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programming numerical algorithms for astrophysical applications.


Sep
18
comment How fast is a comet moving when it crosses Earth's orbit?
who is Wolfram?
Sep
16
comment What are the biggest problems about the numerical, finite-element GR models?
Perhaps, this sort of calculation is not so interesting (compared to QCD). What has been done is the merging of two BHs (including the gravitational radiation and the resulting anisotropic effects)
Sep
15
comment What is the difference between Sphere of Influence and Hill sphere?
@HDE226868 Excellent spot! Unfortunately, this is on another stack exchange site, so we cannot close this as a duplicate. However, duplicating the answer is clearly not worth the effort.
Sep
15
comment Are there stars that don't emit visible light?
@jwenting Jupiter is not a star, but a planet. Stars are defined to undergo (or have undergone) hydrogen burning (H$\to$He fusion). This requires a minimum mass of about 0.08M$_\odot$. Objects smaller than that, but massive enough to have some fusion (Li) early on are brown dwarves. The mass limit here is about 10M$_{\mathrm{Jupiter}}$.
Sep
13
comment Are there sufficient observational data to measure non-Newtonian perihelion advances of any Asteroid and Comet orbits?
Use ADS to search for publications (via author names, title words, keywords, or words from the abstract) and even read their abstract for free. Almost all astronomy papers are also published on the arXiv (linked from ADS), where you can obtain (a preprint version) for free.
Sep
11
comment Are there sufficient observational data to measure non-Newtonian perihelion advances of any Asteroid and Comet orbits?
If you want to write a scientific publication, then search the published literature.
Sep
11
comment How many astronomers are there in the world today?
I didn't know your source, but I would have estimated the same number. However, there are many more (about the same number) with a PhD in astronomy who didn't follow it up with an academic career.
Sep
8
comment When will the Milky Way “arrive” at the Great Attractor, and what all happen then?
Given the accelerated expansion of the universe, is it at all clear that the MW will be arriving there (supposing it it indeed on course)? Note that the mysterious force (coined dark energy) driving the accelerated expansion is opposing the gravitational attractions.
Sep
7
comment Milky Way Formation
Neither, but both!
Sep
6
comment Could the universe have evolved differently?
Well, the underlying hope is that all those fine tunings are only apparent but not real. In other words, the universe naturally obtains an apparently fine-tuned situation in a way still unbeknown to man. In yet other words, the universe only appear fine-tuned because of our ignorance/lack of knowledge.
Sep
6
comment Birthdate differences calculation relative to earths orbit duration
Since birth times are recorded in calender time rather than sidereal or orbital times, you simply take the difference in calender times: You are 365 days (since 1938 was not a leap year) and 18 hours older than your friend.
Sep
5
comment What known comets are binary?
@PeterHorvath see edit.
Sep
5
comment Are ascending node of sun, the point of intersection of prime meridian and equator and center of earth all collinear?
@SF. Plase promote your comments to an answer.
Sep
5
comment Estimating the tangential and cross component of the galaxy's shear using Gnomonic projection
Please elaborate what you mean by shear? When I read the title I thought about the shear in the galactic velocity fields and Oort's constants ...
Sep
5
comment Why are explosions always used to represent the Big Bang?
not a science question .
Sep
5
comment Why are explosions always used to represent the Big Bang?
Where is the evidence? I've not yet come accross the comparison with an explosion.
Sep
5
comment Potential Re-Capture of Rogue Planets
voting without commenting is fine and should be the norm. As to your question, I think your first paragraph contains an error: you are interested in objects of the second category (not first); please correct.
Sep
5
comment is there any theory or observational evidence that our universe is electrically neutral or not?
Note that the paper by Düren (the one you quoted in your comment) has not appeared in any peer-reviewed journal. That is a serious indication that it didn't make it through the review process for some good reasons, e.g. it violates known observational constraints.
Sep
3
comment Determining effect of small variable force on planetary perihelion precession
See my edited/corrected answer. The formula has changed ...
Sep
3
comment Could the universe have evolved differently?
You didn't ask it like that ("slightly different").