Astronomy and Cosmology

Hi everyone, alright my question is this, what are the reasons for such a strong and widespread belief that some dark, as of yet unobserved type of matter must be present in the universe? My knowledge of the topic is rather superficial but the way I reason is this, there is mathematically and physically appealing theory called general theory of relativity and for quite some time this theory has been repeatedly tested (with positive outcomes). The precision of the tests is nothing like the experiments in quantum mechanics, but hey, GTR always gave better predictions than any other theories and up to date. I think that only Brans-Dicke theory and some of the f( R) theories…

From my knowledge the theory of the accelerating expansion of the universe is based only on the observation of the Doppler effect. Is it possible that light's frequency is dropping (for some unidentified reason) traveling throughout the cosmos and the stars are moving away with a constant speed? If dark energy is blowing up everything (including us), then it is merely a question of perspective if the universe is expanding, or the forces that hold matter together are decaying. In the case of photons this process could also mean loosing frequency. Am I contradicting some scientific observations?

Considering the fact that the Universe is principally made up of Dark Matter, how is it that the spacecraft Voyager that started its journey about forty years ago and has travelled a billion or so miles in space has not hit/encountered Dark Matter?

I am struggling to find consistent information about where to look in the sky this evening for a chance to see the Neo (I am in outer London on northeast). Between Leo and the Plough seems the most regular advice from 8pm - but that's a big space and an uncertain time. I have tried pasting the orbital elements into fourmilab yoursky without success Any clues - preferable a sky map with a nice line drawn on it?

Hello everybody! Please, pay no attention to my bad English, because I’m non-native speaker. Just try to see the point. I had a debate with my acquaintance concerning the following issue: Is there any physical possibility that humans are under surveillance of extraterrestrials? By surveillance I mean observing individual people by means of optics with great magnification. Well, I believe it doesn’t happen. Here is my little analysis of this matter. Let’s imagine any possible ways of such surveillance and fantasize about them: 1. Optical telescopes in space (like spy satellites). Such telescopes need big aperture of main mirror to be able to…

http://www.nasa.gov/topics/solarsystem/features/asteroidflyby.html The simulation of the flyby doesn't seem to be correct. The attached image is my plot(s) for the flyby path of 2012 DA14. I had to reverse the side elevation, at least it was symetric, scale it, and plot each against the other as the NASA/JPL images and the simulation were in opposition. BTW, pink is the color you get when you reverse a dark image. I don't think it will hit, there is a possibility it will become a satellite, NASA only said it would not hit the Earth or any other planet although they made no mention of the moon which usually helps to capture quasi moons. The last image is fr…

Hello there, I am simulating a planetary system and there was some anomalies like Green atmospheres. That anomaly gave me the question of what kind of elements are present in that planet's atmosphere that makes it color green or simply what are the different compositions of different colored atmosphere? Our home planet Earth has blue atmosphere since its main components are nitrogen (78.09%), oxygen (20.95%), argon (0.93%), and carbon dioxide (0.03%). The atmosphere also contains small amounts, or traces, of water (in local concentrations ranging from 0% to 4%), solid particles, neon, helium, methane, krypton, hydrogen, xenon and ozone. The color of our atmosphere is …

the sun is losing mass faster than the earth is. so later in the future, the gravitational force beetween the earth and the sun should decrease. my question is, will this actually happen and if it does, will the orbit of the earth be stable or could it shoot out into the universe?

please comment if you want, we would like to know what you think ... http://www.youtube.com/watch?feature=player_embedded&v=zIrgQKm5mwQ

It seems to me that stars orbiting black holes would cause some gravitational distortions within the disk, and that these distortions might cause some of the black holes material to be ejecected out from the center of the phenominon much like the jets of quasar. If this is happening all the time the black holes would probably be shrinking at a regular or at least a prdedictable rate. Does this happen? or has this been considered in any theories? if so, does the material expand into stable particles? perhaps strong force particles with no structure to capture electro magnetic energy?

Here is something I discovered on another web site, that refers to "physics.org". "13 light years away: Earth-like planets are right next door February 6th, 2013 "Astronomers have found that 6 percent of all red dwarf stars have an Earth-sized planet in the habitable zone, which is warm enough for liquid water on the planet's surface. Since red dwarf stars are so common, then statistically the closest Earth-like planet should be only 13 light-years away. Credit: David A. Aguilar (CfA) "Using publicly available data from NASA's Kepler space telescope, astronomers at the Harvard-Smithsonian Center for Astrophysics (CfA) have found that six percent of red dw…

Let’s suppose that Big Bang was prepared and initiated by some “Creator” in other Universe and that our Universe is located within it being a smaller part of it. Is it theoretically possible to “create” in such a way several completely identical Universes with identical future and evolution? I mean is it theoretically possible that aeons ago somewhere existed the same Universe as ours with the same creatures and living beings and with the same events? Thanks in advance.

I need to know about black holes like 1)mass 2)volume 3)speed 3.5)temperature 4)if something goes is black hole what will its speed 5)formation 6)destruction 7)what is its role in universe 8)can we produce them 9)how much it's powerful 10)can we damage black holes 11)is there any power in universe to destroy black holes 12)how much black holes are present in current universe 13)what is relation of black holes with time etc. these are some of question when we want to learn about bh please give answer to each question

So light red-shifts over time as it travels over vast distances of space, eventually to the point where it would be immeasurable by our current technology, but for the faint radio photons we do manage to pick up, how do we determine that it wasn't a photon that traveled in the opposite direction from it's sources and then looped around the universe in a 4 dimensional hyper-sphere?

Globular clusters have a few well known characteristics They contain only old stars All stars within a globular cluster are approximately the same age They contain very few heavy elements The heavier the supermassive black hole at the center of a galaxy, the more globular clusters orbit around that galaxy Based on the above I speculate that globular clusters around the Milky Way were formed by gas emitted from the jets of the supermassive black hole at its center, by the time our galaxy was a quasar. I've just had the thought this evening. Not that I would claim to be the first, it seems too easy of an idea to not have been proposed before. Anyway, what would …

If I know my physics correctly, the singularity at the center of a black hole has infinite mass. How can something that is infinite ever decrease in gravity? Wouldn't the pull of gravity from the black hole always be faster than the speed of light from any point in the universe?

Hello, I have come to these forums to request help a guidance on how to develop specific portions of a game that I'm working on. To keep it simple, I'm working on a text based space strategy game where players start with a single planet, and must construct structures, research technologies and colonize other planets to expand their empire. I'm working on solar system formation at the moment. I could simply make every planet in the system random, and take the easy route, but I really ant to do this right. I obviously can't build a full-fledged simulation, but I can make it realistic as possible. I know that every solar system should start with a certain amount…

The age of universe is said to be around 13 billion years.However we know that stars exist 40 billion years far! Since the fastest means we have is the light then how do we know about their existence?

In the seventeenth century, Descartes rejected the concept of the vacuum, which is one big thing he got wrong, we say. He believed that an invisible liquid, like a very fine olive oil filled all the empty spaces in the universe, so there was no void anywhere. In his model, planets are carried around by swirling vortices in this fluid. Now, is not this surprisingly close to modern discoveries, like evidence of the presence of dark matter, which resembles Descartes's fluid? Might be more in his theory.

Are +/- 90 north/south latitude degrees, +/- East/west 180 longitude degrees, 24 hours per revolution; 60 minutes and seconds subdivisions being used when exploring and charting other planets ? Is the absence of the decimal system being carried to other worlds exploration in favor of the senseless duodecimal / sexagesimal / dozenal and earthly time divisions ? Would it be better to start using a rational decimal system for -say 100 hours with decimals time- per revolution; dividing a circle in 'new' 100 degrees with decimals ? Why yes and why not ? <Sorry. title should spell 'committed'>

Hello, I just wrote the following manuscript: http://fr.calameo.com/books/000145333298884fdee60. By deriving the standard formula of the luminosity distance, I obtain a time varying speed of light (from light propagation). Therefore, a new definition of the luminosity distance is provided. Given this new definition, the Hubble constant must remain unchanged in order to fit the supernovae data. Your comments and ideas are welcome...

The Universe is expanding, but if we turn the clock back and energy is drawn back into the void so that that 13.7billion years ago the universe came from nothing. We could then have a continuously expanding universe which has no beginning. Mass, energy continuously emerging from the void as the universe expands... You see the Big Bang theory in its current form with specific moment of creation can not explain the following... http://www.sciencedaily.com/releases/2013/01/130111092539.htm

Pardon me if this has been asked before. I am an avid follower of the latest scientific discoveries but by no means a professional scientist. If anyone could provide a link or explain an answer, I would greatly appreciate it. If the Universe is expanding and speeding up, would it not be logical to assume that the expansion would eventually (if not already) reach the speed of light? Would we eventually arrive at that speed and what would the implications be? Also, how do we know, from observation that the Universe isn’t slowing down? When we view the Hubble Ultra Deep Field it appears that Galaxies are moving exponentially faster away from everything. That observat…

In the standard model of Cosmology, spacetime is expanding. I tend to regard spacetime as some kind of physical entity, given that it can be affected by matter to become curved. Also in the analogy of the balloon, galaxies are carried apart because they are fixed on the surface of the balloon,which is a physical thing. So I think that in the real Universe galaxies are carried apart because they interact with spacetime, which must be physical (how else would the galaxies know to move apart?) But my question is, the same way that if you inflate a balloon, if you inflate it beyond a certain limit, it will pop, then if spacetime is being stretched constantly, and even …

The expansion of space is accelerating, space is expanding faster than before. From the supernova obsservation that is a fact. What I don't understand is why do we need dark energy to explain that acceleration, when ther is a simple explaination: Gravity is opposed to space expansion. Space expansion happen when gravity is not strong enought like between galaxy cluster. Earlier in the cosmos history cluster where closer together and gravity between cluster was bigger because of smaller distance, but not close enought so the space expansion brought these cluster further apart. If the distance between cluster increased, then the gravity between them decreased, so there wa…