Relativistic trip to Sirius and the beauty of relativity

Professor Muller gives another example of relativistic strangeness. A trip to a star seven light years away turns out to be a one year journey.

Apparent paradoxes turn out not to be paradoxes at all. Muller explains the complete self-consistency of the theory.

Full lecture:
http://video.google.co.uk/videoplay?docid=8773586855870787823

All Lectures:
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Category:

Education

Tags:

• Relativity
• Einstein
• physics
• science
• sirius
• lightspeed
• Lorentz
• spacetime
• university
• Richard
• Muller

[brysoncj]

So to "personify" light a little bit- electromagnetic propagation in a vacuum is "ageless;" all distances are infinitesimally short and time is infinitely long in its frame. So light propagating through a medium such as glass or water experiences objects of finite length and can now "age," as a second no longer takes an infinity to occur. (Does this make any sense???) It would be so cool if we found a transparent substance through which light's speed were slowed to perceptible levels!

[theinquisitor]

A photon "experiences" no time. Whether the time between it's emission and absorption is a nanosecond or 10 billion years, it's instantaneous to the photon.

As I understand it, the reason light is slowed in a medium is not because it's straight line momentum is decreased, but because the medium causes it to bounce around inside and take a longer path to reach the other side. Or it might have to do with continual absorption and reemission, but I don't think the actual speed of light slows.

[TheCopaceticMan]

@theinquisitor

reemitted, possibly in the same direction it came from, or any other direction along the xyz axis. That it what causes it to 'bounce,' and those science television shows never explain that, they just give you the concept.

[theinquisitor]

@TheCopaceticMan, indeed many documentaries badly mangle the concepts. Especially the big bang and evolution. That combined with the active propaganda against science makes it no wonder that science is so misunderstood, disrespected and dismissed by so many in our society.

Also, I think that's right about the light bouncing around inside the medium, but it would be nice to hear some explicit clarification from a physicist on the matter.

[SuperMagnetizer]

To find a Proper Velocity, then, involves dividing a Proper Length as measured by someone in the same frame as the Length being measured, by a Proper Time, as measured by someone in the same frame as the Time being measured. Or a contracted length can be divided by a contracted time. In both cases, because the units are consistent, the answer is correct. V = 8.838m / 26ns = 5.846m / 17.197ns = 1.134c. The pion exceeds the apparent speed of light.

[theinquisitor]

I'm sorry SuperMagnetizer, but this is beyond me. I don't really have a response. Hopefully someone who does will read your comments so they won't fall on deaf ears, or blind eyes or whatever metaphor is appropriate.

[PittmanNeil7285]

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[SuperMagnetizer]

At v = 0.990c during trip to Sirius (s = 8.65 c-yr away), imagine you are tuned into Sirius TV. Due to Lorentz factor g = 7.09, the time t for the trip is now t = (s / g) / v, or t = (8.65 c-yr / 7.09) / 0.990c = 1.23 yr. When do you intercept most of the 8.65 years' worth of Sirius TV signals? During the initial acceleration or during the 0.990c coast? BTW, ship time to Sirius also equals 8.65 c-yr / (7.09 x 0.990c) = 1.23 yr, where V = 7.02c. (Refined numbers, for your pleasure.)

[SuperMagnetizer]

At v = 0.99c during trip to Sirius (s = 8.65 c-yr away), imagine you are tuned into Sirius TV. Due to Lorentz factor g = 7.1, the time t for the trip is now t = (s/g) / v, or t = (8.65 c-yr / 7.1) / 0.99c = 1.23 yr. When do you intercept most of the 8.65 years' worth of Sirius TV signals? During the acceleration or during the 0.99c coast? BTW, ship time to Sirius also equals 8.65 c-yr / (7.2 x 0.99c) = 1.23 yr, where V = 7.03c.

[JaySoap]

@brysoncj If I am not mistaken, the closest thing to perceptible is through a Bose-Einstein condensate.

[TheCopaceticMan]

@theinquisitor

Also I wouldn't say that those documentaries mangle the concepts, I would say that they are not explained as well as they could be. They could include the equations, but then the general population would have no idea what they were talking about.

[TheCopaceticMan]

@theinquisitor

You don't have to ask a physicist, I learned that in chemistry last year. Of course, my teacher never explicitly said any of that. I took what she taught us about photon absorbsion and reemission and elaborated the idea to explain the 'bouncing' photons. It is really a simple concept, as long as you have a undertanding of chemistry.

[TheCopaceticMan]

@theinquisitor

This second part I understand very well. The photon is not truely slowed down, the it seemingly bounces around in a certain medium, so the distance it travels in a certain direction is slowed, which is like running in a zig zag line. You may be traveling a fifteen meters/second, but in a certain direction you may have only covered five meters in the same amount of time. The reason why the photon 'bounces' is because the photon is absorbed by the electron clound, then...