The scale of the universe is incredibly
difficult to imagine. think of the biggest thing you can think of - a blue
whale maybe, the Great Pyramids of Giza, the Burj Khalifa in Dubai, Mount Everest.
They may be about as large as you can imagine. But the scale of the universe is
many many orders of magnitude bigger than that. It's much bigger than you can
probably imagine. And the crazy thing is that the universe is also smaller than
you can ever imagine. Think of the smallest thing you can
imagine - a bacteria maybe, an atom? Keep going because the universe is many
orders of magnitude smaller than that. And that's the problem. Most of us can't
grasp the scale of the universe because it's utterly unrelatable,
to anything that we experience in our daily earthly lives. For example, there
are at least 10 sextillion stars that's 10 followed by 21 zeroes. That's
thousands of times more than all the grains of sand on all the beaches of
Earth. But you've probably heard this before. What you may not have heard is
that the universe is even smaller than it is large. For example, the smallest
length theorized to be possible, the Planck length, is about 1.6 x 10^-35
meters. This is so small, that if an atom was the size
of the earth, a Planck length would be much smaller than even the head of a pin.
In fact a Planck volume, which is Planck length cubed, or about 4 x 10^-105 cubic meters is so small that there are more Planck volumes
inside a cubic meter, than there are cubic meters in the known universe. Let's
explore the scale of the universe using some genius animations created by Cari
and Michael Huang, who have generously given us permission to use them. The link
to their website is in the description below. So exactly how long is a Planck
length and how can we visualize something that small. What is the
fundamental reason that this is the smallest length in the universe? That's
coming up right now... Let's start with the scale of the human
being because this is probably the most relatable scale we can think of. Just
imagine things that are about the size of your body - things like the giant
earthworm that lives along streams in Australia, or a big each ball which can
be found near oceans and beaches all across America. We're looking right now
at scales that are 10 to the power 0, or 1 meter in length. Now let's go smaller
by one order of magnitude. So now we're looking at things that are on the scale
of about one tenth of a meter or 10 centimeters. these are things like the
Shrew which are some of the smallest mammals found on earth, or a chicken egg
that you might have had for breakfast this morning. Now we're going to move a bit
faster. Let's go a thousand times smaller than the scale of a human being, on the
order of one millimeter or one thousandth of a meter. Here you're going to
find things like a grain of sand, which can be about half a millimeter in length
or dust mites that may be crawling all over your bed, because they love to eat
dead skin cells. Yeah, if you itch in the morning, this could be the culprit. You
can't usually see them with the naked eye. Let's go a thousand times smaller
than this scale. Now we're going a hundred times smaller than the width of
a human hair, or about one millionth of a meter, and ten times smaller than even a
bacteria. Here we're going to find things like large viruses. Unlike bacteria, 99%
of which are harmless to you, the vast majority of viruses (inside your body) will make you sick.
And our antibiotics are totally ineffective against viruses. Let's keep
going to a thousand times smaller than this. This is nanometers, or one billionth
of a meter. Now we're exploring a universe that we can't see with our
optical microscopes. This is around the order of the size of the DNA molecule,
the blueprint of all life on Earth. This is on the scale of molecules, like the
glucose molecules that your body uses as a source of energy, and the scale of the
biggest atom, cesium. Why is this atom so big even though it doesn't have the most
electrons? ...because it has the best combination of a large valence shell and
low nuclear charge, which allows electrons to wander further away from
the nucleus. Let's go a thousand times smaller than even this. This is one
trillionth of a meter this is on the scale of the wavelength of gamma rays.
This is the highest energy electromagnetic radiation, consisting of
the most energetic photons. Gamma rays are emitted during nuclear explosions,
and a high-energy cosmological phenomena, such as exploding stars, just before they
collapse into a black hole. Now let's go a thousand times smaller than this. This
is 1 x 10^-15 m, or 1 quadrillion of a meter. This is the size
of particles that make up the nucleus of atoms, protons and neutrons. The size of a
typical atom, however, is a hundred thousand times larger than its nucleus.
So if an atom was the size of Michigan football stadium, the biggest stadium in
the United States, the nucleus would be a marble sitting in the middle of the
50-yard line. You would think that we're getting close to the smallest size
theorized to exist, the Planck length. But we are nowhere close. You have to go a
quadrillion times smaller than 1 quadrillion of a meter, or 1 x 10^ -30 meters. And you would still have to go another hundred
thousand times smaller than that, or 1 x 10^-35 meters, then
you would be at the Planck length. In fact if an atom was the size of the
earth, a Planck length would be smaller than the size of an atom. It would be
about the size of a proton. But what exactly is a Planck length? And why is it
the smallest length? Planck length is actually derived from three fundamental
constants of the universe that define the properties of space-time, the speed
of light - C which signifies the maximum speed of communication in the universe.
the gravitational constant - G which signifies the magnitude of gravitational
force between two massive objects. The reduced Planck constant, h-bar
which links how much energy of photon carries depending on its electromagnetic
frequency, defined by this equation. These are really the only constants that
define the fundamental properties of the universe, and all its contents. By taking
different mathematical combinations of these constants, and reducing their units,
you can get a length. So as you can see here, if we take the units of the three
fundamental constants and manipulate them mathematically, we can come up with
a length - L sub p, which is the Planck length. And by a similar mathematical
manipulation, we can also get Planck time, and Planck energy. But what does this
Planck length actually mean? What does it signify? Why is it significant? Well,
cosmologically is the smallest length at which gravity would have an effect. it's
the scale and size of strings in string theory. It's also the scale at which
space-time is believed to become quantized in the theory of loop quantum
gravity. Why is this the smallest length? Why isn't it some other number? Well the
main reason is is because it comes from the fundamental constants of the
universe. And in 1964 C. Alden Mead determined that using the known laws of
quantum mechanics, and the laws of gravitation, it is impossible to
determine the position of an object to a precision smaller than the Planck length.
So from what is currently known about quantum mechanics, a length smaller than
the Planck length, has no meaning. Now note that I said "known laws." It is
possible that at lengths smaller than the Planck length, gravity or quantum
mechanics behaves completely differently, that we may not yet be aware of. Since we
don't have a working theory of quantum gravity, this is quite possible. And until
we find out what happens at such small scales, we just need to wait for the next
Einstein to reveal it to us. One of the remarkable things about the Planck
length is that since it's derived from the fundamental constants of the
universe, which by definition applies to everything, this length is going to be
the same no matter what language you speak, what units you might use, or even
what planet you might come from. So that's right, if we ever come across
aliens from another world, and compare notes,
we both will have the same length of the smallest length possible in the universe.
So we have a common language already with those shy aliens that only seem to
show up in fuzzy pictures and remote areas of the United States. In part 2 of
this video we're gonna explore the other end of the scale, how large the universe
is - which by the way, is much larger than you can imagine.
And if you like this video, please give us a thumbs up, and share it with your
friends. Be sure to check out some of our other popular videos. I'll see you in the
next video my friend!
