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Dec
22
comment Conditions of friction on constant acceleration
+1 for considering the revolving case.
Dec
2
awarded  Notable Question
Dec
1
comment What happens in extrema cases of red shift?
Red shift occurs because objects are moving away from us. For the wavelength to become 0, the object would be moving away at the speed of light, which is impossible according to currently accepted relativity theory.
Nov
23
comment Hourglass on the Moon
@dmckee You are correct. The missing piece of the puzzle is that sand falls slower on the moon. Combining that with the facts above should yield an answer, though the answer may depend on the length of the stem.
Nov
23
revised Hourglass on the Moon
clarified
Nov
23
comment Hourglass on the Moon
@Nathaniel Believe it or not, the rate is nearly constant as well! (see my answer)
Nov
23
answered Hourglass on the Moon
Nov
22
comment Metallic coin over wooden block in glass of water
Hint: Archimedean Principle
Nov
22
comment Why does a rolling disc topple less easily than a standing one?
The magic word you seek might be "gyroscope"
Nov
19
comment Flash evaporation
I'm pretty sure alcohol cools better than water.
Nov
8
comment Is the reversible process possible
The Second Law of Thermodynamics pretty much states perfectly reversible processes are impossible. At a quantum level, however, short-term repeatable processes might occur, but at low probability and not in a controllable way.
Nov
4
comment How does heat travel?
When molecules bounce off each other, the slower one usually gets faster and vice versa. So the average kinetic energy of the colder/slower molecules increases while the kinetic energy of the hotter/faster molecules decreases. Your "firstly" occurs during a chemical reaction. Additionally, radiation is how heat travels through empty space.
Oct
30
comment How many galaxies in the observable universe have we counted and mapped?
This isn't super helpful, but en.wikipedia.org/wiki/Star_catalogue describes several large star catalogs (which include galaxies), including ones with over 1 billion known objects.
Oct
29
comment Arrow of Time in Information transfer
By quantum theory, you could send newly-generated information back in time, provided it wasn't observed until the time it was sent.
Oct
29
comment Time dilation: faster or slower?
Actually, time goes slower when you accelerate (or "decelerate", which is just acceleration in a different direction). In your example, both frames are moving at a constant velocity. Remember, if someone whizzes by you at .90c, they actually think they are fixed and you are moving at .90c in the other direction. In other words, you both see each other the same way. It's only if one of you accelerates to the other's frame will there be non-symmetry. This is one of the fundamental mistakes made in the book "Time For the Stars"
Oct
26
comment Can one calculate the distance from Earth to the camera, given a single picture?
I think this only applies if the camera is facing down towards the center of the sphere. In this case, it appears the camera isn't facing straight down, and the edge forms a foreshortened circle aka an ellipse.
Oct
26
comment How can I estimate the density of fog?
elmhurst.edu/~chm/vchembook/123Adensitygas.html confirms that fog is denser than air (since, as you note, it sinks and condenses), but doesn't provide any actual numbers. Also possibly helpful: en.wikipedia.org/wiki/Liquid_water_content wxguys.ssec.wisc.edu/2011/09/12/…
Jul
2
awarded  Curious
Dec
17
awarded  Popular Question
Oct
12
awarded  Self-Learner