00:00:00
Hi!
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You’re on a rock.
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Floating in space.
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Surrounded by more rocks.
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And gas.
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And a bunch of nothing, mainly.
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Oh hey, look at that, the rocks are going
around the gas.
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Hold on, what the heck, is going on here?
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To understand, let’s look a little bit of
Physics.
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Wait, did I say a little bit?
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To find out what kind of magic this is, we’ll
have to go back in time.
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Okay, not that far.
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Stop!
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Yeah.
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That’s perfect.
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This is gravity guy.
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But most people call him “Isaac Newton”.
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One important thing he said is that Force
equals mass times acceleration.
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Now what do all these words even mean?
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Force is just a push or pull on something,
in a certain direction.
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Mass tells you how much of something there
is, and it’s also a measure of inertia,
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but we’ll get to that later, and acceleration
is the derivative of velocity with respect
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to time, but that’s too many big words for
my taste, so let’s just say it’s how fast
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velocity is changing.
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The key takeaway is that if you apply a Force
to a fixed mass, you get a predictable amount
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of acceleration.
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If you know all the forces acting on a basketball
mid-air, you can predict with 100% certainty
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if the ball will go in the hoop or your neighbours
windshield.
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“Whoa, did an apple just fall on my head?”
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Yes Newton, it did.
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“That must have happened for a reason”
said Newton, as he discovered that two masses
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attract one another, making the apple fall.
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Yes, even you, no matter how ugly you think
you are, attract pretty much the whole universe,
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at least a little bit.
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Hey, can you put that on paper?
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“yup” said Newton, who gave us the Law
of Universal Gravitation.
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In other words, how much two bodies pull on
each other, given their mass and distance,
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times a constant.
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Bigger mass?
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Bigger Pull.
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Bigger distance?
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Smaller pull.
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Actually, a lot smaller pull.
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You see, the as the distance increases, the
Force gets smaller by the square.
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That my friends, is the Inverse-Square Law.
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Gravity is also the reason why the planets
in our solar system orbit the sun.
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They got their initial velocity when the solar
system formed out of spinning gas, and since
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there’s nothing in space to stop them from
moving, they’ll keep moving.
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Hey, that’s Newton’s first Law.
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The sun is so massive, that the force of gravity
keeps pulling the planets towards the sun,
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but the planets are fast enough to essentially
fall towards the sun but miss it, and this
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goes on forever, creating a round orbit.
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Actually, that’s kind of a lie.
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Most orbits orbits are not perfectly round
but more egg-shaped and pluto’s orbit is
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just…a complete mess.
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But you get the idea.
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In this case, the gravity is what we call
a centripetal force.
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One thing many people confuse is mass and
weight, and no, they are not the same.
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Mass tells you how much of this blob there
is, and Weight is the force of Gravity the
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blob would feel.
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To make things clear, your mass would be the
same on the earth and on the moon, but the
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“weight” you would perceive, is different,
because the moon has a weaker gravitational
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pull, meaning, a weaker force acting on your
mass.
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So really, you’re not overweight, you’re
just on the wrong planet.
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Aight, enough about Newton, let’s break
some stuff.
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If you ever dropped your phone, it might look
like this: What the hell ground, why’d you
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do that?
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The answer is Energy.
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You know, the thing kids have after eating
gummy bears.
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Energy has the unit Joule.
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And it’s not like Force, it’s doesn’t
have a direction, it’s just a number, that’s
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kind of chilling there, as a property of a
thing.
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You see, there’s two main kinds of energy:
Kinetic energy, and potential energy.
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In plain English, energy of movement, and
stored energy due to some circumstance.
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For example, when you held your phone, it
stored gravitational potential energy, due
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to being held above the ground, at a certain
height.
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Once you dropped it, the potential energy
was converted into kinetic energy, as the
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phone fell.
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Then it smashed into the ground, and the phone
absorbed some of the energy making the screen
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go boom.
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Work is defined as Force applied over distance.
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For example:
If you lift an apple by 1 meter, you would
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have done about 1 Joule of work.
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This happened by converting chemical energy
stored in your body to gravitational potential
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energy stored in the apple.
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As you may have noticed, Energy and Work have
the same unit “Joule”.
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So they must be the same thing?
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Uhhh, No.
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Energy is the total amount of work that a
thing could possibly do.
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Work is just the stuff that actually happened
and required energy.
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You know, force applied over a distance, which
most often implies converting energy from
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one form to another.
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If you try to lift a weight that’s too heavy
for you, you’d feel like that took a bunch
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of work, right?
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Well, yes, but your feelings are invalid in
the face of Physics!
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Mathematically, no work has been done!
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Because, work is a force applied over a distance.
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And since you didn’t move the weight at
all, no distance means no work.
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The key thing to remember about energy is
that it cannot be created or destroyed, only
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converted.
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Aka, the conservation of energy.
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Okay, but a car, that’s moving has kinetic
energy.
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When the car stops, assuming the car doesn’t
smash into a wall, where does that energy
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go?
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When you apply the brakes, there’s friction
between the brakes and the wheels, causing
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the car to slow down, and creating heat as
a byproduct.
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That heat is then dissipated to the surrounding
air.
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And that makes the molecules in the air move
faster.
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And things that move have kinetic energy.
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So ultimately, the kinetic energy is transferred
from the car to the air.
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With this knowledge, we can define that Temperature
is just the average kinetic energy of atoms
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in a system.
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You see, all atoms, not just molecules in
the air, wiggle.
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Like this.
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The faster they move, the hotter things get.
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That is temperature.
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All that talk about hot stuff, I think it’s
time we talk about Thermodynamics.
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It tells us that jumping in lava is probably
a bad idea, but more importantly, the absolute
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mess that is entropy.
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Literally, it tells you how much disorder
there is in a system, indicating the number
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of possible states a system can be in.
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For example, get an ice cube, no not that
one, yes that’s perfect, and put it in the
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sun.
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The sun will obliterate the ice cube and turn
it into water.
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Looking at the structure of ice and water,
we can see that ice is more neatly organized
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than water, which just kind of goes all over
the place.
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Also, the water could look like this, or this,
or even this, but the ice will always look
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a little something like this.
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In total, the system went from low entropy
to high entropy, meaning more disorder and
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more possible microstates.
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This trend applies everything.
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The whole universe is on an unstoppable path
to higher entropy.
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It’s also the reason why time seems to go
only forwards, or at least, that’s what
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we believe at this point.
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Practically, entropy tells us that some forms
of energy are more useful for doing work than
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others.
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Burn some gasoline, and your car will move,
spitting out heat and gas.
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That heat and gas is pretty much gasoline,
just in the form of higher entropy.
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And as you can imagine, this stuff won’t
really make your car move, and the gas won’t
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spontaneously turn back into liquid gasoline.
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Meaning, the form of gasoline with lower entropy
is more useful for doing work.
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Okay, but if you put some water in the freezer,
will it not decrease in entropy?
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Yes, BUT the fridge is not an isolated system
and will heat up the room more than it will
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cool down the water, increasing the total
entropy.
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Wanna see some magic?
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Woah, what just happened?
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Some electrons apparently moved through some
wires and let there be light.
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What is going on here?
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Objects have a fancy something called a charge.
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It can be positive or negative.
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Or, if you have the same amount of both, an
object is neutral.
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Electrons have a single negative charge.
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The flow of electrons is called electric current.
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To describe it, we use three parameters: Current,
Voltage, and Resistance.
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Current is the amount of electrons passing
through a wire in a given amount of time,
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Voltage is what pushes the electrons to move,
but simply put, it’s a difference in electric
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potential, so you can imagine it as a slope
that goes from high potential to low potential,
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where the flow of current goes downhill, and
resistance is pretty self explanatory.
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This is Coulomb’s Law.
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Wait a minute, this is just Newton’s Law
of Gravitation in disguise!
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This tells us that electric charges attract
each other in a similar way masses do.
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Opposites want to cuddle, while like charges
literally couldn’t think of a more disgusting
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thing than to be with one another.
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These four equations explain pretty much all
of electromagnetism.
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But don’t be scared just because they look
scary!
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I mean, yeah, they do, but it’s simpler
than it seems at first.
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The first one states that if there is an electric
charge, there will be an Electric field, or
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this big E, emerging form it.
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Add another and you have an electrostatic
field.
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These lines tell us in which direction a charged
particle would feel a force at any given point.
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The second one tells us the same for magnetic
fields, AND, even though electric charges
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are cool and can be alone, magnetic poles,
are not.
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They’re very lonely.
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There will always be a north pole together
with a south pole, and a single pole can never
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be alone.
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Okay now here’s where things get kind of
freaky.
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You know how electric charges only act on
other charges, and magnets only affect other
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magnets?
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Well that’s only true if they’re not moving.
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The third and fourth maxwell equations tell
us that a moving magnet creates an electric
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field, and a moving charge or electric field
creates a magnetic field.
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One consequence of this is that current can
seemingly come “out of nowhere” by moving
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a magnet next to a conductor.
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The moving magnet creates and electric field,
which makes the electrons inside the conductors
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go crazy.
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That is called induction.
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It’s the reason why your phone charges when
you put in on the charging pad, even though
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it is not directly connected to a cable.
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In other words, electric and magnetic fields
are so tightly linked that they are the two
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parts of the same bigger thing.
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Let’s say we have a charge.
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Since it doesn’t move, it has a static electric
field.
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If we accelerate the charge, there will be
a magnetic field around it.
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That magnetic field interacts with the electric
field, which again changes the magnetic field,
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and this is a sort of chain reaction that
makes the electromagnetic field radiate outwards
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into space as an electromagnetic wave.
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Depending on the frequency, the human eye
can actually see this, it’s called light,
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but most of the spectrum is invisible to the
human eye and is used for things such as Bluetooth,
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wireless charging and confusing human apes
into thinking magic is real.
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Hey, can we go back to the water and look
at those molecules?
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Yeah, those, what are they made of?
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The molecules are made of Atoms.
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Atoms are made of a core and some electrons.
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The core is made of protons and neutrons,
both of which are made of quarks.
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They’re strange yet charming, from up top
down to the bottom.
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Oh yeah there’s some more stuff, like for
example the overweight brothers of the electron.
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All of this together makes up the standard
model, which we believe to be the smallest
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things in the universe.
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At least that’s the excuse we have for not
knowing what quarks are made of.
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Fun Fact!
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Depending on the number of protons in the
core, you get different elements.
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Depending on the number of Neutrons in the
core, you get different Isotopes of the same
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element.
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Most of which are a little overweight and
very unstable.
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So they fall apart, into smaller atoms.
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That releases ionizing radiation.
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Not so fun fact: That stuff will kill you.
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Do not play with radioactive atoms.
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If you have a large group of atoms, you can
predict when half of those will have fallen
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apart.
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That’s the halflife.
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Depending on how unstable an isotope is, it
will survive a certain amount of time.
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Some don’t want to live, some really don’t
want to live, but some will live far longer
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than you probably will.
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Oh yeah, did I mention that light is like
the fastest thing in the universe?
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To be exact, 299, 792, 458 meters per second
in a vacuum.
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“That is pretty fast” said everyone.
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Also, “Light is a wave” said everyone.
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Why?
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If you shoot it through two teeny tiny slits
it creates a fancy pattern due to interference,
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which is just a wave thing.
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You see, when two waves cross, they can add
up, or cancel each other out.
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These gaps, are the spots where they cancel
each other out, so in this case, light behaves
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like a wave.
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“Nah, screw that, everything you know is
wrong” said Albert Einstein, probably smoking
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crack, after hearing about the photoelectric
effect and discovering that light comes in
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tiny packets called photons.
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I sure hope that doesn’t unravel a whole
new area of phyiscs, haha.
00:10:11
“Anyway” he said, as he continued to casually
drop an absolute bomb on the entire field
00:10:16
of physics with his theory of relativity:
He assumed the speed of light is constant
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because it arises from two other constants.
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He also assumed the laws of physics are the
same for everyone, regardless if moving or
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at rest.
00:10:27
Now think about it: If two people turn on
a flashlight, but one person is standing still,
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while the other person is on a moving train,
wouldn’t the person standing still see the
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other person’s light as going faster than
the speed of light?
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The reality is: NO!
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It would be the same as their own flashlight.
00:10:41
That’s impossible, except if time passes
slower for that person from the perspective
00:10:44
of this person.
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In other words, if the speed of light is constant,
time must be relative.
00:10:49
Also, gravity is not actually a Force, sorry
Newton, but rather a consequence of masses
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bending spacetime.
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Einstein thought that the universe is a mesh
of space and time, and anything with a mass
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bends this fabric.
00:11:00
Also, all objects move freely on a straight
line when moving through space.
00:11:04
Gravitation is simply the result of objects
following these bent lines, which appear straight
00:11:07
to them.
00:11:08
If you have a hard time understanding this,
you can imagine two people on earth, walking
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in parallel, straight lines.
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On a short distance, the straight lines will
never meet.
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Now imagine one standing on the east cost,
and one the west coast of the US.
00:11:16
If they both walk north, eventually, they
will meet at the north pole.
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Because of the curvature of the earth, they
ended up at the same point even though they
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both walked “straight” relative to themselves.
00:11:25
“Oh yeah by the way Energy and mass are
kind of the same thing” he added, which
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explains why atom bombs are so frickin powerful.
00:11:31
According to this formula, even just tiny
atoms can release a humongous amount of energy
00:11:35
by giving up just a fraction of their mass
during fission.
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What is Fission?
00:11:40
It’s the same thing Oppenheimer used to
make this thing go boom.
00:11:42
You see, there’s two main ways to gain energy
from changing nuclei: Fission and Fusion.
00:11:46
Fission aims to split the nucleus of an atom
into two or more smaller nuclei, which is
00:11:50
most often achieved by blasting the core with
neutrons.
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Fusion is the opposite, where you combine
two smaller nuclei to get one bigger one.
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The energy came from something we call a “mass
defect” where the resulting nucleus is lighter
00:12:01
than the starting nuclei.
00:12:02
This “missing” mass is what was converted
to energy during Fusion.
00:12:06
Fission and Fusion are cool, but you have
got to be careful or you might just blow up
00:12:09
the planet.
00:12:10
That totally didn’t almost happen before…multiple
times.
00:12:13
Hey remember when Einstein said light is a
particle?
00:12:16
He accidentally discovered a whole new field
of physics which he though is just a giant
00:12:20
hoax: Quantum Mechanics.
00:12:21
This stuff is crazy.
00:12:23
Another german guy called Max Planck said
“yes, Einstein, you’re right.
00:12:26
Light does come in tiny packets.
00:12:27
Actually, all energy comes in tiny packets”.
00:12:30
Or “Quanta”.
00:12:31
He is the daddy of Quantum Mechanics.
00:12:32
Wanna know where an electron is inside an
atom?
00:12:33
It’s here!
00:12:34
And there!
00:12:35
And everywhere, at the same time, actually!
00:12:36
That’s a superposition.
00:12:37
It’s not in one state, it’s in multiple
states at once - at least until you measure
00:12:41
it.
00:12:42
Then it chooses one cozy spot to be in.
00:12:44
Schrödinger gave us an equation that gives
you a probabilistic model of where you can
00:12:47
find it if you were to measure.
00:12:49
You can imagine this as a cloud, and the denser
it is, the more likely it is for an electron
00:12:53
to be there.
00:12:54
But still, where exactly it will end up once
you measure it, is random.
00:12:57
Speaking of observing particles, they’re
also super sensitive about their private data.
00:13:01
Look at these two images of a flying ball:
in one, you can clearly see where the ball
00:13:04
is, but not in which direction it’s moving,
and in the other you can see where it’s
00:13:08
moving and approximately how fast, but not
where exactly it is at the moment.
00:13:12
That is essentially Heisenberg’s uncertainty
principle: You can never know both the exact
00:13:16
position and the exact speed of a quantum
particle at the same time.
00:13:19
Okay, let’s recap, a small thing can be
a particle and a wave at the same time, and
00:13:22
when we try to look at them, weird stuff happens.
00:13:24
But you know what, it gets even weirder.
00:13:27
Think back to the double slit experiment:
We know that a light beam acts as a bunch
00:13:30
of waves and we get interference.
00:13:31
But here’s the weird thing: Even if you
send individual photons, after sending enough
00:13:36
of them and detecting where they end up, you
get interference.
00:13:38
Like, how can that be?
00:13:40
What did a single particle interfere with?
00:13:42
Well, we think it interfered with itself,
because it acted as a wave and went through
00:13:45
both slits at the same time.
00:13:48
That’s a superposition.
00:13:49
“Okay, well let’s just measure which slit
it goes through”.
00:13:51
Uh, yeah, that’s not going to happen.
00:13:53
Once you start measuring which slit the photon
goes through, it stops acting like a wave
00:13:56
and the interference pattern disappears, as
every particle chooses just one of the slits
00:14:00
to go through.
00:14:01
Sounds kinda suspicious to me.
00:14:03
Anyways, all this knowledge is going to cost
you one subscribe and a thumbs up, thank you
00:14:07
very much, and you can decide if maybe you’d
want to tip with a comment, perhaps?
