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1500 questions
54
votes
9 answers
Why does wavelength affect diffraction?
I have seen many questions of this type but I could nowhere find the answer to "why". I know this is a phenomenon which has been seen and discovered and we know it happens and how it happens. But my question is why would wavelength affect the amount…
rahulgarg12342
- 2,469
53
votes
5 answers
Why doesn't a typical beam splitter cause a photon to decohere?
In many experiments in quantum mechanics, a single photon is sent to a mirror which it passes through or bounces off with 50% probability, then the same for some more similar mirrors, and at the end we get interference between the various paths.…
Mark Eichenlaub
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53
votes
3 answers
Does black hole formation contradict the Pauli exclusion principle?
A star's collapse can be halted by the degeneracy pressure of electrons or neutrons due to the Pauli exclusion principle. In extreme relativistic conditions, a star will continue to collapse regardless of the degeneracy pressure to form a black…
kd88
- 1,887
53
votes
2 answers
Can we infer the existence of periodic solutions to the three-body problem from numerical evidence?
I recently found out about the discovery of 13 beautiful periodic solutions to the three-body problem, described in the paper
Three Classes of Newtonian Three-Body Planar Periodic Orbits. Milovan Šuvakov and V. Dmitrašinović. Phys. Rev. Lett. 110…
Emilio Pisanty
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53
votes
10 answers
Can Jupiter be ignited?
Our solar system itself contains two candidate "Earths"
One is Jupiter's moon Europa and another is Saturn's moon Titan. Both of them have the problem of having at low temperature as Sun's heat cannot reach them.
Jupiter is made up mostly of…
Xinus
- 1,251
53
votes
4 answers
On a hot day, when it's cooler outside than in; is it better to put a fan in an open window pointing inwards or outwards?
If it's really hot inside, but cooler outside; what is the best way to place a single fan to try and cool a room down?
I always assumed it would be better pointing inwards (and this thread suggests the same).
However; today I had a thought - if the…
Danny Tuppeny
- 632
53
votes
8 answers
A planet with a square orbit?
To understand how gravity influence objects, time and space, I have been thinking of how a planets shape would change the orbits of its moons.
More specifically: can I design a planet whose moon move in a square orbit?
Below is a diagram of my first…
erik m
- 1,153
53
votes
4 answers
What wavelengths of light does a banana reflect?
I do know that there are at least two types of yellow light: a light of a single wavelength of ~580 nm and a combination of green light and red light. (Technically, there could be more yellow light.) And the following two figures are making me…
dkssud
- 723
53
votes
7 answers
Why does carbon dioxide not sink in air if other dense gases do?
Why does carbon dioxide not sink in air if other dense gases do?
We evidently do not suffocate by carbon dioxide sinking to the bottom of the atmosphere and displacing oxygen and yet there are gases that do sink. This is commonly a problem in coal…
chasly - supports Monica
- 3,006
53
votes
3 answers
Why does the speed of a ping pong ball increase when the space in which it can bounce decreases?
I was playing table tennis the other day when I my ball fell off the table. I placed my paddle above it in order to slow it down, and then I brought the paddle to the ground so that the ball would come to a stop. A diagram of what I did is…
Nico Damascus
- 701
53
votes
4 answers
Gas pipes - why does gas burn "outwards?"
I've often wondered if a gas cylinder is connected to a hob (say, or a boiler or whatever) and someone turns the knob to allow gas to flow, why is that when a flame is held to light the gas it isn't possible for the newly lit gas (i.e. ignited gas)…
nox
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53
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7 answers
Can Noether's theorem be understood intuitively?
Noether's theorem is one of those surprisingly clear results of mathematical calculations, for which I am inclined to think that some kind of intuitive understanding should or must be possible. However I don't know of any, do you?
*Independence of…
Gerard
- 6,791
53
votes
8 answers
How does tilting a bike make it turn sharper?
Note that my question is not why do you tilt your bike when on a curve. It's about the reduction in turning radius when one tilts the bike inwards.
Short to-the-point answers are welcome.
AlphaLife
- 11,871
53
votes
4 answers
Red shifted to what?
I searched and found a lot of questions and answers about red shift here but none with the answer to mine. (sorry if it is there somewhere and I did not find it.)
Everyone is saying the light from the far away galaxies is red shifted and I could…
OCTAV
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53
votes
9 answers
Why are $L_4$ and $L_5$ lagrangian points stable?
This diagram from wikipedia shows the gravitational potential energy of the sun-earth two body system, and demonstrates clearly the semi-stability of the $L_1$, $L_2$, and $L_3$ lagrangian points. The blue arrows indicate lower potential energy, red…
Ehryk
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