What happens to our universe?

Question

The universe is and has been expanding outward rapidly for quite some time now. Surely there is only so much room for expansion right? Is there an end point of which expansion is no longer possible? What are the possible outcomes of this scenario?

Answer 1

"Surely there is only so much room for expansion right?"

Presumably, the universe is all there is. I'm trying to think of an analogy...its difficult. Anyway, saying that there is "only so much room" implies that there is something OUTSIDE of the universe which constrains its growth.

Having said that, there COULD be a constraint to growth, but it exists INSIDE the universe (as it must)...gravity! As the universe expands, gravitational attraction among all matter could become the dominant force in the universe, eventually halting and reversing the direction of expansion (i.e. it could cause the universe to contract). This is one possible scenario. For others, I suggest you read a book on the subject...off the top of my head i would suggest Hawking's "A Brief Histroy of Time"... personally, I felt his writing is too dense for the general public, but you may find it enlightening.

Answer 2

What is the Universe expanding into?

This question is based on the ever popular misconception that the Universe is some curved object embedded in a higher dimensional space, and that the Universe is expanding into this space. This misconception is probably fostered by the balloon analogy which shows a 2-D spherical model of the Universe expanding in a 3-D space. While it is possible to think of the Universe this way, it is not necessary, and there is nothing whatsoever that we have measured or can measure that will show us anything about the larger space. Everything that we measure is within the Universe, and we see no edge or boundary or center of expansion. Thus the Universe is not expanding into anything that we can see, and this is not a profitable thing to think about. Just as Dali's Corpus Hypercubicus is just a 2-D picture of a 3-D object that represents the surface of a 4-D cube, remember that the balloon analogy is just a 2-D picture of a 3-D situation that is supposed to help you think about a curved 3-D space, but it does not mean that there is really a 4-D space that the Universe is expanding into.

http://www.astro.ucla.edu/~wright/cosmology_faq.html#XIN

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Why doesn't the Solar System expand if the whole Universe is expanding?

This question is best answered in the coordinate system where the galaxies change their positions. The galaxies are receding from us because they started out receding from us, and the force of gravity just causes an acceleration that causes them to slow down, or speed up in the case of an accelerating expansion. Planets are going around the Sun in fixed size orbits because they are bound to the Sun. Everything is just moving under the influence of Newton's laws (with very slight modifications due to relativity). [Illustration] For the technically minded, Cooperstock et al. computes that the influence of the cosmological expansion on the Earth's orbit around the Sun amounts to a growth by only one part in a septillion over the age of the Solar System. This effect is caused by the cosmological background density within the Solar System going down as the Universe expands, which may or may not happen depending on the nature of the dark matter. The mass loss of the Sun due to its luminosity and the Solar wind leads to a much larger [but still tiny] growth of the Earth's orbit which has nothing to do with the expansion of the Universe. Even on the much larger (million light year) scale of clusters of galaxies, the effect of the expansion of the Universe is 10 million times smaller than the gravitational binding of the cluster.

Is the Universe expanding or is it just that our definitions of length and time are changing?

The definitions of length and time are not changing in the standard model. The second is still 9192631770 cycles of a Cesium atomic clock and the meter is still the distance light travels in 9192631770/299792458 cycles of a Cesium atomic clock.

Will the Universe expand forever or recollapse?
This depends on the ratio of the density of the Universe to the critical density. If the density is higher than the critical density the Universe will recollapse in a Big Crunch. But current data suggest that the density is less than or equal to the critical density so the Universe will expand forever. See Part 3 of the tutorial for more information.

Answer 3

Your question begins with an incorrect assumption...that there is some limit to the expansion. Why would you say "Surely?" I mean, what tells you there is a brick wall somewhere out there? How did you come by that information?

Let me begin to help you...And you must really try hard to grasp some ideas of hugeness...I mean really huge...

The Sun is 93,000,000 miles from us.
The Sun is the Star of our Universe.
Other Stars exist and are the Suns of their Universes.
Some of those Stars are 100 light years away from us.
Some more - some less.
Light travels at 186,000 miles per second.
And there are 31,536,000 seconds per year.
If you multiply the speed of light per second times the
number of seconds in a year, you get:

5,865,696,000,000 miles per year that light travels.

It takes light from some stars 100 years to reach us.

so that is 100 times the number above... which is:

500,865,696,000,000 miles away.

And I cannot begin to tell you if that is one of the most distant Stars. Only a knowledgeable astromoner can do that, which is certainly not me. But, to conclude my statement, how can you possibly begin to suggest that there is a finite wall or closure to the entire universe at say one mile beyond that? How high and how wide is this wall? Is it a circle, a triangle, a parallelogram, a hexagon, a sphere, a spiral, a cone, a helix, or a double cone penetrated by a double helix? What is the wall made of that is of sufficient strength to withstand collisions with Stars and Planets and Moons? If there is a wall of some kind out there, why haven't we seen it glow from the reflection of the light of stars shining upon it? Why don't radio signals bounce back from it?

Could it be that there are no answers to these questions?

Answer 4

Generally the further away an object is in space from us, the faster it is traveling away from us as well. Now some objects are thought to travel close to light speed on the edge of our visible universe, due to the Universe expanding (accelerating reference, not inertial reference like High School physics, so faster than light is possible). Some galaxies near or on the edge of "the known Universe" might someday "disappear" and we will never be able to travel or even communicate with them ever again, even though they still exist.

Typically, the farther something is from us, the faster it is traveling away from us. So when the objects get far enough away, they will be traveling faster than light. So minus a worm hole or bending space-time, these objects are "here today", "gone tomorrow". So our universe is expanding, but somewhat of a paradox also shrinking, since some worlds will one day be no longer accessible to us, since even a light signal from us, could not reach them.

Answer 5

When I read this question, I tried to picture our universe as it appears from the outside. it occured to me that there is likely nothing outside the universe, thus no place to look at the universe form the outside. I realized that the universe is the be all end all of everything, and that I am extremely small and pointless. /emo rant

Answer 6

There is plenty of room for expansion. One of my friends hit the end of space w/ his saucer and banged it all up, it's gonna need some major bodywork if he can limp it back to our planet.

Answer 7

after expanding for a long time,it will start contracting into the point from which it started

Answer 8

Discovery channel.
In about 5 billion years our galaxy will colide with another galaxy. The other galaxy will appear in our sky's for about 100, 000 years or so before the collision. BOOOOOOOOOOOOOOM!!!!!

Answer 9

You assumption is incorrect. There's no "there" there, so there's nothing to stop the universe from expanding.

Answer 10

A cosmic crunch