Astronomy and Cosmology

What would you rate as the most likely candidate for T=0 on the time axis of the Universe ? - the Planck Time - the time protostars formed - the time hydrogen transmuted to heavier elements (useful to humans). Please opine.

What was the time-scale of the Big Bang ? attosecond / femtosecond / picosecond or impossible to quantify ? I mean, how much time did it take for the dissolution of symmetries ? Please opine.

Quick question. The length of our days is longest on the 21st of June, and shortest on the 21st of Dec. Does anyone know during what period of the cycle are the day lengths increasing (and decreasing) at the fastest rate? Are the day lengths increasing (and decreasing) at the slowest rate near the solstices, to gradually increase faster, until the days are getting longer at the fastest rate around the spring equinox? If that is true, then we should now be experiencing the most dramatic change in weather during this month. Maybe this should be moved to "earth science" thanks. http://en.wikipedia.org/wiki/Equinox

http://en.wikipedia....sive_black_hole "From the motion of star S2, the object's mass can be estimated as 4.1 million M☉,[15][16] " However, the mass of the whole milky way galaxy is : 0.8–1.5×1012 M☉. This is astonishing ratio of four/one million... (On 4 Kg of mass in the black hole, there are 1,000,000 Kg (1,000 Tons) of mass in the spiral arms. Actually, the black hole is like an engine which rotates the whole spiral galaxy while spiral arms are similar to the biggest propeller in the universe. It is similar to an engine of 4 Kg which rotatse a propeller of 1,000,000 kg (or 1,000 tons)? In this kind of ratio, the spiral arms should be disconnected from the g…

When Hubble first observed the expansion of the universe, the obvious conclusion was that if we extrapolate backwards, there was a point in time where the size of space was 0. Now we have observed that space is expanding at an accelerating rate. If we visualise the graphs of these two, with time being the x axis and the 3 dimensions of space's size being the y axis. In the uniform expansion model the graph is linear with a 1:1 gradient and neatly crossing the origin. But, if we visualise this graph by extrapolating backwards from a universe with accelerating expansion, the line forms an asymptote with the x axis pushing the origin back to infinity. So how can there ha…

Now, I understand that any discussion of the very early Universe is entirely hypothetical and to say it is extremely speculative is being generous. However, there are a few concepts regarding the Grand Unified Epoch, the Inflationary Epoch, and the Electroweak Epoch that I am hoping someone will have the patience to explain… According to http://en.wikipedia.org/wiki/Inflation_(28cosmology) “Reheating” “Inflation is a period of supercooled expansion, when the temperature drops by a factor of 100,000 or so. (The exact drop is model dependent, but in the first models it was typically from 10^27K down to 10^22K.) This relatively low temperature is maintained du…

I tried looking for a number, but everywhere they just say "FTL" could you help me out with the specifics?

I know that there is talk about Black Holes being actually Black Stars, but I'm actually wondering about the stars being twisted and moved by something in the middle of our galaxy. If this is a black hole could it give birth to another one? What if a super nova directed our way hit an on coming baby black hole, what would happen to the black hole? I mean besides stars being blasted around and meteors for debris.

Is this correct, the acceleration affecting the Earth (towards the Moon and Sun) by new moon can be calculated as follows Acceleration due to gravity of the Earth + Acceleration due to gravity due to the Moon, - minus – the opposite acceleration (centrifugal force) I believe this is correct but wonder if there are other contributions. Now let us say the Earth, Moon, and Sun is not aligned, but the earth is 10 degree from both, before new moon, how does this affect the acceleration due to gravity of the earth (towards the Moon and Sun) What confuse me is by new moon the earth accelerates towards the moon, but normally it is opposite, the Moon accelerates towards …

I set the HORIZONS interface to give the "one-way (down-leg) light-time" of the sun. It reaches its minimum at 7:00am UTC/GMT, but most sources assign perihelion to 12:00 or 11:00am UTC/GMT. What's the discrepancy from?

Well the Sun's magnetic field is not an easy topic: http://en.wikipedia.org/wiki/Stellar_magnetic_field I wrote up a series of questions today: 1. Would this event happen if the Sun was on its own? (like not part of a solar system (SS).) 2. If this event is due to the presence of the planets, what are the planets doing? 3. What methods of interaction could the planets have on the Sun? (The only answers to that so far are gravity,light, magnetic fields, and transfer of angular momentum.) 4. If there were periods where the Sun is accelerated and decelerated, could this be causing the Solar Magnetic pole reversal (SMPR)? 5. Does this periodicity matc…

Firstly a direct quote from the NASA website So the first question is why is our sun an exception to the rule? There is thankfully some research being done into this at the Binary Research Institute. The research centers on the changing of the rate of precession of the Equinoxes. Research shows that the rate of change of Precession is different for objects within our solar system as opposed to rate of change observed outside our solar system. Also the wobble is not constant it is being influenced by some outside force. The other interesting wrinkle in this is that one candidate for a star involved in a multiple system with our own sun put forward is t…

Normal gravity exerts an attractive force between masses of ordinary matter, or a bending of space-time resulting in the same effect. Just because dark matter and dark energy don't interact with ordinary matter or energy, this has nothing to say regarding how these phenomena interact amongst themselves. It defies common sense (at least mine) that they don't interact. Could there be "dark" analogues to the fundamental particles, fundamental forces that we encounter in our realm? And, if there is dark matter, does "dark gravity" logically follow? Would it exert a repulsive, rather than an attractive, force between whatever constitutes dark matter, a sort of bending outward…

Hi! I have an idea and I wonder if it is possible or absurd : What if the Higgs field depends on matter density (in a large scale) ? If the Higgs field give mass to particles, it implies that where the field is low, particles, freed from it, are relatively more affected by gravitational forces. So it could explain the missing mass mystery : Instead of dark matter, it's just a very smooth scalar field (much smoother than gravitation), where value is the inverse of the supposed dark matter field. It would be shaped like the supposed halo of dark matter. I think gravitational effects would be similar. What do you think ?

Will it be possible at some point of time in the future to terraform Titan without causing it to lose much of it's atmosphere? Today Titan's atmosphere is very cold, with very low energy, if we simply heat it up, it will just perish. The same also applies to Moon, Mars etc. Can we?

Do we orbit the center of mass of the solar system or just the center of mass between the Sun and The Earth? It was discussed on another thread on the forum but I've lost track of it. So if the two biggest objects in our Solar System have a Barycenter outside of the radius of the Sun then would Mercury be orbiting this center of mass as well? Maybe that is the solution to the 3 body problems - do we have to go back to the combined Center of mass and orbit that. Even if we say that Mercury orbits the center of the Sun, and the Sun orbits around the barycenter (between it and Jupiter) that would mean Mercury is orbiting in some unusual way too. How does that start off? …

For two bodies to orbit a common barycenter the centrifugal forces would have to balance the centripetal forces caused by the gravitational attraction between the two masses. With the Pluto-Charon pair we will need to know where the barycenter is (defined by the mass of each body and their separation) and their velocities (defined by their orbital period and orbital radius) This is a representation of what we want to analyse: http://en.wikipedia.org/wiki/Orbit#mediaviewer/File:Orbit2.gif Here is an actual photo of the two bodies orbiting each other: http://pluto.jhuapl.edu/News-Center/News-Article.php?page=20150212

For anyone interested in the New Horizons Pluto encounter you can view it's progress here: http://pluto.jhuapl.edu/

I know I want to go to school for Astronomy Or possinly Cosmology, but the schooling for both a couple of years. and I am getting near the end of high school so I have time to plan/think about what to dop but me nore my family are in great money situations. So I was wondering what people typically do to get through many years of schooling in this kind of situation.

Hello can someone tell me who first coined this word? The concept of an orbital barycenter is implied by Newton's laws of motion - (BTW was he the first to suggest that both the Sun *and* the Earth move) ? I've tried some google searches and haven't found this information, which surprised me. Thank you.

Okay, I received 30 astronomy problems to solve for my homework. This is an advanced course, but I originally wanted to attend an introductory course at my local high school (I virtually have no background in astronomy). I solved all of them except these 5 challenge problems. Can someone walk me through them? I have been trying to answer these for a week now. I need to finish these by tomorrow afternoon for my third period class! Thanks! The Crab Nebula subtends an angle of 5.5 arcminutes in the sky. If it is 6300 LY away, what is its linear diameter in light years? What focal length of eyepiece should be used with a 20 cm diameter objective that has a 100 cm foca…

A very cool video showing the scale of the solar system

The 2015 Planck data has been released. The dataset is still in strong agreement with LCDM and tightens the constraints on inflation. They corrected the polarization error on the CMB anisotropy. This brings the data much closer to the WMAP values. As well as removing the anisotropy itself. They have several other interesting maps http://www.cosmos.esa.int/web/planck/publications my advise read the overview first then the individual articles.

It has been long said that Jupiter prevented a planet from forming between Mars and Jupiter, in fact some sources seem to indicate the Jupiter may be the reason Mars is so small. Thought experiment, if it was possible to move a planet between Mars and Jupiter, for the sake of this thought experiment lets assume a planet about the mass of Earth. Would such a planet be stable in that orbit? (ignoring the asteroid impacts it would attract of course)

Question In the northern hemisphere, does the Moon ever enter the North part of the night sky? Thanks.