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Apr
9
comment Membrane Theory
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Apr
9
comment Question about aircraft/rockets
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Apr
9
comment Why can't I use conservation of energy to find ratio of final velocities on different planets?
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Apr
9
comment Effect of Coriolis force
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Apr
5
comment Can someone help me to do the math?
You're asking for a large chunk of the mathematics in all of physics. That will take at least an entire bookshelf. This is the sort of thing that takes years of study to learn, and not just casual study but rather study to the exclusion of most everything else.
Apr
5
comment Is there a way of detecting nearby type 1a supernovas?
@hsnee The light in a core-collapse supernova takes a few hours to diffuse out of the star from the imploding core, whereas the neutrinos take just a few seconds.
Apr
5
comment Is there a way of detecting nearby type 1a supernovas?
(I don't remember off hand what the neutrino vs. light delay would be. It's possible that the smallness of the progenitor means you wouldn't have much warning anyway.)
Apr
3
comment Stacked motors thought experiment
What exactly is a grinder? I feel like there's a better word.
Mar
31
comment Boundary Conditions For Strings?
@ACuriousMind I'm going to go out on a limb here and assume the "string theory" in this question is about a literal piece of string.
Mar
30
comment Do gravitational waves travelling through a medium produce sound?
Could you elaborate on why the sound is lower frequency in the second case? Unless we are talking about cosmological distances (hundreds of millions of light years) where the expansion of the universe comes into play, the frequency shouldn't change.
Mar
26
comment How does quadcopter's battery capacity relate to it's maximum flight time?
This isn't "check my work." This is "where did my well-reasoned concepts go wrong?"
Mar
26
comment Why can't space become fuel for spaceships?
@DIYser You should look up the density of the densest nebulae in the universe, and compare that number to the best vacuum ever made in a lab on Earth ;)
Mar
25
comment Gravitational imaging
@CuriousOne It's actually even worse than that. One can construct perfectly reasonable mass distributions with vastly different angular components that agree exactly as far as any external probe can tell. Gravitational mapping is very underdetermined, and assumptions about the smoothness of the distribution not only help clean up noise, but also are needed to make the inverse problem have an even remotely unique solution.
Mar
25
comment When did the universe become lighter than water at 1 g/cm3
Yes, the result holds that the universe was very dilute at the time. What I'm saying though is that what is 46 billion light years across now was 46 million, not 14 billion, light years across when the CMB formed. The 1000 is just the redshift of the CMB, and the formula for getting the size of the universe then is given here.
Mar
25
comment When did the universe become lighter than water at 1 g/cm3
Also, only about $5\%$ of that $9.9\times10^{-30}\ \mathrm{g/cm^3}$ is the sort of regular matter we usually think of.
Mar
25
comment When did the universe become lighter than water at 1 g/cm3
Your numbers are more than a little off. The current diameter is 46 billion light years. Also, the CMB was emitted at a redshift of $z = 1000$, so the universe was $1000^3$ times more dense then than now. In general light at a redshift of $z$ was emitted when the linear size of the universe relative to today was $a = 1/(1+z)$. Because the universe has been expanding at a non-constant rate, comparisons of diameters and ages doesn't generally work.
Mar
24
comment How does heat conduction differ from convection?
@user36790 Sufficient effort to be upvoted? No. But sufficient effort to not be closed for that reason alone? Certainly yes, since there is no minimum amount of research effort.
Mar
24
comment How does heat conduction differ from convection?
@user36790 Please stop abusing the close vote system. "No research effort" is not a reason to close.
Mar
22
comment What could this star-like object in the morning sky have been?
@docscience Venus is only just rising at 6:15 in Chicago right now, so it wouldn't be more than 10 degrees above the horizon. Of course the altitude may be misestimated. A better match to altitude (though worse in direction) would be Saturn.
Mar
22
comment What could this star-like object in the morning sky have been?
@user36790 Astronomy questions are on topic here, and across the entire network "would be better elsewhere" is not a sufficient reason to close a question -- it must actually be off topic at the original site.