Question about gravity and speed of light

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Discussion Overview

The discussion revolves around questions related to Einstein's theory of relativity, specifically focusing on the measurement of the speed of light in a moving frame and the implications of gravity as curvature in space. Participants explore concepts of time dilation, the behavior of light in gravitational fields, and the interpretation of these phenomena in popular media like the movie "Interstellar."

Discussion Character

  • Exploratory
  • Debate/contested
  • Conceptual clarification

Main Points Raised

  • One participant questions the measurement of light speed in a lab moving at half the speed of light, suggesting that time dilation would affect the results.
  • Another participant clarifies that time dilation is an observational effect and that both the moving lab and an external observer would measure the speed of light as 'c'.
  • There is a discussion about the curvature of space caused by mass, with some participants asserting that this curvature affects different masses differently, particularly photons compared to larger bodies like Earth.
  • Some participants express confusion about the implications of time dilation, particularly in relation to GPS satellites and the portrayal of time in "Interstellar".
  • One participant emphasizes the importance of specifying a frame of reference when discussing speed, arguing that it is meaningless to speak of speed without context.
  • Another participant points out that while light follows the curvature of spacetime, it does not mean that it orbits massive bodies like the Earth does.
  • There are references to the portrayal of time dilation in "Interstellar", with some participants noting that it is a dramatization and not a representation of real science.

Areas of Agreement / Disagreement

Participants express multiple competing views on the effects of time dilation and the nature of gravity's influence on light. There is no consensus on the interpretations of these concepts, particularly in relation to popular media representations.

Contextual Notes

Participants highlight the need for clarity regarding frames of reference and the distinction between intrinsic and extrinsic curvature in spacetime. Some discussions remain unresolved, particularly concerning the implications of time dilation in different contexts.

Who May Find This Useful

This discussion may be of interest to those exploring concepts in relativity, the behavior of light in gravitational fields, and the intersection of science and popular culture.

  • #31
apurvmj said:
Twin paradox says one of the twin will be younger if he is traveling at the speed high enough to notice time dilation.
No, it doesn't. It says that each twin will see the other twin as younger. The only "paradox" occurs when you arrange for the two twins to be again together and motionless with respect to each other. And then which is younger will depend upon exactly how they returned to that situation.
 
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  • #32
Nugatory said:
Travelling relative to what? It is meaningless to speak of any speed without saying what it is relative to - remember that as far as you in the space lab are concerned, you are at not moving at all, it's just that if you look out the window you might see other things moving by relative to you.

Nugatory... No question is meaningless.
Technically he would be relative to "something" and that something is the light in his cosmological traveling lab. Light would be moving in all directions inside the lab. The reason he will be moving slower to relative light speed and space is because he is simply moving away from light at half the speed of light. Light will have to bounce off the object he sees then also have to catch up to his eyes at half its normal speed. (light speed travels 50% slower in the direction he moves away from it) remember that light travels at 186,000 mph, but from his new perspective it now tops at 93,000 mph (which is still astonishingly faster than sounds average speed of 760 mph) meaning that his interactions and perception wouldn't to much different from normal. MY QUESTION IS... IS SPEED AND TIME INTERTWINED?!.
 
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  • #33
Jaami M. said:
Technically he would be relative to "something" and that something is the light in his cosmological traveling lab. Light would be moving in all directions inside the lab. The reason he will be moving slower to relative light speed and space is because he is simply moving away from light at half the speed of light. Light will have to bounce off the object he sees then also have to catch up to his eyes at half its normal speed. (light speed travels 50% slower in the direction he moves away from it) remember that light travels at 186,000 mph, but from his new perspective it now tops at 93,000 mph (which is still astonishingly faster than sounds average speed of 760 mph) meaning that his interactions and perception wouldn't to much different from normal.

This is entirely incorrect. As measured by the person aboard the station, the light moves at c, not at 1/2 c. You cannot define velocities relative to light and have any meaningful statement, as light moves at c for ALL inertial observers, no matter what their velocities relative to each other are.
 
  • #34
apurvmj said:
ok... then what made lead actor in movie 'Interstellar' look younger than rest of the universe. Am I making sense?

From the theories I've learned of and from my understanding it's because of the black hole he entered. Now whether it's possible to survive a black hole or not, when he left it he was in the future. This happened because of how time-space Bends and warps around the black hole, because of its Immense Gravitational Field, making "time" also warp. Ultimately making your perceptive relevance to other humans appear to move slower. From my understanding, if he ENTERED a BLACK HOLE, he should be teared limb from mole is to atom! Or at least his daughter should be long gone, and humans should be terraforming Mars and be fishing on Jupiters moon Europa by now! But remember that interstellar is just a movie. There are so many theories of black holes, from creation of another universe to space travel.
 
  • #35
Drakkith said:
This is entirely incorrect. As measured by the person aboard the station, the light moves at c, not at 1/2 c. You cannot define velocities relative to light and have any meaningful statement, as light moves at c for ALL inertial observers, no matter what their velocities relative to each other are.
Your completely right, sorry about that. But the argument is still valid via argument correct?
 
  • #36
Jaami M. said:
From the theories I've learned of and from my understanding it's because of the black hole he entered. Now whether it's possible to survive a black hole or not, when he left it he was in the future. This happened because of how time-space Bends and warps around the black hole, because of its Immense Gravitational Field, making "time" also warp. Ultimately making your perceptive relevance to other humans appear to move slower. From my understanding, if he ENTERED a BLACK HOLE, he should be teared limb from mole is to atom! Or at least his daughter should be long gone, and humans should be terraforming Mars and be fishing on Jupiters moon Europa by now! But remember that interstellar is just a movie. There are so many theories of black holes, from creation of another universe to space travel.
molecule*
 
  • #37
Jaami M. said:
Your completely right, sorry about that. But the argument is still valid via argument correct?

What? I don't know what you're asking.

Jaami M. said:
From the theories I've learned of and from my understanding it's because of the black hole he entered.

Yes, the planet they landed on was close to the supermassive black hole, so they experienced a great deal of time dilation relative to the Earth. So much so that something like 20-30 years passed on Earth while they only experienced a few hours.

Jaami M. said:
From my understanding, if he ENTERED a BLACK HOLE, he should be teared limb from mole is to atom!

Not for supermassive black holes. For those the tidal forces near the event horizon are low enough to allow passage without pulling you apart.
 
  • #38
Drakkith said:
Not for supermassive black holes. For those the tidal forces near the event horizon are low enough to allow passage without pulling you apart.

I'm speaking of when he Entered the black hole, not orbiting near it. (going inside the tesseract (from the black hole( on his own)))
 
  • #39
Jaami M. said:
I'm speaking of when he Entered the black hole, not orbiting near it. (going inside the tesseract (from the black hole( on his own)))

You can certainly enter a supermassive black hole without being torn apart by gravity, as I said. What happens beyond the even horizon is unknown.
 
  • #40
Drakkith said:
You can certainly enter a supermassive black hole without being torn apart by gravity, as I said. What happens beyond the even horizon is unknown.
That's true.
 
  • #41
Jaami M. said:
From the theories I've learned of and from my understanding it's because of the black hole he entered.

No; in the movie Interstellar the lead actor goes very close to the horizon of a black hole and stays there for a while, but he never enters the hole (never goes below the horizon). If he had, he wouldn't have been able to come back.
 
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  • #42
Everyone... please watch that h this clip and tell me of I'm wrong...-_- he Entered the Black hole...

 
  • #43
Jaami M. said:
Everyone... please watch that h this clip and tell me of I'm wrong...-_- he Entered the Black hole...


Or is that not a black hole? Is it just a wormhole or? What is it
 
  • #44
Jaami M. said:
Or is that not a black hole? Is it just a wormhole or? What is it
It is made up movie nonscience
 
  • #45
phinds said:
It is made up movie nonscience
But remember non-fiction science films become a reality. Flying (planes), digital screens, super computers in our hands, traveling to the moon etc.. It good to know what is to know.
 
  • #46
Jaami M. said:
please watch that h this clip and tell me of I'm wrong...-_- he Entered the Black hole...

He's traveling through a wormhole, which is not the same as a black hole. There are mathematical solutions of the Einstein Field Equation that describe wormholes, but they require "exotic matter", which is not believed to be physically possible to obtain.

Jaami M. said:
non-fiction science films become a reality.

Interstellar is not a "non-fiction science film". It's fiction.
 
  • #47
PeterDonis said:
He's traveling through a wormhole, which is not the same as a black hole. There are mathematical solutions of the Einstein Field Equation that describe wormholes, but they require "exotic matter", which is not believed to be physically possible to obtain.
Interstellar is not a "non-fiction science film". It's fiction.
Lol sorry, I've had 5 hours sleep, I just found this website last night and I've been on it ever since. There's not many people that I can talk to about physics. So when I do it's like coming out of water taking a huge breath in. Lol I should take a break
 
  • #48
PeterDonis said:
He's traveling through a wormhole, which is not the same as a black hole. There are mathematical solutions of the Einstein Field Equation that describe wormholes, but they require "exotic matter", which is not believed to be physically possible to obtain.
You only have to go up to 0:20. But Cooper did travel inside a black hole(Gargantua)
 
  • #49
Jaami M. said:
You only have to go up to 0:20. But Cooper did travel inside a black hole(Gargantua)

No, you have misunderstood somehow. That is NOT what it says.
 
  • #50
Jaami M. said:
But remember non-fiction science films become a reality. Flying (planes), digital screens, super computers in our hands, traveling to the moon etc.. It good to know what is to know.
No they don't. Hollywood is not a research lab.
 
  • #51
And as phinds mentioned above, Interstellar is science fiction, not science fact.
Discussions of it do not belong here in the relativity forum, although there is at least one long thread about the movie in the General Discussion section where non-science is sometimes discussed.

This thread is closed.
 
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