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1500 questions
38
votes
5 answers
Why do tidal waves appear so suddenly in some rivers?
As tide approaches in lower part of some rivers (e.g. Ganges), a several feet high tidal wave enters from the sea against the flow of the river (making a great noise), and the water level suddenly rises as the wave proceeds.
I would expect the water…
Archisman Panigrahi
- 3,130
38
votes
8 answers
Is electricity really the flow of electrons or is it more involved?
I am new to the physics category of the Stack Exchange site. I apologize if my question is wrong, too broad, simple, or worded incorrectly. I am just trying to figure out what is true and false when it comes to electricity and its vast world. I want…
spiderman0297
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38
votes
4 answers
Why are steel thermal mugs much better than plastic ones?
I have several thermal mugs, two of them by the same brand, have the same look, shape and size except that one is in steel (inside and outside) and the other one, plastic. Both have an insulating layer of air or vacuum.
I do not need a thermometer…
38
votes
4 answers
Why do you have to blow sideways on a flute?
If you were to play a flute, you would want to blow sideways across it, kind of like a bottle, like in Fig 1. Why would this be better than blowing straight in to the hole, like in Fig 2? It seems like more air would go into the flute, which seems…
Derian
- 471
38
votes
2 answers
Why does ice make such peculiar sounds?
I've come across a couple of videos where some interesting sounds are produced using ice.
(Click on the images to see the video.)
Here, they drop a block of ice into a deep crevice and as the block falls, you can hear some strange sounds. These…
AlphaLife
- 11,871
38
votes
3 answers
Why is high temperature superconductivity so hard to solve?
The phenomenon of high temperature superconductivity has been known for decades, particularly layered cuprate superconductors. We know the precise lattice structure of the materials. We know the band theory of electrons and how electronic orbitals…
quack
- 381
38
votes
5 answers
Why does a weather vane arrow point in the direction of the wind?
It seems that a weather vane will rotate in order to minimize energy and thus orient itself parallel to the wind.
What I do not understand is why it is implied that the weather vane arrow should point in the direction of the wind.
I do not…
user391339
- 611
38
votes
1 answer
Is there any evidence that dark matter interacts with ordinary matter non-gravitationally?
As far as I understand it, dark matter direct detection experiments are based on the idea that dark matter interacts with ordinary matter, it just has a very small cross-section. So far, there's been no confirmed detection.
Is there any evidence at…
Allure
- 20,501
38
votes
4 answers
Why are solar panels kept tilted?
I have noticed that, in my country India, most of the solar panels are tilted southward at an angle of ${45}^{\circ} .$ Even on buildings with inverted V-shaped roofs, solar panels are still oriented southward on both the sides of…
Chemist
- 591
38
votes
5 answers
Why is the covariant derivative of the metric tensor zero?
I've consulted several books for the explanation of why
$$\nabla _{\mu}g_{\alpha \beta} = 0,$$
and hence derive the relation between metric tensor and affine connection $\Gamma ^{\sigma}_{\mu \beta} $
$$\Gamma ^{\gamma} _{\beta \mu} = \frac{1}{2}…
Aftnix
- 919
38
votes
9 answers
How does an isolated body in deep space 'know' it's rotating?
We can imagine an object floating in the known universe, maximally distant from any other large mass. Maybe it has been there since coalescing after the big bang.
What physical phenomena tell it whether it is rotating relative to the rest of the…
chasly - supports Monica
- 3,006
38
votes
4 answers
Can a Foucault pendulum really prove Earth is rotating?
According to this article, a Foucault pendulum proved Earth was rotating. I'm not sure it really proved it.
If Earth weren't rotating and a Foucault pendulum started in a state with zero velocity, it would keep swinging back and forth along the same…
Timothy
- 1,648
38
votes
6 answers
Reason for the discreteness arising in quantum mechanics?
What is the most essential reason that actually leads to the quantization. I am reading the book on quantum mechanics by Griffiths. The quanta in the infinite potential well for e.g. arise due to the boundary conditions, and the quanta in harmonic…
user7757
38
votes
7 answers
Can you be blinded by a 'dim' light?
From what I can tell, if you pick a color near the extreme of the visible light spectrum, let's say red, and trace a path across the spectrum until you are outside of the visible range, at some point the red color will begin to darken and dim until…
JakeStrang
- 451
38
votes
1 answer
What does a Galilean transformation of Maxwell's equations look like?
In the 1860's Maxwell formulated what are now called Maxwell's equation, and he found that they lead to a remarkable conclusion: the existence of electromagnetic waves that propagate at a speed $c$, which turns out to be the speed of light, implying…
Keshav Srinivasan
- 3,031