Astronomy and Cosmology

I've been reading a bit lately about the possible fate of the universe. So far I've seen a few models, and they all seem interesting to me. I've seen threads about these prophecies individually, but I'm not entirely sure which one is most plausible, so I'm curious as to your ideas. First off is the Big Crunch, the idea that when there is enough matter in the universe, gravity will cause the expansion to move backwards, thus collapsing the universe into a black hole singularity.The next one I found was called the Big Chill, the idea that as the universe is expanding, matter will get spread more and more thinly, until the temperature approaches absolute zero.After that, the…

I was wondering what anti-matter is and what its relationship with normal matter is any one know?

Kepler spacecraft was successfully launched on 6 March. It's job is to watch a particular patch of 100,000 stars for several years to detect transiting HZ (habitable zone) planets which are roughly about earth size. If anybody knows more about the Kepler mission please contribute comment. http://kepler.nasa.gov/ This website has an FAQ. My understanding is that HZ planets are ones whose semimajor axis (average distance to star) is 0.95 - 1.37 AU adjusted for luminosity. That might be wrong but it is something like that. The idea is that for a star as luminous as the sun they look for planets whose distance is around the same as the earth's, namely fro…

Imagine a SETI program on a planet at 4 light years away (nearest star system from us). What can you pick up from earth? We're broadcasting countless simultaneous things on the same frequencies (how many FM radio channels exist that broadcast on 92.4 FM (39000 hits in google), how many phones are in the same frequency, how many TV stations)? While these signals are located on different places on earth, and don't seem to interfere with each other here (because one source is much stronger than the other), at 4 light years, the different locations on earth are no longer of any significance, and all signals seem to originate from one source (the tiny dot called "Earth").…

Stephen Hawking hospitalized, reported very ill Published: 4/20/09, 11:25 AM EDT LONDON (AP) - Famed mathematician Stephen Hawking has been rushed to a hospital and is seriously ill, Cambridge University said Monday. The university said Hawking has been fighting a chest infection for several weeks, and was being treated at Addenbrooke's Hospital in Cambridge, the university city north of London. "Professor Hawking is very ill," said Gregory Hayman, the university's head of communications. "He is undergoing tests. He has been unwell for a couple of weeks." Hawking, 67, gained renown for his work on black holes, and has remained active despite being diagnosed at 21 …

Hey guys, I was discussing with a friend about the evolution of stars, our sun especially. It's now absolutely well known that the radius of a star when it turns into a red giant is increased a lot, but he asked me whether there is a formula or any other way using which you can calculate this radius increase yourself. Of course there must be some way, and I couldn't answer him. So is there a formula, or other way so you can calculate yourself what the radius of our sun (for example) will increase when it turns into a Red Giant? Regards, shade

I was waving my phone around in the dark and i noticed that it left a trail of light like it was in two places at once what causes this?

What would happen if the magnetic field of Earth was shut down for a second??? As I understand it, the magnetic field protects us from most of solar radiation. So, would this radiation have time enought to hit Earth in full force, if Earth's magnetic field did turn off for just a second? And if it did, how much damage would the solar radiation do to living beings and electronic equipments??? Would it burn everything??? Would it be the end of the world for us humans??? The reason for this question is the upcoming swap of the magnetic poles. I'm rather worried that during the incident, the magnetic field might go off for a while. Is this probable?? Mind you,…

In experiments like LIGO we want to observe extremely weak gravitational waves from sources millions of light years away - we are assuming that their strength decreases like R^-3. But because of this distance, even slightest interactions with the vacuum and other objects on the way, could diffuse/absorb them - and so the amplitude would decrease exponentially, making such observations completely hopeless. In November 2005 LIGO has reached assumed sensitivity "At its conclusion, S5 had achieved an effective range of more than 15 Mpc for the four-kilometer interferometers, and seven Mpc for the two-kilometer interferometer." http://www.ligo.caltech.edu/~ll_news/s5_ne…

can there be a model of an expanding universe

And again, assuming that a black-hole might be the best ... visual characteristic for gravity, would it be logical to assume a ... big-bang would be the best visual opposite ... for anti-gravity? Merged post follows: Consecutive posts mergedIf it is a stupid assumption, and I need to be hit with the dummy stick, please by all means do so.

What is the speed of darkness?

Yesterday as I was walking during night, though it was cloudy,I saw that a perfect circle of clear sky formed around the moon.I was wondering that if that is some physical phenomenon or just coincidence?

I'm always a bit uncomfortable with the explanations offered regarding dark matter (and even more with dark energy, but let's save that for another thread). I know that the popular theory is that dark matter consists of particles that have little or no interactions with other particles, and that these particles are everywhere. This theory is for example explained in (warning: it's >1 hr!). In fact, it's probably explained much better than I just did . But... what I wanted to discuss: is there any proof that dark matter is not just normal matter, made of atoms? If dark matter is just normal matter (solid particles of varying size), that is relatively unifor…

I was wondering about a theory I had and was wondering if I can get any supporting evidence to assist me or to shut down the theory all together, so please if you have any imput to provide, don't hesitate. I've wondered about the existence of space for some time now, as I'm sure several people have, I was trying to learn more about stars when I came across a term "nucleus star" then I wondered, is it possible that space is I gigantic atmosphere, so enormous, that we are an electron equivalent, on a large scale atom, or some sort of variant of this?

http://www.stsci.edu/institute/conference/blackholemergers An interesting thing you immediately get if you click is eight images. Four on the left are stills from a computer simulation of a merger, calculated step by step using numerical GR methods. The four on the right are actual photographs, some with false color showing temperature, of real things which look like stages in the merger of supermassive BHs. That is, the observed thing looks somewhat like what they got by running the numerical model. This field is just getting started. Maybe at this point they don't have much more than those eight images. But I'd expect they'll be getting more interesti…

I am not an expert in physics, but I am an astute spectator of the reoccurring systems around me. After watching quite a few documentaries surrounding Stephen Hawking, I have been honing in on an idea that I have had for quite some time. I suggest that our universe is made up of infinitesimal parts. Black holes break down our known universe (dimension, gravity, time...) into these smallest of parts and translate them into the Big Bang beginning of another universe. I would translate this to one universe giving birth to another. This would be like a mothers' body breaking down everything she ingests in order for the fetus's body to be able to cr…

is the flow of the big bang and big crounch are continuous? So now there life in another time and after the cosmos will end there life after a new big bang? Life cycle remain

A star's Habitable Zone (HZ) is the region, around said star, where water exists as a liquid. In essence, the Habitable Zone is the Water Zone (Venus, Earth, Mars). Within this Water Zone, closer in towards the central star, water cannot condense. In essence, this is the Steam Zone (Mercury). But, beyond the Habitable Zone, farther from the central star, where water freezes, is the Ice Zone (Jupiter, Saturn)*. Roughly speaking the Habitable Zone is bounded between Rain Line (where water condenses as a liquid) and the Snow Line (where water freezes out as snow). * Carroll & Ostlie. Introduction to Modern Astrophysics, pg. ~893. Even farther from the central s…

what is the universe expanding into? it has to all go somewhere, whether it be compress the outside while inplode the inside, or simply expand into some sort of space between spaces, where does this giant terrarium we live in expace to? any ideas?

Why is our moon so perfectly round and spinless? I mean should it not be a bit irregural shaped, like most moons in our solar system? Especially if it was formed from a chunk of earth off Earth? So why is it a near perfect sphere? Also, why does the Moon not have spin at all??? The very same side faces eath all the time! Why is this??? How is this even possible??? I mean take a basketball and hang it from the ceiling. Then shoot at it with a bb gun, you know, the one that fires light plastic bullets. The basketball will start to spin, even though the projectiles are very light, and the ball very heavy. Now why has this not happened with Moon? It has be…

I was reading about a massive solar flare that happened in 1859. It got me thinking. Talk is that solar flares can destroy our power grid, and also computers. But would it be able to destroy a disconnected hard drive? A hard drive is essentially in a metal box, which acts as a Faraday's cage? I have a backup of most of my data on a harddrive that I don't need anymore. It's therefore disconnected from everything, and it just lies in a drawer. Is that any guarantee? Or should I really go for optic storage (CDs) to make sure I don't lose anything from a solar flare? Next week: planning to protect my data from an asteroid crash.

it's said that light speed is the fastest possible speed for anything to travel at but why is that couldn't somthing move faster light speed if so what all comments welcome

Imagine an extremely buoyant balloon rises vertically to -say stratosphere- , and stays up there; Could it be called being in a geostationary orbit ? -Ignore winds-

This all started last night and this begining story might fool you but i still think it is credible. So here it goes. Last night me and a few of my friends decided it would be a good idea to smoke marijuana (which i do not do regularly and had not done in 3 years) and watch some of my 50+GB of space documentries from numerous sources. So we did and as we were all watching this in complete silence and coming up with our own meaning of the universe, I think i might have stumbled upon something. okay the documentery was talking about the super massive black hole at the center of the milky way and how in 1999 there was i massive explosion at the galactic center. now i was thi…