Hello Spacelab, I'm Lawrence Krauss,
Director of the Origins Project at Arizona State University,
a theoretical physicist and also the author of "A Universe From Nothing".
And I'm here today to answer the following question:
"Why is there something rather than nothing"
Well, the question, "why is there something rather than nothing?",
has been around as long as people have been asking questions,
and it's gotten a lot of different answers.
First, as a scientist, I should say that really
"why" isn't a a good question.
When we say "why", we really mean "how".
Because "why" implies that there is some purpose,
and there may be no purpose to the universe.
In deed, as far as we can tell from all the evidence,
there's no evidence of purpose.
So when you say "why does something happen"
you really mean "how does it happen".
So, the question is "how does something come from nothing?".
It seems to violate the laws of physics.
But in fact the answer is quite interesting,
because, it turns out, the simplest answer may be
that nothing is unstable.
You will always produce something.
In deed, once you combine quantum mechanics and relativity
empty space, which apparently of course is nothing,
is not so simple.
It's actually a boiling, bubbling brew of virtual particles
popping in and out of existence,
in a time scale so short you can't see them.
And in fact, if you wait long enough,
and allow gravity to operate,
empty space will eventually start producing particles.
And in fact, therefore, the answer to the question
"why is there something rather than nothing" or
"how is there something rather than nothing"
is nothing is unstable.
You're guaranteed if you wait long enough
to have something.
And if you want to ask the question
you'll always be the places with something.
So actually, empty space can produce enough particles
to account for all hundred billion galaxies in all,
and a hundred billion stars in each galaxy.
Now, you might say, well empty space isn't nothing.
But, if quantum mechanics actually applies to gravity,
then space and time themselves become
quantum mechanical variables.
And whole universes can pop into existence.
Spaces and times and matter and energy
can pop into existence without violating any laws of physics.
In fact, the total energy of our universe may be zero.
In fact, when we look out, it looks like
it is zero.
And that gives us good evidence
that perhaps it popped into existence
from nothing.
Because no energy to begin with
and zero total energy in the end,
because the positive energy associated
with the mass of elementary particles
is countered by the negative energy of gravity.
Now, the question is of course
what happened before our universe came into existence.
Was there anything at all?
And the answer is we don't know.
A simple answer is, that the question about
what happened before may not be a good question,
because since space and time are tied to matter,
when space and time pop into existence
time itself pops into existence,
and therefore, there may have been no before.
The question may simply not be a good question.
So there may have been no sense
in which you can even ask
what happened before our universe began.
Alternatively, current ideas from physics suggest
that perhaps our universe may be one
of potentially an infinite number of universes
which are popping into existence at various times.
There may be universes being created right now
and other universes ending.
And if that's the case,
then it's possible that the characteristics of our universe
are precisely those that allowed us to evolve.
So when we ask why does the universe have
the properties it does,
the answer is simply
well if it didn't we wouldn't be here to answer the question,
or ask the question.
Now, I should say finally
the question itself is really rather arrogant
because it assumes the universe will always have something in it,
but in fact, in the far future
as far as we can tell, all the galaxies
we can now see are moving away from us
faster and faster and faster.
And that means eventually the entire universe
that we can now see will disappear.
When those galaxies are moving away from us
faster than light, which is allowed in general relativity.
So in the far future there may just be one galaxy
in which we live in, and then the stars will burn out
and the universe become cold, dark, and empty.
And then the simple answer to the question
"why is there something rather than nothing?" is
just wait, there won't be for long.
Thanks for the great question.
If you have a question, leave it in the comments below.
The question with the most likes will be answered
in the next round by another expert.
Hello SpaceLab, I'm Emily Rice
a professor of astronomy at the college of Staten Island
and I'm here today to answer your questions.
The first question is:
If I was able to stand on a neutron star
would I become extremely dizzy?
What effect would this extreme rotational speed have on the body?