Mark M

738 reputation

bio	website
	location	Philadelphia, PA, USA
	age
visits	member for	9 months
	seen	Oct 31 '12 at 15:14
stats	profile views	60

	738 reputation	bio	website		visits	member for	9 months
7 badges		location	Philadelphia, PA, USA		seen	Oct 31 '12 at 15:14

summary answers questions tags badges favorites bounties reputation activity

61 Actions

suggestions reviews revisions comments badges posts accepts all

Sep 5	answered	Observable universe does it account for farther away galaxies measure of the observable universe?
Aug 25	comment	Has the speed of light changed over time? @lurscher Why do you think it is more valid to say that the speed of light changed, rather than the wavelength of the sodium line, or the half-life of the ammonia resonance? I could choose to try to measure the wavelength of said sodium line using light, and conclude that it varied, not the speed of light. I don't agree with your point.
Aug 25	revised	Has the speed of light changed over time? added 1782 characters in body
Aug 25	answered	Has the speed of light changed over time?
Aug 16	answered	How is light affected by gravity?
Aug 15	comment	Why is Neutron Heavier than Proton? Well, you're right that we haven't observed it, but it would be very hard to make sense of the asymmetry of matter and anti-matter if protons don't decay (since that would imply baryon number is conserved).
Aug 15	answered	A relative time dilation paradox.
Aug 14	revised	Could the Heisenberg Uncertainty Principle turn out to be false? edited body
Aug 14	answered	Space Expansion vs. Relative Motion
Aug 14	comment	Is it possible to build an instrument which can travel faster than light? Also, note that neutrinos do not travel faster than light. There was a measurement error at CERN, a loose cable.
Aug 14	answered	How to make a monopole magnet?
Aug 14	revised	Could the Heisenberg Uncertainty Principle turn out to be false? added 1813 characters in body
Aug 14	comment	Could the Heisenberg Uncertainty Principle turn out to be false? @drake Right, I 100% agree. The HUP can be deduced from both wave mechanics and matrix mechanics, so it's quite clearly a fundamental part of QM.
Aug 14	comment	Could the Heisenberg Uncertainty Principle turn out to be false? @drake You can't derive it from the SE, but from the wave mechanics formulation (which is what I guess Annix means). See the'Proof of Kennard Inequality using Wave Mechanics' sub-section here: en.wikipedia.org/wiki/… However, I agree with you that the HUP is fundamental (see my above post.).
Aug 13	comment	Could the Heisenberg Uncertainty Principle turn out to be false? @Annix This isn't true. Firstly, Heisenberg's matrix mechanics is an equally valid formulation of QM as wave mechanics, see Zettlli page 3. Second, the uncertainty principle is a part of wave mechanics. As you say, you can easily derive it from the Schrodinger equation. I find it odd that you say that this somehow makes the uncertainty principle irrelevant. You can't simultaneously know position and momentum to perfect accuracy, since localizing the position of the particle involves adding plane waves, which then makes the momentum uncertain.
Aug 13	awarded	Critic
Aug 13	comment	What is the likelihood of ever discovering the graviton? @Annix They used neutrons stars in the paper, which is pretty much as high an energy you can get for gravitons. Not only that, but a detector the size of Jupiter positioned directly outside of it. And still you only get one every ten years.
Aug 13	comment	What is the likelihood of ever discovering the graviton? @Annix In my answer, I was referring to direct detection of gravitons. Of course, you may argue that since quantum mechanics requires waves to have quanta with energy proportional to their frequencies (Planck's law, $E = hf$), and since gravitational waves exist, then so must gravitons.
Aug 13	comment	What is the likelihood of ever discovering the graviton? We certainly haven't ruled gravitational waves out, because we have seen their effects through the Binary Pulsar 1913+16 (astro.cornell.edu/academics/courses/astro201/psr1913.htm) for which the 1993 Nobel Prize in physics was awarded. So, we know they exist (and therefore have very strong confidence gravitons exist in some form). In order to detect GWs, detectors such as LIGO (astro.cornell.edu/academics/courses/astro201/psr1913.htm) have been constructed. LISA (lisa.nasa.gov) is also being planned, which should certainly detect GWs.
Aug 13	answered	Could the Heisenberg Uncertainty Principle turn out to be false?