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Sep
30
awarded  Yearling
Sep
28
asked Pluto's internal heat source
Sep
25
comment What will be destroyed? The Moon or the Death Star?
(Of course, in the Star Wars movies the Death Star can travel faster than light, and most things that look like laser beams seem to travel slower than light. But that's all movie stuff and has nothing to do with physics.)
Sep
25
comment What will be destroyed? The Moon or the Death Star?
I'm curious why you think that "Since Death Star is traveling almost at the speed of light, when the laser gets to the Moon, the surface of the Death Star is already there." The Death Star is only travelling at almost the speed of light, whereas the laser is travelling at the speed of light, so it should get there before the Death Star.
Sep
20
comment Why fast eye movement splits a white LED into the RGB components?
It might be clearer if you move the light while keeping your eyes still, but then you have to move it really fast. I see this all the time with many different types of light and can even use it to estimate the frequency of the pulses - it always amazes me that other people don't notice it.
Sep
20
comment Why fast eye movement splits a white LED into the RGB components?
@Sparkler try this: in a dark room, focus your eyes on a point about a foot to the left of the phone, then move your eyes rapidly to a point about a foot to the right of it, so that the light passes right through the centre of your vision. You should notice that it leaves a trail across your visual field for a split second, and with a bit of practice you should see that trail broken up into distinct red, green and blue segments, caused by the light changing colour as you moved your eyes across it.
Sep
17
revised Operator algebra in integral form
Removed inappropriate bickering about style
Sep
9
comment How would Boltzmann Brain function with all anti-matter in it?
@MatasVaitkevicius that's a fair point. Perhaps you also have to imagine that the antimatter particles are emitted with sufficiently low velocity that they eventually return due to gravitational attraction, after the brain has done all its imagining of the universe, and then annihilate all the matter particles again.
Sep
9
answered How would Boltzmann Brain function with all anti-matter in it?
Sep
6
comment Second law of thermodynamics (in terms of entropy)
@DanielSank The "closed" versus "isolated" distinction is very common in thermodynamics texts. Essentially "isolated" means the situation where the microcanonical ensemble is appropriate, "closed" means canonical ensemble and "open" means grand canonical ensemble. The terminology might be irritating, but it's standard.
Sep
4
comment Can I electrify a pin by applying current in its base?
Cross posting is generally discouraged, but its not a legitimate reason to vote to close.
Aug
31
comment Would this pump water up? and if so, how far?
@adrian a Stirling engine does not turn ambient heat into work, it extracts work from the temperature difference between two thermal reservoirs. It is impossible to do it with only one. That is exactly what "perpetual motion machine of the second kind" means.
Aug
30
comment Is the MaxEnt “interpretation” of statistical mechanics the current mainstream approach?
I would advise leaving this question open for a while to get a few answers rather than accepting the first. The currently accepted answer is not wrong and is fairly balanced, but it is only one person's view, not an authoritative answer.
Aug
29
comment Why Does The Moon Apear White/Grayish and The Sun Yellow?
To add to @MarcvanLeeuwen's point, the moon is often clearly visible in broad daylight, and as far as I've ever noticed, always appears pure white in such conditions.
Aug
26
comment Would this pump water up? and if so, how far?
If the energy is to come from thermal ambient energy then you are breaking the second law. This is called a "perpetual motion machine of the second kind," and it's just as fundamentally impossible as creating energy from nothing (which breaks the first law and is called a perpetual motion machine of the first kind).
Aug
23
comment Hysteresis and dissipation
Ok, but the hysteresis in that case most certainly does involve dissipation. Without it all collisions would be elastic and the inner piece would continue bouncing around inside the outer one for ever.
Aug
23
comment Hysteresis and dissipation
What is a "loose running mechanical fit"?
Aug
17
comment Will climate change cause the Moon to move away from the Earth at a faster rate?
This is an interesting question, but probably a difficult one to answer. It's been suggested in the past that the movement of the continents has affected the rate of recession of the moon, mostly because vertically-oriented continents block the water from flowing with the tide. But the fluid mechanics are fiendishly hard to model. I would guess the effect of raised sea level would be extremely small, but I don't know.
Aug
11
comment Quantum entanglement faster than speed of light?
When the entanglement collapses, the particles are no longer entangled, and measuring whether the collapse has happened would be the same as measuring whether they're still entangled. There is no measurable change of any kind when the other particle is measured, magnetic or otherwise. Entanglement, or the collapse thereof, cannot be detected or measured in any way, except by comparing the results of the two measurements - which you can't do without sending a signal between the two points.
Aug
11
comment Quantum entanglement faster than speed of light?
This will not work because "some apparatus that only reacts when the entanglement is collapsed" fundamentally cannot exist. There is no way to tell whether a particle is entangled with some other particle or not.