If stars attract each other, why scientists say that Universe is expanding? Should not it be the other way?

Answer 1

Well, the thing is, gravity *should* be slowing down the expansion of the universe.

What's been discovered, however, is that the expansion is accelerating - and nobody knows why. They call the force that causes this "Dark Force" - because nobody, as yet, can explain it.

Answer 2

The universe is still expanding from the force of the big bang. The sum of the forces attracting all bodies is not great enough to overcome it (yet).
The critical mass density of the universe is about 5*10^(-27) kg per m^3.
If the actual density is greater than this, the universe with continue to expand forever, but at a slower and slower rate.
If the actual density is equal to the critical mass density, the universe will stop expanding and remain at whatever size it is.
If it is smaller, the universe will stop expanding and shrink into a big crunch, which may result in another big bang.

Answer 3

Well there are two forces implied. The first is the expantion force of the Universe that pushes everything outwards in a radial fashion. And the second force is the one of atraction of the stars and galaxies, that seeks to pull everything together (the Big Crunch theory). Problem is that the second force, the one that pulls everything togheter is alot smaler than the first one, the one that pushes everything away. Statistically, the atraction is only about 11% of the expantionary force. I'm not a scientist though, so don't take this info for granted. This raises an interesting question though: If the force of atraction is only 11%, then that means that we have less matter now than at the begining of the universe, where did the missing matter go?

Answer 4

The Big Bang was an explosion, so all the matter is expanding as a huge growing bubble.
Gravity pull diminishes with the square of the distances and distances are still growing because of the explosion.
Will gravity eventually stop the expansion and start contracting it is something the astronomers are still uncertain about, because it takes very sophisticated measurements of the total quantity (density) of matter in the Universe.
By the way, the expansion seems to be accelerating simply because of the geometrical relationship between the diameter of an expanding sphere, its volume and its surface. The surface of an expanding globe grows faster than its volume.

Answer 5

All objects with mass have a gravitational attraction to each other. I see your point about gravity, but if gravity did not exist then there would not be a universe to expand from. So in being, it must mean that stars with large masses are attracted to one another and the universe as a whole is expanding outward from all places until gravity disappears and starts rip apart the universe.

Answer 6

What keeps expanding is space itself. The local gravitational interaction between stars can be much stronger than that, so the stars can attract. Even whole galaxies can attract. That won't stop space itself from moving apart so fast over long distances that the universe as a whole keeps expanding.

Two different scales... two different results. Both are correct because both keep happening for totally different reasons.

Answer 7

Think about it in a more "local" way...

If you're driving down the road at 100km/h (or 60 miles/hour) - and a fly hits your windshield - does it slow the car down???

The force exerted by the fly is in the opposite direction you are travelling in - but at a much LOWER scale. For something as large (and fast moving) as a car, this force is all but cancelled out.


To put this in terms of the universe - the pull of a single star (or even group of stars) is NOTHING compared to the force from the Big Bang ;););)

Answer 8

The dark force is pulling the stars apart and the Universe is spreading out faster and faster. Hawkins was so wrong when he thought the gravity of the Universe was going to pull all the star towards eachother. Don't worry we are going to send a dark force satallite into space and passed the moon and we might find out what this dark force is and how it was made and what it is.

Answer 9

This is where inertia kicks in. Inertia is the tendancy of all objects to resist a change in velocity (speed in a certain direction). Thus, space continues to expand, but all the gravity between objects does slow it down a bit.

Answer 10

That is an exceptionally good question. The universe is expanding... but we don't know why it appears to be doing so at an accelerating rate! The term "dark energy" has been coined as a mathematical fudge factor to cover our ignorance.

Answer 11

the word gravity is just another word to describe magnetic attraction or repulsion, on a planetary/galaxy scale that level of repulsion is pretty strong, even to the point of driving large objects like planets away from one another, the rest of the arguments are just interludes of human vanity, or theories if you like. most human so called scientists havent the faintest idea as to what is really going on in the cosmos, our most upto date information on any of the stars is that what occured over 200-300 million years ago, or more