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1500 questions
41
votes
6 answers
How does rotational "artificial gravity" differ from normal gravity?
I am not a physicist, just a curious mind. I was reading a novel by Iain Banks where it was mentioned, that shifting from artificial rotational "gravity" (in space, on a rotating space craft) to real gravity caused some level of discomfort.
And this…
Mark Cassidy
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41
votes
10 answers
When you hit a baseball, does the ball ever travel faster than the bat?
It seems impossible, yet I'm thinking that maybe because the ball compresses against the bat a bit it acts a little like a spring, and DOES travel faster than the bat?
EDIT:
This is just a clarification, and not really part of the question, but I…
joshuaronis
- 3,055
41
votes
5 answers
Is light actually faster than what our present measurements tell us?
It is well established that the light speed in a perfect vacuum is roughly $3\times 10^8 \:\rm m/s$. But it is also known that outer space is not a perfect vacuum, but a hard vacuum. So, is the speed limit theoretically faster than what we can…
user182521
41
votes
3 answers
Can ants walk on liquid mercury?
I'm not a physicist, but I was wondering:
Can ants walk on dense liquid like mercury and why?
Apolo
- 513
41
votes
1 answer
How is a (rifle scope) reticle in focus?
The lens zooms and focuses something very far away, yet the reticle inside the lens assembly is in perfect focus just like the far objects. How?
Mark Legault
- 463
41
votes
6 answers
What is the physical meaning of the action in Lagrangian mechanics?
The action is defined as $S = \int_{t_1}^{t_2}L \, dt$ where $L$ is Lagrangian.
I know that using Euler-Lagrange equation, all sorts of formula can be derived, but I remain unsure of the physical meaning of action.
RRRR
- 563
41
votes
6 answers
Could someone jump from the international space station and live?
Felix Baumgartner just completed his breathtaking free-fall skydiving jump from $120,000\,\text{feet} = 39\,\text{km}$ above the Earth, breaking the speed of sound during the process.
I was wondering if the next step could be jumping from the…
Reactgular
- 626
41
votes
5 answers
Why aren't rainbows more common?
Why are rainbows relatively rare? On any given day, there are billions of water drops in the air of varying sizes and dispersions, all of which light is passing through and refracting. What physical phenomenon has to occur so that these drops…
DanGoodrick
- 517
41
votes
7 answers
Why does the full Moon appear?
I know that the full Moon appears when Sun, Moon and Earth are in a straight line, but if we consider that they are in straight line, why is the Moon illuminated?
I mean to say that Earth should block all the rays of the Sun and shouldn't allow any…
Awesome boy
- 592
41
votes
2 answers
Does special relativity make magnetic fields irrelevant?
I've heard that special relativity makes the concept of magnetic fields irrelevant, replacing them with relativistic effects between charges moving in different velocity frames. Is this true? If so, how does this work?
Terry Bollinger
- 21,997
41
votes
3 answers
What is the reason for this pattern of noise in electric kettles?
It always seemed to me that the noise from electric kettles follows a pattern: It starts low, then increases, and decreases again before the water starts to boil.
To verify this, I performed a little experiment: I recorded the kettle using my…
Lior
- 3,309
41
votes
2 answers
Why are scientists involved in the Avogadro Project using silicon-28 atoms instead of carbon-12?
My question is, why use silicon-28 atoms to calculate the kilogram when you already have carbon-12 atoms defining the constant?
Does the Avogadro Project intend to define the constant by replacing the idea of carbon-12 and putting silicon-28 in its…
Captaine Code
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41
votes
5 answers
Normalizable wavefunction that does not vanish at infinity
I was recently reading Griffiths' Introduction to Quantum Mechanics, and I stuck upon a following sentence:
but $\Psi$ must go to zero as $x$ goes to $\pm\infty$ - otherwise the wave function would not be normalizable.
The author also added a…
xletmjm
- 887
41
votes
4 answers
How do we know that gravity is spacetime and not a field on spacetime?
How do we know that gravity is the curvature of spacetime as opposed to a field, which couples equally to all objects, on spacetime?
Luke
- 2,240
41
votes
5 answers
Why doesn't Earth appear smudgy or blurred in space photographs due to its fast rotation?
Whenever we take a photograph of something moving at a considerably high speed, its image appears fuzzy/smudgy/distorted due to motion blur. Why doesn't this happen in case of Earth photographs from space, taking into account the fact that Earth…
user139580