Ask MetaFilter questions tagged with astrophysics

Branching-out cosmological models

MattS — Mon, 07 Dec 2009 12:46:31 -0800

In the realm of astrophysics, are there any charts, graphs, or models (or even physical examples of star clusters, etc) that somewhat resemble the branches of a tree? Asking for a friend.

I've heard of fractal trees, aka Pythagoras trees, but what concept (if any) might they illustrate that relates specifically to astrophysics?

Are there any other charts, models, systems of geometry, etc that have branches or "root systems" that, when drawn out, look like a tree?

It can be a bit of a stretch, but I'm looking for a tree-like illustration of some astrophysical, inter-dimesional, or space-related concept.

Thank you!

"It's obviously a wormhole due to these scientific recordings that show...xyz"

MattS — Mon, 16 Nov 2009 21:55:45 -0800

Let's say you were an astrophysicist who saw a wormhole open up in the sky above you, and you had video of it, magnetometer readings, whatever else you'd need to record it. What kind of recorded "proof" might be used to identify it as a wormhole-- after the fact? Asking for a friend, who is not an astrophysicist, but working on a sci-fi project.

Her character can have whatever scientific recording devices necessary at the scene of the wormhole, but what could the astrophysicist character later point to in terms of photographs, electromagnetic readings, etc that would identify (or strongly suggest) that the event that had happened in the sky above them was a wormhole?

Obviously this is theoretical, but what might scientifically distinguish a wormhole from just an electromagnetic storm, aurora borealis, etc? And what kind of devices specifically would be required to record such information? Keep in mind all recordings must be taken from the ground, not from, say, a satellite.

Thanks for any help on this.

"Stuck in (Red) Shift"

np312 — Sun, 15 Nov 2009 21:32:04 -0800

Help me brainstorm clever astrophysics bumper stickers! I've seen stickers along the lines of "Save Pluto" and "I brake for black holes." But I'm trying to come up with clever, pithy ideas for bumper stickers, where by reading them you would immediately know the driver was an astrophysics fan.

To be specific, this is a bumper sticker for not just a space fan, or a science fan, but for a fan of astrophysics.

I've looked online and I haven't seen anything of the sort. This isn't for commercial reasons, but for a story I'm working on. The shorter and funnier the slogan, the better.

Thanks!

Is expansion slowing down galaxies?

knave — Tue, 16 Jun 2009 11:09:14 -0800

Does expansion of the universe decelerate orbits of planets and/or rotation of galaxies? My understanding of the expansion of the universe is that, essentially, new space is appearing everywhere. I've heard it said that gravity holds solar systems and galaxies together, and they don't expand or grow in size from this inflation. However, the space between galaxies does grow, because gravity at these distances can't compete with the expansion. (Correct me if any of this is wrong.)

That leaves me wondering... If gravity is overcoming the small amount of inflation within solar systems and galaxies, then it must come at a cost. Gravity doesn't introduce new energy into a system, so my intuition says correcting the orbit of a body to its original distance must come at a cost of orbital speed.

Is this thinking correct, or am I missing something?

Big Bang Baffles Bonzai

Bonzai — Wed, 20 Feb 2008 23:55:07 -0800

Why is the Big Bang possible? I know that a black hole is formed when X amount of matter is in one place. I know that nothing (except Hawking radiation) can escape a black hole.

So if all the matter in the universe was once contained in a single point how could it have possibly escaped from all that gravity? Obviously it did, but ... how?

Would our Sun really eat Earth?

Burhanistan — Tue, 05 Feb 2008 07:29:37 -0800

Would an expanding Sun really swallow the inner planets? Not that it keeps me up at nights, but would the Sun's projected eventual expansion into a red giant actually swallow up the inner planets? Is there actual astronomical evidence of this occurring in other star systems? I have an unfounded theory that the orbits of the planets would somehow be rebalanced further away from the sun by some combination of less gravity from the Sun (red giants are less dense) and other factors I'm not taking into account. Any research to support this?

Why isn't the moon headed to the earth?

dpx.mfx — Mon, 21 Aug 2006 07:48:39 -0800

AstroPhysics: Why doesn't the moon move towards the earth, and other satellite related questions. From time to time there is a story about how a satellite that one country or another launched several years ago is going to reenter the earth's atomosphere and crash into the ocean/land/burn up/whatever. This makes me think that satellites are in orbits that move continuously closer to the earth (googling around shows this to be, possibly, "orbit decay"). I assume this is becuase the satellite does not have enough velocity to continue in its orbit, and gravity pulls it down. And that makes sense to my tiny brain.

But what I can't figure out is why other orbits don't decay. The moon doesn't get closer to the earth, and the earth doesn't get closer to the sun (and neither to do the other planets), unless someone forgot to tell me something in grade school. Why? Googling gets me lots of stories about satellites and orbits, but no explanation for the differnce between planets and man-made objects. (And some man-made objects don't have orbit decay, maybe? Like the space station? Becuase that isn't going to crash back to the earth, is it?)

Is there an Astrophysicist in the house?

reflecked — Thu, 04 May 2006 16:34:19 -0800

I would like help understanding the CHANDRA xray satellite mission. I'm having trouble understanding X ray astronomy, specifically the CHANDRA mission. After reading the majority of the information from Harvard's CHANDRA site, MIT's, and Penn State's, as well as numerous data searches in Astronomy journals, I still have huge gaps when trying to visualize what is happening.

Most importantly, I can't figure out what is happening with the High and Low Energy Transmission Gratings as they rotate to reflect the rays. I "get" the Rowland circle pattern that the gratings are mounted in, but can't visualize what is called the "Rowland torus" that occurs when the Low energy waves are manipulated by reflection.

What I'm looking for is someone who can walk me through what happens to an X ray from the time it enters the sun-shaded aperture until a recording is made on the data grid.

:) No, I'm not taking a class. If I was, I'd likely have the maths needed to understand more completely.

What would happen to the moon?

Grod — Wed, 25 Jan 2006 14:19:56 -0800

If there's anyone here who groks physics and math and astronomy and astrophysics here's a great big what-if for you. Pretend the planet Earth was destroyed. Smashed into chunks ranging in size from grains of sand up through mountains. Presumably the atmosphere would be lost to space, much of the former planet would fall slowly into the sun or flee outward. What was left would form a new astroid belt, depending on how the actual destruction was caused it would probably become a planet again, at some point. Assuming that nothing directly impacted the moon, what would happen to it? Most of the earth's mass would still be around, just spread out a bit more. Assuming the moon's orbit didn't intersect the debris, would it continue to orbit? Would it fall towards the sun? Fly away from the sun? What?