Talk:Relativity (Misconceptions)

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A few comments, but are the following statements from the article correct: "For example, if one points a laser at the Moon, a simple flick of the wrist will cause the “spot” to move across the Moon’s surface faster than the speed of light. Some carefully constructed scissors could be made where the point of contact between the blades moves faster than the speed of light." I believe that the "'spots' on the moon move faster than light" is a misconception, but the idea put more to the point is that no information (whatever that mysterious word means) can be transmitted faster than light. Its perfectly possible to flicker a spot on the moon faster than light in morse code rhythm just fine, but the time it takes for you to sign that morse code and the time it takes for the code to reach its target will be exactly (distance)/(speed of light) --Yahweh 14 August 2005 02:37 (PDT)

the spots on the moon thing is correct (if you want a rather exteream exaple imagain putting a string of sensors 1 lightyear from a plusar and mesuring the rate at which the radio waves set off the sensors). Information though is limited to the speed of light in a vaccume.Geni 14 August 2005 03:12 (PDT)

[edit] Fair warning

I'm planning on substantially rewriting and expanding this entry. epepke 27 September 2005 21:57 (GMT)

That's what it's for. --Diamond September 27, 2005 22:04 (GMT)

Yeah, I know. Anyway, I've done the first cut; check it out. I'm a bit fagged after writing all the text, and some of it may be dopey and would doubtless improve from a wordsmithing. I've tried to retain the spirit of the original, concentrating on the misconceptions for debunking and with a minimum of explanation. I figure that if someone wants to know more, they can always look on Wikipedia or elsewhere on the web. I've also tried to keep the best language from the original. epepke 28 September 2005 02:59 (GMT)

Adding links to Wikipedia or other sources for various definitions would be a good idea. --Diamond September 28, 2005 06:39 (GMT)

I quite agree. Perhaps someone who is good at doing that, enjoys doing that, and wants to get credit in the noosphere for doing that will come forward and do it. epepke 29 September 2005 01:29 (GMT)

[edit] Tachyons not detectable?

Very nice additions, epepke! Is it true that tachyons do not interact with subluminal matter? An accelerating tachyon with an electric charge should emit photons.

A tachyon would be completely outside the scope of Maxwell's equations. Just from simple-minded principles, if an FTL universe is quantum, which it should be, for any period of time by the time an accelerating charge started generating a photon, it would be long gone, thus driving the amplitude of emitting a photon to zero. One could argue from weak but plausible principles that there might be something like Maxwell's equations, and so an accelerating tachyon charge should emit something like a photon, but that would just be another kind of tachyon, and you have the problem of detectability again. Also note that there's a limit to how much it could be like Maxwell's equations. From ME, you can make an antenna, which has electrons going back and forth, and this will emit radio waves. You can't do that, even theoretically, with a tachyon, because tachyons cannot be decelerated to lower than c.

Frankly, I think that tachyons are tantamount to pure fantasy and there is no compelling reason to think very hard about them except for fleshing out a science fantasy story. I felt compelled to include them because they were in the original, and also to give a flavor of a lot of physics "theory," which often consists of nothing more than playing around with numbers. Yeah, you can plug in v>c and get results that are no longer infinite (but still weird) and assign the name "tachyon" to that, but that's really all it is. epepke 28 September 2005 21:28 (GMT)

[edit] Can we consider splitting this topic up?

As far as I can see, this article is really trying to compress lots of separate topics:

• Galilean Relativity
• The Aether
• Newton's Absolute Space and Time
• The Michelson-Morley Experiment
• James Clerk Maxwell
• Maxwell's Electrodynamics
• The Invariant Speed of Light
• Albert Einstein
• Lorentz-Fitzgerald Contraction
• Mach's Principle of Relativity
• Einstein's Special Relativity
• Einstein's General Relativity
• The Casimir Effect

and from the Skeptical perspective:

• Objections to Einstein's Relativity
• Misconceptions about Einstein's Relativity (which is what this article is really about)
• Tachyons and Faster-than-Light Theories

Now personally I don't mind the fact that we compress lots of topics to get to a particular point, but perhaps we should consider, as we move forward, defining some or most of these terms and linking to good sources for others.

Perhaps there should be a Relativity category?

I hope that when the new server is established, we will invite others of a scientific bent to write some of these articles. --Diamond October 13, 2005 09:52 (GMT)

It is a bit long and unwieldy. Most of the "other" topics that you mention are part of the section on the history of relativity. I think it's important to have a history somewhere, because one of the misconceptions about relativity is that it represents some sort of massive "paradigm shift" from Newtonian mechanics, whereas in fact it's completely consistent. But maybe that could go in a separate page. How's about a short page on relativity that links to History, Details (not yet written), and Misconceptions? The master page could link to the Misconceptions page. epepke 14 October 2005 16:37 (GMT)

IMO, the "misconceptions" ought to be the primary focus, since that relates directly to the purpose of the wiki. I don't see that it's necessary to have a complete primer on relativity, except to the extent that it would explain why the misconceptions are wrong.

I propose splitting this into "Relativity (Misconceptions)" and "Relativity (Technical Primer)", with a disambiguation page under "Relativity".

This could be done without any further writing. We could also have "Relativity (History and Personalities)", but that might be outside the scope of the wiki.

Any objections?