Astronomy and Cosmology

If the Hubble telesope can look back about 13 billion years and takes pictures of 100's of galaxy's all clumped together, is it possible for the Hubble to look in another direction and take photos of the same galaxy's it took the first time?

I'm trying to get my head around the rate of expansion and limitations of the speed of light? If the expansion of the universe is approx. 71 km/sec / megaparsec, and the distance to the observable universe horizon is 14 gigaparsecs, then the rate of expansion at the furthest observable point works out at about 3 x the speed of light. Isn't this impossible so what am I missing?

If the age of the visable universe is 13.8 billion years, according to the latests I could find on line, why is the universe not 27.6 billion years old, since what we are seeing is 13.8 billion years in the past?

So I'm wondering do we have more reason to believe that the big bang is happening in the sense that were cooling down from the singularity or that were projected from a singularity with energy still being emitted?

Recently I watched Ender's Game and, with out spoiling it, there is a scene in the movie where mass is ejected out of an object moving through zero-gravity in order to change the object's speed and direction. When I watched it, it struck me as too much change for the mass ejected to mass retained ration and I want to verify it. SPOILERS: The specific scene I am refering to is the scene in the battle dome where Ender has his army form a 'wedge' of sorts around a main player and then floats their way through the battlefield, ejecting kids at certain angles to make his needed course adjustments. I know some of the work I need to do to verify if the right math was used, such…

Question from a neophyte - If the Universe is 46 billion light years in diameter (Wikipedia) yet only 13.8 billon years old then is or has the universe expanded faster than the speed of light, does the outer 2/3 of the universe predate the big bang, does Wikipedia have it wrong, or is there one of those counterintuitive "warped or folding space phenomenon going on? I'm sorry. 46 billion light year radius according to Wikipedia

What if we are not accelerating away from something, but instead we are accelerating towards something? If the big bang started as an infinitely dense mass then shouldn't it all eventually collapse back in on itself as a star does to a black hole? I had a theory that I thought of that I found to already be out there called the Orange Theory, I found it on YouTube, while not a very good place for factual information, it demonstrated my concept well. I figured under that theory that we would be located and the observable universe would be on the expanding half, but this would support the idea that space would not be equally assuming we could observe enough of it to see the …

This question, while it had a genesis in reading about climate change isn't about climate per se. When we read about meteoric impacts we tend to think of them as occurring on land or in the water. I've read no end of articles about the ejecta and ash from a land impact and we've had big budget movies about water impacts. Giant waves, the whole bit, we all know what will happen if a big enough rock hits the water. So what happens when it hits ice? 20,000 years ago much of North America and EurAsia was covered with a couple of miles of ice. A meteorite large enough to bury itself a mile underground hitting so much ice wouldn't even make it to the dirt. It would …

I recently read that the moon has a period of 2 weeks of daytime and 2 weeks of night during which the tempatures go from hot enough to boil water to -270 F. I was wondering: 1) How long of a period would tempatures be between, say 60 and 85 degrees? 2) If one built an igloo how thick wouldthe ice have to be to sheild you from cosmic ray poisoning during the day? night? 3) When water boils on the moons surface how high does the steam go into the 0 atmosphere? and does the steam create a temporary high pressure zone within the 0 atmosphere? perhaps a 5" high bubble or several feet, I guess what I'm asking is what is the range in simple elemetry terms? 4) Is their an…

Hi... I'm New here and this is my first question... I'm not sure if here the proper sub-forum to ask this question... 2013 is almost over, every year in the edge of the year, I'm alwys curious about... According to the Gregorian calendar, the calendar system which internationally the most widely accepted and used in civil calendar. In Gregorian Calendar, 1 Year = 365 days, 5 hours, 49 minutes, 12 seconds. By that, can be defined as: 365 days, 5 hours, 49 minutes, 12 seconds is the exact time Earth will finish 939,889,368 km of its orbit around the Sun. Or, in other word, by that time Earth will completely Finished and begins new orbital period around the …

So soon the moon moves between the Sun and the Earth, by eclipse, - and the 3 objects will be aligned, - how fast can the Earth possible accelerate due to that ? And how can it be calculated ?

what helps us the theory of multiple universe to understand our universe? simon

Probably, our Universe has a Sphere appearance with layered structure, where layers with extending space alternate with layers where the space is reduced.These layers, probably ,differ density of galaxies.Congestions of galaxies drift passing gradually a layer with extending space to a layer with being reduced space.We a in extending part of the Universe. Movement just as passes the Sun through maxima and minima of waves of density of galactic substance of Milky Way.

I would like to propose an idea. 1) If Dark energy pushes outward on the galaxies expanding the universe and dark matter pulls inward within the galaxies, could there be one force that causes both? 2) Let us suppose that this force was the result of antigravity (antimatter?) particles that repels both normal matter and other antigravity particles. 3) Assume these antigravity particles are charged and form uncharged hydrogen-like molecules. Once the charges are balanced in the molecule, the antigravity force would cause them to isolate themselves from both matter and other antigravity molecules. The antigravity particles would probably not be able to form anything larg…

I read a recent article on this topic that reported on new mathematical proof of this holographic universe idea. This article immediately triggered a nagging question for me, prompting me to search the internet for an answer, but with no success. So, I am posting this for some of your ideas on my question: If we are indeed some sort of string holographic image, where does our "reality" exist? Are we living our actual lives in the 2D alternate universe?....or is that 2D universe purely info and data? Or is our reality this 3D projection? I'm so confused.

An interesting comparison of the images of typhoons and galaxies is shown on link: http://dl.dropbox.com/u/26262175/TyphoonAndGalaxies.pdf What do you think about it?

It is said that a Virtual particle has the ability to become a real particle. "Most" real particles have mass. My question "If" all of the universes virtual particle potential was turned in to real particles, how much mass would it represent.

While there is a space of the Universe,the Universe is expanding,but the galaxies collide,their masses grow. Large mass of the substance bend,reduce the space around.Space will all shrink and shrink,and eventually expanding to a stop, the Universe will shrink and can happen a new Big Bang.

If ISON was travelling several times faster than Voyager is, then why will it take 40k years for Voyager to reach the end of the Oort Cloud, but the ISON orbit is like 200-300k years from one end to the other?

hello, I shot the attached pic 4/23/13 at 4am (35sec exposure) and did not notice the green in the picture until I uploaded to my computer. Can anyone help identify? is that comet Ison?

Is electron a fundamental particle or not somewhere said it is & somewhere it is not ?

I'm not sure if this is the correct forum to ask this question, given that it's more concerned with science fiction than science fact. Still, it does bring into play Newton's field equations. So here goes: assuming a spaceship or probe of some kind is travelling between (say) the Earth and the Moon and it happens to have a suitably advanced propulsion system that enables it to maintain a continual thrust throughout the voyage; this being so, would the craft make its mid-voyage 'turnover' at the halfway point between the Earth and Moon? Or would it be more advantageous to perform this manoeuvre at the gravitational 'null point' between these two bodies - that is to say, wh…

Tonight Horizon Program about the current visit of Comet ISON going around the Sun in the next few days/weeks Link to Horizon Program Now available for viewing Late Nov 2013 to Dec 2013 http://www.bbc.co.uk/iplayer/episode/b03k3881/Horizon_20132014_Comet_of_the_Century_A_Horizon_Special/ Mike Set off from the Ort Cloud .... some Four and a half billion years ago ... just coming by now 4.5 billion years later.Everybody should be able to see it in the northern hemisphere........ look east South East just above horizon DECEMBER 1st 2013, just below the Moon and Mercury. Thats this weekend ... rising by 10 degrees a day... I am over there view…

http://jersey.uoregon.edu/elements/Elements.html I recently stumbled upon this link while looking for a good tool to use to help identify elements by spectra, but I noticed some things I didn't quite understand. Why is it that Thorium and Uranium have such a wide ranged emission spectrum while plutonium has a much smaller one. I read that the more electrons and higher shell configurations give more possibilities to emit light, especially if the electrons are in higher shells. Could somebody clarify?

Is there a way we can estimate light (lux) levels in broad daylight on Titan? eg would it be like a cloudy day here on Earth, dusk or no more light than with a full moon? Would the clouds be thin enough for an astronaut to see Saturn? Do the clouds ever part to give a clear sky? I've heard the sky would be orange with green methane rain. Would it always be foggy or could we see long distances? I'm an art student and I want to do a landscape painting of the surface of Titan cheerz Gian x