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1500 questions
51
votes
4 answers
Why does LIGO do blind data injections but not the LHC?
The LIGO group has a team that periodically produces fake data indicating a possible gravitational wave without informing the analysts. A friend of mine who works on LHC data analysis told me that none of the LHC groups do this. Why does one of…
tparker
- 47,418
51
votes
2 answers
Why do I see better under water using swimming goggles?
I am myopic (I don't really know if this is relevant or not) and I usually swim without contact lenses. My vision is clearly better underwater when I am using swimming goggles.
I have tried to understand why this happens and I think that it is…
S -
- 1,533
51
votes
3 answers
When water climbs up a piece of paper, where is the energy coming from?
Take a glass of water and piece of toilet paper. If you keep the paper vertical, and touch the surface of the water with the tip of the paper, you can see the water being absorbed and climbing up the paper. This climbing up is intriguing me. Where…
Malabarba
- 5,061
51
votes
8 answers
Difference between live and neutral wires
In domestic electrical circuits, there are 3 wires - live, earth and neutral. What is the difference between the live and neutral wires?
As there is AC supply, it means that there are no fixed positive and negative terminals. Current rapidly…
51
votes
3 answers
Are there tides in the atmosphere?
Analogous to the tides of Earths oceans, do the Moon and Sun cause our atmosphere to bulge in what could be described as a low and high tide?
Alex
- 5,973
50
votes
5 answers
The meaning of action
The action
$$S=\int L \;\mathrm{d}t$$
is an important physical quantity. But can it be understood more intuitively? The Hamiltonian corresponds to the energy, whereas the action has dimension of energy × time, the same as angular momentum.
I've…
Emerson
- 1,277
50
votes
5 answers
Is it possible to have a geostationary satellite over the poles?
My understanding of orbital mechanics is very limited, but as I understand geostationary satellite, they stay in place by having an orbital speed corresponding to the spot they're orbiting over.
So my basic intuition tells me that it's not possible…
mikl
- 627
50
votes
6 answers
Can you exit the event horizon with a rocket?
The reason given in most places about why one cannot escape out from an event horizon is the fact that the escape velocity at the event horizon is equal to the speed of light, and no one can go faster than speed of light.
But, you don't really need…
Lahiru Chandima
- 607
50
votes
4 answers
What if the LHC doesn't see SUSY?
A question in four parts.
What are the main problems which supersymmetry purports to solve?
What would constitute lack of evidence for SUSY at the proposed LHC energy scales (e.g. certain predicted superpartners are not in fact observed)?
Are…
Nigel Seel
- 3,346
50
votes
9 answers
Was there anything intrinsically inconsistent about Newton's universe?
I am not a physicist - just a curious person.
We know from observation that Newton's formulation of physics is incomplete. We could suppose that, on a planet of perpetual fog, no-one would have thought to question it. Prior to discovering flight, we…
chasly - supports Monica
- 3,006
50
votes
3 answers
What is the meaning of the third derivative printed on this T-shirt?
Don't be a $\frac{d^3x}{dt^3}$
What does it all mean?
VodkaTampons
50
votes
4 answers
How can an object absorb so many wavelengths, if their energies must match an energy level transition of an electron?
I believe I have a misunderstanding of some principles, but I have not, even through quite a bit of research, been able to understand this problem.
My current understanding of transmission, reflection and absorption is as follows:
transmission…
Ultralite
- 613
50
votes
2 answers
Was the 2013 meteor over Russia stronger than an atomic bomb?
Reports of the Russian meteor event (2013) say that it released more energy than 20 atomic bombs of the size dropped on Hiroshima, Japan:
Scientists estimated the meteor unleashed a force 20 times more powerful than the Hiroshima bomb, although the…
BrianC
- 499
50
votes
5 answers
How does many worlds interpretation work for non-50/50 probabilities?
The many-worlds interpretation of quantum mechanics has always been explained to me at a high level using examples of binary events (e.g. atom either did or did not decay at any given moment in time), which leads to a conceptually clean idea of…
Sean49
- 925
- 6
- 11
50
votes
5 answers
Can anything be seen from the center of the Boötes void? How dark would it be?
Let's say I was at the very center of the enormous Boötes void, way out in deep, deep space. What could I see with the naked eye? I assume I could see no individual stars, but could I resolve any galaxies? If I gazed in the direction of a…
Paul Young
- 3,536