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Relativity and the speed of light

drhead
Posts: 1,475
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9/27/2013 1:09:16 PM
Posted: 3 years ago
I'm not sure I'm understanding this properly. Consider this thought experiment:

Suppose that you have something that is essentially a Schr"dinger's cat box, except instead of using a radioactive source as a trigger, it uses a solar panel to activate when a beam of light hits it. This is on a cart that is moving at about half the speed of light. A laser is set up so that it will send out a short pulse of light timed perfectly to hit the solar panel and kill the cat.

Now, if I chased after the light pulse at the speed of light, it would go the same speed from my perspective, since the speed of light is the same from any frame of reference. Wouldn't it be possible, with the combined effect of the light going faster and the cart moving slower due to the time dilation effect, for me to have the cat alive from my perspective (since I never saw the laser hit the solar panel) and for the cat to be dead from its own perspective? What would happen, and why?
Wall of Fail

"You reject religion... calling it a sickness, to what ends??? Are you a Homosexual??" - Dogknox
"For me, Evolution is a zombie theory. I mean imaginary cartoons and wishful thinking support it?" - Dragonfang
"There are no mental health benefits of atheism. It is devoid of rational thinking and mental protection." - Gabrian
Graincruncher
Posts: 2,799
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9/27/2013 1:49:18 PM
Posted: 3 years ago
I'm fairly sure it would work that way, on the basis that a relative frame is getting information via light from what is technically the past.
drhead
Posts: 1,475
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9/28/2013 2:21:51 AM
Posted: 3 years ago
At 9/27/2013 1:49:18 PM, Graincruncher wrote:
I'm fairly sure it would work that way, on the basis that a relative frame is getting information via light from what is technically the past.

If that is true, then that would mean that everyone perceives things from a frame of reference where things are different in very slight ways. Everyone would be in what is essentially their own reality that is different in minute ways. This is why I think something is wrong with this, this would make little sense. Does the solar panel only get influenced inside the reference frames where light is perceived as influencing it?
Wall of Fail

"You reject religion... calling it a sickness, to what ends??? Are you a Homosexual??" - Dogknox
"For me, Evolution is a zombie theory. I mean imaginary cartoons and wishful thinking support it?" - Dragonfang
"There are no mental health benefits of atheism. It is devoid of rational thinking and mental protection." - Gabrian
Jack212
Posts: 572
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9/28/2013 6:17:49 PM
Posted: 3 years ago
At 9/27/2013 1:09:16 PM, drhead wrote:
I'm not sure I'm understanding this properly. Consider this thought experiment:

Suppose that you have something that is essentially a Schr"dinger's cat box, except instead of using a radioactive source as a trigger, it uses a solar panel to activate when a beam of light hits it. This is on a cart that is moving at about half the speed of light. A laser is set up so that it will send out a short pulse of light timed perfectly to hit the solar panel and kill the cat.

Now, if I chased after the light pulse at the speed of light, it would go the same speed from my perspective, since the speed of light is the same from any frame of reference. Wouldn't it be possible, with the combined effect of the light going faster and the cart moving slower due to the time dilation effect, for me to have the cat alive from my perspective (since I never saw the laser hit the solar panel) and for the cat to be dead from its own perspective? What would happen, and why?

If you traveled at the speed of light, you'd measure your trip from take-off to cart as taking zero time. So the laser would hit the panel and kill the cat at the start of the experiment, before you could assess the cat's health (even if health assessment was instant).
drhead
Posts: 1,475
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9/28/2013 8:24:19 PM
Posted: 3 years ago
At 9/28/2013 6:17:49 PM, Jack212 wrote:
At 9/27/2013 1:09:16 PM, drhead wrote:
I'm not sure I'm understanding this properly. Consider this thought experiment:

Suppose that you have something that is essentially a Schr"dinger's cat box, except instead of using a radioactive source as a trigger, it uses a solar panel to activate when a beam of light hits it. This is on a cart that is moving at about half the speed of light. A laser is set up so that it will send out a short pulse of light timed perfectly to hit the solar panel and kill the cat.

Now, if I chased after the light pulse at the speed of light, it would go the same speed from my perspective, since the speed of light is the same from any frame of reference. Wouldn't it be possible, with the combined effect of the light going faster and the cart moving slower due to the time dilation effect, for me to have the cat alive from my perspective (since I never saw the laser hit the solar panel) and for the cat to be dead from its own perspective? What would happen, and why?

If you traveled at the speed of light, you'd measure your trip from take-off to cart as taking zero time. So the laser would hit the panel and kill the cat at the start of the experiment, before you could assess the cat's health (even if health assessment was instant).

The cart wouldn't start under the light, though. The idea is that the laser would intercept the cart from the cart's frame of reference. If it took zero time from my perspective, the light would hit the ground in front of the cart.
Wall of Fail

"You reject religion... calling it a sickness, to what ends??? Are you a Homosexual??" - Dogknox
"For me, Evolution is a zombie theory. I mean imaginary cartoons and wishful thinking support it?" - Dragonfang
"There are no mental health benefits of atheism. It is devoid of rational thinking and mental protection." - Gabrian
Floid
Posts: 751
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9/28/2013 10:12:18 PM
Posted: 3 years ago
I think the idea you are after is called relativity of simultaneity and your thought experiment is unnecessarily complicated.

Is it possible for the cat to be dead from its perspective and alive from your perspective? Yes. Here is the easy scenario: You are 1 light year from the cat (makes for an easy calculation) and the cat dies. From the cat's frame of reference it is dead, from your frame of reference it is alive for the next year because that is the shortest possible time it could take that information to reach you.

Now you can setup a scenario where you are moving towards the cat at rate X and the signal killing the cat is moving at rate Y etc and the same is true, it just makes it more difficult to calculate how long the contradictory states exist.
Jack212
Posts: 572
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9/29/2013 5:03:52 AM
Posted: 3 years ago
At 9/28/2013 8:24:19 PM, drhead wrote:
At 9/28/2013 6:17:49 PM, Jack212 wrote:
At 9/27/2013 1:09:16 PM, drhead wrote:
I'm not sure I'm understanding this properly. Consider this thought experiment:

Suppose that you have something that is essentially a Schr"dinger's cat box, except instead of using a radioactive source as a trigger, it uses a solar panel to activate when a beam of light hits it. This is on a cart that is moving at about half the speed of light. A laser is set up so that it will send out a short pulse of light timed perfectly to hit the solar panel and kill the cat.

Now, if I chased after the light pulse at the speed of light, it would go the same speed from my perspective, since the speed of light is the same from any frame of reference. Wouldn't it be possible, with the combined effect of the light going faster and the cart moving slower due to the time dilation effect, for me to have the cat alive from my perspective (since I never saw the laser hit the solar panel) and for the cat to be dead from its own perspective? What would happen, and why?

If you traveled at the speed of light, you'd measure your trip from take-off to cart as taking zero time. So the laser would hit the panel and kill the cat at the start of the experiment, before you could assess the cat's health (even if health assessment was instant).

The cart wouldn't start under the light, though. The idea is that the laser would intercept the cart from the cart's frame of reference. If it took zero time from my perspective, the light would hit the ground in front of the cart.

You'd measure the distance between the cart's initial position and final position as zero. From your perspective, the whole setting of the experiment would collapse to a point and re-expand when you stopped moving. This experiment could never be performed, however, as accelerating you to the speed of light would require an infinite amount of energy.
Sidewalker
Posts: 3,713
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9/29/2013 5:43:51 AM
Posted: 3 years ago
At 9/28/2013 10:12:18 PM, Floid wrote:
I think the idea you are after is called relativity of simultaneity and your thought experiment is unnecessarily complicated.

Not really, he was going for quantum superposition and confused it with relativity of simultaneity. What Wolfgang Pauli would say about his thought experiment is, "It's not even wrong".

Is it possible for the cat to be dead from its perspective and alive from your perspective? Yes. Here is the easy scenario: You are 1 light year from the cat (makes for an easy calculation) and the cat dies. From the cat's frame of reference it is dead, from your frame of reference it is alive for the next year because that is the shortest possible time it could take that information to reach you.

That is just a matter of the relative awareness of the state of the cat, it has nothing to do with quantum superposition, the cat is not both dead and alive in either example.

Now you can setup a scenario where you are moving towards the cat at rate X and the signal killing the cat is moving at rate Y etc and the same is true, it just makes it more difficult to calculate how long the contradictory states exist.

That still doesn't set up the "contradictory states" being discussed, the Schr"dinger's cat thought experiment is about a quantum mechanics principle where a physical system can theoretically exist in two states at the same time until an observation is made to "collapse" the wave function, that contradiction isn't a function of the theory of relativity. What you are both addressing is the special theory of relativity which is deterministic and would explicitly prohibit the contradictory states mentioned. It gives you a contradiction regarding the relative sequencing of events in time, but it doesn't give you a physical system in two different states at the same time.
"It is one of the commonest of mistakes to consider that the limit of our power of perception is also the limit of all there is to perceive." " C. W. Leadbeater