Astronomy and Cosmology

Hello, For the last few years I've been programming a number og small apps for visualizing gravitational interaction, elliptic orbits and the sort of thing. So far I've done this the Newtonian way, by using an integration algorithm to find the new velocities and positions of each body based on gravitational interaction. Now I'd like to express movement as Kepler orbits instead, and in order to be able to do that I started reading through the wikipedia articles on Kepler orbit, Kepler's laws of planetary motion, and orbital elements. Strangely, I can't seem to find a way to calculate an orbiting body's position as a function of time. It seems like there's always an…

Does it have to be 25,000 mph? What if you traveled 10 miles per hour straight up and took a longer amount of time?

Hey everyone, I just registered, this looks like a very cool forum. I was just on a site called Scale of the Universe, it's very cool, it lets you zoom in and out from an atom to the universe. If you zoom all the way out it says the observable universe is 140 Ym but the whole universe is estimated to be 930 Ym across. If the observable universe is based on the light leaving that point at the start of time and only reaching us now, how can anything beyond that point (anything in the non observable universe) have got there from the point of the big bang? Wouldnt it have to have travelled there faster than the speed of light? Hope you can help! Thanks.

Hello I’m sorry. I can’t English well. My native language is not English. [birth of the Universe from “Nothing”] [ Birth of the Universe from the Zero Energy State ] 1)There was a pair creation of positive and negative energy in the early universe. 2)The total energy of universe is 0. Stephen Hawking and Alan Guth et al. argued that gravitational potential energy is negative energy, and that such gravitational potential energy can offset all positive mass energy during a period of inflation. 3) The acceleration in the expansion of the universe observed suggests the existence of positive energy out of mass energy, and alternatively, it correspon…

With no datum possible could it be that the reason why the universe is accelerating in its expansion be that the universe is spinning as well as expanding and thus a centrifugal force is able to overcome gravity? Although it is evident that the universe is not expanding on one plane could this be because we are still at the initial stage of the start of the universe. An oval shape might develop.

Hello, This question is driving me mad and I cant figure it how to solve this. Given: inclination angle 98 deg height of pergiee 700 km for 14 rev/day w = 7.29211x10 -5 rad/sec R= 6378.1363 km mu=U= 398600.4415 I know that period is P = 2*pi* sqrt(a^3/U) and by manipulating the period equation I can get the value of semi major axis but if you put the value in equation of e = 1 - rp/a this turn to negative which is not possible This is going to be used in Flower Constellation. Thanks in advance for any help.

I,m interested in supernova. Supernova explosion is well known. Why it should have to be exploded? There are many steps, but it can be simply explained like this. One star -----> mass loss ---->gravity decrease ------> supernova ------>explosion. What I don' t understand well is gravity decrease and supernova explosion phenomena. If gravity decreased, the nuclear reaction rate would decrease, and inside star energy would be decreased. There is no reason it should have to be bigger. Are there any unknown star phase exist?

http://www.bbc.co.uk/news/science-environment-11837869 http://arxiv.org/abs/1011.3706 The BBC has an article with a link to unpublished research suggesting that microwave background may hold clues to events that happened prior to our Big Bang. Thoughts?

Would a beam of neutrinos, arcing across the Cosmos, over Cosmological distance & time scales, "redshift", their Wave Functions spreading out with the expansion of the underlying spacetime fabric ? Would neutrinos' slight masses affect their physics any ??

Please ponder a hypothetical closed Cosmos ([math]\rho > \rho_{crit}[/math]), composed completely of matter ([math]\Omega_M > 1[/math]). In (1+1)D, its spacetime diagram (x,t) would be spheroidal, 'circuloidally' [eliptically ?] closed in time (lines of longitude), and closed in space (lines of latitude). Now, denser universes don't expand out as big, or for as long, as more rarified (but still cosmically closed) universes. Thus, the Radius of Curvature for Time, and the Radius of Curvature for Space, for a cosmically closed, matter only, universe, seem like they would be closely correlated. Is this so, and is there any (simple) relation between the two …

Consider the classical cartoon, describing entropy -- a state where all the molecules of gas, confined to a box, happen to occupy only half of that available volume, is said to have "lower entropy", than a state where the same molecules are spread out more evenly. Now, make that "box" into the whole cosmos. And, make "half the box" into the gravitationally condensed over-densities, associated with Large Scale Structure. By "ordering" the matter, which was once spread out evenly across the cosmos (at the Big Bang), into Galaxies, Clusters, Super-Clusters, and the Cosmic Web, does gravity reduce the entropy of the cosmos ???

Ok, so I had two different sources which conflict with each other about what a gamma ray burst would do at what range. One source which recently recorded a gamma ray burst and said "if it were aimed at us..." which seems weird to begin with, but it was also not even in our galaxy, and they said it would stop photosynthesis and damage the Earth's atmosphere, particularly the ozone. Then I found some other sources which said that if a gamma ray burst occurred within 3,000 light years of us, it would severely damage the atmosphere and do things like cause photosynthesis to cease, and at a distance from the center of the galaxy or more, it would only do a very small amount of…

Hello...Would we be able to detect a planet on that had an orbit at the same speed as Earth but was was always blocked from view by the sun? Also...We have sent satellites to the further reaches of our solar system. I think it could be a a good idea to make one that orbits around the sun instead of the Earth in the opposite direction to Earth at a speed that would take it a long time [1/2/3/4 Earth years...preferable 1 EY] to revolve around the sun. Every time it passed the Earth we could remotely download the data it has collected and send people up to upgrade/repair it. We could also have robonauts on it to operate it or automatically maintenance it when it is beh…

if the entire matter of the universe was present at the big bang , how do we explain child birth ? new atoms must be produced to grow an infant . after all we choose to reproduce , therefore the population grows . but where did the atoms come frome ?

Hello again, this is my second thread about what would happen when we humans make first contact with another advanced alien race. i would like your opinion. how would we handle that situation? how might the aliens handle the situation? would there be peace or war?

Phobos, the Martian moon, quickly approaches to the surface of the planet due to tidal effect (because Phobos's orbital period is shorter than a Martian day). Only a few hundred million years ago Phobos had to housed almost in a stationary orbit. The probability of formation of Phobos in accuracy in a stationary orbit is negligible. Therefore we must explain how Phobos could be in this orbit. The author offers the following explanation. After its formation the system of Martian moons consisted of three bodies, like modern Plutonian system. In addition to the tiny moons Phobos and Deimos Mars had another large moon (moon X). Phobos was in orbital resonance with the moon X…

Hopefully this is a fairly straightforward question: I am currently writing on Solar radiative output, and have run into a term several times that I cannot find a definition for, "Centre-to-limb radiance variation" f (μ, λ) If talking about total solar irradiance as measured by a radiometer, I am figuring the centre is the centre of the Sun, however, I cannot find an answer as to whether the limb is referring to the range of the radiometer from the centre, or whether it is referring to the centre to edge of disc radiance variation in the direction of the radiometer. Any help is muchly appreciated as those 5 words are driving me crazy at the moment!

I was wondering what was the Observable Universe in the old times : If we were the inhabitants of a young Galaxy, only 600 million years after the Big Bang, what would have been our Observable Universe look like? On the basis of standard cosmology.

In one of the episodes of Into the Wormhole with Morgan Freeman he compares atomic particles to those of pixels in a video game. Like you can only zoom in so far until even the world that we live in becomes pixelated. For the question that I have, lets assume this is true. After considering this, it seems that if our universe is being compared to a computer, then would the speed of light be the maximum processor speed? If so, what could that mean? I was just thinking about this and i don't know if any research has been done on this, but I figured a forum would be a good start. Thanks!

I couldn't find the exact place to put this topic. It's about geometry, but also about the way we observe objects, and space more generally. In another thread, I made a comparison between a flat 2d diagram representing the expansion of the universe, and a perspective drawing. Of course, the answer was "it is not a perspective drawing". Which is undoubtedly a correct answer. But there is a common point, which is the scale factor. Explaining. Lets take a simple square like the one here below: 1 Lets put a scale factor of 2, and approximatively double the size of the square, and lets represent both squares side to side so that we can compare: 2 We have the r…

I don't really understand dark energy or dark matter, can some one explain it to me a little? Also, why is dark energy causing universal expansion?

Nice closeup shot of comet: http://blogs.discovermagazine.com/badastronomy/2010/11/04/amazing-close-ups-of-comet-hartley-2/

I was watching a Susskind lecture where he pointed out that all but the nearest Galaxy to ours (Andromeda?) is moving away from us - It was a lecture on Special Relativity, which is the main context behind my question. Do Galaxies come in pairs? Is Andromeda of a similar magnitude to the Milky Way? Any help much appreciated. Rgds, Skaff.

Ive seen the picture of the kuiper belt asteroid. They are not spherical . Even some of them are very long shape and very strange shape. Any reason? Any theory? But Asteroid main belt asteroids are spherical- not sphere.

i was wondering what is the fastest speed humans have reached in space travel to this day and what is the next leap in space travel i mean after space rockets working on combustion of a carburant that sure seem to have a speed limit how can we jump to much higher speeds to reach distant planet within our lifetime if someone has the answer please reply thx