What Was Cosmic Inflation? The Quest to Understand the Earliest Universe
Δημοσιεύτηκε στις 30 Μαΐ 2017
The
Big Bang was a tremendous theory, but it had a few problems. In 1980
Alan Guth developed the revolutionary theory of cosmic inflation, and
astronomers have been looking for evidence to this day.
Support us at: http://www.patreon.com/universetoday
More stories at: http://www.universetoday.com/
Follow us on Twitter: @universetoday
Like us on Facebook: https://www.facebook.com/universetoday
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Team: Fraser Cain - @fcain / frasercain@gmail.com
Karla Thompson - @karlaii
Chad Weber - weber.chad@gmail.com
The
Big Bang. The discovery that the Universe has been expanding for
billions of years is one of the biggest revelations in the history of
science. In a single moment, the entire Universe popped into existence,
and has been expanding ever since.
We know this because of
multiple lines of evidence: the cosmic microwave background radiation,
the ratio of elements in the Universe, etc. But the most compelling one
is just the simple fact that everything is expanding away from
everything else. Which means, that if you run the clock backwards, the
Universe was once an extremely hot dense region
Let’s go
backwards in time, billions of years. The closer you get to the Big
Bang, the closer everything was, and the hotter it was. When you reach
about 380,000 years after the Big Bang, the entire Universe was so hot
that all matter was ionized, with atomic nuclei and electrons buzzing
around each other.
Keep going backwards, and the entire Universe
was the temperature and density of a star, which fused together the
primordial helium and other elements that we see to this day.
Continue
to the beginning of time, and there was a point where everything was so
hot that atoms themselves couldn’t hold together, breaking into their
constituent protons and neutrons. Further back still and even atoms
break apart into quarks. And before that, it’s just a big question mark.
An infinitely dense Universe cosmologists called the singularity.
When
you look out into the Universe in all directions, you see the cosmic
microwave background radiation. That’s that point when the Universe
cooled down so that light could travel freely through space.
And
the temperature of this radiation is almost exactly the same in all
directions that you look. There are tiny tiny variations, detectable
only by the most sensitive instruments.
When two things are the
same temperature, like a spoon in your coffee, it means that those two
things have had an opportunity to interact. The coffee transferred heat
to the spoon, and now their temperatures have equalized.
When we
see this in opposite sides of the Universe, that means that at some
point, in the ancient past, those two regions were touching. That spot
where the light left 13.8 billion years ago on your left, was once
directly touching that spot on your right that also emitted its light
13.8 billion years ago.
This is a great theory, but there’s a problem.
The
Universe never had time for those opposite regions to touch. For the
Universe to have the uniform temperature we see today, it would have
needed to spend enough time mixing together. But it didn’t have enough
time, in fact, the Universe didn’t have any time to exchange
temperature.
Imagine you dipped that spoon into the coffee and
then pulled it out moments later before the heat could transfer, and yet
the coffee and spoon are exactly the same temperature.
What’s going on?
To
address this problem, the cosmologist Alan Guth proposed the idea of
cosmic inflation in 1980. That moments after the Big Bang, the entire
Universe expanded dramatically.
And by “moments”, I mean that the
inflationary period started when the Universe was only 10^-36 seconds
old, and ended when the Universe was 10^-32 seconds old.
And by “expanded dramatically”, I mean that it got 10^26 times larger. That’s a 1 followed by 26 zeroes.
Before
inflation, the observable Universe was smaller than an atom. After
inflation, it was about 0.88 millimeters. Today, those regions have been
stretched 93 billion light-years apart.
This concept of inflation was further developed by cosmologists Andrei Linde, Paul Steinhardt, Andy Albrecht and others.
Inflation resolved some of the shortcomings of the Big Bang Theory.
The
first is known as the flatness problem. The most sensitive satellites
we have today measure the Universe as flat. Not like a
piece-of-paper-flat, but flat in the sense that parallel lines will
remain parallel forever as they travel through the Universe. Under the
original Big Bang cosmology, you would expect the curvature of the
Universe to grow with time.
The second is the horizon problem.
And this is the problem I mentioned above, that two regions of the
Universe shouldn’t have been able to see each other and interact long
enough to be the same temperature.
Big Bang was a tremendous theory, but it had a few problems. In 1980
Alan Guth developed the revolutionary theory of cosmic inflation, and
astronomers have been looking for evidence to this day.
Support us at: http://www.patreon.com/universetoday
More stories at: http://www.universetoday.com/
Follow us on Twitter: @universetoday
Like us on Facebook: https://www.facebook.com/universetoday
Google+ - https://plus.google.com/+universetoday/
Instagram - http://instagram.com/universetoday
Team: Fraser Cain - @fcain / frasercain@gmail.com
Karla Thompson - @karlaii
Chad Weber - weber.chad@gmail.com
The
Big Bang. The discovery that the Universe has been expanding for
billions of years is one of the biggest revelations in the history of
science. In a single moment, the entire Universe popped into existence,
and has been expanding ever since.
We know this because of
multiple lines of evidence: the cosmic microwave background radiation,
the ratio of elements in the Universe, etc. But the most compelling one
is just the simple fact that everything is expanding away from
everything else. Which means, that if you run the clock backwards, the
Universe was once an extremely hot dense region
Let’s go
backwards in time, billions of years. The closer you get to the Big
Bang, the closer everything was, and the hotter it was. When you reach
about 380,000 years after the Big Bang, the entire Universe was so hot
that all matter was ionized, with atomic nuclei and electrons buzzing
around each other.
Keep going backwards, and the entire Universe
was the temperature and density of a star, which fused together the
primordial helium and other elements that we see to this day.
Continue
to the beginning of time, and there was a point where everything was so
hot that atoms themselves couldn’t hold together, breaking into their
constituent protons and neutrons. Further back still and even atoms
break apart into quarks. And before that, it’s just a big question mark.
An infinitely dense Universe cosmologists called the singularity.
When
you look out into the Universe in all directions, you see the cosmic
microwave background radiation. That’s that point when the Universe
cooled down so that light could travel freely through space.
And
the temperature of this radiation is almost exactly the same in all
directions that you look. There are tiny tiny variations, detectable
only by the most sensitive instruments.
When two things are the
same temperature, like a spoon in your coffee, it means that those two
things have had an opportunity to interact. The coffee transferred heat
to the spoon, and now their temperatures have equalized.
When we
see this in opposite sides of the Universe, that means that at some
point, in the ancient past, those two regions were touching. That spot
where the light left 13.8 billion years ago on your left, was once
directly touching that spot on your right that also emitted its light
13.8 billion years ago.
This is a great theory, but there’s a problem.
The
Universe never had time for those opposite regions to touch. For the
Universe to have the uniform temperature we see today, it would have
needed to spend enough time mixing together. But it didn’t have enough
time, in fact, the Universe didn’t have any time to exchange
temperature.
Imagine you dipped that spoon into the coffee and
then pulled it out moments later before the heat could transfer, and yet
the coffee and spoon are exactly the same temperature.
What’s going on?
To
address this problem, the cosmologist Alan Guth proposed the idea of
cosmic inflation in 1980. That moments after the Big Bang, the entire
Universe expanded dramatically.
And by “moments”, I mean that the
inflationary period started when the Universe was only 10^-36 seconds
old, and ended when the Universe was 10^-32 seconds old.
And by “expanded dramatically”, I mean that it got 10^26 times larger. That’s a 1 followed by 26 zeroes.
Before
inflation, the observable Universe was smaller than an atom. After
inflation, it was about 0.88 millimeters. Today, those regions have been
stretched 93 billion light-years apart.
This concept of inflation was further developed by cosmologists Andrei Linde, Paul Steinhardt, Andy Albrecht and others.
Inflation resolved some of the shortcomings of the Big Bang Theory.
The
first is known as the flatness problem. The most sensitive satellites
we have today measure the Universe as flat. Not like a
piece-of-paper-flat, but flat in the sense that parallel lines will
remain parallel forever as they travel through the Universe. Under the
original Big Bang cosmology, you would expect the curvature of the
Universe to grow with time.
The second is the horizon problem.
And this is the problem I mentioned above, that two regions of the
Universe shouldn’t have been able to see each other and interact long
enough to be the same temperature.
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