4,370 reputation
1331
bio website black-holes.org
location Ithaca, NY
age 35
visits member for 3 years
seen 19 mins ago

I am a theoretical astrophysicist working mostly in relativity.


Mar
26
awarded  Custodian
Mar
26
reviewed Leave Closed How to use the Born rule to find the expected outcome of this simple Stern-Gerlach experiment
Mar
26
reviewed Leave Closed Constant part of a photo taken
Mar
26
reviewed Reopen Hartree-Fock: Coulomb integral
Mar
23
comment Is the total mass of Earth's atmosphere essentially constant in time?
I don't think I get your point. The Oxygen isn't lost; it's converted chemically, but its mass and position are essentially unchanged. As I pointed out above, the mass increase due to Carbon alone is roughly 1/4 of the mass increase of $\mathrm{CO}_2$, and that's the number I used. Also, the number I cited accounted for reabsorption in the oceans and biomass. Without the Carbon, instead of ocean acidification, you still get ocean oxygenation. So I don't see how it would change the mass balance significantly.
Mar
18
comment Could we send a man safely to the Moon in a rocket without knowledge of general relativity?
+1 I agree with Rob that your first point is not in principle a sound argument; observational errors were far larger than human scales. However, your second and third points are really important, and a great addition to the conversation. It's good to have a solid grasp of the fundamental theory, but when the question asks what is possible, practical knowledge is more important. Even if GR were substantially stronger and completely unknown, a control loop could easily account for its effects.
Mar
12
comment How does dark matter halo outside a galaxy help to explain galaxy rotation curve?
Yeah, there's certainly an assumption that the particles are moving -- presumably on highly eccentric orbits. But it doesn't really matter what any one particle is doing, as long as the overall density is basically constant. And remember that DM is generally modeled as non-interacting, so there won't be a lot of dissipation, which means it won't settle into a disk or anything, so there's no angular dependence. (You may also be interested in the cuspy halo problem.)
Mar
12
comment Can quaternion math be used to model spacetime?
Unsolicited advice: If you're looking for a more formal next step, Frankel's "Geometry of Physics" is excellent. [Or "Geometric Algebra for Physicists", obviously. :) Though this is a little more specialized.]
Mar
12
revised Can quaternion math be used to model spacetime?
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12
revised Can quaternion math be used to model spacetime?
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12
revised Can quaternion math be used to model spacetime?
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Mar
12
comment Can quaternion math be used to model spacetime?
Well, to be honest, I do sometimes disagree with Penrose's approaches to certain issues. (E.g., I am dumbfounded that he doesn't use GA.) But Road To Reality is a great book.
Mar
12
revised Can quaternion math be used to model spacetime?
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revised Can quaternion math be used to model spacetime?
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12
comment Can quaternion math be used to model spacetime?
Good question. Short answer: no. I was gonna write a longer answer reply here, but it's too long, so I'll just add a footnote above. :)
Mar
12
awarded  Enlightened
Mar
12
awarded  Nice Answer
Mar
12
comment Can quaternion math be used to model spacetime?
+1. But then, I'm a sucker for any mention of Penrose. :)
Mar
12
revised Can quaternion math be used to model spacetime?
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11
revised Can quaternion math be used to model spacetime?
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