an event horizon as described by de Sitter:

de Sitter universe - Wikipedia, the free encyclopedia

This is called cosmological redshift instead of Doppler redshift, although some people fail to differentiate between the two.

 

[Michael]

Now ask him if "space" (still not physically defined in GR by the way) does any really cool expansion tricks in the lab, or whether that's a statement of faith on his part?

 

[Loudmouth]

Now ask him if "space" (still not physically defined in GR by the way) does any really cool expansion tricks in the lab, or whether that's a statement of faith on his part?

Your windmill is discussed in a different thread.

 

[AV1611VET]

Now ask him if "space" (still not physically defined in GR by the way) does any really cool expansion tricks in the lab, or whether that's a statement of faith on his part?

Loudmouth, does "space" do any real coo...

Your windmill is discussed in a different thread.

... nevermind.

 

[Michael]

According to the consensus theory in astrophysics,

Translation: Starting with an appeal to authority fallacy.....

the cumulative expansion of the space between us and distant galaxies can be greater than the speed of light.

What is "space", and how *exactly* does it 'expand'? Only spacetime and distance are defined in GR, not 'space'. Spacetime can expand as objects in motion stay in motion, but objects cannot move faster than C.

This is called cosmological redshift instead of Doppler redshift, although some people fail to differentiate between the two.

FYI AV, they typically *never* differentiate between the two. In fact they tend to "bait" the would be believer with Doppler shift and then *switch* them to space expansion claims, and thereby use Doppler shift to try to support their unsupported *space expansion* claims.