Astronomy and Cosmology

I just can't understand why the rings of Saturn are stable... My knowledge of the theory of gravity, which may be limited, is that there is only an attraction force (when we look at macroscopic things like rocks and planets). These rings seem to defy everything I know of gravity. Why don't the rings form a few moons, or at least larger lumps of rock? Any disturbance in the homogeneity of the rings should irreversibly cause the formation of lumps of rock. There are plenty of disturbances (even from outside, in the form of asteroids and comets), but also moons, and a size distribution in the rocks (they are not all equally big). Can anyone explain to me how the popu…

I have recently come across in my book about how people are able to hold plasma in a magnetic field, in which the north and south pole reach and equilibrium. Anyway, I was wondering, would the same be true for anti-matter within a vacuum?

It is said that dark matter is needed to hold the galaxy together, otherwise stars would just fly off out of the galaxy at the speeds they travel. Our sun moves at about 175 mps, almost stationary by galactic standards. The ancients thought the Earth was flat. If you look at any circle close enough, a small enough piece of it will look straight. An arc second is just 102 feet at the equator. The Sun/Earth take 200,000,000 years to travel once around the galaxy, some 188,400 light years. An arc second of that is over 847 billion miles and it takes the Sun/Earth over 153 years to travel that distance, for the equivalent curvature over a distance of 102 feet on Earth. …

Okay, I know there is observational evidence for spinning black holes, so therefore I must be confused about something, and I want you to tell me what. If you have a star that is spinning, therefore it has orbital angular momentum (mass revolving around a point), then as it is collapsing in a black hole, it shoots out particles that probably take some of that with it, but not all, and because angular momentum is conserved the black hole will spin. However, it is my understanding that the actually 'massy' part of the black hole is a simple point structure with a large mass and density with (almost?) infinite curvature. But if it is a point, there is no mass to r…

Bojowald's What happened before the Big Bang? article in the August 2007 issue of NATURE PHYSICS is now available to non-subscribers http://npg.nature.com/nphys/journal/v3/n8/index.html During August it was accessible only if you paid, but they just made it free. The link gives the TOC for the August issue. Scroll halfway down the page to where it says LETTERS and click on the PDF for the Bojo piece. Or get the article directly in HTML http://npg.nature.com/nphys/journal/v3/n8/full/nphys654.html In this piece Bojowald derives (in the context of his quantum cosmology model) some definite limitations on what can be known about the universe prior to the begin…

Have you guys heard of this site here: http://www.atlasoftheuniverse.com/universe.html Basically, it is an attempt to map the entire visible universe. Each little speck represents clusters of galaxies. Damn, that's pretty big. The map also allows you to zoom in on our part of the universe, and gives some interesting facts about the number of stars within a given patch of space. There's alot more in it too, like the big bang data, and so on.

How common is planetary “wobbling”. The earth has the chandler wobble: http://en.wikipedia.org/wiki/Chandler_wobble http://hpiers.obspm.fr/ As well as various other types of wobbles: http://www.agu.org/sci_soc/prrl/prrl0622.html So, how common is wobbling? Is everything wiggling and wobbling out there?

I was interested to hear some thoughts from someone who understands the technical details of the idea proposed by the British astrophysicist, Dr Hongsheng Zhao. Please see the sciencedaily and arxiv articles below...at face value it seems like chalk and cheese to me, but as a lowly undergrad, I'd like to hear an expert opinion on the idea... http://www.sciencedaily.com/releases/2008/01/080131094056.htm http://arxiv.org/abs/0710.3616

I have this great confusion. I am not able to distinguish between sky and space. I feel that sky is the space but space is black but sky is blue(generally) I am a kid in this field. So can anyone please take the pain of explaining in a easy and liberal manner. Thank you

Is human thought "data"?

So I need to clarify some details about this flat universe ideology. Is the universe supposed to be 2 dimensional? Is it supposed to be, say, one galaxy thick, on average, give or take a galaxy? Or is it supposed to be, say, one nanometer thick? Of course, I just found out that there are other competing philosophies, but I was wondering why this is even considered. Even the hyperbolic philosophy makes no sense. I envision a spiky ball of fuzz.

In space there is neither friction nor gravity.Then how is it possible to stop a missile or a spacecraft in the space. We need friction to stop a moving vehicle. Is there a special mechanism behind it.

What is the temperature of space just beyond the earths atmosphere?

Hey guys, In a lunar eclipse the moon dissappears as it goes through the umbra, but when it is completely inside, it turns red. I am not sure why... Lunar eclipse happens when the earth is between the moon and the sun. Technically, shouldn't the moon completely "disappear" (be blackenned out)? Why is it red...? Thanks in advance ~moo

NASA article dated 24 January about GRB, includes some animation http://science.nasa.gov/headlines/y2008/24jan_glast.htm?list45222 GammarayBurst astronomy is featured in the agency's news because the satellite instrument GLAST is scheduled for launch the first half of this year. Currently the launchdate is set for 16 May. Here's a GLAST webpage http://glast.gsfc.nasa.gov/ As the animation in that 24 January article shows a gammarayburst can take only 5-10 seconds, with the main peak coming in a spike that lasts only one or two seconds. Nobody knows the mechanism---some kind of star explosion that differs from supernova. On the other hand GRB oftentime…

It certainly looks like the larger the universe gets, the more space you get between galaxies. Which is why I have trouble picturing why we would collide with Andromeda.

we all hear about talk of the space tourism industry getting off the ground in the next decade or so - what interests me more though, is that given NASA's snail pace progress in solar system exploration, as well as bureaucratic processes that bog it down, can we expect private companies to explore the solar system with robotic probes? Would it depend solely on potential profit? If so, would there be a demand realistically, for purchasing the data gathered, to make it commercially viable, if no private company wants to do so for the sake of discovery alone?

Do you know what a blue moon days? The average period of lunar revolution is nearly 27.6 days. certain months of certain calendar has nearly 32 days. If a full moon day appears during the first or the second day of the month, another full moon day appears during the end of the month. This day is known as blue moon day

To inform you if you have a clear night and live Europe or America a nice lunar eclipse will happen ! Lunar eclipse animation More details

Hi everybody. Can any one say what's beyond or outside the universe.If it's going on expanding,where is the free space for it's expansion? what is there????

http://news.nationalgeographic.com/news/2008/02/080204-galaxy-life.html Methanimine was found in the Arp 220 galaxy by Arecibo. "Methanimine can form the simplest amino acid, glycine, when it reacts with either hydrogen cyanide and then water, or formic acid." The other reagents (HCN, water, formic acid) are comparatively plentiful.

I just have a quick question about the singularity that theoretically was the universe before the Big Bang. I don't know the exact calculations, but it seems like the singularity would have an escape velocity far above the speed of light. If so, how did matter escape from the singularity? (I'm not talking about space; space is massless, and so can travel past the speed of light without violating general relativity, right?). I had a theory about it, but I don't have the skills to tell if it's possible, let alone prove/ disprove it. Thanks in advance.

Most stars are somewhat less massive and somewhat cooler than the sun. In fact the average is about half solar mass. This means the light from them is REDDER. More like the light from a 100 watt lightbulb-----the tungsten filament is about 3000 kelvin, roughly half the sun surface temp. that means that in other planetary systems, light around 700 nanometers is relatively much more abundant. That is down around the borderline with infrared. Incandescent lightbulbs make a lot of infrared which is why they are so inefficient. You cant see most of the photons coming off the filament. If humans are to develop a type of algae which will thrive on common ocean planets…

Hi, I did have a piece of shareware that allowed one to simulate galaxy collisions - for the life of me I can't find it now! I do have one called "galaxy32.exe" but it is 10 years old and not the one I was using.... It was freeware BTW. If anyone knows of the s/ware (or equivalent) can you please let me know? thanks dave

This has been bugging me lately. I was trying to find where the center of the universe is. I was dissapointed to find out that, as far as i have learned, there is no center. I have a little bit of understanding but need some help I remember something about the Big Bang occuring everywhere in space or time or whatever, and that in such extreme environments, the laws of the normal world might not hold, hence the uniform dispersion of heat. I have also read about the "ballon" metaphore used for the expansion of the universe. But it still doesnt make sence to me. If the universe is indeed expanding, in the sence that i understand it is(which may be wrong), then by goi…