Can the Speed of Light Be Changed and What Does It Mean for Space Exploration?

AI Thread Summary
The discussion centers on the concept of altering the speed of light and its implications for space exploration. While light can appear to change speed when refracted through different media, the fundamental speed of light in a vacuum, denoted as 'c', remains constant and cannot be increased. Theoretical discussions suggest that changing physical constants could lead to significant alterations in the universe, but such changes are speculative and would likely disrupt fundamental aspects of physics and chemistry. The conversation also touches on the idea that traveling near the speed of light could allow for effective space travel without needing to change the speed of light itself. Ultimately, the consensus is that while the speed of light is a critical limit, it is not a barrier that can be bypassed through conventional means.
  • #51
bino, honestly, I agree with you about the appearance to be contracted. It's all just a way of saying our eyes are unable to measure things that move at relativistic speeds, but opinionated comments are, unfortunately, not allowed on this forum. :cry:

Light does not get "sucked" into black holes, rather it falls into black holes. The gravitational pull of a black hole is large due to it's seemingly infinite density. This pull creates an escape velocity that is larger than the speed of light. Inevitably, light is unable to escape.
 
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  • #52
employee #416 said:
Light does not get "sucked" into black holes, rather it falls into black holes. The gravitational pull of a black hole is large due to it's seemingly infinite density. This pull creates an escape velocity that is larger than the speed of light. Inevitably, light is unable to escape.

that is once youre in the event horizon. Light can be deflected or bent from a black hole towards another object. The reason for this is that light has a mass, but it has no rest mass. So gravity has an effect on light particles. :smile:
 
  • #53
Yes, that light is also shifted. Gravitational-red shift takes place.
 
  • #54
so in other words c can't outrun a black hole. or is it that it is just absorbed by the hole atoms?
 
  • #55
bino said:
according to http://www.fourmilab.to/cship/lorentz.html the length of the ship and the lattice only appears to be contracted. it is not actually smaller it just looks like it is smaller.

yes it will look smaller to the observer. The person in the spaceship will measure the spaceship to be normal length. But the reason space contracts is because the observer sees the space as moving by him at high speed and contracting. Making distance differen at different speeds.
 
  • #56
bino said:
so in other words c can't outrun a black hole. or is it that it is just absorbed by the hole atoms?

look up black holes on the search, it will give you threads talking and explaining black holes. Its a lot easier than me answering all of your questions.
 
  • #57
so if the ship looks like it is getting smaller as it gets closer to c would the ship then dissapper if it hits c?
 
  • #58
pervect said:
I've usually taken the position that 'c' is what's actually constant[/color], the speed of transmission of energy through a media, which is what "speed of light" means if you take it literally, is not.

bino said:
ok are you saying that c is not constant?

See the part in blue[/color]. He just said that it is constant.

employee #416 said:
Yeah, I think the reason why emission and absorption is not constant is that light is absorbed through different densities.

The average speed of light is different in different media because they have different indices of refraction.

If it is absorbed in a material that has a low density, it will be absorbed less, but pass it through a dense material, and it will be absorbed fast. Emission of the photons occurs as a result of absorption.

It has to do not only with the number of absorbers per unit area, but also the length of time that each atom holds the photon.

bino said:
according to http://www.fourmilab.to/cship/lorentz.html the length of the ship and the lattice only appears to be contracted. it is not actually smaller it just looks like it is smaller.

No, if an observer who is watching the ship zoom by measures the length of the ship, he will really measure it to be less than the proper length of the ship (the length in the ship's rest frame). Conversely, the people on the ship will really measure the rods of the lattice to be shorter than their proper length. It's not an optical illusion.

bino said:
why is light sucked into black holes?

The photons are just following the geodesic, as they always do. In the case of black holes, the geodesic leads irrevocably to the center of attraction, with no path of escape.
 
  • #59
employee #416 said:
bino, honestly, I agree with you about the appearance to be contracted. It's all just a way of saying our eyes are unable to measure things that move at relativistic speeds, but opinionated comments are, unfortunately, not allowed on this forum. :cry:

It's not just opinionated, it's also wrong.
 
  • #60
theoretically yes. You saw the graph. And just to add, the ship cannot ever reach c, anything with mass cannot move at c. It can go 0.9999999999999...c, but never 1c. At 1c, there is an assymptote.
 
  • #61
they both get shorter in retrospect of each other?
 
  • #62
yes. It all depends on the frame of reference. The guy on the ship will see a person in space contract and himself as being normal, but a guy in sace will see the ship contract and will view himself as being fine.
 
  • #63
so wouldn't they counter balance each other?
 
  • #64
If two trees are 20 feet apart when you are standing still, if you go past them at 80% of the speed of light, they are only 12 feet apart. and if my ship i was 20 feet in length at rest, and i go 80% the speed of light the ships length would be 12 feet. is that right?
 
  • #65
bino said:
they both get shorter in retrospect of each other?

Yes: Each claims that the other is shorter, and that nothing is out of the ordinary with regards to their own length.

so wouldn't they counter balance each other?

No, because each claims that they are at rest, and that the other is moving.

If two trees are 20 feet apart when you are standing still, if you go past them at 80% of the speed of light, they are only 12 feet apart.

Assuming you have done the calculation correctly, yes. That is, the trees are 12 feet apart in your frame.

and if my ship i was 20 feet in length at rest, and i go 80% the speed of light the ships length would be 12 feet. is that right?

It would be shorter in the frame of the trees. You must specify the frame of reference.
 
  • #66
if a ship going one direction going 90% c and i was going the opposite at 90% and we fly past each other, what would happen then?
 
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  • #67
Tom Mattson said:
It has to do not only with the number of absorbers per unit area, but also the length of time that each atom holds the photon.
So, in other words, when measuring the density of emission and absorption, the amount of time should be included. How can that factor be determined?

Tom Mattson said:
It's not just opinionated, it's also wrong.
Or maybe you're wrong. Just because opinions contradict with the standard model, doesn't make them wrong. You are unable to use the standard model to counter new theories or opinionated ideas.

Tom Mattson said:
No, if an observer who is watching the ship zoom by measures the length of the ship, he will really measure it to be less than the proper length of the ship (the length in the ship's rest frame). Conversely, the people on the ship will really measure the rods of the lattice to be shorter than their proper length. It's not an optical illusion.
Has anything moving at relativistic speeds ever been measured? I'm not saying by equations, but by means of physical rulers. Until then, you are unable to claim it not to be an optical illusion. Just because a formula is derived from the transformation of triangles (might I add the way our eyes measure distances is through triangles...this is not always accurate) does not mean it is necessarily true.
 
  • #68
bino said:
if a ship going one direction going 90% c and i was going the opposite at 90% and we fly past each other, what would happen then?

then you would have to use relativistic velocity addition. Find the relative speed to eachoter, and calculate the contraction. In this case, they could both contract according to achother and they would both be right. I've give you an example of relativistic addition.

u' = \frac{u + v}{1 + \frac{uv}{c^2}}

u' = \frac{0.9c + 0.9c}{1 + \frac{(0.9c)(0.9c)}{c^2}}

u' = \frac{1.8c}{1 + \frac{0.81c^2}{c^2}}

u' = \frac{1.8c}{1.81}

u' = 0.994c
 
  • #69
the pictures didnt come through to me.
 
  • #70
Yea, LaTeX messed up I guess. I can't see it either.
 
  • #71
employee #416 said:
So, in other words, when measuring the density of emission and absorption, the amount of time should be included. How can that factor be determined?

You can determine the index of refraction by sending a light pulse in and measuring the speed with which it comes out. The ratio of the speed of light in vacuum (c) to the speed of light in the medium (c') is the index of refraction (n). Simply put, n=c/c'.

Or maybe you're wrong. Just because opinions contradict with the standard model, doesn't make them wrong. You are unable to use the standard model to counter new theories or opinionated ideas.

No, you're wrong, and there's no "maybe" about it. While it's true that one theory cannot be used to falsify another theory, it is also true that experimental evidence can falsify a theory. And Galilean relativity (the only kind in which there is no length contraction) has been falsified experimentally.

Has anything moving at relativistic speeds ever been measured? I'm not saying by equations, but by means of physical rulers. Until then, you are unable to claim it not to be an optical illusion. Just because a formula is derived from the transformation of triangles (might I add the way our eyes measure distances is through triangles...this is not always accurate) does not mean it is necessarily true.

Length contraction has not been measured directly, but the invariance of the speed of light has been, as has time dilation. It is not logically possible for the speed of light to be absolute and for time to not be absolute, and simultaneously have space be absolute.
 
  • #72
bino said:
if a ship going one direction going 90% c and i was going the opposite at 90% and we fly past each other, what would happen then?

You will observe a length contracted ship go past you at 0.994475c and whose length is contracted from its proper length by a factor of 1/0.43589.
 
  • #73
Each claims that the other is shorter, and that nothing is out of the ordinary with regards to their own length. how can it be that the length of an object can get shorter to someone but not to someone else? i could understand it if it only looks shorter to the observer. it is like looking at a barn from 1ft away and looking at it from 200 ft away. the barn is smaller from farther away.
 
  • #74
Tom Mattson said:
You can determine the index of refraction by sending a light pulse in and measuring the speed with which it comes out. The ratio of the speed of light in vacuum (c) to the speed of light in the medium (c') is the index of refraction (n). Simply put, n=c/c'.
Heh, first year physics. :redface: You use index of refraction in Snell's law to find the angle at which light is bent, right? This can also be interpreted as the angle at which light is absorbed and emitted from the old medium to the new medium?

Tom Mattson said:
No, you're wrong, and there's no "maybe" about it. While it's true that one theory cannot be used to falsify another theory, it is also true that experimental evidence can falsify a theory. And Galilean relativity (the only kind in which there is no length contraction) has been falsified experimentally.
Hehe, Tom, you cease to amaze me. Experimental evidence relies on our eyes as a confirmation, right? What our eyes see is not what is really happening. Just because something appears to be shorter, does not make it shorter. The true length is ALWAYS there. Things only appear to not be there. If a color-blind person needed a ruler that was blue and said, "Pass me the green ruler." You know the ruler is blue, but the color-blind person sees it as green, because he can not distinguish between colors. Optical illusion.

Tom Mattson said:
Length contraction has not been measured directly, but the invariance of the speed of light has been, as has time dilation. It is not logically possible for the speed of light to be absolute and for time to not be absolute, and simultaneously have space be absolute.
I would seriously argue you on that statement. I would really like to stay being a member on this site. Can you provide me with a link on how time dilation works and how it is derived? Lenght contraction is very well an optical illusion that people view as reality. I'm assuming the same about time dilation, but am fully knowledgeable in that area.

bino said:
Each claims that the other is shorter, and that nothing is out of the ordinary with regards to their own length. how can it be that the length of an object can get shorter to someone but not to someone else? i could understand it if it only looks shorter to the observer. it is like looking at a barn from 1ft away and looking at it from 200 ft away. the barn is smaller from farther away.
This is how our eyes are at flaw of measuring things. Lorentz transformation relies on the way our eyes measure things. It takes a triangle and transforms it to come up with 4 vectors. Blah blah blah blah. So, Lorentz transformations state that an object's length contracts as it is moving at relativistic speeds. A barn LOOKS smaller when viewed from farther away, but we konw the true length is there, right? Is that not a way of saying our eyes can not measure the true size just as our eyes are unable to measure the true length of things moving at relativistic speeds?
 
  • #75
bino said:
Each claims that the other is shorter, and that nothing is out of the ordinary with regards to their own length. how can it be that the length of an object can get shorter to someone but not to someone else?

Length contraction is a function of speed. In a frame in which the speed of an object is 0, the length is said to be the "proper length". The reason each observer claims that the other is shortened from the proper length and nothing is amiss with their own dimensions is that each observer regards himself at rest, and the other moving. That is, each observer imputes a nonzero speed to the other, and since length contraction is a function of speed, each observer would measure a shortened length for the other.

Now that's about a fundamental an explanation as anyone can give. If you want to know why this phenomenon of length contraction is a function of speed in the first place, or why it occurs at all, the only answer anyone can give is, "Because that's the way it is".

We happen to inhabit a universe in which there is an ultimate speed limit. Two direct consequences of that are time dilation and length contraction.

i could understand it if it only looks shorter to the observer. it is like looking at a barn from 1ft away and looking at it from 200 ft away. the barn is smaller from farther away.

That's not a very useful analogy, because that's not the nature of relativistic length contraction.
 
  • #76
Tom Mattson said:
You will observe a length contracted ship go past you at 0.994475c and whose length is contracted from its proper length by a factor of 1/0.43589.
interesting.
 
  • #77
employee #416 said:
Heh, first year physics. :redface: You use index of refraction in Snell's law to find the angle at which light is bent, right? This can also be interpreted as the angle at which light is absorbed and emitted from the old medium to the new medium?

Yes, the index of refraction of a medium is also the ratio of the speed of light in vacuum to the speed of light in the medium.

Hehe, Tom, you cease to amaze me. Experimental evidence relies on our eyes as a confirmation, right?

No. In fact, relativistic measurements do not involve human senses at all, but rather electronic and mechanical subsitutes. Of course, our eyes read the dials, but that's hardly relevant.

What our eyes see is not what is really happening. Just because something appears to be shorter, does not make it shorter.

If something is measured to be shorter, then it is shorter. Measurements are what tell us what is real.

The true length is ALWAYS there.

No, it isn't. You're stuck in pre-relativistic thinking here. One thing SR teaches us is that there is no preferred frame, and there is no "real" length of objects.

Things only appear to not be there. If a color-blind person needed a ruler that was blue and said, "Pass me the green ruler." You know the ruler is blue, but the color-blind person sees it as green, because he can not distinguish between colors. Optical illusion.

This is an irrelevant argument by analogy. If you want to talk about SR, then why not just stick to SR?

Tom: Length contraction has not been measured directly, but the invariance of the speed of light has been, as has time dilation. It is not logically possible for the speed of light to be absolute and for time to not be absolute, and simultaneously have space be absolute.

416: I would seriously argue you on that statement.

And I would tell you to open a physics book and study, because this is really basic stuff.

I would really like to stay being a member on this site.

Then stop being so arrogant. You have obviously not studied physics, and here you are telling us that you can do our jobs better than we can.

Can you provide me with a link on how time dilation works and how it is derived? Lenght contraction is very well an optical illusion that people view as reality. I'm assuming the same about time dilation, but am fully knowledgeable in that area.

I repeat: In SR, neither length contraction nor time dilation are illusory. Lifeless detectors can be used to measure these effects, and they cannot be tricked the way human minds can.

Here is the original paper by Einstein:

On The Electrodynamics of Moving Bodies

This is how our eyes are at flaw of measuring things. Lorentz transformation relies on the way our eyes measure things. It takes a triangle and transforms it to come up with 4 vectors. Blah blah blah blah. So, Lorentz transformations state that an object's length contracts as it is moving at relativistic speeds. A barn LOOKS smaller when viewed from farther away, but we konw the true length is there, right? Is that not a way of saying our eyes can not measure the true size just as our eyes are unable to measure the true length of things moving at relativistic speeds?

This is completely wrong. The Lorentz transformation has nothing to do with human eyes or optical illusions. It states what is really happening, and all experimental tests of its predictions have come out positive. If you want to be allowed to post here, then you are going to have to stop posting your opinions that are based only on your own incredulity and ignorance.
 
  • #78
yes it is a cheap analogy but if you take a picture of a barn then measured it the barn would still be smaller. the same as if you take a picture of something going near light speed. the object would be smaller.
 
  • #79
Bunches of question on light being answered .. I got one!

Light moving through a gravitational field will have its direction of travel changed. Is it proper to say that that light is accelerated?
 
  • #80
bino said:
yes it is a cheap analogy but if you take a picture of a barn then measured it the barn would still be smaller. the same as if you take a picture of something going near light speed. the object would be smaller.

But it's still irrelevant. We don't measure the lengths of objects by photographing them. We measure the lengths of objects by simultaneously recording the locations of their endpoints in some coordinate system, and subtracting the coordinates.
 
  • #81
Nacho said:
Bunches of question on light being answered .. I got one!

Light moving through a gravitational field will have its direction of travel changed. Is it proper to say that that light is accelerated?

From a Newtonian point of view, yes. But from a general relativistic point of view, no. Light follows geodesics, and in GR there is no acceleration along a geodesic.
 
  • #82
I understand .. Thanks Tom.
 
  • #83
but wouldn't the end points change as i got closer?
 
  • #84
bino said:
but wouldn't the end points change as i got closer?

No. They are fixed in space.
 
  • #85
wouldnt they be if i were going faster?
 
  • #86
bino said:
wouldnt they be if i were going faster?

Wouldn't they be what if you were going faster?

It doesn't matter if you are moving past the barn or not. If you simultaneously record the locations of the endpoints of a rod in your coordinate system, then the difference in coordinates is the length of the barn in your frame.
 
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  • #87
wouldnt they still be fixed endpoint?
 
  • #88
bino said:
wouldnt they still be fixed endpoint?

The location of the endpoints--at the time you made the length measurements--are fixed.
 
  • #89
and if i measured the length from 1ft away then i measured it from 200ft away. the measurements would be different.
 
  • #90
the object is getting smaller right?
 
  • #91
bino said:
and if i measured the length from 1ft away then i measured it from 200ft away. the measurements would be different.

No, it wouldn't. The measurement of length is a function of the relative speed between the observer and the observed. It has nothing to do with the coordinates of the person doing the observation.

edit to add:

the object is getting smaller right?

The object isn't "getting smaller". If a rod is moving, then it is smaller than it is in its own rest frame. But nothing actually happens to the rod. It's not as though the rod is physically shrinking by some compressive force.
 
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  • #92
Tom Mattson said:
No, it wouldn't. The measurement of length is a function of the relative speed between the observer and the observed. It has nothing to do with the coordinates of the person doing the observation.

edit to add:



The object isn't "getting smaller". If a rod is moving, then it is smaller than it is in its own rest frame. But nothing actually happens to the rod. It's not as though the rod is physically shrinking by some compressive force.
that just proves my point neither the ship or the lattes is physically getting smaller.
 
  • #93
Proves my point also. :smile:
 
  • #94
employee #416 said:
Yeah, I think the reason why emission and absorption is not constant is that light is absorbed through different densities. If it is absorbed in a material that has a low density, it will be absorbed less, but pass it through a dense material, and it will be absorbed fast. Emission of the photons occurs as a result of absorption.

Our eyes would see Terrel rotation, not Lorentz contraction.

http://www.math.ubc.ca/people/faculty/cass/courses/m309-01a/cook/terrell1.html
 
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  • #95
I wasn't even talking about contraction. Nowhere in there did i mention Lorentz transformation. I was talking about emission and absorption of photons and that's strictly it.
 
  • #96
employee #416 said:
Or maybe you're wrong. Just because opinions contradict with the standard model, doesn't make them wrong. You are unable to use the standard model to counter new theories or opinionated ideas.

He's not wrong.

When opinions are in opposition to observed facts, especially well-observed facts that have been confirmed by a multitude of observers, the opinions are wrong.

Has anything moving at relativistic speeds ever been measured? I'm not saying by equations, but by means of physical rulers.

We see muons reach the Earth's surface.

This is proof of both time dilation (from our point of view), and the Lorentz contraction (from the muon point of view). Otherwise, muons simply wouldn't be able to reach the Earth's surface.
 
  • #97
bino said:
that just proves my point neither the ship or the lattes is physically getting smaller.

The length of an object is not the same for a moving observer and a stationary one.

The phrase "physically getting smaller" is unfortunately ambiguous. Measurements made of a moving object *will* show that it's length contracts.
 
  • #98
bino said:
that just proves my point neither the ship or the lattes is physically getting smaller.

It does not. Your statement that the ship "is physically getting smaller" implies that something is happening[/color] to the ship. That is not the case. The fact of the matter is that there is no single "length of the ship". But in your mind, you are at least tacitly denying this, and so you think that when someone measures a length of the ship that differs from the proper length, that something must have been done to the ship to make it so. But that is not right, because there is in fact nothing special about the so-called proper length, other than the fact that it is the length that is measured when the ship happens to be not moving.
 
  • #99
employee #416 said:
Proves my point also. :smile:

By what twisted logic do you reach that conclusion? Recall that your point was that length contraction is an illusion. Nothing I have said supports that view. Indeed, everything I have said specifically denies it.
 
  • #100
Silly Tom! Ok, maybe you were not saying what I thought. All-in-all length contraction is an illusion. Refer to the barn example that bino threw out. The bar up close appears to be normal size, but when you inch away from it, it appears to get smaller. It looses measurement off of height and width from the front view. When you are far away from the barn, it looks fairly small. You know that the true length is not that small. Your eyes are playing tricks on you. Do you agree with that? When something is moving at relativistic speeds, your eyes are unable to measure it anywhere near accurate, so it APPEARS TO CONTRACT, when you know that the true length is still in tact.
 
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