Astronomy and Cosmology

I've been curious about time travel for a while now. Is it be possible? If so, how can it be done? I think that if one is able to manipulate the space-time continuum, that might be the way to do it, though I must admit I cannot began to imagine how someone is to go about doing such a thing. Another idea of mine is that if someone is able to externalize the reversal of a clock or wristwatch, then maybe it can be done. A while back, I read a little bit of Stephen Hawking's A Brief History of Time (the chapter about time travel) and I didn't understand a whole lot of it, but I've watched programs on the History channel that discuss theories regarding wormholes possibly causi…

I've heard that the bigger the star the shorter it's life span. so, how big would a star have to be live a single instant in time?

Is it possible, or are there any theories that might suggest that the gas and dust surrounding large black holes might have been created by the matrix of energy fluxuations, accelerations, and particle collisions surrounding the event horizon of the black hole. Instead of being left over from the Nova, or past "meals" of the entity?

Hi All, I am new to this forum - so, be gentle with me. My question is this : I am told/read that all the heavy elements, that is all above Hydrogen and Helium have been created in large stars with enough heat and pressure or/and by Supernovae. These heavy elements require temperatures in a Supanovae above somewhere above 10^9 Kelvin. These temperatures occured in the very early stages of expansion of the universe - around 100 - 1000 seconds. So, why do we not think the heavy elements were created then ? George

During the infancy of a planetary system, it usually consists of a young star, surrounded by a disc of spinning gas and dust. Eventually, turbulence in the disc results in the accumulation of clumps of matter, which over time grow into massive objects, which can eventually become planets, if they become so great as to achieve hydrostatic equilibrium and clear their orbits. Now, early on, before the planetlets have come into their own as rulers of a Hill sphere, the matter passing by them in adjacent orbits would be travelling faster if closer to the primary, and slower if farther out; thus, from a corotating reference frame, outer dust particles should be moving backw…

Has heliocentrism been disproved? http://www.youtube.com/watch?v=MCV6xbtmKMQ&feature=channel_video_title

Ok, first off I'm 22 and I know I'm young, I have no scientific studies degrees or anything even saying I'm an expert in this field. So if you have anything to say to be Dick about it just post your reply and i'll tell you what I think. As far the big bang theory goes it states simply that the universe.was created by a massive explosion. Here's my point its ever so large flaws. If space lacks oxygen or at least enough for human survival, remember an explosion needs fuel, and even though its hydrogen, highly flammable, not so much explosive unless under pressure, which space obviously lacks, then how in the world could it be one mass explosion? Considering the fact tha…

What would be the practical problems and effects upon animals kept in a bioshere on Mars. eg Sheep, Cows etc ?

Could some sort of "primordial turbulence" have imparted motion, to collapsing cloud 'clumps', so that their collisions could have triggered star-formation bursts (w/o need for as much DM) ??

Hi, New here, just needed to fire off some burning questions. Been watching some vids on cosmology and here are few things I really don't get and can't find internet data about: 1) Shouldn't gravitational pull be strongest at the surface of a planet (assume uniform density for sake of simplicity). The gravitational pull inside the planet should have some cancelling effects on one another, and in the core will be net zero. This is validated by some google searches. But then, why do we believe the planets have a core? Isn't it more sensible to think we're just a spherical shell, perhaps many kilometers thick, held toward a center of gravity? 2) Following up on q…

I'm looking for some good tracking software to track the live decent of UARS a 1200 lbs satellite as it crashes to Earth later today. (for Windows 7) I need something that has the ability to track UARS in real time with second by second updated info and not just a 'prediction' track based on where it's orbit should be, as a simulation would. There is also another German made satellite that's going to crash soon I want to track. I'm looking for something easy to use, accurate.

I want to know that " Is Venus a morning and evening star in the end of September?"

Here is a Gif i made for my experimental media class as a tribute to Carl Sagan. Hope you enjoy.

winner(s) in Physics to be announced tomorrow 4 October this site will show who http://nobelprize.org/ the physiology and medicine prize was awarded today (Monday 3 Oct) and it went to two Australians who discovered that ulcers are caused by bacteria in the stomach, instead of by stress (as everyone thought) so could be cured by a simple course of antibiotics. can physics (in its present circumstances) match that for importance? anyone have any ideas about what category of research it should go to?

[math]T^4® = \frac{3 G M \dot{M}}{8 \pi \sigma r^3} \left[1 - \sqrt{\frac{R}{r}} \right][/math] [math]C_S^2 \approx \frac{k_B T}{\bar{m}}[/math] [math]v_K^2 \equiv \frac{G M}{r}[/math] [math]\dot{M}_{Edd} \equiv \frac{4 \pi c}{\sigma_T} \bar{m} R[/math] Defining [math]\dot{M} \equiv \mu \dot{M}_{Edd}[/math], then w.h.t.: [math]\therefore \left(\frac{C_S}{v_K}\right)^8 \approx \mu \left( \frac{k_B}{G M \bar{m}} \right)^3 \left( \frac{3 k_B c R}{2 \sigma \sigma_T} \right) r \left[1 - \sqrt{\frac{R}{r}} \right][/math] [math] \approx 2 \times 10^{-10} \left( \frac{\bar{m}}{m_H} \right)^{-3} \left( \frac{M}{M_{\odot}} \right)^{-3} \left( \frac{R}{R_{\o…

These questions have been bugging me for a very long time: What day does the star Betelgeuse rise at 10:00 PM? What day does the star Betelgeuse transit at 10:00 PM? What day does the star Betelgeuse set at 10:00 PM? What bright star is just rising at 2:00 AM on December 10? What bright star is just transiting at 7:00 PM on September 15? What bright star is just setting at 9:00 PM on April 20? What constellation is located at the zenith at 9:00 PM on September 10? I have been trying to use the program Stellarium to find the answers but I am very confused on how to go about it. Please help and thank you.

I don't know that much about it, but I was just imaging what might happen if Kepler were many light years away with Sol in its field of view. I imagine: 1. A very small probability that Venus and/or Earth could be detected via transit (considering their diameters and orbits and the chances of favorable orientation with far away Kepler spacecraft). 2. I may be wrong, but I suspect that Mercury and Mars may not be detectable by Kepler. 3. The planets in the outer solar system seem to be too distant from the sun to be detected by Kepler (guess based on what I know of the transmit method). 4. The many fascinating moons in the solar system would obviously go undetected …

I realized today that, if the sun went out immedeatly, we would still see light for 8 minutes, but the earth would go out of orbit immedeatly. This means that the force of gravity works faster than the speed of light, and therefore could possibly be used to go faster than light in a spaceship, if the force of gravity could be harnessed. Any thoughts?

hello I just found a timelapse video recorded by the International Space Station. Id like to have your impressions .. I think it is just awesome Don't forget 1080p http://www.youtube.c...h?v=r3SuPCjv7RY

What would make an alien planet so dark that t would be black as coal can be? New Discovery: The Darkest Alien Planet That is as Black as Coal.

Now (z=0) -- According to D.Maoz' Astrophysics in a Nutshell, our cosmos, today, is isotropically smooth, at large size scales, >100 Mpc. Then (z ~ 1100) -- Judging from the "CMBR Power Spectrum", which shows a peak at an angular size scale of (slightly less than) 1 degree, our cosmos, nearly 14 Gya, was isotropically smooth, at large-for-back-then size scales, >1 degree. QUESTION -- should not these size-scales correspond? Should not "1 degree then" somehow correlate, to "100 Mpc today" ? Naively using online dark-energy-incorporating cosmological calculators (and cf. PF), the proper distance to z~1100 is ~45 Gly, at which absolute distance, ~1 degree rep…

So we know that there's matter, and then we know there's anti-matter. How do scientists know just from that when we have no evidence about the big bang itself or before that there should be equal parts of matter and anti-matter or that they should have annihilated each other completely? Yeah, there's less anti-matter, but obviously that's just the result of how matter/anti-matter naturally work. There's just naturally a process where unknown particles create different properties that add up to make only specific things and break down and build up in only specific ways, so where did all these assumptions come from?

Our sun exhibits periodic field reversals (~10 years). Our earth exhibits periodic field reversals (~105 years). Our sun reverses field, at "solar maximum", when their are the maximum number of local field anomalies, called "sun spots". And, our earth, long-over-due for "scheduled" field reversal, is starting to show localized, anomalous, field-reversed regions, e.g., South Atlantic Anomaly (SAA). QUESTION: Could you call the SAA an "earth spot"? To wit, are "earth spots" and "sun spots" similar, if different-size-scaled, manifestations, of the same underlying Magnetic Dynamo field-reversal process ??

Star rotation rates, and (dynamo-driven) magnetic field strengths -- which are themselves mutually co-related -- decline with star age (Landstreet 2007). Mass-loss, from outflows correlated with the initially rapid rotation & strong fields, can account for such "braking" (Nariai 1969). Qualitatively, similar is seen, in the "spin down" of Pulsars, due to the emission of EM energy, causing "magnetic braking". Thus, could there be a connection, if crude, between (1) stellar coronae, which generate stellar winds & "astro-sphere nebulae"; (2) Pulsar Wind Nebulae; (3) magnetic braking & star spin-down ? To wit, could stellar coronae be so anomalously hot, b/c t…

If, in the FRW metric, the 'interval' is: [math]ds^2 = (c \, dt)^2 - R(t)^2 \left( \frac{dr^2}{1 - K r^2} + r^2 \left( d \theta^2 + ( sin(\theta) d\phi )^2 \right) \right)[/math] And if, in GR, that 'interval' is derived from the 'metric' tensor, via: [math]ds^2 = g_{\mu \nu} ds^{\mu} ds^{\nu}[/math] And if [math]ds \equiv \left[ c dt, dr, d\theta, d\phi \right][/math]; then, why wouldn't the 'metric' tensor be: [math] \left( \begin{array}{cccc} 1 & 0 & 0 & 0 \\ 0 & R^2 / 1- K r^2 & 0 & 0 \\ 0 & 0 & R^2 r^2 & 0 \\ 0 & 0 & 0 & R^2 r^2 sin(\theta)^2 \end{array} \right)[/math] or, if [math]ds \eq…