The description of how our universe has evolved
from the moment of the big bang until today is known as the big bang model.
But this model has some problems. For example, it doesn’t quite tell us why the universe is so
homogenous, that is, looks pretty much the same everywhere, why it appears geometrically flat,
and why there are no magnetic monopoles. As I discussed in the last video, cosmic inflation
solves these problems, and accounts for much of the structure of the universe we observe today.
Inflation occurred when the entire universe shortly after its beginning expanded
exponentially fast, faster than the speed of light, for a very short period of time,
perhaps only a trillionth of a trillionth of a trillionth of a second,
such that the volume increased by a factor of something like 10^78.
One implication of this cosmic inflation is
that the universe on scales much larger than our observable universe may not be so homogenous.
In the 1990s, scientists realized that this inhomogeneity on large scales could
mean that inflation ended at different times in different places. And if that were true,
then it would mean that the universe is likely far bigger and far more complex than we realize.
In fact, the universe we are familiar with may be only a tiny fraction of all that exists.
This concept is called ETERNAL inflation, and its implications
are profound. What is this eternal inflation?
And what would it imply for the true nature of reality? That’s coming up right now…
If you’ve watched my videos before, then you know that I like to ask big questions, that sometimes
don’t have clear answers. When this happens, some viewers invoke the hand of a creator.
Most scientists try to stay away from this idea.
But I recently found an inspirational science video on MagellanTV, today’s sponsor, that took
on the question of a creator head-on in a rational way. And I think you would enjoy seeing it.
It’s called simply, “The Cosmos.” And it asks the question, given how much knowledge we’ve gained,
and how much we have yet to learn, is there is any evidence of a creator beyond the cosmos?
Magellan offers thousands of fascinating documentaries like this.
It’s a new kind of documentary service created by the film makers themselves.
Featured topics include science, history, travel and technology.
Magellan has a special offer right now for Arvin Ash viewers. If you click the link
in the description, you can get free one month trial. You have got nothing to lose,
and a world of knowledge to gain at your fingertips, just by clicking the
link in the description. So be sure to take advantage of that.
We stated in the previous video that Inflation occurred due to our universe
having a lot of energy in the form of a scalar field – the inflation field.
This field caused an enormous expansion of the universe but only for a split second.
As the universe quickly cooled, it decayed into other fields and particles. After this expansion,
the universe kept expanding but at a much slower rate.
Using the equations of physics, and knowing approximately the total energy
that this field would need to have, which can be calculated based on the
total current energy of our universe, we can approximate how long inflation should last.
And most models show that it would last for a miniscule amount of time, something like
10^-32 to 10^-36 seconds.
But here’s the key point about these calculations. This prediction
of how long inflation lasts, tells us only how long it should last ON AVERAGE.
But quantum mechanics ensures that there will always be some randomness.
Inflation could last a bit longer or shorter than expected in different parts of the universe.
This is analogous to radioactive decay. Let’s take an isotope of Thorium for instance, Thorium 231.
Its half-life is about 1 day.
This means that if we have a kilogram of Thorium.
After one day, about ½ kg will decay, to something like Protactinium 231.
The following day, half the remaining 0.5 kg of Thorium will decay. So we will be left with a 0.25
kg of Thorium after two days. Similarly, the third day, half of the 0.25 kg will decay, and so on.
What this means is that if you start out with 100 atoms of Thorium-231, then after 1 day,
50 of them will have decayed to Protactinium-231, and 50 will remain as Thorium.
But the nature of quantum mechanics is such we can’t predict in advance,
which of the 100 atoms will decay and which will not.
So if we pick one atom at random and wait for it to decay, we could wait for 1 day, 2 days,
3 days or more. There is no telling. All we know is that if we have a large number of atoms,
about half will decay every 24 hours or so. But we don’t know which ones.
Inflation may work similarly.
In the 1980s, Paul Steinhardt, Andrei Linde and Alexander Vilenkin realized that the exponential
expansion of cosmic inflation, although it stopped in our part of the universe,
could continue without end in other unobservable parts of the universe.
Like the concept of half-life, quantum uncertainty may cause on average,
half the volume of the expanded universe to stop inflating after about 10^-32 seconds,
but it could continue in the other half of the universe.
So here is the astonishing part. Let’s say, space expanded exponentially, by at least
10^78x or more, and stopped in one part of the universe. This becomes like a
bubble - a bubble universe. This could be our universe, or any arbitrary universe.
But space could continue to keep expanding exponentially
in another part of the universe, and after another 10^-32 seconds,
it stops in another half of the just expanded universe, forming another bubble universe.
So now we have two universes, but the space between these two universes keeps
expanding exponentially. And as parts of this newly created space stop inflating,
more bubbles form. But again the space between these bubbles keeps expanding exponentially.
Steinhardt and others realized that if the if the decay of the inflation field happens
slower than the rate of expansion of the universe, then inflation could go on, in principle forever,
creating more and more bubble universes.
Now there is a big difference between the analogy of radioactive decay and
inflation. In radioactive decay, since we have a limited amount of material, and no new material
is created with the passing of every half-life, eventually all of the material decays over time.
But in eternal inflation, since new space is being created all the time, inflation never stops.
This is why it’s called ETERNAL inflation. For all practical purposes
each of these parts where inflation stopped looks like a separate universe,
or bubble, and is independent of what happens in other parts of the universe.
In fact, space expands so much between them, expanding faster than the speed of light,
no information can ever travel between the bubbles, no matter
how long you wait. And they will never collide. So they are informationally isolated from each other.
If the theory of eternal inflation is correct, we are inside one of these bubbles. And it is
highly unlikely that we are in the first bubble, or even in the first few bubbles. Given the vast
number of bubbles being created at every instant, we could be in any one of them.
So our most accepted current STANDARD theory of the big bang goes something like this:
About 13.8 billion years ago, the big bang happened. We don’t know what caused it or what
happened before this event. But about 10^-32 seconds later, cosmic inflation happened,
causing the universe to expand exponentially. Then it ended.
And then the universe continued to expand but at a much slower pace.
And these events largely explain what we observe in the universe today, 13.8 billion years later.
With ETERNAL inflation, the story changes to something like this.
We don’t know what happened at the beginning. But a fraction of a second later,
inflation happened. This could have happened arbitrarily far
in the past. It is also possible that there may not have been a beginning at all.
Many bubble universes formed and are continuing to form. At some point within this space,
our bubble formed. It was probably not the first, and is certainly not the last.
Inflation will continue forever continually sprouting new bubbles of universes in the space
that is created within it. But what we observe in our bubble 13.8 billion years after its formation,
can be explained by the big bang model.
So, what we think of as the start of the universe may be just the point at which
inflation simply ended in our part of the universe.
But what the universe is on much larger scales is an unimaginably vast multiverse of universes.
You might be wondering,
what is the nature of these other universes? Are they like ours or are they different?
Well, no one knows for sure, but it’s probably a good bet that the fundamental laws of
quantum mechanics would still apply, since inflation is derived from quantum mechanics.
Most physicists also think there is probably some
overarching, overall laws of nature that describe the entirety
of the multiverse, and these laws describe how the inflation field expands, and how bubbles form.
Are these universes the same as ours? There is nothing in the laws of physics that requires a
universe to have the same laws as ours or the same fundamental constants as ours.
For example the masses of fundamental particles like electrons could be different, or the fine
structure constant, which determines the strength of the electromagnetic force could be different.
Depending on the various combinations of fundamental constants, you could have universes
where no stars formed, or universes where only neutrons exist, or various other universes.
You might be thinking this sounds outlandish, perhaps even preposterous.
Prove to me that this is true.
Well, the unfortunate fact is that we will never be able to directly detect
these other universes because the space between them is expanding so fast
that no communication at the speed of light could occur.
Short of creating a wormhole between one universe to another,
which is probably not possible, we can’t know whether they actually exist.
However, the key to understanding the early universe lies in the study
of high energy physics. If we can replicate the energies and temperatures close to the big bang,
it might give us a clue as to whether eternal inflation could be correct.
Currently, the state of the art facility, and one of man’s greatest technological achievements,
the Large Hadron Collider, in Switzerland can come nowhere close to the energies near the Big
Bang. For example the highest energies created in the LHC are about 10^13ev (electron volts)
but the energies near the big bang were many magnitudes higher, closer to 10^24 eV.
So we can’t simulate those conditions, but perhaps a new generation of colliders will get us closer.
There may also be some clues about the early universe in gravitational waves.
Our instruments are not yet sensitive enough, however to detect these very weak background
gravitational waves which probably fill the sky like the cosmic microwave background does.
These gravitational waves would have been remnants of the big bang.
A 2018 paper published posthumously by Steven Hawking and coauthor Thomas Hertog
alludes to the idea that the background gravitational waves
may hold the clues that tell us about whether potential multiverses exist.
The planned European Space Agency gravitational wave observatory,
LISA, may be able to detect these.
Just like in the past, in 1543, when Copernicus showed that the earth was not the center of
the universe, but that it revolved around the sun. That made the sun the new center.
Then in 1911, American astronomer Harlow Shapley showed that the sun
was not the center of the universe. And you have to remember,
that what we called the universe up to this point was just the Milky Way galaxy.
Then in 1924, American astronomer Edwin Hubble
showed us that our galaxy was just one of many in an ever expanding universe.
Likewise, we may someday find out that the Big bang was not the beginning of everything.
13.8 billion years ago was simply OUR big bang, not THE big bang.
And that it’s only a tiny blip of a bubble in a vast ocean of bubbles
that is getting exponentially larger with every passing fraction of a second.
So it appears that in our historical search for cosmic significance, the more we look,
the more technologically sophisticated instruments we employ, the
more we discover that we are perhaps even more insignificant than we ever imagined.
If you like this video, please give us a thumbs up. And if you have any questions for me
or our viewers, put them in the comments section. I will see you in the next video my friend.