Camera near the speed of light

[Voltaire6022]

If you were infinitely close to the speed of light, and you attempted to take a picture of yourself, would it work? Would there be any way to make it work using relative velocities?

 

[Pengwuino]

What? Structure the question better.

 

[Voltaire6022]

Say two people are on a spaceship traveling at near speed of light. If one wants to take a picture of the other, would that be possible?

EDIT: The picture would be taken by the person in the rear of the craft, facing the front.

 

[elfmotat]

They shouldn't see nor feel anything strange, assuming they are moving with constant, uniform velocity (with respect to some other observer, of course - in their frame they are stationary). So yes, they will be able to take a picture.

 

[Pengwuino]

Yes, if they are both on the same spaceship traveling at near the speed of light, they would be able to take pictures easily. They wouldn't even notice anything strange because relative to each other, both of them are at rest.

The spaceship traveling near the speed of light must be traveling at that speed relative to something else, and it certainly isn't traveling at that speed relative to the people inside of it. You would have to say the spaceship is traveling near the speed of light relative to say, a passing planet or star or whatever. And even then, on board, nothing peculiar will happen.

The interesting question, on the other hand, would be if someone on a passing planet tried to take a picture of someone on the spaceship, then you'd see relativistic effects!

 

[Voltaire6022]

Much less exciting than what I was hoping, but thanks :P

 

[nitsuj]

The interesting question, on the other hand, would be if someone on a passing planet tried to take a picture of someone on the spaceship, then you'd see relativistic effects!

That's not an interesting question, especialy not the interesting question.

Yea I bet that photo would turn out real well.

At speeds "infinitely" close to c, the answer they "wouldn't notice anything different and could take pictures easily" is moot.

 

[HallsofIvy]

That is, after all, the whole point of "relativity". The two people are, relative to each other, stationary.

 

[elfmotat]

That's not an interesting question, especialy not the interesting question.

Yea I bet that photo would turn out real well.

What? You don't think that a photo showing relativistic effects would be interesting?

At speeds "infinitely" close to c, the answer they "wouldn't notice anything different and could take pictures easily" is moot.

That doesn't really make any sense. That IS the answer - how can it be "moot?"

 

[nitsuj]

What? You don't think that a photo showing relativistic effects would be interesting?



That doesn't really make any sense. That IS the answer - how can it be "moot?"

Never said I don't think that a photo showing relativistic effects would be interesting.

I said that it is not an interesting question, let alone, the interesting question.

it is not possible so that makes it moot.

 

[elfmotat]

it is not possible so that makes it moot.

In principle it is possible, so the question is not moot.

 

[Pengwuino]

Never said I don't think that a photo showing relativistic effects would be interesting.

I said that it is not an interesting question, let alone, the interesting question.

it is not possible so that makes it moot.

Why is it not possible? In a sense that's what astronomy is all about... although maybe the things they see are more often GR effects than SR ones

 

[pervect]

In principle it is possible, so the question is not moot.

I think there may be a semantic issue here. If you had a photo that showed effects depending on "velocity through space" or "absolute velocity", they wouldn't be relativistic effects. They'd be evidence that relativity was wrong.

Note that we (or at least I) don't want to start a debate on "is relativity right or wrong" here. The experimental evidence is out there for those who want to study it (such as the failure of previous attempts to measure the absolute velocity of the Earth through space through the M.M. experiment, for starters).

The forum is mostly dedicated to helping people who want to understand relativity to understand it. And part of understanding relativity is understanding that things don't look any different depending on your velocity, this is one of the fundamental principles.

 

[elfmotat]

I think there may be a semantic issue here. If you had a photo that showed effects depending on "velocity through space" or "absolute velocity", they wouldn't be relativistic effects. They'd be evidence that relativity was wrong.

Note that we (or at least I) don't want to start a debate on "is relativity right or wrong" here. The experimental evidence is out there for those who want to study it (such as the failure of previous attempts to measure the absolute velocity of the Earth through space through the M.M. experiment, for starters).

The forum is mostly dedicated to helping people who want to understand relativity to understand it. And part of understanding relativity is understanding that things don't look any different depending on your velocity, this is one of the fundamental principles.

I think you may have misunderstood what nitsuj was saying. He wasn't arguing that photographs taken in an inertial reference frame near traveling near c relative to another observer wouldn't show relativistic effects within that frame - he was arguing that it's impossible to have a spaceship traveling near c to begin with, so the question is moot. If you read my original post in this thread you'll see that I'm well aware of the principle of relativity.

 

[nitsuj]

I think you may have misunderstood what nitsuj was saying. He wasn't arguing that photographs taken in an inertial reference frame near traveling near c relative to another observer wouldn't show relativistic effects within that frame - he was arguing that it's impossible to have a spaceship traveling near c to begin with, so the question is moot. If you read my original post in this thread you'll see that I'm well aware of the principle of relativity.

I'd like to point out I said specifically the answer is moot.

I never read the definition of moot until now.

http://www.merriam-webster.com/dictionary/moot"

Doesn't make sense? It could define moot.

 

[nitsuj]

Why is it not possible?

I don't know. Is it?

Is it possible for there to be a ship with two people on board with a camera all traveling "infinitely close to the speed of light" and take a photo?

And at the same time on a planet passed by the ship a camera takes a photo of the ship while it passed by at "infinitely close to the speed of light"?

And that photo to show relativistic effects?

Sounds rather abstract and deprived of practical significance.

 

[elfmotat]

I don't know. Is it?

Is it possible for there to be a ship with two people on board with a camera all traveling "infinitely close to the speed of light" and take a photo?

And at the same time on a planet passed by the ship a camera takes a photo of the ship while it passed by at "infinitely close to the speed of light"?

And that photo to show relativistic effects?

Sounds rather abstract and deprived of practical significance.

Why do you think thought experiments should be limited to the practical? Would you prefer the scenario "say there's a mu-meson particle moving at..." ? I don't really understand what your point is.

 

[Pengwuino]

I don't know. Is it?

Is it possible for there to be a ship with two people on board with a camera all traveling "infinitely close to the speed of light" and take a photo?

And at the same time on a planet passed by the ship a camera takes a photo of the ship while it passed by at "infinitely close to the speed of light"?

And that photo to show relativistic effects?

Sounds rather abstract and deprived of practical significance.

Yes, but that's like saying "what if I had a fusion powered rocket strapped to a 9 headed alien who eats glue and mates with cows. A cow attempts to take a picture of this fusion powered alien from Earth as it flies by...". These abstract concepts are simply human methods of imagining what is going on. Just because the description is not practical or possibly even silly doesn't mean we can't use it to understand what is actually happening in the universe. We just know that instead of a 9 headed alien traveling by Earth, we have a proton slamming into a target in a high energy physics experiment.

 

[nitsuj]

I don't really understand what your point is.

Here is the OP's question

"Say two people are on a spaceship traveling at near speed of light. If one wants to take a picture of the other, would that be possible?

EDIT: The picture would be taken by the person in the rear of the craft, facing the front."

After givin a moot answer...

The OP left with "Much less exciting than what I was hoping, but thanks :P".

So the OP belives a photo can be taken at near c speeds on a spaceship.

Perhaps the OP would have found it even less exciting to hear the impossibilities of accelerating a spaceship with people on board to near c speeds.

 

[elfmotat]

So the OP belives a photo can be taken at near c speeds on a spaceship.

And rightfully so, because a photo CAN be taken at speeds near c on a spaceship - whether or not we can build such a spaceship is irrelevant. OP's question was about the principle, and he was given an answer. I'm starting to think you're trolling me...

 

[DaveC426913]

Justin, this is a question of principle. There is absolutely nothing in principle stopping the scenario from occurring.

Consider another question:
"Is it possible to take a picture on Pluto?"
Justin: "It is moot since we cannot get to Pluto."
Everyone else: "Of course it is possible to take a picture on Pluto."

Now, on to what would happen in the spaceship:

If we were to accelerate arbitrarily close to the speed of light, inside our spaceship it would be as if we were utterly stationary. There is no reason why a picture would not be completely normal.

Now, if we looked out the window, we'd see the universe whizzing by incredibly foreshortened and red/blue-shifted, but that's something else.

 

[nitsuj]

Justin, this is a question of principle. There is absolutely nothing in principle stopping the scenario from occurring.

Consider another question:
"Is it possible to take a picture on Pluto?"
Justin: "It is moot since we cannot get to Pluto."
Everyone else: "Of course it is possible to take a picture on Pluto."

Well Said Dave! I see their perspective more clearly now.

 

[PAllen]

Note, there are 'observers' who see the space station and its occupants moving at 'virtually the speed of light'. They are called cosmic rays. Just as valid a frame as any other. Outfitting them with cameras is a bit of problem ...

 

[tkav1980]

This may be a stupid question but since this thread is about taking pictures while traveling near c, relative to let's say the earth. What would a picture taken looking out the side window look like. Assuming the lense of the camera was perfectly perpendicular to the direction of travel, and what would the picture look like out of the front and rear windows?

I'm going to take an uneducated guess and say everything out of the front window would be more blue, and the rear window more red. But would the length contraction be noticable? and would the length elongate out of the back window?

 

[elfmotat]

This may be a stupid question but since this thread is about taking pictures while traveling near c, relative to let's say the earth. What would a picture taken looking out the side window look like. Assuming the lense of the camera was perfectly perpendicular to the direction of travel, and what would the picture look like out of the front and rear windows?

I'm going to take an uneducated guess and say everything out of the front window would be more blue, and the rear window more red. But would the length contraction be noticable? and would the length elongate out of the back window?

 

[tkav1980]

Verry cool. Thank you for that!

 

[DaveC426913]

Way cool video.

Also: awesome avator elfmotat.

 

[Integral]

Consider this. Objects very distant from the Earth are observed to have velocities near the speed of light with respect to earth. So with respect to these distant objects the Earth is traveling at a relativistic velocity.

Now, can you take a picture?

 

[tkav1980]

Consider this. Objects very distant from the Earth are observed to have velocities near the speed of light with respect to earth. So with respect to these distant objects the Earth is traveling at a relativistic velocity.

Now, can you take a picture?

Well Since we have some pictures of verry distant galaxys I'll say yes.

This may be the wrong part of the forum for this question, but I read on Discovery channel's website that some of the most distant ones are photographed using gravitational lensing. After watching that animation linked a few posts above, how does that effect change the picture?

Sorry if my answers are...well dumb...I don't possesses the math skills to really analize this type of thing so I am really just guessing based off of what I've seen and read.

 

[DaveC426913]

Well Since we have some pictures of verry distant galaxys I'll say yes.

Correct.

But the other point being: since from their point of view it is us speeding through the universe at near c, and we don't have trouble taking picture of each other here on Earth... therefore moving at near c does not affect the ability to take pictures.

This may be the wrong part of the forum for this question, but I read on Discovery channel's website that some of the most distant ones are photographed using gravitational lensing. After watching that animation linked a few posts above, how does that effect change the picture?

This is unrelated. Grav lensing simply distorts the image:

Wiki gravitational lens for more info.

 

[tkav1980]

Correct.

But the other point being: since from their point of view it is us speeding through the universe at near c, and we don't have trouble taking picture of each other here on Earth... therefore moving at near c does not affect the ability to take pictures.


.

Is this because the speed of light is constant no matter what inertal refrence frame its observed from? Meaning, We see them moving near c, they see us moving near c, but both of us agree on the value of c regardless of our velocity compared to c.

 

[nitsuj]

Consider this. Objects very distant from the Earth are observed to have velocities near the speed of light with respect to earth. So with respect to these distant objects the Earth is traveling at a relativistic velocity.

Now, can you take a picture?

interesting, what are these objects? and at what distance are they from us?

 

[DaveC426913]

Is this because the speed of light is constant no matter what inertal refrence frame its observed from?

Yes.

Meaning, We see them moving near c, they see us moving near c, but both of us agree on the value of c regardless of our velocity compared to c.

No. Other way around. Our velocity when we compare it to c is always c. Their velocity when they compare it to c is always c.

But yes, we both agrgee that c wrt us is c.

interesting, what are these objects? and at what distance are they from us?

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

 

[tkav1980]

Yes.

No. Other way around. Our velocity when we compare it to c is always c. Their velocity when they compare it to c is always c.

But yes, we both agrgee that c wrt us is c.

Hey, I really appreciate you taking the time to explain things. I think we both said the same thing when talking about velocites as they relate to c, but i tend to put things on paper so to speak that most people have a hard time understanding. It's simply the way i type.

I should have said from our point of view they are moving at x % of c, however they will measure c as c. in essence from their point of view our measurements don't mean anything since we are measuring from a different inertial frame. Still no matter who measures it, no matter what frame, c is always c.

 

[HallsofIvy]

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.

 

[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.