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Jan
23
comment Measuring force of a punch
Ask them to punch 10 times and try hit the centre each time. Take the maximum force as the one that hit the centre.
Jan
10
comment $N$-body simulation in General Relativity
There are loads of articles on this, see for example arxiv.org/abs/1511.05124
Dec
29
revised How do virtual photon cloud produce discrete magnetic field lines in bar magnet?
large to macroscopic
Dec
28
answered How do virtual photon cloud produce discrete magnetic field lines in bar magnet?
Dec
25
revised What numbers do we examine when predicting how much damage an object will do when it strikes another object?
typo correction
Dec
25
answered What numbers do we examine when predicting how much damage an object will do when it strikes another object?
Dec
3
comment Is the Universe Past-Eternal?
A bouncing Universe is one possibility but it requires a violation of the null energy condition: arxiv.org/abs/1406.2790
Dec
3
comment What happens to gas molecules after ionization?
Sounds interesting, but I think more detail is needed.
Nov
20
awarded  Enlightened
Nov
20
awarded  Nice Answer
Oct
17
answered The temperature in space is about 3K, however there are almost no atoms in space. How can there be residual heat?
Sep
2
comment Origin of cusps in simulated dark matter halos
Yes, via their gravitational attraction.
Aug
26
comment Origin of cusps in simulated dark matter halos
The most popular explanation is that there is no cusp due to the presence of baryons which need hydrodynamic simulations to be accurately described.
Aug
14
comment Relativistic Energy
There is a nice Wikipedia article on mass in general relatvity:en.wikipedia.org/wiki/Mass_in_general_relativity . What John has described is known as the Newtonian limit for the mass.
Aug
4
comment Density of dark matter along the galaxy
There is a small inaccuracy in your post, close to the center of the galaxy the NFW gives $\rho\propto r^{-1}$ not $\rho\propto r^{-2}$.
Jul
29
awarded  Civic Duty
Jul
27
comment Why does humidity cause a feeling of hotness?
OK, he is saying tempratures between 30°C and 36°C at high humidity are worse than temperatures greater than 37°C at low humidity. Not sure why it wasn't clear to me at first.
Jul
27
comment Why does humidity cause a feeling of hotness?
Is there a typo in the last sentence?
Jul
15
comment Mass density of dark matter in solar system near us
Or in other words, roughly 400 thousand protons' mass of dark matter per cubic meter or about half a proton's mass per cubic centemeter.
Jul
15
comment Mass density of dark matter in solar system near us
With error bars (adding uncertainties in quadrature) it is $(0.4\pm 0.1)$GeV/cm$^3$.