Astronomy and Cosmology

Recent theories, regarding the origin of Saturn's rings, link them to that planet's icy inner moons — "the tiny particles that form the rings today... [are] pieces of moon" (Ron Miller. Saturn, pg. 32). However, evidence indicates that the rings are relatively young: There are many reasons that the rings are considered relatively young. One of these is how clean the ring particles are. The rings are very bright be/c the ice particles they are made of have not yet had time to be covered with dark dust. Another reason is that the gravitational effects of all of Saturn's moons — the same forces that create the thousands of large and small gaps in the rings — make…

How is it that the critical density of the universe can drop faster than the actual density? Merged post follows: Consecutive posts mergedBump. Does it have to do with the fact that critical density is a ratio? Sombody help me out here!

Hi everyone, As foolish as this might sound, I have to say I am wondering if whatever is at the core of our earth is what our sun is made up of as well. I have heard scientists speculate that the earth's core is the source of gravity. Can I safely say that our sun's source of gravity can be found at it's core? which brings me to the next question, can there be two or more different sources of gravity or can there just be one universal source of gravity? Please do ignore this post if you find it rather nonsensical Appreciate your replies whatever it may be. -Mia

I would like to point my antenna at the L4 and L5 points. I know that they are leading and lagging the sun by 60 degrees so does that mean that I can simply calculate the suns position and then add and subtract 60 degrees? Sound to simple to be right. Regards....... Jim http://www.SETI.Net

Had problems posting for a bit and asked this question on an other side. Feeling a bit guilty. It does not seam reasonable to me that a black hole should loose mass "if the black hole is not feeding". I keep thinking that it don't have a choice. There is a continues flow of radiation under pressure flowing in to it all the time, from all sides. Or would this ocean of waves stop and jest sitall around the edge of the black hole and not try the impossible task to fill it and equalize pressure. It seams that there is reasonable agreement that at least a quantity of E=M, or can be. So, if all this radiation ends up in the black hole, how can it loose mass? Nobody answered…

In the big bang model, our current universe started with a big explosion from a small object with extremely high density, the debris of this explosion re-grouped and evolved into stars and galaxies. The debris carried initial momentum of the explosion which makes the universe keeping expansion, the proposed dark energy causes the expansion even faster. We do not have any reason to think that such explosion was not uniform in three dimension space. So if the big bang was uniform in 3 dimension space, then, we should be able to find the center of the explosion (or the center of the universe) because the density of the galaxies/stars in the center direction should be highe…

With all of the stars throughout the universe over the past ten billion years or so that have cycled through their various elements to finally explode in a massive disarray of heavy elements, it certainly seems that there should be a large amount of bits and pieces of shrapnel and ejecta scattered throughout the universe that never re-assimilated into proto-planetary discs in star-forming regions. That's a lot of matter unaccounted for, exerting its aggregate momentum on the rest of the matter spinning around in galaxies or outward from the big bang. I am referring to the wiki for dark matter which describes it as non-baryonic matter that is not detectable by electro…

You have a binary star system s1,s2 with 0.1 light year separation. s1 goes supernova. Would the gravitational perturbation of the right motion of s2 be instant or light transit time delayed. If instant, depending on the orbital dispositions we could observe perturbation before the supernova.

Lightening on Earth produces a very specific RF. Would that RF be influence by the medium in which it was produced? I know the color of the light is... and just another EM frequency. As i understand it the RF signal strength is strong... compared engineered transmitters. Could we not "listen" for those transmission and decipher some of the atmospheric information transmitted? I know on the cosmic scale its a week signal... but it's a shot in the great vast dark.

Hi, A bit confused - is gravity a result of graviton interaction, warped spacetime, or a combination of the two? Tom C

http://www.esa.int/esaMI/Planck/SEMVW10YDUF_0.html Planck mission is a big deal. More accurate observation of the microwave Background. Planned for launch 14 May, along with another satellite observatory called Herschel. Wish 'em luck!

http://wmap.gsfc.nasa.gov/ i stumbled across a new (to me at least) idea, that being the universe is flat. wtf? when did this happen.

I dont even know if this is the section but...if a trip to saturn becomes accessible how could a planet in a state like ours (not unified) possibly settle who gets what?? (like titan) eventually there will be alot of space to cover and if things stick to the status quo (and they probably will) then we could have serious problems in our own backyard over something so far away... i guess what im looking for is...do we achieve a REAL unified planet by then?? or does china try to fight over a hospitable planet for their overpopulated country? (very loose example) also keep in mind how fast science and politics have changed over the last 100 years (science clea…

My question is this: was there an amount of helium formed after the Big Bang, along with hydrogen? Or is all helium the product of nucleosynthesis at the cores of stars? Can you please point me at sources about this?

Hello. This is one of my coursework questions I was wondering if I could get some insight here.. here is the question: The size of the Universe if conveniently parameterized by a scale factor, a(t), which simply describes how big the Universe is at other times relative to its present size (ie. at the present we say that a is 1, and at some time in the past when the Universe was half as big as it was today, then a was 0.5). A matter-dominated Universe grows with time as [math]a \propto t^{\frac{2}{3}} [/math]. Assuming the Universe is 13.5 billion years old at present, how old is the Universe at redshifts, z, of z = 0.5 ... etc, z= 100? Assume that we presently live in…

I've never heard of this before, but as we are able to make things smaller, the cost for robotic space exploration should decline. The day may come when all the technology of the Apollo mission can be condensed into a probe of only a few pounds. If that probe has super sensitive cameras, with telescopic and microscopic capabilities, and other sophisticated sensing devices, they should be able to do most of the things a manned mission can do, at far lower cost. The mission controllers on Earth will feel like they are actually there on Mars, or Europa, Titan, or Pluto.

Hello. This is question for my course work, I was wondering if I could get some insight, here is the question: Assume that the vast majority of the photons in the present Universe are cosmic microwave radiation photons that are a relic of the big bang. For simplicity, also assume that all the photons have the energy corresponding to the wavelength of the peak of a 2.73K black-body radiation curve. At Approximately what redshift will the energy density in radiation be equal to the energy density in matter? (hint: work out the energy density in photons at the present time. Then work it out for baryons, assuming a proton for a typical baryon. Remember how the two qua…

dont rely have a great understanding of the topic... one of the things that are discrediting the big bang theory is dark energy which as far as i know has not been detected.... were it shows that there is not enough gravity in the universe for their to be organised structures in galaxies and the univers so this dark matter acts as an extra amount of gravity that keeps order... but if all objects have no fixed positions and can be in more than one place at one time on an atomic level would this amplify the affect of normal gravity. could any one fill me in abit more.

I have some questions on black holes. 1. Is there any information regarding the ratio of how much matter/energy supermassive black holes swollow in relation to how much they eject in the form of plasma jets (blasars) or any other radiation. my reason for this question is is related to my next question. 2. Will black holes ever reach a "maximum" filled state where it cannot consume anymore due to space energy density limits , and then only spew out these jets we now observe in blasars. There may be an effective upper boundary ( radius) as to where black holes cannot grow larger. Then they would only serve as catalysts …

Just a quick thought. If there was no gravity would space time or the "fabric" of space be able to exist? Or would a universe it self not be able to exist? Thanks

As seen on this site, the Oberon moon of Uranus shows a 6 km peak, protruding from the (lower-left) limb of its Voyager 2 photograph: This image of Oberon shows several large impact craters towards the center of the picture. Many of the crater floors are covered by an unknown dark material. On the bottom-left limb, a high mountain rises 6 kilometers (4 miles) above its surroundings. Bright rays similar to those seen on Jupiter's moon Callisto, can be found on Oberon's surface. (Copyright Calvin J. Hamilton) CONCLUSION (??): This 6 km peak, is actually the central peak (140° east, 25° south), of a crater, which is roughly as wide, as the Mommur Chasma is …

Does Moon revolves around itself ? Merged post follows: Consecutive posts mergedDoes Moon revolves around itself ?

Who wants to beat that Extrema-philes hitched a ride on the Viking Lander and have already colonized Mars? If not the Viking Lander, than perhaps one of the numerous Soviet ones.

Most asteroids are not spherical. For example, the Martian mini-moon Phoebos "is an irregularly shaped rock just less than 28 kilometres across" whose volume is over 15% voids. Of course, the situation is similar for smaller Deimos (Mars' other mini-moon). Now, in addition, according to the National Geographic Channel documentary Naked Science -- Avoiding Armageddon (TV), most asteroids are "rubble piles" of loosely bound bits kept together by gravity. As an analogy, this author reminds the reader about Buzz Magnets, Thus, most asteroids are not solid, but are, rather, pretty porous, w/ potentially vast interstitial spaces. Indeed, whe…

Was watching a Christopher Hitchens debate.. In his opening he was talking about how all galaxies are moving away from each other, the "red spectrum". Then shortly after he spoke of the Andromeda galaxy on a collision course with us. How? -BC