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Aug
24
comment With gravitational lensing, is it possible to mathematically compute the correct image of the galaxy that is being distorted?
Agreed with 1), but not yet with 2). Consider a continuous background image like CMB. How would that be not a problem?
Aug
22
comment With gravitational lensing, is it possible to mathematically compute the correct image of the galaxy that is being distorted?
1) You might not know the lens mass distribution (would it all still be possible?), 2) Even on the famous Hubble photo you see that one same object may give two images.
Aug
19
comment With gravitational lensing, is it possible to mathematically compute the correct image of the galaxy that is being distorted?
"That would be possible theoretically." - can you prove it/give a reference? Or in other words, given a well resolved image of gravitationally lensed object, how would one go about reconstructing the original?
Aug
4
accepted Generalised planets?
Aug
4
comment Generalised planets?
Greatly many thanks for a very good and interesting reply!
Jul
2
awarded  Curious
Jun
16
answered How would the night sky look from inside a globular cluster?
Jun
15
comment How are black holes found?
You should definitely check the time it would take for a three solar mass black hole to evaporate.
Mar
19
comment Why is the interstellar medium so hot?
@chris: Cosmological expansion should affect the temperatures of IGM similarly as it affects the CMB temperature, that's why I am mentioning it. But then IGM would be too cold comparing to 10^4 K. It indeed seems plausible that it was reheated when it was reionized. Thanks again for your comments!
Mar
18
comment Why is the interstellar medium so hot?
@chris, very useful point, thank you again! Do you know if the primordial IGM cooling is mainly due to cosmological expansion or radiative cooling?
Mar
17
comment On analogies between gas and stellar systems
Indeed interesting, @chris, thank you!
Mar
1
comment Do telescopes harm while observing sun through them?
@Gerald, very illustrative, thank you!
Feb
28
comment Do telescopes harm while observing sun through them?
So, what exactly will happen if you point, say, VLT at the Sun?
Feb
23
comment If we lived in a multiverse, what would our universe most likely then be named?
@Rhys, very reasonable and good question. If questions whether pluto is a planet and alike are discussed at IAU meetings, why would it be unreasonable to speculate on the possible names for our part of the multiverse?
Feb
10
comment A clock travelling “faster than the speed of light”
Yes, you would age by four years and travel very very far and everyone you know would get 400000 years older. However, you, having stopped at that distant location would have to wait for about 400000 years for these events to unfold as you point your powerful telescope at the Earth. Remember that when you look far you see the past, but not the present.
Feb
10
comment Integral calculus for the Olympiad?
The question is opinion-based. I recomend that you talk to someone in person. There is not so much you need to know about calculus to solve these problems. Good link, @Gerald.
Feb
9
comment What would happen if a body were to fall into a neutron star?
@StanLiou: Given that the energy release per unit mass at the moment of impact is much larger than nuclear binding energy per unit mass of the impactor, ionisation and nuclear bonds are irrelevant. The outcome would be the same as if the object would be just a set of protons and neutrons.
Jan
25
comment Can we calculate the average temperature of the Heliosphere?
I am not entirely happy with the question to answer it. There is no clear specification for the temperature, which is asked: neither location, nor the component is clearly specified. Your answer is much more fun in this sense, it gives eventually a nice picture of what is going on.
Jan
24
comment Can we calculate the average temperature of the Heliosphere?
So given the above said, I don't think this is the correct answer to the question, if there is any. However, there is a great deal of interesting phenomena touched upon in your answer and comments.
Jan
24
comment Can we calculate the average temperature of the Heliosphere?
From the SOHO paper you pointed to, it seems likely that due to expansion the relaxation time for the plasma gets rather rapidly long comparable to the timescales it takes to reach the Earth and hence most likely the heliosphere. In this case plasma just gets decoupled from any thermodynamics happening inside heliosphere and any temperatures associated with it, until it starts schocking the ISM.