Full transcript
0:00here we can see the orbital data for the
0:02various planets in our solar system as
0:04well as an asteroid actually borer talk
0:06more about Cirrus later one thing worth
0:09mentioning is that the centricity z' of
0:11these planets remember is quite low with
0:13mercury being the one kind of exception
0:15this lowest centricity means again that
0:18the orbits are almost circular they are
0:21ellipses but there's so close to being
0:24circular and we did define previously
0:27any idea of pure Hylian and aphelion
0:29remember Fillion was the farthest away
0:31when I planet would get from the Sun and
0:34perihelion the closest well if we were
0:37looking at say a moon orbiting a planet
0:40or a satellite something we've put into
0:44space if a satellite was orbiting a
0:46planet then we use the terms perigee and
0:49Apogee perigee being the closest Apogee
0:52being the farthest away again a four-way
0:55so Apogee the furthest that this moon or
0:58satellite would get from the planet so
1:01similar terms but we can also look at
1:05these orbits in terms of plots the you
1:08can see most of the actual planets that
1:11we put on here like Jupiter the Sun
1:13again they don't look very circular they
1:15all tend to have be oriented more or
1:18less with the Sun in the center again
1:20not quite because it's an ellipse so at
1:21a focus we can see they're all very
1:24uniform orbits many of these other
1:28objects we're looking at are actually
1:30things like asteroids or comets comets
1:35can have very eccentric orbits look more
1:39at this later but it means that they're
1:41spending a lot of their time away from
1:43the Sun and then speed up a lot when
1:46they get close to the Sun so we will
1:48look at comets and asteroids and
1:50everything meteoroids later on but you
1:53can see already their orbits are a lot
1:55more eccentric than the planets now
1:59let's talk more about actually launching
2:02satellites into space because this is
2:04something obviously that's become quite
2:06huge with humanity right now I mean we
2:09have tons of satellites in space we're
2:11also trying to launch missions to other
2:13planets other moons to study our solar
2:15system well what we need to do is
2:19consider the idea of scape speed we've
2:21been talking about gravity and if you
2:23were to launch something or throw
2:24something on earth gravity pulls it back
2:27down well you can see this image is
2:29showing if you launched it a little bit
2:31harder it goes a little bit further well
2:34we can actually define an escape speed
2:37the escape speed is how fast something
2:40has to be traveling to escape the
2:43gravitational pull of the earth and
2:45actually make it into space and actually
2:47go out and start exploring and it's
2:49approximately 11 kilometers a second so
2:52if we launch a rocket 11 clowns per
2:54second it should make it out into space
2:57and actually be able to explore in fact
2:59I mean anything if I launched a potato
3:00at 11 kilometers a second you should go
3:02out into space and go Bowlby forth where
3:05no potatoes gone before well actually
3:07probably been tons of potatoes on
3:09missions before who knows not too sure
3:11on that though so don't quote me many
3:13lots of potatoes in space but any escape
3:16speed how fast you'd have to launch
3:18something to get it off the planet now
3:20technically we want to put into orbit we
3:22might not have to launch it that fast
3:24cuz we're not actually trying to escape
3:25the pole again if you can actually get
3:28it into an orbit then it's constantly
3:31falling towards the planet orbiting
3:33around it we have that free fall
3:35condition so it's falling around the
3:37planet constantly being pulled by the
3:39gravitational pull of the planet towards
3:42it and just because of its inertia
3:43falling around of course I did mention
3:46before depending on what part of the
3:49atmosphere we launch it because there's
3:50different orbital paths some lower some
3:53higher partly to avoid cluttering our
3:57skies too much but if it's lower
4:00sometimes our atmosphere can actually
4:01kind of swell and that can cause
4:03friction and cause these eventually over
4:06time to start to degrade their orbits
4:08and fall back towards Earth so it is
4:11important that we keep track of these
4:12things so that if they do come back down
4:14we can guide where they land likely into
4:17an ocean to be safe but one thing we
4:21kind of ignored is the gravitational
4:25influences of all the forces
4:27when we looked at Newton's second law I
4:29said we have to consider all of the net
4:30forces acting on an object to figure out
4:32its acceleration and we talked about the
4:35gravitational law between two masses
4:37well the thing is sure earth is orbiting
4:42around the Sun and the gravitational
4:45pull of the Sun pulls on us and
4:47technically we pull in the Sun but the
4:50moon is also pulling on us and so are
4:53all the other planets and these all can
4:56cause minor gravitational poles and so
4:59the acceleration we have our motion
5:01through space actually depends on all of
5:04these forces and this becomes an
5:06incredibly difficult process even if
5:09we're just talking about all the planets
5:11if we have to summarize the other seven
5:13planets how they're acting on us and the
5:15Sun and our Moon and consider them at
5:18all of the different times because
5:19they're moving too and thus they're
5:21distance from us is constantly changing
5:23that's all law to math thankfully NASA
5:27has tons of supercomputers but this is
5:29the kind of work that has to be done by
5:31computers used to be they try to
5:32calculate these things by hand and kudos
5:35to those people and incredible amounts
5:37of work but thank me we have computers
5:39that can try and map this out to
5:41actually determine the movement of
5:43bodies through space but again there
5:47wasn't always computers around to do
5:49this or that wasn't powerful enough
5:50computers to do this and actually one of
5:53the early successes of this was related
5:57to the discovery of Neptune Neptune
6:01remember early on we didn't know about
6:03all the planets some of them were far
6:04enough and faint enough that we couldn't
6:06see them well even when they had the
6:10they had looked at the orbit of Uranus
6:13or Uranus depending on how you want to
6:15say it when they looked at it its orbit
6:18wasn't what we predicted based on the
6:23different foremost form Kepler and
6:25looking at Newton and figuring out how
6:27it should be impacted there is a slight
6:30perturbation a slight discrepancy in its
6:34movement and so they actually started
6:37realizing this might be because of an
6:40their planet and there's actually two
6:42different people who did the math on
6:43this and kind of worked it out at the
6:45same time and so they're usually both
6:47credited with the discovery and I mean
6:48other people end up actually finding it
6:50but it was based on the science it was
6:53based on our understanding of mechanics
6:55and how this planet should be moving
6:59that we realized Neptune must be out
7:02there there must be another planet
7:04causing this weird change in the path
7:07and you might have heard things about
7:10Planet 9 that they think there might be
7:12another one out there things like that
7:13are from looking at the difference in
7:16the orbit of something when we look at
7:18the orbit and see weight is not behaving
7:20the way it should some other
7:22gravitational influence must be acting
7:24on it so this was a great success of our
7:28understanding of gravity and orbits and
7:30so we were able to find another planet