What is an orbit? How do orbits work? We will discuss how low earth orbit can be achieved by launching satellites in space using high horizontal velocity during launch.

Launching satellites in orbit is possible by understanding Newton's theory of gravity and how Einstein refined the ideas of how gravity works and the definition of gravity. Finally, we will discuss zero gravity in low earth orbit and how satellites and astronauts float in space.

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Hello welcome to get smart in science.
here we're going to explain what an
orbit is and i have a few key questions
that i want to point out to you that
we're going to answer here and the goal
is to take something seemingly
complicated and break it down so that
it's understandable and only a few
minutes.

First thing we're going to talk
about it how it is in orbit work we're
going to talk about how orbits can exist
and go on and on forever seemingly
without stopping.

We're going to talk about why astronauts
seem to be weightless when they're in
orbit and how does the spacecraft enter
in orbit and stay the there and along the
way we'll talk a little bit about
history of orbits and kind of the
evolution of those ideas.

So the first
thing here is we all know that we have
the Sun at the center of the solar
system. Right that's what we know today
in the 21st century and the planets go
around the Sun so here we have mercury
venus here's earth with the moon there
Mars Jupiter Saturn Uranus Neptune and
Pluto.

Now
if you zoom in even further any
spacecraft satellites, space station
anything like that that's in orbit
around the Earth is going around and
around the earth itself. So just like the
moon goes around and around the earth
all satellites whether their weather
satellites space shuttle space stations
are always in motion are always going
around the earth in low earth orbit.

Later in 1687 the famous Isaac Newton
which I know you've heard of who lived
between these years and two 1726
published his very famous law of
gravitation which again we still use
today and the big thing about it i'm
going to talk a little bit more about
what his law of gravitation really is
but the takeaway from it is this right
here
he basically used his law of gravity to
correctly predict using math that the
orbit of the planets always follow an
elliptical path.

so whereas Kepler looked
at the night sky and figured out that the
planets must be moving in ellipses Isaac
Newton developed a theory of gravity and
an equation that describes gravitational
force and he used that equation to again
predict that all the planets should move
that way so he knew he was on the right
path and that his law of gravity must be
pretty close to being correct because he
used his law of gravity to predict how
the planets actually move in real life.

now here's where things get interesting
we're going to take a few minutes to
talk a little bit about Newton's law of
gravity now there's a lot of stuff on
the page here so don't worry too much
about absorbing it all at once let's
take it one step at a time
basically what Newton said is that
everything that has mass in the universe
whether it's a planet or a peanut or a
tree they all exert a gravitational
force on everything else in the universe
and that gravitational force is
calculated or can be calculated by this
equation.

Now I'm not going to do a bunch
of calculations here but i do want you
to know that there's an equation that
exists that Isaac Newton developed and
this is basically what it is so the
illustration here you can see
in one just means mass number one so
this could for instance be the earth and
this could for instance be a space
station or a moon let's call it the moon.

that's we all know going around the
earth but forget about the fact that its
orbiting Earth it's just some moon out
there right so what Newton's laws
basically saying gravitational laws
saying that there's a force that exists
between these two things just because
they have mass and just because we live
in this universe where gravity exists.

so
if you look at it here this mass here is
pulling on this moon with some force we
call it f it's pulling at this
direction right because gravitational
force is attractive and then of course
we have this moon here also pulling on
the earth so gravity always kind of
works in pairs like that each body is
pulling on the other one.

right so let's
go down this list and i'll talk a little
bit more about the equation Newton's law
of gravity basically says that all
objects with mass attract each other.

everything whether it's a peanut a
bumblebee a bulldozer a planet a black
hole if it has mass it's always has this
attractive force we call the
gravitational force number to gravity is
always attractive that means that
gravity never repulses we never have
repelling bodies pushing away from each other.

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