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1500 questions
36
votes
7 answers
Is it possible to "cook" pasta at room temperature with low enough pressure?
It is known fact, that boiling point of water decreases by decreasing of pressure. So there is a pressure at which water boils at room temperature.
Would it be possible to cook e.g. pasta at room temperature in vacuum chamber with low enough…
Viliam
- 505
36
votes
5 answers
Jumping into water
Two questions:
Assuming you dive head first or fall straight with your legs first, what is the maximal height you can jump into water from and not get hurt?
In other words, an H meter fall into water is equivalent to how many meters…
Uri
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36
votes
4 answers
Swimming in Spacetime - apparent conserved quantity violation
My question is about the article Swimming in Spacetime.
My gut reaction on first reading it was "this violates conservation of momentum, doesn't it?". I now realize, however, that this doesn't allow something to change its momentum; it only allows…
Keenan Pepper
- 7,697
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36
votes
2 answers
Motivation for the use of Tsallis entropy
Every now and again I hear something about Tsallis entropy,
$$
S_q(\{p_i\}) = \frac{1}{q-1}\left( 1- \sum_i p_i^q \right), \tag{1}
$$
and I decided to finally get around to investigating it. I haven't got very deep into the literature (I've just…
N. Virgo
- 33,913
36
votes
8 answers
Does the curvature of spacetime theory assume gravity?
Whenever I read about the curvature of spacetime as an explanation for gravity, I see pictures of a sheet (spacetime) with various masses indenting the sheet to form "gravity wells." Objects which are gravitationally attracted are said to roll down…
Dale
- 6,014
36
votes
5 answers
What exactly is the fireball caused by a nuclear bomb?
This seems like a pretty simple question, but I can't seem to come up with a satisfactory answer. When a nuclear bomb is detonated a large fireball forms. What is the fuel that drives this fireball? Or is it not a fire in the traditional sense (i.e.…
jordanr
- 477
- 4
- 4
36
votes
2 answers
To what degree of precision are atoms electrically neutral?
It is said that if, say, the electric charge is not a Lorentz invariant, neutral atoms are no longer neutral, which is not experimentally valid. I want to know to what degree of precision atoms are measured to be electrically neutral and what would…
Mohammad Javanshiry
- 2,513
36
votes
1 answer
Zero modes ~ zero eigenvalue modes ~ zero energy modes?
There have been several Phys.SE questions on the topic of zero modes. Such as, e.g.,
zero-modes (What are zero modes?, Can massive fermions have zero modes?),
majorana-zero-modes (Majorana zero mode in quantum field…
wonderich
- 7,798
36
votes
5 answers
Why do we observe particles, not quantum fields?
My understanding is that, in the context of quantum field theory, particles arise as a computational tool. We perform an expansion in the path integral in some parameter, and the terms in these expansions correspond to Feynman diagrams which can be…
Charles Hudgins
- 1,570
36
votes
4 answers
Floating a ping pong ball in the air just using a pen!
Caution: Apparently this problem is harder than it seems!
There is a well known phenomena, which I first learnt about when I was a 10 years old kid. You can levitate a ping pong(or whatever not-so-heavy) ball in the air by blowing throw an empty…
Ali
- 6,006
36
votes
2 answers
Why isn't the molecule of water linear straight?
When you see models of water you see something like this:
The hydrogens in the water molecule become negatively charged because the oxygen pulls electrons more. So why don't they repel and move to the opposite sides of the oxygen? Or just form on…
Trevor Blythe
- 479
36
votes
10 answers
Why are only infrared rays classified as "heat rays"?
I've often heard that Infrared rays are called "heat rays". However, I feel like this term is a misnomer. Don't all the wavelengths of electromagnetic radiation carry energy?
Judging by how gamma rays are highly penetrating and are dangerous when…
Cross
- 3,310
36
votes
4 answers
Why are the edges of a broken glass almost opaque?
Unfortunately I broke my specs today which I used in this question.
But I observed that the edges are completely different then the entire part of the lens. The middle portion of the lens was completely transparent but the edges appeared opaque (and…
Ankit
- 8,306
36
votes
7 answers
Why can’t gravitons distinguish gravity and inertial acceleration?
If gravitons mediate the gravitational force, couldn’t the detection of gravitons by an observer be used to distinguish whether they are experiencing gravitational acceleration vs. inertial acceleration, contradictory to general relativity? If this…
Jack Edwards
- 481
36
votes
3 answers
Why can't many models be solved exactly?
I have been told that few models in statistical mechanics can be solved exactly. In general, is this because the solutions are too difficult to obtain, or is our mathematics not sufficiently advanced and we don't know how to solve many of those…
Daphne
- 463