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"I would never die for my beliefs because I might be wrong."

-- Bertrand Russell


Jun
17
comment Can we use quantum entanglement as a way to send information or data?
Entanglement is used as a means to create secure communication, but the essential information is still sent through a classical channel.
May
27
comment Is there physics behind the layout of a piano keyboard?
Or better even, isomorphic keyboards.
May
27
comment Is there physics behind the layout of a piano keyboard?
The thing is, there's definitely physics involved in the workingsof a piano. But the specific layout of the keyboard is really just a convenient choice. If you search a bit for it, you'll find many other keyboard layouts that were used in history. Take for instance enharmonic keyboards. Those are way better than our more common keyboards in that you can play just intervals with them. If pure physics was the motivation to select a keyboard, we should all opt for an enharmonic one.
May
18
comment Speed of light as a universal speed limit
@Mew: But you can postulate the existence of particles (tachyons) that are already faster than the speed of light and hence don't need to be accelerated. This is consistent with the Lorentz-transformations. However, it does indeed lead to the problem with the future being able to influence the past. It also has another problem of instability, in that it is possible to keep extracting energy out of those tachyonic particles.
Apr
21
comment Quantum entaglement and the arrow of time
If the article means that they have a quantum mechanical explanation for the special initial conditions that lead to the arrow of time, why not. But anything else is misguided. I also note the "complex and disgusting mess that explains nothing" in your quote. Doesn't really invite to read further.
Apr
15
comment The speed of light and unstable matter
No, with the critical mass, you are thinking about something like an atomic bomb. Now, the thing is that while the mass would increase, you'd still have as many atoms in the material. And therefore not enough to get a chain reaction and thus an explosion.
Apr
13
comment What is the principle of equivalence in thermodynamics?
Yes, that's it.
Mar
30
comment First-order wave equation: Why is its presence not common?
It's still first order.
Mar
30
comment First-order wave equation: Why is its presence not common?
The Dirac equation is a first order wave equation.
Mar
16
comment Quantum Wave Mechanics
If something satisfying a wave equation is not a wave, then what is? This is not a physics question but a semantics discussion.
Mar
14
comment Superconducting loop as a particle detector?
en.wikipedia.org/wiki/Cryogenic_particle_detectors
Mar
5
comment Does limit $\hbar \rightarrow 0$ in Quantum Mechanics mean anything?
@Lubos: yes of course, lapsus.
Mar
5
comment Does limit $\hbar \rightarrow 0$ in Quantum Mechanics mean anything?
Non-relativistic limits are limits with $c \to 0$, not $\hbar \to 0$.
Feb
25
comment What's wrong with this faster-than-light gedankenexperiment?
I think your confusion stems from the fact you seem to think that "interference" is a quantum state. It isn't. Interference is what happens when we make a measurement that's incompatible with the state we measure.
Feb
25
comment What's wrong with this faster-than-light gedankenexperiment?
Why would Bob see an interference pattern though? Just because the particles are entangled doesn't mean that the interference experiment gets replicated on Bob's side. He still has to decide between putting a double slit down or not.
Feb
2
comment Would not gravity negate entropy?
"If gravity acts on all matter and all energy in the universe, wouldn't the universe eventually condense into pockets of energy and matter". Erm... well, if you look around you, that's actually the situation we are in. No need to wait for the heat death of the universe.
Feb
1
comment Can light be launched outwards from an event horizon?
Read up on lightcones a bit first, the last picture shows what happens in the black hole case. If that doesn't answer your question yet, I'll try to write a full reply.
Feb
1
comment Can light be launched outwards from an event horizon?
Escape velocity is really a Newtonian concept. The event horizon is not defined in terms of escape velocity, but rather as the boundary of a region beyond which the outside world can not be affected anymore. Another way to express this is by looking at what happens with light cones in the geometry of a black hole. As you get closer to the whole, the future light cone tips towards the black hole. On the event horizon, it lies completely inside the boundary.
Feb
1
comment Can light be launched outwards from an event horizon?
The thing is, once you're on the horizon, there does not exist an "outward" direction anymore.
Jan
31
comment About Boltzmann H-theorem
Could you specifically reference the derivation you mention. The assumptions should be in there. But just out of the top of my head, you're going to have to assume some specific initial conditions (they have to be "typical"). The way Boltzmann did it was with the Stosszahlansatz. But more modern derivations use more explicit assumptions on the initial conditions.