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1500 questions
40
votes
2 answers
How loud is the thermal motion of air molecules?
In other words, given a magical room with walls that produce no vibration and transmit zero vibration from the outside, and nothing on the inside except room temperature air, what would be the noise level in dB SPL (sound pressure level) from the…
endolith
- 5,666
40
votes
5 answers
How does non-commutativity lead to uncertainty?
I read that the non-commutativity of the quantum operators leads to the uncertainty principle.
What I don't understand is how both things hang together. Is it that when you measure one thing first and than the other you get a predictably different…
vonjd
- 3,701
39
votes
2 answers
Why doesn't the windshield fog up where my kid drew on it with her fingers?
A few weeks ago the inside of my car windshield was fogged up and my older kid used her finger to draw a face in the condensation.
Weeks later, the windshield fogged up again, and the face became visible again. My younger kid asked why.
“The older…
Mark Dominus
- 2,688
39
votes
1 answer
Why are pear-shaped nuclei possible?
In a recent question, Ben Crowell raised an observation which really puzzled me. I obtained a partial answer by looking in the literature, but I would like to know if it's on the right track, and a fuller explanation for it.
It is a well-known fact…
Emilio Pisanty
- 132,859
- 33
- 351
- 666
39
votes
4 answers
Could pressing the brakes on a car in mid-air affect its pitch rotation?
In a racing video game series named Trackmania, there is a game mechanic where when you hit a jump and the car is in mid-air, you can stop the car from pitching downward by tapping on the brakes.
I am curious if this mechanic has some basis in real…
39
votes
6 answers
Why don't planets have Circular orbits?
This might be a completely wrong question, but this is bothering me since many days ago. Given the mass (Sun) curves the space around it, gravitation is the result of such curved space (Correct me if I am wrong, source: A Documentary film). Given…
aravind ramesh
- 525
39
votes
4 answers
Stability of rotation of a rectangular prism
I've noticed something curious about the rotation of a rectangular prism. If I take a box with height $\neq$ width $\neq$ depth and flip it into the air around different axes of rotation, some motions seem more stable than others. The 3 axes which…
Kyle Oman
- 18,441
39
votes
5 answers
Why doesn't light kill me?
Why does each individual photon have such a low amount of energy? I am hit by photons all day and I find it amazing that I am not vaporized.
Am I simply too physically big for the photons to harm me much, or perhaps the Earth's magnetic field…
Shawn McDowell
- 369
39
votes
11 answers
Why is it easier to carry a person while spinning than not spinning?
I was carrying my friend around the other day when I was spinning her she was light but when not spinning her and just carrying her around she was heavy, why is that?
Linkin
- 2,093
39
votes
12 answers
Does information have mass?
Does information itself have any detectable mass? If so, how is the mass of information measured if at all possible? Mathematically, is it possible for information itself to have mass? What would be the equation to ask this question or to…
Brando
- 649
39
votes
4 answers
Does the sun rotate?
As implied from the question, does the sun rotate? If so, do other stars not including the sun also rotate? Would there be any consequences if the sun and other stars didn't rotate? Me and my friends have differing views on this, and would like some…
yuritsuki
- 1,638
39
votes
7 answers
Quantum mechanics on a manifold
In quantum mechanics the state of a free particle in three dimensional space is $L^2(\mathbb R^3)$, more accurately the projective space of that Hilbert space. Here I am ignoring internal degrees of freedom otherwise it would be $L^2(\mathbb…
MBN
- 3,785
39
votes
5 answers
Does the halflife time of a radioactive material decrease if its temperature increases?
If at high temperatures atoms are more intensely interacting with each other or emitted photons that also could make the core vibrate. Is in these circumstances the radioactive material more likely to fission faster? Can this be used to get rid of…
Krešimir Bradvica
- 2,219
39
votes
3 answers
Why does glass, in spite of being amorphous, often break along very smooth surfaces?
When a crystalline material breaks, it often does so along planes in its crystalline structure. As such this is a result of its microscopic structure.
When glass breaks however, the shapes along which it breaks are typically very smooth as well,…
doetoe
- 9,254
39
votes
6 answers
Difference between theoretical physics and mathematical physics?
I'm a huge fan of mathematical physics and I know what the formal definitions of those two areas are, I've seen them. But I still get completely baffled when someone asks me to explain it simply. The difference is obvious to me, but I just can't…
user20250