Camera near the speed of light

[tkav1980]

For example, suppose you are standing on the side of a road, with a baseball catcher's mitt.
Standing on the back of a flat bed truck, moving toward you at 40 mph, I throw a baseball to you with, relative to me, a speed of 60 mph. By Newtonian theory, the baseball would have a speed, relative to you, of 60+ 40= 100 mph. By relativity, the baseball's speed relative to you would be very slightly less than 100 mph but the difference would be too small to measure.

If I were to shine a light toward you with, relative to me, speed c, by Newtonian theory, the speed of that light, relative to you, would be c+ 40. But, according to relativity, the speed of that light, relative to you, would still be c. That is what is meant when we say that the speed of light, relative to any observer is c.

That part I understand. No matter whes your velocity is or my velocity is, light will always be measured at c. c, when it comes to the motion of ANY observer, is constant, its not an additive or multiplicative(sp?) property.

This may be a bit out there, but why is that? Is there a known mechanism for this?

 

[DaveC426913]

This may be a bit out there, but why is that? Is there a known mechanism for this?

It is a postulate. It is not shown; it is supposed.

"If this were the case, what would we see?"

Turns out, if it were the case, what we should see describes exactly what we do see. SR is a spectacularly accurate model of how our universe seems to work. That makes it probably right. More accurately, it makes it right enough that we can proceed with a subsequent century (so far!) of excellent science without it ever failing us.

 

[nitsuj]

Distant galaxies billions of ly away near the edge of the observable universe.

Yea that's what I woulda guessed.

And that's comparable to the spaceship traveling at nearly c flying by a planet? (rhetorical)

 

[DaveC426913]

Yea that's what I woulda guessed.

And that's comparable to the spaceship traveling at nearly c flying by a planet? (rhetorical)

Yes.

 

[nitsuj]

Yes.

wow,

So with billions of LY inbetween us and the distant galaxy, doesn't expanding space account for the majority of the "speed".

I find it pretty funny to think that some galaxies out there travel at near c speeds, through space. ? what would propel them to those speeds?

But yup I hear you Dave, just like a spaceship, well comparable enough to draw conclusions as has been in this thread.

I may as well go back to reading Brian Greene.

 

[DaveC426913]

doesn't expanding space account for the majority of the "speed".

It does. But the 'how' doesn't affect the 'what'.

 

[nitsuj]

It does. But the 'how' doesn't affect the 'what'.

And I don't believe that. The difference between the to are immense.

So dave, I sure you believe then that galaxies can travel FTL, since the how doesn't affect the ?.

 

[DaveC426913]

And I don't believe that. The difference between the to are immense.

So dave, I sure you believe then that galaxies can travel FTL, since the how doesn't affect the ?.

I said nothing about FTL.

The point is, us moving at .99c (relative to some planet, say, Earth) and trying to take a picture - is identical to us stationary with Earth moving at .99c and trying to take a picture.

We can prove this to ourselves easily, because there are currently things that are moving wrt to us at .99c (which means we are moving .99c wrt them), so why would we suddenly be unable to use a camera?

So:

A spaceship traveling away from us at .99c will see us traveling away from them at .99c. That fact that they see us moving at .99c does not in any way affect us being able to take pictures with a camera.

A galaxy traveling away from us at .99c will see us traveling away from them at .99c. That fact that they see us moving at .99c does not in any way affect us being able to take pictures with a camera.

 

[nitsuj]

I said nothing about FTL.

The point is, us moving at .99c (relative to some planet, say, Earth) and trying to take a picture - is identical to us stationary with Earth moving at .99c and trying to take a picture.

We can prove this to ourselves easily, because there are currently things that are moving wrt to us at .99c (which means we are moving .99c wrt them), so why would we suddenly be unable to use a camera?

So:

A spaceship traveling away from us at .99c will see us traveling away from them at .99c. That fact that they see us moving at .99c does not in any way affect us being able to take pictures with a camera.

A galaxy traveling away from us at .99c will see us traveling away from them at .99c. That fact that they see us moving at .99c does not in any way affect us being able to take pictures with a camera.

I think, actually accelerating a spaceship to nearly c is vastly different then saying well, some massive object out the is moving that fast (which there isn't) so it's all the same because it's relative.

My comment about galaxies traveling FTL has the same basis as your comment regarding galaxies traveling near c (space expanding/very long distances/very old galaxies), so I assumed you'd agree it's true.

 

[DaveC426913]

I think, actually accelerating a spaceship to nearly c is vastly different then saying well, some massive object out the is moving that fast (which there isn't) so it's all the same because it's relative.

It is vastly different in many ways, but it is not vastly different in a way relevant to the discussion.