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

[bino]

they both get shorter in retrospect of each other?

 

[Nenad]

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.

 

[bino]

so wouldn't they counter balance each other?

 

[bino]

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?

 

[quantumdude]

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.

 

[bino]

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?

 

[employee #416]

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?

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.

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.

 

[Nenad]

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

 

[bino]

the pictures didnt come through to me.

 

[employee #416]

Yea, LaTeX messed up I guess. I can't see it either.

 

[quantumdude]

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.

 

[quantumdude]

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.

 

[bino]

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.

 

[employee #416]

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. 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?

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.

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.

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?

 

[quantumdude]

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.

 

[bino]

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.

 

[quantumdude]

Heh, first year physics. 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.

 

[bino]

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.

 

[Nacho]

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?

 

[quantumdude]

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.

 

[quantumdude]

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.

 

[Nacho]

I understand .. Thanks Tom.

 

[bino]

but wouldn't the end points change as i got closer?

 

[quantumdude]

but wouldn't the end points change as i got closer?

No. They are fixed in space.

 

[bino]

wouldnt they be if i were going faster?

 

[quantumdude]

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.

 

[bino]

wouldnt they still be fixed endpoint?

 

[quantumdude]

wouldnt they still be fixed endpoint?

The location of the endpoints--at the time you made the length measurements--are fixed.

 

[bino]

and if i measured the length from 1ft away then i measured it from 200ft away. the measurements would be different.

 

[bino]

the object is getting smaller right?