Mark Beadles

1,494 reputation

515

bio	website	markbeadles.com
	location	Columbus, OH
	age	46
visits	member for	1 year, 7 months
	seen	Jan 28 at 17:55
stats	profile views	189

	1,494 reputation	bio	website	markbeadles.com	visits	member for	1 year, 7 months
515 badges		location	Columbus, OH		seen	Jan 28 at 17:55

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Feb 4	comment	Physics of the Internet? This user's profile indicates he is a HS student. I am willing to give him the benefit of the doubt.
Feb 2	comment	Energy required to reach 1 wavelength Thanks, @Community♦ for catching my error in the sign of the exponent.
Feb 2	comment	Energy required to reach 1 wavelength As @Martin alludes to above, it's not correct to think of photons as "using" or "needing" energy to travel. They always travel; that's what they do, and always at the speed of light. A photon doesn't need to "reach" a frequency: when it is emitted, it already has that frequency. It's not like a mechanical wave. Photons essentially are energy. And absent hitting something, a photon will keep travelling to infinity.
Jan 31	comment	What experiment would disprove string theory? I like the metaphor of the extension of the positive integers to the signed integers as a model for the extension of relativity+quantum theory to string theory. But I think a better metaphor is the extension of Euclid's axioms. It turned out there were multiple consistent (even "correct") extensions of the axioms. But of course, only one extension is "true" (or "real) for any given universe. This is rather the question being asked here: is there any experimental way to know which extension reflects reality?
Jan 31	comment	What experiment would disprove string theory? Your indication of the importance of quantum gravity to this question is a great point.
Jan 29	comment	How can I measure the conductivity of a copper rod? Well, you could always measure the length and the resistance with a ruler and ohmmeter, and just calculate $\sigma=1/(\rho * l $)
Jan 29	comment	Why does electron-positron annihilation prefer to emit photons? Thanks for the clarification, that is helpful.
Jan 29	comment	Why does electron-positron annihilation prefer to emit photons? OK, it was not clear from your question that this was what you were asking, as opposed to the more general question.
Jan 27	comment	What is the inertial frame that explains the Foucault Pendulum? I'm making a statement. :) Sorry, not trying to talk at cross purposes. As the wikipedia article also states, the Foucault pendulum is not in an inertial frame. It is rotating, by an angle of −2π sin(φ) per day where φ is the latitude. At the poles the pendulum indeed does not rotate.
Jan 27	comment	What is the inertial frame that explains the Foucault Pendulum? @JohnRennie the triangle you describe rotates with the Earth. Consider the point on that plane, which is on the ceiling where the pendulum is attached. This point is in a building attached to the surface of the earth and therefore rotates with a period of 24 hours. Therefore that plane is itself rotating around the center of the earth as well.
Jan 27	comment	What is the inertial frame that explains the Foucault Pendulum? The sidereal day is 23.93447 hours.
Jan 26	comment	What is the inertial frame that explains the Foucault Pendulum? @JohnRennie What you say is true only at the poles. Elsewhere the pendulum must rotate.
Jan 26	comment	What is the inertial frame that explains the Foucault Pendulum? @Vam'çá it's not gravity that is causing the apparent rotation. I say "apparent" rotation because that's what it is. We are seeing the effect of a combination of real and fictitious forces that, when observed from our viewpoint as stationary with respect to the accelerating Earth, looks like rotation.
Jan 26	comment	why is there no ninth gluon? @mbq thanks for checking it for me!
Jan 26	comment	why is there no ninth gluon? See also this question and its answer on "colorless" gluons.
Jan 25	comment	why is there no ninth gluon? Interesting - it postulates that the color symmetry is broken $U(3)$ instead of $SU(3)$ and that the broken symmetry gives an extremely massive singlet gluon.
Jan 23	comment	Earth's stationary iron core @RonMaimon Of course you are right and I spoke loosely. Sorry.
Jan 23	comment	Earth's stationary iron core In physics when we say "stationary" we must always ask "stationary relative to what?"
Jan 23	comment	Earth's stationary iron core Great links, Adam - in particular I'm fascinated by the discovery that the core is asymmetrical.
Jan 22	comment	What is the meaning of c (velocity of light) in E=mc^2 (atom bomb) Possible duplicate of this question; you may want to take a look at that.