If gravitational forces attract than why is the Universe moving away from its center(recession velocities)?
964622
If the only things involved in the position of everything in space were momentum and gravity then perhaps all the planets and galaxies and superclusters could have enough momentum to fly away forever like something can have enough momentum to have an escape velocity from the earth.  Also if everything didn't have enough momentum then it would eventually all fall back in together into a "big crunch".\n\nThere is another factor at play, though, in the expansion of the universe called "dark energy" which is something that causes space itself to expand!  So as space itself expands everything in it is carried along outwards with the expansion.  Imagine space is a table and some crumbs on it are galaxies.  As the whole table expands the little crumbs will spread apart from each other.\n\nDark energy is very hard to study and is not well understood.  The sources I cited give good overviews and should give you a better understanding.
459100
As the distance between galaxies increases, the gravitational attraction between them reduces, the momentum that the receding galaxies have makes them move at an apparent faster rate. Those galaxies that are strung close together being held together by their gravitational forces and hence their momentum is retarded by this gravitational force
358909
There is no "outskirt" to the universe-Each point is the center, just as every point on the surface of a sphere is a center.  One of the primary engines of motion is gravity, which is a warping of space/time.  There is a "thing" we call space/time, which has certain properties, but not necessarily substance (as mass, for example).  According to current theory, at the sub-quantum level, there is a bubbling of space/time in which energy is created and destroyed, but it exactly evens out-the "zero-point" energy.  So, yes, there is a thing called space-time which allows things to exist, but no, there is no outskirts of the universe.
745488
Your presumption is entirely likely my friend.  Things in the Universe that have mass and hence gravity, tend to rotate around something else.  All plants spin on their axis, all planets orbit around the Sun, the Sun rotates around the center of our Milky Way galaxy, our galaxy rotates around other galaxies in the local cluster of galaxies, the local cluster rotates around other clusters and so on right up to the Universe itself.
494727
The answer to your question lies with something called "inflation." The mechanics of inflation are very involved, but basically here's the gist of it: Long before the universe was even one second old it began to expand faster than the speed of light. Sounds like a violation of relativity, but it's not because at this point in the evolution of the universe there was no mass, only space-time which is not restricted by relativity. The bottom line is that with this FTL expansion rate, nothing could possibly pull the universe back into the initial singularity.\n\nFor a detailed look at inflation, check this website --> http://www.lifesci.sussex.ac.uk/home/John_Gribbin/cosmo.htm
402813
No, I think it'll take too long for them to join together.  They're generally so far apart that the gravitational pull on each other is very very small.  Besides, the universe is constantly expanding, so instead we'll end up in a position where everything is just cold and the density of matter is very small.  That's just one theory, though.
150657
gravity is highest at the centre of the earth. so you will be accelerating towards the centre.since there is no resistence (assume so that there is no air), you would not stop at the centre due to inertia of motion and continue to go beyond the centre to teh other side. but due to increasing pull on you, you will turn back and continue to oscillate about the center of the earth.\n\nits good for theory but humanly imposible
297729
You are correct, but the effects are so insignificant, it doesnt nearly matter.\n\nAll object in the universe have a gravitational attraction to one another.\nTake the Earth and bowling ball example,\nThe Earth exerts a force on the bowling ball, and the bowling ball exerts a force on the Earth.  Both on these forces cause the other object to accelerate towards a common center of mass.  In the case of the Earth's gravitational force on the bowling ball, the force is huge in comparison to the bowling ball's force exerted on the Earth, so much so that we can easily neglect the 2nd force.\n\nLets look at some numbers.....\nIf we say the Earth has a mass of 5.9742 E24 kg and say we will say we have a very heavy bowling ball with a mass of 1000 kg, then we can calculate the gravitaional force between them if we know the distance.  Lets estimate their centers of mass are 6380 (~larger than radius of Earth), we can calculate the gravitational force to be,\nF_g = (G*M*m)/r^2\nF_g = 9789.58 Newtons, which would cause an acceleration of 9.7895 mm/s^2 for the bowling ball and a miniscule 1.63 E-21 m/s^2 for Earth.  To put that in perspective of just how slow acceleration is, if you were to accelerated you car from at a constant acceleration of 1.63 E-21 m/s^2, it would take you about 86500000000000 YEARS to go from 0 to 10 miles per hour!  I think for simplicity sake, Newton did all right.\n\nEDIT:\nYes, the bowling ball very much so does pull on the Earth.  How is the "universe" to know which object is suppose to be the planet and which is the bowling ball?  ALL objects in the universe have a gravititational attraction to ALL other objects.  The Earth pulls in the bowling ball, and the bowling ball pulls on the Earth.  There are 2 equal forces pointed in opposite directions, therefroe momentum is conserved (which is a physical LAW).
296792
Your experimental model is corrupt in terms of current known information about matter and energy in a space-time continuum.  No prediction or calculation can be applied.\nWith two point masses, the only force in the system would be do to gravity.  This is an assumption based upon multiple moving masses in what we would call the normal physical universe.\nIf the distance between their centers (d) was sufficiently small, the points would be touching one another and no force would be exerted on the masses.  If the distance was sufficiently large, then it is possible that the force would be so small that the masses would not move.  Only in a finite range of distances would any gravity possibly exist.\nOne can make no assumptions about G as a gravitational constant, since G assumes that one of the masses is the earth.  One would need additional information about the masses to solve the problem.
539221
Due to Newton's Law of Gravitational Force (see link), as the distance between two objects decreases, the gravitational force will increase exponentially.  \n\nIt all depends on your position in reference to the center of mass.  If you are on the surface of the earth, your distance from the earth is normally defined as the distance from you to the center of the earth, or center of mass.  \n\nAs you get closer to the center though, the force due to gravity changes differentially since your position in the mass itself is changing and gravitational forces are acting on you from various directions (the earth can be thought of as a sum of different aggregate masses at this point).  Therefore, the gravitational force of the earth will be "less" at the center, since the sum of all aggregate forces would be acting in opposition of each other.  However, since gravity is a relatively weak force, it would not be your biggest concern, because, at the center of the earth, it's not the force of gravity on you that matters, it's the pressure and temperature that will kill you.\n\nMagnetic and gravitational forces are completely separate types of forces and should not be considered in the formulation of this answer.
694313
it's just the way we observe galaxies moving away from each other.  The further out from each other they are, the faster away from each other they move.\n\nFrom this and by analysing measures done on large numbers of galaxies, and then by taking these velocities and distances but plugging in older times in the data, it was found that, well, at some point back in time, all that stuff must have been concentrated at one point.\n\nAs the quality of experimental data improved, the Big Bang was the only theory that survived.\n\nBut in the early days, it was far from the only proposed model, so it is not at all, as you seem to believe, that physicists decided that you had to "build with explosions" ;-)\n\n\nhope this helps
95460
Your thinking is correct! There's a phrase that's unfortunately left out when we read about the universe -- "observable universe." We see a galaxy 13-billion light years distant as it was 13-billion years ago. During the 13-billion years it took light from there to reach us, that galaxy has moved beyond the limits of the "observable universe." Remember, the farther away a distant galaxy is when we observe it, the faster it's rushing away.\n\nIn the case of the galaxy 13-billion light years away, it's recessional velocity is 3^11 km/sec. That's NOW. But in the 13-billion years it's taken light to get here, that same galaxy has moved another 1.2^16 light years farther away, and that puts it well beyond the limits of the "observable universe."
1046649
Space is expanding at an accelerating rate, and carrying everything along with it. The energy that causes this is called dark energy. What it is is unknown, but it may be a property of space itself.\n\nIf it was just the leftover momentum from the big bang, it would gradually slow. The fact that the expansion is accelerating means it's something else.
1149831
So far our observations are leaning more towards open, because our universe is expanding at an accellerating rate, and it shows no sign of slowing, if it were closed (which we havent found enough matter in the universe to help this theory) then the expansion would slow, come to a stop, and come back and collapse back in on itself. But so far evidence is telling us it won't.
465388
The Earth is round for the same reason that things don't fall off it.  Gravity is a force in the universe that attracts all forms of matter equally, this means that pieces of matter will eventually move together and form clumps, if this is happening from every direction then the most likely shape it will form is a sphere.\n\nThis gravitational attraction is pretty small.  However, the Earth is pretty big, so the combined effect of all that gravity is just enough to keep your feet firmly planted on the surface :)\n\nThere are a few other related effects that come into play, such as centrifugal force, which keeps everything spinning and moving.
547799
The main reason is because of the general expansion of the universe.  \n\nThe best analogy is to imagine a polka-dot balloon.  As you blow up the balloon, all the dots are moving away from each other.  From the point of view of any one of the dots, all the other dots seem to be moving away from it, and the further away a dot is, the faster the dot seems to be moving.\n\nThus with the galaxies in the Universe; as we look at them with our telescopes, it appears that the farther away a galaxy is from us, the faster it is moving away from us.  But actually, all the galaxies including ours are moving away from each other as the Universe expands.\n\nThe red-shifting is part of what's known as the Doppler effect.  You'll easily notice this effect with regard to sound.  As, say, a car with a stuck horn passes by you, you'll hear a higher pitch to the horn as it approaches you and then it lowers as it moves past and away from you.  This is because the car is moving, relative to you, at a significant fraction of the speed of sound; so as the car approaches, the sound waves start to "catch up" with each other, shortening the wavelength and producing a higher tone.  Then as the car moves away from you, the sound waves get "left behind," the wavelength is stretched out and the tone sounds lower.\n\nThe same thing happens with light, though the relative speed has to be much greater in comparison with the speed of light.  The further away a galaxy is from us, the faster it is moving away relative to us, and the light from the stars in that galaxy is red-shifted as the wavelengths are stretched out.  If the stars were moving towards us with the same speed, the wavelengths would be shortened and the light would be blue-shifted.
193535
Good question-Its because the local group of galaxies, which include ours and andromedo, among others, are called a group beceause they are close enough to be effected by each other's gravity, and thus are attracted to one another, slowly.  Members of the universe outside our gravitational effects are speeding away from us.