So, I have a torch and some neodymium magnets.
Let's see what happens when I heat them up.
So, these were magnets...until we heated them
up--and they forgot.
The same phenomenon that made the magnets
forget that they were magnets ensures that
no memory is permanent and even you will forget
everything you ever knew.
Oh, by the way, did you turn off the oven?
It's a simple yes or no.
I know, sometimes you can't remember.
Maybe what you need is a little switch--something
where it says, "Yes, I turned it off" or "No,
it's still on."
'Cause that would be a simple way to remember
one single bit of information, whether it's
good-bad, yes-no, or one-zero.
But what if you wanted to store many pieces
of information, like the information that's
encoding this video, which is 1 gigabyte?
That's 8 billion ones or zeros.
Eight billion little switches would be the
size of Manhattan if you put them right next
to each other.
Luckily, we store information in a smaller
kind of switch.
So, in a hard drive, we have small magnets
whose north poles point up for one or down
for zero.
There are actually several trillion magnetic
switches in here.
But why aren't hard drives even smaller?
It's because the microscopic world is a dance
party, with molecules bumping and jiggling.
Here are some pollen grains in water--and
scientists thought the pollen was actually
alive, until Einstein proved that it was just
water molecules that were hitting it and making
the pollen grain dance.
And just like the water, the molecules in
the hard drive are bouncing and jiggling and
they're making those little magnets bounce
too.
And that's sort of a problem because they
could eventually jiggle and flip over.
And if that happens, then we lose the information
that that single magnetic switch was holding.
And that's what happened when I heated the
magnets with the blowtorch.
Each of those magnetic balls is made of many
small magnets, which are all pointing in the
same direction--until you heat it and the
microscopic bumping increases, flipping over
some of those magnets and de-magnetizing the
ball.
If you tried to make a hard drive with even
smaller magnets than we currently use, then
that flipping over could occur at room temperature
fairly quickly and they could lose their information
in a matter of days.
Current hard drives can only hold information
for about 200 years.
So, what does this have to do with information
in your brain?
Your memories?
When you remember something, a particular
sequence of neurons is triggered.
An electrical signal travels down one neuron
over a small gap to the next neuron, and that
signal continues along the neurons until all
the neurons that are related to that one memory
have been triggered.
So, that little space between neurons?
That's called a synapse and that controls
whether or not the signal can travel from
one firing neuron to its neighbor.
And that signal can only cross if there are
enough of a certain kind of molecule at that
first neuron.
Those molecules are called neurotransmitters.
The problem is that, over time, microscopic
bumping can push those neurotransmitters out
of place, preventing the signal to go from
one neuron to the next.
So, if you're trying to remember something
but one link in that chain of neurons is missing,
you won't be able to get to the rest of the
memory.
On a day-to-day basis, there are other mechanisms
that can cause you to forget.
Things like similar memories interfering with
each other and the presence of a different
kind of neurotransmitter that actually makes
you forget instead of remember.
But if we could live much longer, or if you
went into cryogenic sleep for centuries, then
every memory you have would become dislodged
because all of this bumping would knock neurotransmitters
out of place.
It's all because of this little microscopic
party.
And, like any party, it makes you forget.
And the cool thing is...that...um...I forget.
By the way, the loss of data from bumping
doesn't just affect brains and computers.
It affects words that you write down, because
the ink can actually be bumped out of place.
And it affects DNA, which is why--I'm so sorry
to say this--finding dinosaur DNA is actually
impossible.
Oh, I remembered: subscribe.
That's what it is.
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