20,600 reputation
44582
bio website
location Princeton, NJ
age 25
visits member for 2 years, 3 months
seen 1 hour ago

I am a graduate student studying astrophysics at Princeton. I received my bachelor's in physics and mathematics from Caltech (2011).


Oct
14
comment The example of relativity of simultaneity given by Einstein
@user1688944 Basically yes. If you see two flashes simultaneously, you know each flash's distance from you (in your frame) equals $c$ times the time elapsed since it went off (in your frame). Nonzero relative velocity generically implies a disagreement on elapsed time, and thus a disagreement on distances. However, at least in 1D, this would lead to a contradiction if the observers were forced to see both flashes at the same point in spacetime, as the symmetry of the situation means boosts to other frames should keep the distances equal as they change.
Oct
14
comment What are the demographics of stars visible to the naked eye?
The overall scaling @Kitchi refers to is discussed here, and in particular this answer cites a source for the 6000 (though that source could stand to be clearer on their methods).
Oct
11
comment How does electricity 'decide' on it's pathway?
Also related: physics.stackexchange.com/q/28311
Oct
10
comment Why can't Iron fusion occur in stars?
Related: What elements can be created in the fusion process of different types of suns? The full answer to this question, though, will need a good deal of stellar structure to explain.
Oct
10
comment The inner workings of the Olbers paradox
@Akash No, and the reason is more math than physics. If the universe is homogeneous (i.e. Earth isn't special), for every bit of light deflected away from us, an equal amount will be deflected toward us that otherwise would have gone elsewhere. Homogeneity begets a symmetry that allows you to assume every light ray travels on a straight line.
Oct
9
comment A question once confused Confucius
In other words, the children are thinking logically but yet are both wrong.
Oct
8
comment Magnitude of New Comet C/2012 S1 (ISON)
At least one claim has now been made that ISON is done for: arxiv.org/abs/1310.0552
Oct
8
comment When motion begins, do objects go through an infinite number of position derivatives?
Hi user92356, and welcome to Physics Stackexchange! The "soft-question" tag is really just for meta-level questions about physics (rather than any question that is "soft" in the generic sense); tags that convey the subject matter are better. I might suggest "classical-mechanics" for a start, but I don't want to make that change without your approval, as perhaps you wanted e.g. a quantum-mechanical viewpoint.
Oct
4
comment Temperature of thermochemical reaction between propane and nitrous oxide
Mols and enthalpies... this might get a better response at chemistry.stackexchange.com
Oct
4
comment Paper in physics - calculations; rounding or not?
Would you really always round uncertainties up? I can imagine that practice is meant to fight off the tendency for people to overestimate how "good" their precision is, but representing $1\sigma$ errors as $0.02$ rather than $0.012$ can be just as misleading, and in many cases would work in the author's favor ("our results are in statistical agreement with those of our previous paper...").
Oct
3
comment Isn't gravity non-local and non-causal?
@user6818 Nope. That's the equivalence principle (or the diagonalizability of the metric, if you like to think about it that way) for you.
Oct
3
comment Which cyan colored line is produced in the Thomson e/m apparatus?
Btw, that ping won't notify John Rennie. See meta.stackexchange.com/questions/43019/…
Oct
3
comment If I am travelling on a car at around 60 km/h, and I shine a light, does that mean that the light is travelling faster than the speed of light?
Waves - whether they are sound or light or water - are local phenomena, which means how the wave decides to move is determined by its immediate surroundings, not by whatever the source may have been doing far away. The speed of the source affects the frequency of the wave, but two waves of the same frequency in the same medium will move at the same speed, which for light in air is, as you said, a bit slower than $c$.
Oct
2
comment If I am travelling on a car at around 60 km/h, and I shine a light, does that mean that the light is travelling faster than the speed of light?
The first paragraph is wrong. Even in media where the speed of light is less than $c$, the speed of propagation is still independent of the speed of the source.
Oct
1
comment Analyse astronomical data
IDL does much the same as Matlab, but worse, which is why everyone (other than astronomers) abandoned it long ago. If your data analysis is supposed to produce code that others will also use, then you're probably stuck with the in-house preference, since very few astronomers are fluent in Matlab and there are many canned routines written for astronomy in IDL. The same for IRAF (for image reduction) - it's almost unusable, but that's just what everyone uses.
Sep
30
comment How big an egg can be?
This question appears to be off-topic because it is about biology (and might belong on biology.stackexchange.com).
Sep
30
comment How is mobile communication made possible from airplanes?
I'm pretty sure this is better suited for engineers than physicists. In any event, 120 km/hr is very slow compared to the speed of light, and I've certainly used a cell phone in a car going faster than that, so wherever this question ends up you should cite the claim.
Sep
28
comment Are Fresnel lenses widely used for solar electricity? If not, why not?
@gerrit Dumping heat is one of the hardest things we ask our spacecraft to do, so it seems there would be better ways, but the technicalities would be the basis for a whole other question.
Sep
28
comment Fulvio Melia's linear Universe
Debates like this must be great for various researchers' careers - one can keep publishing more papers, like arxiv.org/abs/1309.6950
Sep
27
comment Does cosmic censorship rule out stable toroidal black holes? How?
Possible duplicate? physics.stackexchange.com/q/33963 Not that there is terribly much detail over there.