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1500 questions
35
votes
10 answers
What is wrong with the high-school definition of a vector?
Why is the high-school definition of a vector as "a quantity with a magnitude and a direction" incomplete? For example, Griffiths Introduction to Electrodynamics book says:
The definition of a vector as "a quantity with a magnitude and direction" is…
Solidification
- 11,483
35
votes
7 answers
How seriously can we take the success of the Standard Model when it has so many input parameters?
The Standard Model of particle physics is immensely successful. However, it has many experimentally fitted input parameters (e.g. the fermion masses, mixing angles, etc). How seriously can we take the success of the Standard Model when it has so…
Solidification
- 11,483
35
votes
9 answers
Is it possible to blur an image in such way that a person with sight problems could see it sharp?
If someone has short or long sight, is it possible to tune image on a computer monitor in such way, that a person could see it sharp as if they were wearing glasses? If not, will 3d monitor make it possible?
serg
- 1,435
35
votes
6 answers
What happens to an electron if given quantized energy to jump to a full orbital?
Let's consider the element neon. Its ground-state electron configuration is: $1s^2 2s^2 2p^6$.
What would happen if enough energy was given for one electron in the $1s$ orbital to jump to the $2s$ orbital (i.e. exactly the $\Delta E$ between $1s$…
João Guilherme
- 459
35
votes
7 answers
What does the minus sign in Maxwell's third equation imply?
If we write out Maxwell's equations with magnetic charges, we get
$$
\begin{align}
\nabla \cdot \mathbf{E} &= 4 \pi \rho_e \tag{1}\\
\nabla \cdot \mathbf{B} &= 4 \pi \rho_m \tag{2}\\
-\nabla \times \mathbf{E} &= \frac{\partial \mathbf{B}}{\partial…
rayhem
- 517
35
votes
4 answers
What stabilizes neutrons against beta decay in a neutron star?
Free neutrons are known to undergo beta decay with a half-life of slightly above 10 minutes. Binding with other nucleons stabilizes the neutrons in an atomic nucleus, but only if the fraction of protons is high enough (at least a third or so). But…
Slaviks
- 4,413
35
votes
9 answers
Do wormholes really exist?
we can see most of the science fiction stories, movies, and television serials use the concept of wormholes. Do wormholes really exist in this universe? I'm curious about it.
And also, what are the types of wormholes?
snowballCode
- 547
35
votes
2 answers
What is the definition of a timelike and spacelike singularity?
What is the definition of a timelike and spacelike singularity?
Trying to find, but haven't yet, what the definitions are.
user23071
- 353
35
votes
12 answers
If a jet engine is bolted to the equator, does the Earth speed up?
If a jet engine is bolted to the equator near ground level and run with the exhaust pointing west, does the earth speed up, albeit imperceptibly? Or does the Earth's atmosphere absorb the energy of the exhaust, and transfer it back to the ground,…
FlanMan
- 497
35
votes
11 answers
Why is the Pauli exclusion principle not considered a sixth force of nature?
Why is the Pauli exclusion principle not considered a sixth force of nature, given it produces such things as repelling of atoms and molecules in solids?
Anixx
- 11,159
35
votes
7 answers
Does spin really have no classical analogue?
It is often stated that the property of spin is purely quantum mechanical and that there is no classical analog. To my mind, I would assume that this means that the classical $\hbar\rightarrow 0$ limit vanishes for any spin-observable.
However, I…
Akoben
- 2,395
35
votes
5 answers
Why is the sky *uniformly* blue?
I've read a lot of answers to the questions why the sky is blue. However all the answers I found contain mostly qualitative analysis: Rayleigh scattering is changing the direction of blue light, so there is more blue light coming to the eye along…
Vlad
- 469
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35
votes
1 answer
Emergent symmetries
As we know, spontaneous symmetry breaking(SSB) is a very important concept in physics. Loosely speaking, zero temprature SSB says that the Hamiltonian of a quantum system has some symmetry, but the ground state breaks the symmetry.
But what about…
Kai Li
- 3,724
35
votes
6 answers
Could there be a star orbiting around a planet?
I wonder if there ever could be a star (really small) which may orbit around a planet (really big)?
Ashish P
- 351
35
votes
6 answers
What happens to matter when it is converted into energy?
According to Einstein’s equation
$$E=mc^2$$
Matter can be converted into Energy. An example of this is a nuclear reaction. What happens to the matter in the process? Do the atoms/subatomic particles just vanish? Any insights into this process are…
Aniruddha Deb
- 539