Astronomy and Cosmology

Ashtekar and Bojowald are two of the most prominent people in Quantum Gravity research. Ashtekar was a co-founder of the LQG approach and Bojowald initiated the field of Loop Quantum Cosmology, where LQG methods are applied to help understand the big bang, inflation and features of the microwave background. In 2001 Bojowald showed that quantum gravity eliminates the classical big bang singularity and leads to a prior contraction phase. Now these two are working on a quantum gravity model of black holes and gravitational collapse (in a way the opposite of big bang expansion). http://www.arxiv.org/abs/gr-qc/0509075 Quantum geometry and the Schwarzschild singularity A…

I'm finishing up a book and in it a physicist Yakov Zeldovitch was explaining how a binary star system oribited each other. He went on to say that if one star collapsed into a black hole the remaining star would continue to circle around what appeared to be empty space. Then he goes on to say that the gravity of the black hole would begin violently stripping matter away from the companion star. I understand the process of a star collapsing into a black hole, but what I don't understand is why the black hole has more gravitational pull than it had when it was a star. I also understand how a black hole keeps pulling in matter and getting more powerful, but where…

Ok, I might be totally off-base here, but I recall hearing something about the moon's rotation slowing the Earth. Or was it speeding up, or slowing down the moon? Something involving the two interacting and altering each other's rotation, anyway. So, this got me thinking, could you possibly calculate, using what we know of this phenomenon, the day length a million years ago (assuming this was the only factor)? What about, say, 65 million years ago? Or 250 million? I'm not really interested in the usual "will the moon fly off or hit the earth?" stuff, but more about day-length in general, and the possible ramifications for paleoecology. Mokele

The Wiki page on "Star Lifting" has some details about removing material from the star, but it's mainly the parts from the popular definition that I've bolded that interest me. What would constitute an "unstable" star, and how could it be stabilized? Is there any way to prolong the lifetime of a star beyond star lifting? What sort of "envelope material" could be mixed with the core? Surely any technique to significantly prolong or reduce the lifetime of a star would alter it's brightness - am I correct?

so as im not an einstein with astronomy. this is either blatant bullcrap or it could possibly be true. what do you guys think, should we now all be shitting ourselfs? thanks the link for the topic http://www.weeklyworldnews.com/features/science/61501

I would like to know what happens to the supermassive blackholes in the center of galaxies when they collide. Do the two holes instantly join like 2 drops of water, or do they sort of "rip" at each other as they pass between each other?

I'm just wondering what the current consensus is, or, if the consensus is still in the affirmative, whether there are any growing beliefs in alternative theories (besides Creationism, obviously). For a while now I thought that the Big Bang was essentially proven beyond any reasonable doubt, but quite recently I read an article that claimed otherwise, citing (if I remember correctly) the discovery of red giants in galaxies too distant for them to have had time to form if the Big Bang model of the universe holds true. Anyway, there was some other theory proposed, in which the universe could have been trillions of years old, going through oscillations of galaxy formation…

Hi, First of all, cause this is my first message, I say hello to everyone and I would like to apologize for my english, it is not my native language. I am looking for a software that could give me the amount of solar energy received on earth according to latitude, longitude, altitude and day of the year. I think that such software exist but I don't where I can find it. Many thanks in advance.

What oh, what is space IF this question is answered plenty more scientifc questions can be answered as well. 1. a. Mathematics A set of elements or points satisfying specified geometric postulates: non-Euclidean space. b. The infinite extension of the three-dimensional region in which all matter exists. 2. a. The expanse in which the solar system, stars, and galaxies exist; the universe. b. The region of this expanse beyond Earth's atmosphere. -SmarterChild, Aim bot OK...so what is it? 1. well i am refering to the physucal space, as in outer space (def 2.) 2. The expanise....IN WHAT? what hold all this? Space, is something, it is not nothing, ot…

Also organic molecules in comet http://www.newscientistspace.com/article.ns?id=dn7961 http://astrobiology.arc.nasa.gov/news/expandnews.cfm?id=597 So I'm starting to wonder from all the places we looked for (if I'm correct) then it was only the moon that didn't have organic molecules (and that is probably because we didn't look good enough.) Aren't we getting in a situation that we will assume that there are organic molecules everywhere. (almost hard to find a place without some) Maybe in a few decates we will find out that there are all kind of small lifeforms everywhere.

There is something i dont quite understand. Maybe this is just a newb question so flame away but, here goes. How do black holes "suck in" light, if it has no mass? Or does it have mass? I googled this but didnt really find anything, so if anyone could explain this in a easy-to-understand way ( thats right, imagine your talking to an idiot =P ) id be grateful.

Unless I am mistaken, a new method of interstellar propulsion has been invented here at SFN, and blike may wish to apply for a patent so that everyone can share in the royalties the method is based on the fact that http://www.scienceforums.net/forums/showthread.php?p=208256#post208256 our galaxy is full of neutron stars whizzing around at speeds up to 1000 kilometers a second. Here is a map that shows over 200 of them with arrows to show the speed and direction----look at Figure 1 on page 2 of: http://arxiv.org/abs/astro-ph/0504584 so the method is TO HOOK A RIDE by means of GRAVITY SLINGSHOT. It takes neglible propulsion compared with what you get, b…

We are looking at stars at night ? We all know the velocity of light and stars are very far away from us. So whether stars are in that point when we are looking at that instant at the same point?

Whats the best summery of all basic info that could be found at a liberary.

Is every part of the universe equally old? The universe is estimated to be several billion years old. If I had a really accurate clock that measured the time from the big bang would it show the same time as anyone elses similar clock?

who believes in the big bang theory and whats your opinion on it?

How would you power a future fusion engine? What's it's fuel? In one article it said helium-3. But are there other kinds of possible fuel? It seems so from the wiki article but I sadly don't understand much of that article. Where would you get helium-3? I know of Luna and Uranus, how about Jupiter, Saturn and Neptune? I also read that with only the helium-3 on Uranus you could send a fusion-driven ship to every star in the galaxy, is this true?

The idea of dark energy I believe was to explain why the observable universe's expansion is accellarating. This seems like such a radical conclusion, surely something else more simple could explain this? Here is my idea: Perhaps the universe has a similar topology to a sphere, meaning that if I travel in any given direction for long enough I will end up at my starting point from the opposite direction. If that were so then perhaps all of the farthest parts of the universe are accellarating away because it is actually being pulled by matter in the opposite direction, with all of the matter actually converging upon a point rather than dispersing. Does this make sens…

http://abc.net.au/science/news/stories/s1460730.htm Could these make up the missing dark matter? I doubt it but still.. Some recalculations might need to be made.

It has always been a heated topic for debate whether we have been "visited" or not. But when will we reach outside our own solar system to prove or disprove life in other areas of space. You see scifi shows and books about interstellar travel all of the time, yet how far is humankind from making a breakthrough and finally starting up the interstellar space race? How far are we from such technology? I hoping sometime in my lifetime.

Several theories claim that the universe is expanding, or that at some point it was. My question is (assuming the universe isn't infinite), what could be at the edge of the universe? If I somehow ended up at the boundary of the universe, I presume there would be a sort of barrier where the universe ends, but if the universe is expanding, there must be something outside the barrier for the empty space to even be created? And on that note, what actually defines space itself? Could it be possible there are an infinite number of universes all within one huge multiverse one one plane (dimension), and while one increases in size, another decreases (Big Bang, Big crunch), like …

what is the minimum thickness for a dyson sphere(with a radius of 1AU) such that it won't fall apart?

Does anyone have a good guide to what it would take to terraform Mars? I'm thinking of writing something about it. I've already looked into http://www.ibiblio.org/astrobiology/index.php?page=mars04, and am thinking of looking into the Red/Green/Blue Mars novels, I hear the science in them is very plausible. Can you also just give me your thoughts on what terraforming Mars would take? Thanks

Hello all! I am in the midst of writing a young reader's Sci-Fi book and am having difficulties with some of the hard and theoretical science aspects! Is anyone here willing to help me out? The sub story is based around terraforming Ganymede and part of the problem I'm having is in finding general terraforming theories. I've found tons of specific stuff for Mars, the moon, and Venus, but most of that doesn't help me! So, the main points I'm stuck on currently are: Increasing Ganymede's gravity without altering its orbit or destroying it Creating an atmosphere (I've got a good idea for this, and will go into details if asked) And, creating a permanent he…

Could it be possible that the universe is older then what we presume, and that the empty space in between galaxies is actually burned out dead galaxies containing super massive black holes, and that these invisible dead galaxies could account for the large amount of matter that is undetectable? How feasable is that hypothesis?