hey it's Kaleigh welcome to gravity and orbits we're going to explore gravity's
part and keeping the earth in orbit around the Sun gravity is a force that
everyone and everything experiences on earth every day it's the force that
keeps us from floating around and keeps the satellites that power our TVs and
our phones in orbit around the earth but most importantly gravity keeps the earth
in orbit around the Sun and this is what gives us life Earth's orbit around the
Sun is what gives our planet the perfect amount of energy to produce life as we
know it remember this guy Galileo he's the guys in the Leaning Tower of
Pisa experiment but he was also the very first scientist to study the night sky
with a telescope but while Galileo was observing the night sky with his
telescope he made one big mistake about gravity he believed that gravity only
existed on earth luckily for Galileo and for all of us scientist Sir Isaac Newton
came around and corrected Galileo he discovered that gravity exists
everywhere in space but really everywhere in space how can that be
did he did he think astronauts would float around and speak space what about
being weightless on the moon it's actually quite interesting when we see
movies or clips from space it looks like the astronauts are weightless but really
what they are experiencing is something called constant freefall constant
freefall means that your body is accelerating at the acceleration due to
gravity or little G we know that this is 9.8 meters per second squared on earth
it's the same feeling a bungee jumper has
jump off a tall bridge up until the bungee catches them but how does the
force of gravity affect our planet recall that our solar system has eight
planets can you name them all plus there is a ton of moons and asteroids you can
learn more about the solar system in the astronomy series that we have on this
website but how does Earth stay in orbit let's first define what an orbit is an
orbit is the path an object takes to revolve or go around another object with
mass due to gravity but what does the gravity have to do with it well remember
this equation for the force of gravity between two objects that are not
touching there's an attraction between the Sun and the earth that is trying to
pull them together if there were no gravity the earth would just fly right
on by the Sun there would be nothing to attract the earth towards the Sun and
keep it in orbit but if there is a force pulling the Sun and the earth towards
each other why doesn't the earth just crash into the Sun the earth has a
velocity that is moving perpendicular to the Sun but as the earth passes by the
Sun the earth feels the gravitational attraction and is pulled towards the Sun
is the combination of the Earth's perpendicular velocity and the
gravitational force towards the Sun that keeps the earth in orbit but what
factors would make the earth crash into the Sun if we made the force of gravity
between the Earth and the Sun larger the earth would crash into the Sun but what
would we have to change to make the force of gravity larger we would have to
give the Sun or the earth more mass and lucky for us
mass cannot be created or destroyed so we never have to worry about the earth
crashing into the Sun now we're going to play a game to explore all the
possibilities of orbit with different masses let's play here we are in the
gravity in orbits lab we're going to do the example of the Sun and the earth
together you can do any of these when you play include the moon just do the
earth in the moon or even try earth and a satellite but we'll stick with this
one for now so what you can do here is you can change the mass of our Sun so we
can either make it smaller or make it way bigger this is what it is in real
time right now or we can change planet Earth's mass we can make it smaller than
it really is what it actually is or we can increase the mass so another fun
thing to do is we can turn on our gravity force arrows so we can see from
the centre of the earth of the center of the Sun there is a gravitational
attraction of both of these objects with mass what do you think will happen to
those force arrows if I increase the mass of the Sun that's right they're
gonna get bigger so but this is just following the law of universal
gravitation and if I change Earth's mass let's say I'm going to make Earth's mass
less those force arrows get smaller so let's just go to what we really see in
our universe today so making the Sun and the earth of the masses that they have
so this is the actual gravitational force that they have and let's say let's
turn on the velocity arrow so you can see how it's always perpendicular to the
orbit and we're gonna run the summation so now you can see these force arrows
keeps earth attracted to the Sun maintains that orbit shape while this
velocity is always trying to pull the earth perpendicular
away from the Sun so that's what our universe actually looks like but let's
see what happens now I'm going to increase Earth's mass what do you think
will happen with this increased force between them
we can turn on our path to help us see
and if I increase it even more you'll see those force arrows got even bigger
now they're passing each other and what do you think is happening to my orbit it
looks like it's getting smaller so orbit would get closer together what would
happen if I increased the sun's mass
those four zeros are so big looks catastrophic pretty cool huh so
I'm gonna give you a chance to play around with all of these things you can
turn the path on and off you can turn the velocity arrow on and off you can
even turn the gravity arrows on and off and you can just visualize how the Sun
and the earth are interacting so have fun and give this game a try and try all
the different ones as well and remember to always be clever