Why Does the Universe Exist?
Most recent answer: 10/22/2007
Timpany School, Vizag,Andhra Pradesh,India
Whoa! That’s quite a question! And the answer actually lies on the border between science, philosophy, and stuff we just don’t know. But rather than answering it myself, let me give you a (rather long) quote from Dr. Leon Lederman, a very cool (and quite famous) particle physicist:
"In the Very Beginning there was a void -- a curious form of vacuum -- a nothingness containing no space, no time, no matter, no light, no sound. Yet the laws of nature were in place, and this curious vacuum held potential. Like a giant boulder perched at the edge of a towering cliff . . .
Wait a minute.
Before the boulder falls, I should explain that I really don’t know what I’m talking about. A story logically begins at the beginning. But this story is about the universe, and unfortunately there are no data for the Very Beginning. None, zero. We don’t know anything about the universe until it reaches the mature age of a billionth of a trillionth of a second -- that is, some very short time after creation in the Big Bang. When you read or hear anything about the birth of the universe, someone is making it up. We are in the realm of philosophy. Only God knows what happened at the Very Beginning (and so far She hasn’t let on).
Now, where were we? Oh yes . . .
Like a giant boulder perched at the edge of a towering cliff, the void’s balance was so exquisite that only whim was needed to produce a change, a change that created the universe. And it happened. The nothingness exploded. In this initial incandescence, space and time were created.
Out of this energy, matter emerged -- a dense plasma of particles that dissolved into radiation and back to matter. (Now we’re working with at least a few facts and some speculative theory in hand.) Particles collided and gave birth to new particles. Space and time boiled and foamed as black holes formed and dissolved. What a scene!"
(from , copyright 1993 by Dr. Leon Lederman and Dick Teresi, published by the Houghton Mifflin Company.)
He goes on to describe the universe’s growth and expansion, but the important part for your question is right here. Basically what he’s saying is that the universe exists because it can exist. Before the universe, there was nothing. But there was the chance for that nothing to become the universe. And since the possibility existed, it was bound to happen eventually. And so here we are.
[There are other possible pictures suggested since that was written, as mentioned below.]
(published on 10/22/2007)
Follow-Up #1: quantum creation
Youre right also that we try to go as far as we can with explanations based on observations and the mathematical theories they inspire, without invoking other hypotheses.
(published on 10/22/2007)
Follow-Up #2: origin of universe?
- Muhammad Shehryar Khan (age 45 years)
DG Khan, Punjab, Pakistan
2. That's a challenging question. If the time evolution of the quantum universe has the properties of quantum field theory (unitarity) then information is somehow conserved. There are disputes about how to integrate that feature with gravitational horizons. If I understand correctly, the current consensus is that unitarity does hold, and that quantum gravity should remove the problems not only at the origin but also at black hole horizons.
3. This is a deep philosophical question. That's another way of saying it's too hard for us.
(published on 05/16/2011)
Follow-Up #3: Why do laws of nature exist?
- Walter (age 37)
Hudson, NC USA
We have no idea. It's hard to even imagine what an answer would be like. Yet it's tempting to wonder about.
(published on 02/26/2014)
Follow-Up #4: Will the universe stop expanding and start contracting?
- Divya barmeda (age 14)
There are several plausible theories of the fate of the universe, the one you are proposing is one of them. However there is experimental evidence that the universe is actually expanding at an ever increasing rate. This is attributed to "Dark Energy", which contributes a repulsive term in the Friedman equation that describes how the energy in the universe drives its expansion.
You might want to check out some of these references:
Just to add a few responses to some points in your question:
1) The dark energy doesn't cause the expansion, it just gradully speeds it up.
2) So far as we can tell from various lines of data, the dark energy density isn't changing. It's not being "depleted". Ordinary matter density does go down as the universe expands, so that makes the acceleration increase a little. As Lee's links point out, however, we don't know what will happen in the very long run. /Mike W.
(published on 11/12/2016)