# All Questions

0answers
60 views

### 2 questions on 4-velocity

Firstly 4-velocity is defined by $u^\mu=\frac{dx^\mu}{d\tau}$ let us consider the component $x_i$ of $x^\mu$ then this derivative can be written as: ...
1answer
113 views

### Why doesn't the electron lose or absorb energy while remaining in a selected orbit? [closed]

Postulate 2: When an electron revolves in any selected orbits, it neither emits nor absorbs energy . The energy of an electron in a particular orbit remains constant. Thus, Bohr, by postulating ...
0answers
65 views

### $E=mc^2$ what is unique about the speed of light? [duplicate]

What unique property of light, makes it the conversion factor between energy and mass? It has to be more than a coincidence that the speed of light, just happens to be the correct number number to ...
2answers
3k views

### Why did “tickling the dragons tail” by Louis Slotin not cause an explosion?

I have been reading the excellent Command and Control by Eric Schlosser and discovered more about Louis Slotin's experiment with "tickling the dragons tail" and the infamous Demon Core. What I don't ...
4answers
3k views

### What does this depiction of a black hole in the movie Interstellar mean?

I was expecting a whirlpool in 3D and the matter glowing from friction as it nears the center, as I expected a event horizon to be negligible visually. How does this depiction work? How big is the ...
0answers
50 views

### $E=mc^2$ is incomplete? [duplicate]

So I was going through youtube and I found out these: http://www.youtube.com/watch?v=mkiCPMjpysc http://www.youtube.com/watch?v=NnMIhxWRGNw Can anyone here explain to me (with derivation if ...
1answer
893 views

### Why can we inflate the balloon?

I have an elementary question: I know from experiences that human can inflate (or fill with water) the standard ballon or latex medical glove. But I know also that in rubber/latex there are a pores. ...
2answers
116 views

0answers
101 views

### Bell vs. diaphragm of stethoscope for low frequency sounds

Why is the bell of the stethoscope used to hear lower frequencies if it has a smaller diameter than the diaphragm? I would have thought that a bigger diameter diaphragm could pick up lower frequency ...
1answer
75 views

### Separation distance of bright fringes in double slit experiment

so I'm working on homework problem that seems like it should be pretty straight forward but the computer won't accept my answer. The question is below. A double slit aperture with slit separation ...
0answers
37 views

### Construction of a magnetic dip “compass”

I want to make a demo magnetic dip compass and was wondering what would be the relative sensitivity (restoring torque) of: 1) two neodymium magnets at the ends of a plastic rod (say 40 cm. i.e. ...
1answer
65 views

1answer
30 views

### AIR PSI formula maybe

How would one figure out the maximum PSI (air only) a particular container may hold knowing only its dimensions? I understand the water formula. P=.434 x height I would like a formula for air ...
2answers
36 views

### What does $\tau$ = $\Delta E_{c}$ mean? [closed]

What does $\tau$ = $\Delta E_c$ mean? Can anyone help? I'm finding it difficult to find on the internet.
7answers
477 views

### Can a ultracentrifuge be used to test general relativity?

With today's ultracentrifuge technology, they can spin so fast that the sample can be subjected to accelerations of up to 2 millions Gs. That is equivalent to two solar masses. Has someone tried to ...
1answer
57 views

### Do entangled particles lose entanglement after polarizing filters?

If two entangled particles are sent through different polarizing filters, do they lose their entanglement after the filters?
2answers
131 views

### Does Bell's inequalities also rule out non-computable local hidden variable theories?

I have beenn reading different articles on Bell's assumptions and interpretations, including superdeterminsm. I always end up dizzy when I try tho think about this specific question, so any hints ...

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