Help with a concept

[Angry Dragon]

Last edited Tue Dec 20, 2011, 02:20 PM - Edit history (1)

Our planet exists in a galaxy with a billion other stars and planets in a universe with billions of other galaxies.
The universe expanded for billions of years. According to the big bang theory. It is said today that the expansion is decreasing.

I have always wondered what the universe is expanding in. Is is expanding within a space of some kind, a vacuum of some kind. What would we find if we escaped the universe?? Would we find nothing or something??

[laconicsax]

1. That's one of the great unanswered questions in physics.

BTW: the universe has been expanding for 13.7 billion years and the rate is increasing, not decreasing.

[Angry Dragon]

2. Some years ago I had read that it was thought it was slowing down

I knew it was at least billions, was not sure on the trillions.

You have thoughts on it??

[laconicsax]

3. There was a change fairly recently.

Astronomers wanted to measure the rate the expansion was slowing down and found that it was actually speeding up.

The age of the universe has been increasingly refined to about 13.7 billion years give or take 130 million.

I haven't the fainest idea what's outside the universe.

[DetlefK]

4. This is easy.

The universe does not expand "into" something, like the volume of a balloon.

Instead of a 3+1 spacetime, imagine the universe to be a 2D space, like the SURFACE of a balloon.
Draw an arrow on the surface of the balloon.
Now expand it.
The arrow gets bigger, but does its point ever leave the surface and touch anything outside of that 2D-universe?

The solution is simple:
The balloon-surface does not contain the direction "height", only "length" and "width". That's why its 2D. The human universe has 3 space-dimensions and this additional axis gives us the mathematical degree of freedom to tilt a 2D-surface (e.g. a piece of paper). We can make those two 2D-axes fit any two arbitrary 3D-axes.

What does that mean for the universe?
Let's just add one more space-dimension to my example. Our universe is 3D, so the outside could be 4D or more. Our universe could expand without bouncing into something, because our universe has no diameter along that new 4th axis and that means, an infinite number of universes like ours could be stapled along the 4th axis, just like pieces of paper can be stapled in a 3D-universe.

What's outside the universe?
My guess is, that there was nothing in vicinity, during and shortly after the Big Bang. Remember: An image of the surface of our universe back from Big Bang-times is imprinted into the Cosmic Microwave Background. And all features of the CMB point to a perfectly isolated universe.

About two years ago, I read a paper on theoretical cosmology, that a circle-like structure would form in our universe, if another universe would bounce into ours. These scientists proposed, that the astronomists should start looking out for this phenomenon.

[Jim__]

5. "The metric expansion of space is the increase of distance between distant parts of the universe wit

Wikipedia has a pretty good article entitled Metric Expansion of Space ( http://en.wikipedia.org/wiki/Metric_expansion_of_space#What_space_is_the_universe_expanding_into.3F ). A short excerpt:

The metric expansion of space is the increase of distance between distant parts of the universe with time. It is an intrinsic expansion—that is, it is defined by the relative separation of parts of the universe and not by motion "outward" into preexisting space. In other words, the universe is not expanding "into" anything outside of itself, although a frequently used analogy is the expansion of the surface of an expanding rubber balloon. If this analogy is used, this surface should be seen as an intrinsic manifold.

Metric expansion is a key feature of Big Bang cosmology and is modeled mathematically with the FLRW metric. This model is valid in the present era only at relatively large scales (roughly the scale of galactic superclusters and above). At smaller scales matter has clumped together under the influence of gravitational attraction and these clumps do not individually expand, though they continue to recede from one another. The expansion is due partly to inertia (that is, the matter in the universe is separating because it was separating in the past) and partly to the repulsive force of dark energy, which is of a hypothetical nature, but it may be the cosmological constant. Inertia dominated the expansion in the early universe, and according to the Lambda-CDM model (ΛCDM model) the cosmological constant will dominate in the future. In the present era they contribute in roughly equal proportions.

While special relativity constrains objects in the universe from moving faster than the speed of light with respect to each other, there is no such theoretical constraint when space itself is expanding. It is thus possible for two very distant objects to be expanding away from each other at a speed greater than the speed of light. Since the parts of the universe cannot be seen after their speed of expansion away from us exceeds the speed of light, the size of the entire universe could be greater than the size of the observable universe.

It is also possible for a distance to exceed the speed of light times the age of the universe, which means that light from one part of space generated near the beginning of the Universe might still be arriving at distant locations (hence the cosmic microwave background radiation). These details are a frequent source of confusion among amateurs and even professional physicists.[1] Interpretations of the metric expansion of space are an ongoing subject of debate.[2][3][4][5]

[hue]

6. Perhaps there are many other Universes...

@ Jim; nice article.

Hi Angry Dragon! Indeed there is evidence that our Universe is expanding.
I admire the way You wonder about our Universe! Last year Stephen Hawking & Leonard Mlodinow came out with a book for the
general public entitled "The Grand Design". Dr. Hawking writes, "There seems to be a vast landscape of possible universes. However...universes in which life like us can exist are rare." It is an interesting, easy to read book. Hope You can find time to read it!

[tridim]

7. The expansion of our universe is the process of space and time expanding.

It's not matter expanding within existing space.

Of course we now have theories that say our universe might be confined within a black hole in a parent universe, which would imply that we are expanding into a parent space as a sort of bubble. Overlapping space? Something about that seems right, but who knows if it is.

[HopeHoops]

8. Either it will reverse and collapse, or the "infinity" is really the center...

...in a dimension that's hard for humans to grasp. Either way, it will all end in disaster, flame, explosions and nasty shit like that but I'm pretty sure humans will have destroyed all life on Earth long before that. Have a beer.

[gtar100]

9. You may find the talk at this link rather interesting and on topic with your question:

http://www.democraticunderground.com/122863

Lawrence Krauss discusses Cosmology and what we know today. If you haven't seen it already, I think it'd be well worth your time.

[Angry Dragon]

10. I did know about this post but

I did not look at the video because I am on dial-up and it would
take infinity to download.............

thank you for the link..........

[Motown_Johnny]

11. Well,

The hard thing to understand is that there isn't anything outside the universe and that you can't ever "escape" it.


An inaccurate analogy would be a shotgun blast. Consider the entire universe compacted down to a very tiny size, kinda like all packed in a shotgun shell. This is inaccurate because the universe was so small we can't even imagine it, but please try to get past this for the moment. Next the shotgun shell is fired and everything in the universe goes rushing down the barrel. This is the expansion phase where it would seem that the laws of physics were different than they are now. After this everything rushes out the end of the barrel. This is where it gets interesting because the universe is not only expanding to the left and right as well as up and down, but some of it is rushing out ahead of the rest while some of it lags a little behind. This is where we are now. The universe is expanding in all three of the spacial dimensions, but not only that. The same way the shotgun blast moves downrange the universe also travels through time. In this way we the universe is traveling through all four dimensions.

Now you and I are just tiny specks on one of the tiny specs inside that blast. We can never hope to travel to the edge of the universe or to escape it. The distances are just to great.





Unless you want to get into the multi-verse stuff, but I don't buy it.

[tama]

12. Not a direct answer to the question

but perhaps can help to expand ones mind:

[Angry Dragon]

13. Thanks to everyone for their input and information

now I need to step back and ponder to see where this leads me