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1500 questions
91
votes
1 answer
Why does my wooden door disperse light into a rainbow color spectrum?
On a clear morning, light comes through this window (viewed from the inside)
It then hits the door on the opposite side (so viewing from the outside the door straight on the other side)
There is nothing particularly special going on.
However, if…
Zach Saucier
- 1,191
91
votes
11 answers
Does centrifugal force exist?
Currently in my last year of high school, and I have always been told that centrifugal force does not exist by my physics teachers. Today my girlfriend in the year below asked me what centrifugal force was, I told her it didn't exist, and then she…
Dylan
- 1,093
90
votes
10 answers
How can magnets be used to pick up pieces of metal when the force from a magnetic field does no work?
I learned that the force from a magnetic field does no work. However I was wondering how magnets can be used to pick up pieces of metal like small paperclips and stuff. I also was wondering how magnets can stick to pieces of metal like a…
sTr8_Struggin
- 1,339
90
votes
6 answers
If gravity is a pseudoforce in general relativity, then why is a graviton necessary?
As far as I’m aware, gravity in general relativity arises from the curvature of spacetime and is equivalent to an accelerated reference frame. Objects accelerating in a gravitational field are in fact inertial and are moving through geodesics in…
Thatpotatoisaspy
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90
votes
3 answers
Why do phones land face down?
Layman here.
I'm not sure if this is the case or not, but my anecdotal evidence is that mobile phones, especially large screen phones, tend to fall face down when you drop them; much to the owner's dismay, this leads to cracked screens.
I'm sure…
Möoz
- 987
90
votes
6 answers
Why is light bent but not accelerated?
Light is bent near a mass (for example when passing close to the sun as demonstrated in the famous sun eclipse of 1919). I interpret this as an effect of gravity on the light.
However, it seems (to me, at least) that light is not accelerated when it…
René Nyffenegger
- 1,143
90
votes
5 answers
Why does a full moon seem uniformly bright from earth, shouldn't it be dimmer at the "border"?
I know the moon is not uniformly grey, it has details, craters, it's not just a colored uniform circle from earth, however, when in a full moon, the intensity of the light received from different parts of the "disc" seems very similar.
Let's define…
Santropedro
- 1,436
90
votes
7 answers
Do Maxwell's Equations overdetermine the electric and magnetic fields?
Maxwell's equations specify two vector and two scalar (differential) equations. That implies 8 components in the equations. But between vector fields $\vec{E}=(E_x,E_y,E_z)$ and $\vec{B}=(B_x,B_y,B_z)$, there are only 6 unknowns. So we have 8…
Warrick
- 9,870
90
votes
6 answers
Am I attracting Pluto?
My question is simple: as the title says, do I exert a gravitational force on distant objects, for example, Pluto? Although it is a very small force, it is there, right?
This leads me to the question, am I exerting a gravitational force on…
Antonio Aguilar
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90
votes
3 answers
Why didn't the Big Bang create heavy elements?
In the case of a supernova explosion it is possible to create heavy elements through fusion. Supernovae have a tremendous amount of energy in a very small volume but not as much energy per volume as there was in our early universe. So, what is the…
Alex
- 6,105
90
votes
14 answers
Superluminal neutrinos
I was quite surprised to read this all over the news today:
Elusive, nearly massive subatomic particles called neutrinos appear to travel just faster than light, a team of physicists in Europe reports. If so, the observation would wreck Einstein's…
Sklivvz
- 13,829
90
votes
2 answers
In the earth's crust, why is there far more uranium than gold?
In parts per million in the Earth's crust Uranium is around 1.8ppm and Gold 0.003ppm. Given that it takes far more energy to create Uranium than Gold, why is this?
user56903
89
votes
3 answers
What does general relativity say about the relative velocities of objects that are far away from one another?
What does general relativity say about the relative velocities of objects that are far away from one another? In particular:--
Can distant galaxies be moving away from us at speeds faster than $c$? Can cosmological redshifts be analyzed as Doppler…
user4552
89
votes
8 answers
Why is information indestructible?
I really can't understand what Leonard Susskind means when he says in the video Leonard Susskind on The World As Hologram that information is indestructible.
Is that information that is lost, through the increase of entropy really recoverable?
He…
HDE
- 2,977
89
votes
4 answers
Why is a $5-60 mph$ time slower than a $0-60 mph$ time for some automobiles?
This doesn't make a lot of sense to me, from a physics 101 point of view. I've read a few blog entries on why this is, but none of them explain it well or are convincing. "something-something launch control. something-something computers." …
Paul C
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