Camera near the speed of light

Click For Summary

Discussion Overview

The discussion revolves around the feasibility of taking photographs in scenarios involving speeds approaching the speed of light, particularly focusing on the experiences of individuals on a spaceship and the potential relativistic effects observable from different frames of reference. The conversation explores theoretical implications and the nature of relativity in this context.

Discussion Character

  • Exploratory
  • Debate/contested
  • Conceptual clarification

Main Points Raised

  • Some participants suggest that if two people are on a spaceship traveling at near the speed of light, they would be able to take pictures of each other without noticing anything unusual due to their relative rest frame.
  • Others argue that the question of taking pictures at such speeds is moot, as it is impossible to have a spaceship traveling at those speeds in practical terms.
  • A participant points out that relativistic effects would be observable if someone on a passing planet attempted to photograph someone on the spaceship, raising questions about the nature of those effects.
  • There is a discussion about the semantics of "moot" and whether the question can be considered valid if it is theoretically possible to take such photographs.
  • Some participants express uncertainty about the practical significance of thought experiments involving speeds close to light, questioning the relevance of such scenarios.
  • A later reply highlights the importance of understanding that relativistic effects depend on the frame of reference and that velocities do not affect observations within an inertial frame.

Areas of Agreement / Disagreement

Participants do not reach a consensus on the validity of the original question regarding the feasibility of taking photographs at near-light speeds. There are competing views on whether the question is moot or if it holds theoretical significance.

Contextual Notes

Some participants mention the limitations of the discussion, including the dependence on definitions of "moot" and the abstract nature of the scenarios presented. There are unresolved questions about the practical implications of relativistic effects and the conditions under which they might be observed.

  • #31
DaveC426913 said:
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.
 
Physics news on Phys.org
  • #32
Integral said:
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?
 
  • #33
tkav1980 said:
Is this because the speed of light is constant no matter what inertal refrence frame its observed from?
Yes.
tkav1980 said:
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.

nitsuj said:
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.
 
  • #34
DaveC426913 said:
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.
 
  • #35
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.
 
  • #36
HallsofIvy said:
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?
 
  • #37
tkav1980 said:
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.
 
  • #38
DaveC426913 said:
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)
 
  • #39
nitsuj said:
Yea that's what I woulda guessed.

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

Yes.
 
  • #40
DaveC426913 said:
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.
 
Last edited:
  • #41
nitsuj said:
doesn't expanding space account for the majority of the "speed".
It does. But the 'how' doesn't affect the 'what'.
 
  • #42
DaveC426913 said:
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 ?.
 
  • #43
nitsuj said:
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.
 
  • #44
DaveC426913 said:
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.
 
  • #45
nitsuj said:
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.
 

Similar threads

Undergrad Ships passing each other at near light speed
  • · Replies 5 ·
Replies
5
Views
386
Undergrad A question about the speed of light and electromagnetism
  • · Replies 51 ·
2
Replies
51
Views
5K
High School One-Way Speed of Light
  • · Replies 93 ·
4
Replies
93
Views
6K
High School Why is it impossible to go faster than the speed of light?
  • · Replies 21 ·
Replies
21
Views
5K
Undergrad One way speed of light
  • · Replies 26 ·
Replies
26
Views
612
Undergrad Can the intersection point of two light beams exceed the speed of light?
  • · Replies 9 ·
Replies
9
Views
1K
Undergrad Conventionality of the One-Way Speed of Light
  • · Replies 6 ·
Replies
6
Views
2K
Undergrad Has anyone measured the speed of light in one direction?
  • · Replies 45 ·
2
Replies
45
Views
7K
Undergrad One-Way Speed of Light: Is it Possible?
  • · Replies 53 ·
2
Replies
53
Views
7K
Undergrad I want a good reference to a discussion of the meaning of "the speed of light is constant"
  • · Replies 60 ·
3
Replies
60
Views
5K