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The ULTIMATE relativity demo?

Thats pretty damn cool.

I do worry though that it gives the impression that relativity is a perceptual phenomenon. For example, whenever I see lack of simultaneity explained by the famous lightning flashes and the observer on the train, I cringe.

The point is many of those effects would be true if applied to sound waves with some finite speed, but do not require a rethinking of how we deal with spacetime measurements. It really needs to be made clear that the effects are measurable via the extended reference frame of the observer, and are not simply a phenomenon experienced by a pointlike observer receiving information about her surroundings at some finite speed...
 
Just noticed at about 1:45 in the VSR movie with the road and the buildng, that you can see walls on the building in the direction of travel that aren't visible at lower speeds at about 0:50 into movie.

So you can see backwards and off to one side? Weird. :D
 
wipeout said:
Just noticed at about 1:45 in the VSR movie with the road and the buildng, that you can see walls on the building in the direction of travel that aren't visible at lower speeds at about 0:50 into movie.

So you can see backwards and off to one side? Weird. :D
Click to expand...

You notice the same thing in all the lightspeed accelerations, if you pay attention. If you look at both movies, at one point they try to explain this with a mercator projection - and a cute little vector diagram, too.
 
Tez, I wouldn't worry if I were You . Most school children in the world can probably parrot that famous formula of Einstein's yet do not understand it. That's OK tho, they will use it as much as they will use the facts of Bolivia's main export and the history of the Tartars. When interviewed about STR Einstein exclaimed that " only about 3 people in the world understand it" , I'm assuming that was Einstein, Bohr and maybe Bethe.( altho he was a gleam in his father's eye when A.E. was working the foundations of STR/GTR.

Unless the specters of Religious myopia and the Luddite mentality ( both of which are raising their ugly heads once more ) gains control of the sciences , I think that You can rest assured that altho misunderstood by most and mangled by many Science and therefore Physics will survive intact. If the masses require a cartoon to gain a foothold, what matter?
 
Truly awesome. I'm showing this to my kids immediately!

Thanks, Scribble.
 
OK, I understand the redshift and the geometric distortion, but why does the scene in front get bright v. the darkening scene behind?

Are you plowing into photons that were originally launched at angles to your direction of travel? I guess that would explain the way things behind you seem to swing around to the front, too. Is that what's happening?

I'd thought that, since all light traveled at "c" in your reference frame, too, that such things wouldn't happen. Ditto for the lack of light behind you -- those photons would still be at c to you (even if they were launched from an object not moving with you) so shouldn't they be flying past you at c?
 
What my relativity intuition would say is that while they're still flying past you at c, they've lost some energy in the process of "catching up" to you, and so would be darker (and blueshifted). What I'm not entirely clear on is why both of these effects happen, rather than just one or the other.
 
From their explanation page: http://www.anu.edu.au/Physics/Searle/Commentary.html
To understand relativistic aberration, consider the ordinary "real" world. When a vehicle moves though rain, to the vehicle the rain seems to fall at an angle. In an analogous process, photons "falling" into the camera appear to come from different angles as the camera moves at different speeds. As the camera moves faster and faster, photons enter it at increasingly steeper angles. This means that things that would appear behind us if we were in their rest frame are wrapped forward into our field of view. The same, reversed, applies to outgoing photons.
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OK, I may have been right about "plowing into" the photons, I guess, but how? They move at c for EVERYONE, even for the moving observer. I buy that light directed at right angles to the direction of travel could appear to come in at about 45° as you get close to c. Isn't there a limit on the wrapping effect -- how could you ever see the back of the road sign as you pass by it? Are you "catching up" to photons coming from its back side? That shouldn't be possible, I'd thought.
HWdopple.jpg

Why would there be a dearth of photons coming up from behind you? Maybe they're so severely redshifted that the demo shows the brightness dropping off becasue our eyes can't see them? So an x-ray emitter behind us, with the same "brightness" as a lamp may look like a lamp?
 
garys_2k said:

OK, I may have been right about "plowing into" the photons, I guess, but how? They move at c for EVERYONE, even for the moving observer.
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Think of the rate individual photons arrive, and the space between them. If an object is moving towards you at 1/2 c, and emitting a photon every second, you will recieve a photon from it every 1/2 second (it's 1/2 light seconds closer when it emits the second photon, so the two photons are only separated by 1/2 light seconds, not 1 light second). If the same object is moving away from you instead, you will recieve those photons every 3/2 seconds.
 
Oh, yea, that was it. The intensity increases/decreases because the number of photons per unit time increses/decreases, and the redshift/blueshift happens because the wavelength of each photon changes.

I'm still not entirely clear on why you can see behind things. Could you explain this, please?
 
Yes, that does explain the intensity question, thank you. But I am also at a loss to figure out how you can see the back of things as you go by. Is it that the photons that are moving toward your travel direction vector, but at an oblique angle to it, can be intercepted?
 
garys_2k said:
Yes, that does explain the intensity question, thank you. But I am also at a loss to figure out how you can see the back of things as you go by. Is it that the photons that are moving toward your travel direction vector, but at an oblique angle to it, can be intercepted?
Click to expand...

It is perhaps a little easier to think of the object as moving and you as stationary. Imagine a cube flying past you. When it's next to you, you expect to see only its side. But if it's going really fast, you see it's back as well. The reason is that light emitted from the back face can travel along a vector with forward motion and still not hit the back face of the cube, because the cube moves out of the way. Another way to think about it is to think about where the parts of the cube are when they emit light. The far back corner is farther away from you than the near back corner. Light you recieve from the two back corners at any one instant do not originate at the same moment. Because the far back corner is farther away, light from it had to travel further and was emitted earlier. So if you consider where the two corners were when they emitted light towards you, you'll find that the near back corner has moved forward enough in that time interval that it's out of the way of light from the far back corner.

Does that help any?
 
Yes, it does; thank you. This whole subject seems to be one of those where I repeatedly think "OK, now I have it," but later find I was missing large parts of it. But yes, the idea that the closer part "gets out of the way" and allows photons to reach the viewer does help.
 
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