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1500 questions
61
votes
18 answers
If liquid and gas are both chaotic states of matter, what's the difference between them on the molecular level?
I'm a laywoman in physics and recently found myself pondering about the matter reflected in the title of this post.
To make my question more precise from the mathematical standpoint, let's suppose you are given a 3D image of the momentary positions…
Mitsuko
- 1,559
61
votes
11 answers
How does light 'choose' between wave and particle behaviour?
Light exhibits wave behaviour in phenomenon such as interference but particle behaviour in the photoelectric effect. How does light 'choose' where to be a wave and where to be a particle?
d_g
- 691
61
votes
3 answers
In a roller coaster, does the rear car have a higher acceleration/speed?
I am wondering about this question since I asked myself: why do people feel more weightless in the rear car of a roller-coaster than in the front car?
To feel the effect of weightlessness, you must accelerate at the acceleration of the gravity…
Citizen602214085
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61
votes
5 answers
What is really curved, spacetime, or simply the coordinate lines?
It is often said that, according to general relativity, spacetime is curved by the presence of matter/energy.
But isn't it simply the coordinate lines of the coordinate system that are curved?
Bob
- 943
61
votes
3 answers
How is 6W equivalent to 40W, as claimed by adverts for LED light bulbs?
Every advert I come across for LED bulbs advertise them as the equivalent of a higher W incandescent bulbs.
This makes no sense to me, if the room requires 40W to lighten it up then it'll always require 40W of energy. How is it possible for 6W of…
Matka
- 689
61
votes
3 answers
Layman's explanation and understanding of Einstein's field equations
Most of us have heard of Einstein's amazing equations which describe the universe around us, yet only some of us understand what the equations are actually saying.
What are these equations actually saying, and is there a simple (relatively) way to…
Tdonut
- 2,315
61
votes
4 answers
How far ahead can we predict solar and lunar eclipses?
The solar system is non-integrable and has chaos.
The sun-earth-moon three-body system might be chaotic.
So, how far into the future can we predict solar eclipses and/or lunar eclipses?
How about 1 million years?
Jiang-min Zhang
- 4,092
61
votes
5 answers
Do anti-photons exist?
I know what anti-matter is and how when it collides with matter both are annihilated. However, what about anti-photons? Are there such things as anti-photons?
I initially thought the idea preposterous. However I am curious because, if anti-photons…
Dale
- 6,014
61
votes
4 answers
If I'm floating in space and I turn on a flashlight, will I accelerate?
Photons have no mass but they can push things, as evidenced by laser propulsion.
Can photons push the source which is emitting them? If yes, will a more intense flashlight accelerate me more? Does the wavelength of the light matter? Is this…
Hello World
- 715
60
votes
3 answers
Why the galaxies form 2D planes (or spiral-like) instead of 3D balls (or spherical-like)?
Question: As we know, (1) the macroscopic spatial dimension of our universe is 3 dimension, and (2) gravity attracts massive objects together and the gravitational force is isotropic without directional preferences. Why do we have the spiral 2D…
wonderich
- 7,798
60
votes
3 answers
What is the difference between implicit, explicit, and total time dependence, e.g. $\frac{\partial \rho}{\partial t}$ and $\frac{d \rho} {dt}$?
What is the difference between implicit, explicit, and total time dependence, e.g. $\frac{\partial \rho}{\partial t}$ and $\frac{d \rho} {dt}$?
I know one is a partial derivative and the other is a total derivative. But physically I cannot…
CuriousAutomotiveEngineer
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60
votes
6 answers
Why has Earth's core not become solid?
The Earth is billions of years old, yet its core has not yet cooled down and become solid. Will this happen in the foreseeable future?
Martin
- 933
60
votes
4 answers
Why does CNN's ‘gravity hole’ in the Indian Ocean dip the sea level instead of raising it?
Ref. There is a ‘gravity hole’ in the Indian Ocean, and scientists now think they know why
According to CNN, the 'gravity hole' is an area of decreased gravity, compared with the surroundings. This article says that the lower gravity causes to sea…
Paul Uszak
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60
votes
2 answers
Why does pressure in a thermos increase after shaking up hot water and soap?
Whenever I wash my thermos, I put hot water and then some soap in; then I seal the one end with my hand or use the lid. After shaking it up, if I slowly remove the lid or my hand, it expels a little air. Why is that? Does it have something to do…
Peter Rankin
- 581
60
votes
2 answers
What is a $p_x + i p_y$ superconductor? Relation to topological superconductors
I often read about s-wave and p-wave superconductors. In particular a $p_x + i p_y$
superconductor - often mentioned in combination with topological superconductors.
I understand that the overall Cooper pair wavefunction may have orbital angular…
Mike
- 691