APOD: Movie: Approaching Light Speed (2011 Oct 18)

[APOD Robot]

Movie: Approaching Light Speed

Explanation: What would it look like to travel near the speed of light? Strange visual effects would appear as documented in the above relativistically-accurate animation. First of all, relativistic aberration would cause objects to appear to bunch up in front you. Next, the Doppler shift would cause the colors of forward objects to shift toward the blue, while things behind you would shift toward the red. Similarly, the world in front of you would seem to move unusually fast, while the world behind you would appear to slow down. Objects to the sides will appear rotated, possibly enabling surfaces normally hidden from you to become visible. Of course, since constant motion is relative, the same effects would occur were you to remain stationary and the entire world advanced toward you.

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[zerro1]

Ouch! better bring lots of motion sickness pills for that ride. I 'll take the slow boat!

[geckzilla]

This is extremely fascinating but I wish the presentation had a high quality version available. Robot lady has a hard time pronouncing some things, as well. But hey, at 240p, even Chris ought to be able to view it without much hassle.

[Boomer12k]

Now I wonder what my bedroom looks like to a photon....

Last time I saw something like that was back in the 80's....er...um...well, heh, heh, some things are better left unsaid....


:-----===== *

[mtbdudex]

Neat to watch, the robot voice reminded me of "Talking Moose" from the late 1980's Macintosh stuff, http://en.wikipedia.org/wiki/Talking_Moose

Click to view full size image

[alphachap]

"The consequences of this fiction have been restricted to optical effects".
What do they mean by that? What other effect would there be?

[tszabeau]

Fascinating video but, if you were going faster than the speed how would light, reflecting off a given object, reach the camera lens or your eyes before you were out of view and able to percieve it?

[Ann]

So far I've only seen the video without sound, so undoubtedly I didn't get everything.

I'm surprised, however, that the world gets so dark as you are approaching light speed.

I've always thought that one reason why it's dark at night is that the universe is expanding (and even accelerating). The photons emitted by the speeding-away galaxies get stretched by the ever-stretching spacetime until they become invisible. (Also, of course, as the universe grows larger, the number of photons per cube light-years goes down, and the existing photons become ever more unable to light up the universe.)

I used to think that if the universe started to contract, it would become ever brighter. I used to think that the sky itself would start glowing first dark red, then orange, then yellow, then blue-white. I used to think that very many galaxies would look brighter, too.

But this video suggests that darkness will fall upon the contracting universe, or at least that is how I interpret this video.

Ann

[WallyBalls]

Was this created on an Atari 400?

[Ann]

Fascinating video but, if you were going faster than the speed how would light, reflecting off a given object, reach the camera lens or your eyes before you were out of view and able to percieve it?

I read somewhere that Einstein made a "thought experiment" that addresses your question. He wondered what it would be like to sit at the end of a light-beam and try to shave, using a shaving mirror. Would he be able to see his own face in the mirror? He concluded that, if he was moving at exactly the speed of light - as he would have to do if he was actually sitting on a light-beam, moving along at the light-beam's speed - then he wouldn't be able to see his face in the mirror. Being able to see your face in a mirror requires that photons are bouncing off your face, "moving ahead of your face" and hitting the mirror, where they can be reflected back at you. But if you move at exactly the same speed as the mirror, the photons bouncing off your face can't "run ahead of your face" so that they can reach the mirror "before you" and bounce back at you.

Apparently this thought experiment was one of the reasons why Einstein rejected the idea that anything that is made of matter can move at the same speed as light.

So Einstein's answer would probably be that you are asking an impossible question, so that there is no answer to it. Or else he would say that there might be tachyons, faster-than-light particles, which, if they exist, are forced to move faster than light. But I don't know more than that about tachyons, so if you want to know more, you should ask someone else. How about asking Neufer?

Ann

[neufer]

"The consequences of this fiction have been restricted to optical effects".
What do they mean by that? What other effect would there be?

The observed scene is static with no clocks in it (other than perhaps the frequency of the observed light).

When Einstein envisioned taking just such a journey he was probably
predominately interested in the slowing down of the clocks and their non synchronicity.

It should also be pointed out that the objects as observed do not correspond
with what the Lorentz transformed objects would be (as measured).

One is essentially observing Lorentz transformed photons
as emitted from Lorentz transformed objects
(as they had once existed at varying times in the past)
such that TWO (not one) Lorentz transformations are involved.

[neufer]

Fascinating video but, if you were going faster than the speed how would light, reflecting off a given object, reach the camera lens or your eyes before you were out of view and able to percieve it?

Einstein's answer would probably be that you are asking an impossible question, so that there is no answer to it. Or else he would say that there might be tachyons, faster-than-light particles, which, if they exist, are forced to move faster than light. But I don't know more than that about tachyons, so if you want to know more, you should ask someone else.

How about asking Neufer?

tszabeau: I'm not gonna try to figure it out — you try to figure it out!

Ann: Let's ask Neufer; he (thinks he) knows everything.

Click to play embedded YouTube video.

If one just plugs tachyons into the relativistic equations
everything just comes out as imaginary numbers:
gamma, mass, time, aberration angles, etc.

However, there is a nice time/space symmetry for electro-magnetic waves (i.e., exp[i(kz-Ωt)]
and, likewise, there is a nice time/space symmetry for tachyons as compared with tardyons.

In the limit of infinite (but non-relativistic) velocity tachyons
such particles are fixed in time but travel in space (which they perceive as their time).

As such I would guess that a tachyon's perception of things is very similar to that of a tardyon (like us)
with possibly some sort of mirror reflection (e.g., we appear to be traveling in the opposite direction).

[orin stepanek]

So! If you were traveling at the speed of light; you would have to slow down so you could see where you were going.

[Fredthebanddirector]

That was cool.

[Steve D]

Some days APOD is great. Some days not so great. This one is truly awful. But it's not like we have spacecraft at Vesta, or Mars, or Saturn, or Mercury to supply images. Would it have hurt to find or make a high quality video, and post it directly instead of second hand via YouTube?

[moonstruck]

Better hope ya don't hit a bug.

[G-Lode]

I believe some of this may ignore the "SPECIAL" part of Einstein's theory. No mater the velocity of the emitting or receiving body the perceived or measured speed of light remains constant. This would seem to discount some of the information presented in the animation at the 'normally hidden' link.

[geoffrey.landis]

I am puzzled. The first visual effect I see on acceleration is that the building in the distance appears to move farther away-- but this occurs at v<<c, well before any relativistic effects will be noticible. As it happens, I have a lot of experience with motion at subrelativistic speeds and when you accelerate, things in the distance ahead do not appear to move away.
What is this effect?

[zbvhs]

When aerodynamicists looked at the region beyond the speed of sound, they found a regime that was tractable and logically consistent. If somehow one was to get past the speed of light into a super-light realm, would they find a regime that was likewise tractable and logically consistent or would everything be all imaginaries and total weirdness?

[Chris Peterson]

When aerodynamicists looked at the region beyond the speed of sound, they found a regime that was tractable and logically consistent. If somehow one was to get past the speed of light into a super-light realm, would they find a regime that was likewise tractable and logically consistent or would everything be all imaginaries and total weirdness?

C is not a barrier, beyond which things are simply different. It is a limit. So the question falls apart with "if somehow one was to get past the speed of light..."

[neufer]

Better hope ya don't hit a bug.

It would be a rather heavy bug for sure but it would still be traveling under 1m/s.

(Bomber safety glasses should still suffice.)

[neufer]

Light from location 1 will appear to be coming from location 2 for a moving telescope due to the finite speed of light, a phenomenon known as the aberration of light.

---

I am puzzled. The first visual effect I see on acceleration is that the building in the distance appears to move farther away-- but this occurs at v<<c, well before any relativistic effects will be noticeable. As it happens, I have a lot of experience with motion at subrelativistic speeds and when you accelerate, things in the distance ahead do not appear to move away.
What is this effect?

The aberration of light like the Doppler effect is fundamentally a linear (i.e., first order) relativistic term. So the next time you walk, bike, or drive try to be a little more observant.

[geoffrey.landis]

So far I've only seen the video without sound, so undoubtedly I didn't get everything.
I'm surprised, however, that the world gets so dark as you are approaching light speed.

It doesn't. The edges of your field of view get dark, but that's because almost everything you see moves to a small cone in the center of your direction of travel, and that center gets very bright, and very blue. Very very bright.

I've always thought that one reason why it's dark at night is that the universe is expanding (and even accelerating). The photons emitted by the speeding-away galaxies get stretched by the ever-stretching spacetime until they become invisible. (Also, of course, as the universe grows larger, the number of photons per cube light-years goes down, and the existing photons become ever more unable to light up the universe.)

All pretty much right.

I used to think that if the universe started to contract, it would become ever brighter. I used to think that the sky itself would start glowing first dark red, then orange, then yellow, then blue-white. I used to think that very many galaxies would look brighter, too.

Right. Although the universe will have contracted to a pretty small size before the cosmic microwave background is blueshifted short enough to be visible!

[neufer]

I believe some of this may ignore the "SPECIAL" part of Einstein's theory. No mater the velocity of the emitting or receiving body the perceived or measured speed of light remains constant. This would seem to discount some of the information presented in the animation at the 'normally hidden' link.

I'm sure that careful attention has been taken as regards to the "SPECIAL" part of Einstein's theory.

Note that the back sides of signs and buildings are generally not seen by the driver except in the rear view mirror. However, the aberration of light allows for photons from the back sides of signs and buildings to be intercepted (at an angle...NOT overtaken) by the vehicle such that they also appear in the front windshield.

[Guest]

Fascinating video but, if you were going faster than the speed how would light, reflecting off a given object, reach the camera lens or your eyes before you were out of view and able to percieve it?

I read somewhere that Einstein made a "thought experiment" that addresses your question. He wondered what it would be like to sit at the end of a light-beam and try to shave, using a shaving mirror...
Apparently this thought experiment was one of the reasons why Einstein rejected the idea that anything can move at the same speed as light.

So Einstein's answer would probably be that you are asking an impossible question, so that there is no answer to it.
Ann

Thanks for answering my question, although, I could have worded it more betterer.
I was not refering, however, to light bouncing off an object going the same speed as the viewer but rather, stationary and/or slower than lightspeed objects such as, the building and sign in the video. I think they would be invisible to my view.
I believe that light, reflected from a handheld mirror would reflect my face if in a faster-than-light craft.
I think that if I tried to clean my razor by sticking it out the window, it (along with my hand) would vanish from view into utter darkness. I don't know if I could pull the razor and my hand back into the faster-than-light field or not, even if I slowed down so... it would probably really smart. Likewise I can't imagine being able to see stars, as their light would be stuck at mere lightspeed and thus unable to catch up with my faster-than-light eye.

I also don't have a clue how Neufer seems to know my other screenname but, I am pretty creeped out about it. Perhaps he does know more about tachyons than the rest of us.