Hello and welcome to episode three of Winners and Losers. Now it was way back in 2014 that
I started this series, and lot of people have requested that I continue it, so I decided
to do just that…so thank you for to everyone who suggested the topic: planets. Well, the
eight planets our solar system anyway. I will not be including Pluto because it’s a dwarf
planet which is part of the Kuiper Belt.
Anyway, doing planets as a topic for Winners and Losers is quite a bit different from episodes
one and two, because most of the categories I looked at… don’t really apply here.
Anything involving population or the economy, for example, are only applicable to Earth.
Now one thing I can do, same as the first two episodes, is start by looking at SIZE.
Now the planets can be grouped into three categories: terrestrial planets, gas giants,
and ice giants, with the largest obviously being Jupiter. So just how big is Jupiter?
Well, Jupiter has a diameter of nearly 143,000 km, about 11 times that of Earth.
Its equatorial circumference is 439,264 km, this is a greater distance from the Earth
to the Moon, which took the Apollo 11 spaceflight more than three days to complete in each direction.
If it were somehow possible to fly a commercial airliner jet around the planet without stopping,
it would take 488 hours to circumnavigate. That’s more than 20 days!
In a parallel universe where Earth were the size of Jupiter… the largest country, Russia,
would be more than 2 billion square kilometres, or about 4 times the surface area of the actual
Earth. Vatican City on Jupiter would be… well, actually still pretty small, at just
55 km2, and actually still smaller than the other one of Italy’s enclaved countries,
San Marino, at 61 km2. The small island nation of Haiti would be larger than Earth’s India,
at more than 3.3 million square kilometres.
Driving from Land’s End to John O’Groats, the two extreme points on the island of Great
Britain, would take 176 hours to drive by car. A flight across the Atlantic from London
to New York would take 77 hours!
If this imaginary planet had the same population density as Earth, its population would be
896 billion. Now of course, Earth actually has a pretty low population density, what
with all the ocean and fairly empty countries like Canada and Australia. So what if this
planet had population of somewhere like... Monaco, one of the most densely populated
areas in the world. Well… such an absurd planet would have a population of 1.3 quadrillion.
Or about the population of 180 thousand Earths.
Looking at the planets by volume, and comparing the largest and smallest, Jupiter and Mercury.
Jupiter is 23 and a half thousand times the volume of Mercury. If we visualise this in
terms of liquid… if Mercury were this tiny serving spoon of water, Jupiter would nearly
60 litres.
Not only is Jupiter huge though, it’s also massive. And by that I’m referring to its
mass. Now the list of planets by size and by mass is almost in the same order, except
for one difference. Uranus and Neptune in 3rd and 4th places are switched. This means
that although Uranus is larger, Neptune is more massive. This is due to it having a higher
density than its neighbouring planet.
Once again, Jupiter is the most massive while Mercury is the least massive. In fact, Jupiter
is so massive, that it has about 2.5 times the mass of all the other seven planets combined.
But despite being so massive, it’s almost nothing compared to the Sun. The Sun makes
up 99.86% of the mass of solar system. Jupiter is about 1000 times less massive.
Looking at the opposite end of the spectrum, at the smallest and least massive planet in
the solar system, Mercury. The closest planet to the sun has a circumference of 15,329 km.
This is almost exactly the same distance as the world’s longest non-stop commercial
flight in history: Singapore Airlines flight 21 from Newark to Singapore, in an Airbus
A340, taking just under 19 hours.
So if Earth were the size of Mercury, it would actually be possible to circumnavigate the
entire planet in a commercial passenger airliner jet without stopping.
The drive from Land’s End to John O’Groats would take just 6 hours, and that flight across
the Atlantic… just 2 hours and 50 minutes.
The population of said fictional planet would be just over the 1 billion mark. Mercury’s
Russia would be 2.5 million km2, still pretty big to fair, but 3 orders of magnitude smaller
than Jupiter’s Russia. Now Mercury’s Vatican City, as you can imagine, would be pretty
tiny, at just 0.065 km2, or 65,000 m2. That’s about 16 acres… or between 8 and 10 football
pitches, depending on the exact dimensions of the pitch. You could fit 52 of these Mercurian
Vatican Cities into New York City’s Central Park.
Ok back to reality now, with all the planets back to the their actual sizes. Of course,
any image like this which shows the planets with their relative sizes to scale, it’s
important to remember that the distances between them, are not.
This is what the distances between the planets look like, but now the sizes are not to scale.
Attempting to show the solar system with size and distance to scale on a YouTube video,
is literally impossible, because all of the planets would be smaller than the size of
single pixel. This is due to the distances between the planets being so vast, relative
to the actual size of the planets. For example, the distance from the Sun to the Earth, is
12 thousand times the diameter of the Earth.
In fact, attempting to make a scale model of the solar system in any context, is extremely
challenging. However, despite this, it has been done several times. The world’s largest
scale model of the solar system is in Sweden, and spans the length of the entire country.
The Sun is represented by an indoor arena called the Ericsson Globe, in Stockholm. An
acrylic model of Neptune with a diameter of 2.5 meters, is located in small town some
229 km away.
Alright, that’s enough about size and mass, let’s move on and look at the planets’
rotational and orbital periods. That is, the time it takes each planet to rotate around
its own axis and to orbit the Sun.
So here is a list of the eight planets with their days and years. Now a couple of things
might jump out at you for being a little… odd. The first thing is you’ve probably
noticed that a day on Earth is equal to 0.997 Earth days… how does that make sense?
Well, for this, we need to understand the difference between a solar day and sidereal
day. All the numbers in this table represent sidereal days, ie how long it takes the planets
to complete one revolution around its own axis. A solar day, however, is how long it
takes the Sun to reach the same point in sky relative to the position of the planet. On
Earth, this is our day, this is exactly 24 hours, by definition.
However, a sidereal day is actually about 4 minutes shorter. The reason for this, is
that the Earth has to spin very slightly more than 360 degrees around its axis for the Sun
to be in the same position, due to the Earth having moved about 1 degree around its orbit.
This extra rotation is how we get the minor difference between a solar day and the sidereal
day.
The difference is even more minor for the gas and ice giants, whose rotational periods
are very fast and orbital periods are very slow, meaning that the difference is negligible.
However, for the two closest planets to the Sun, the difference is quite considerable.
Now going back to the table again, and you might have noticed Venus. A day on Venus is
actually longer than its year. It takes more time for Venus to complete one revolution
around its own axis than it does to complete one orbit around the Sun. Of course, that
is referring to a sidereal day. A solar day on Venus is about 116 Earth days.
What makes Venus especially interesting, is that it is the only planet in the solar system
that rotates clockwise when viewed from above, known as retrograde rotation. That is, it
rotates the opposite way from Earth. This means that on Venus, the Sun would rise in
the west and set in the east.
Going back to the initial table one more time, and you might notice the length of the years
related to the planet’s distance to the Sun. You’ll notice that the further away
a planet is from the Sun, the longer its year is. The reason for this, is Kepler’s 3rd
law planetary of motion…. which states that: the square of the orbital period of a planet
is proportional to the cube of the semi-major axis of its orbit. The semi-major axis, in
simple terms, can be thought of as the “long radius” of an ellipse.
Using P as “Earth years” and a as Astronomical Units, the distance from the Sun to the Earth,
the equation is simply - P squared equals a cubed.
Plotted on a graph, we can see the relationship between distance from the sun and orbital
period of all the planets.
Now since we know all of the planets’ orbital periods, we could therefore work out how old
a person would be on other planets compared to on Earth. A year is the time it takes a
planet to complete one orbit around the Sun, so for example, a person born and raised on
Mars, on let’s say the 1st of January 1990, would be about 15 years old today. On Mercury,
116 years old! On Jupiter, less than 2 and a half! And on the other 3 giant planets,
such a person would have yet to even complete a single year… well, unless you’re watching
this video after the 17th of June, 2019, which is when their first birthday on Saturn would
be.
Now, moving on to the next category: moons.
It probably won’t surprise you to learn that the planet with the most moons is Jupiter.
It has has even been referred to by some as its own mini solar system with so many natural
satellites. Now, just how many moons Jupiter actually has, is more difficult than you might
think. The latest number is 69 moons, with two more having been discovered just this
year. So the number of moons that Jupiter actually has may be different depending on
when you’re watching this video.
The four “main” moons of Jupiter are: Io, Europa, Ganymede, and Callisto, collectively
known as the Galilean moons, are by far the most massive of Jupiter’s moons. In fact,
their combined masses, make up 99.997% of the total mass of Jupiter’s moons.
Now, Ganymede, is the largest and most massive moon in the entire solar system, having a
radius about 40% that of Earth, and is actually larger than the planet Mercury.
In fact, Mercury doesn’t even make the top 10 for largest objects in the solar system.
Saturn also has a moon larger than Mercury, called Titan.
The largest moons in the solar system are mostly dominated by the Galilean moons of
Jupiter, but Earth’s moon actually comes in at number 5, with Neptune’s largest moon
coming at number 7. Although our own moon is only the 5th largest, it’s actually the
largest proportional to the planet that it orbits.
Anyway, like I said, Jupiter obviously has the most moons, and the largest moon, Saturn
comes in at close second with 62 moons, and also the 2nd largest moon, then the two ice
giants in 3rd and 4th. There are only 3 moons among the 4 terrestrial planets. Mars has
two and of course Earth has just one. Venus and Mercury have none.
To end this video, I’m going to look at axial tilt. This is the angle of difference
between a planet’s equator and its orbital plane. You may already be aware that Earth
is tilted at about a 23 degree angle. This is thought to have been caused by a giant
impact about 4 and a billion years ago, which tilted the Earth and the debris from the collision
became the moon. This axial tilt on Earth is what causes us to have different seasons.
Now Earth is not all unique in this respect. The planets can be grouped into three different
categories when it comes to axial tilt. Firstly, there’s Mercury and Jupiter, these are the
most “normal” planets, with only a very slight tilt.
Then next we have the planets that have a significant tilt, like Earth. So here we have
Earth, Mars, Saturn, and Neptune, which all have a 20-something degree angle. Then finally
we have the odd-ball planets - Venus and Uranus. Both of which are… pretty strange.
Earlier in the video I mentioned that Venus rotates clockwise and is the only planet to
do so. Its axial tilt is 177.4 degrees relative to its orbit, which can also be thought of
as 2.6 degrees retrograde. Basically everything in the solar system rotates and orbits anticlockwise,
including the Sun… so Venus certainly “should” rotate anticlockwise. It’s not exactly known
why Venus is the way it is. It’s possible that this was caused by some kind of cosmic
collision, similar to Earth, or more recent hypotheses have suggested that the planet’s
rotation may have been slowed and eventually reversed due to tidal effects of the Sun and
other planets.
Now, there’s Uranus, which is arguably even stranger.
Uranus has an axial tilt of 98 degrees relative to its orbit, which can also defined as 82
degrees retrograde. This means that Uranus actually rotates on its side! Uranus has an
equator which is roughly perpendicular to its orbit. This means that during the northern
hemisphere’s summer, around the north pole would be the hottest part of the planet, and
the Sun would be visible all the time
with the rotation of Uranus not having the same day/night cycle
effect that we have on Earth. Again, it’s not fully understood how exactly this happened,
but again, may have been a giant impact.
Well that’s all for episode three of Winners and Losers, I hope you enjoyed it and feel
free to leave your suggestions for episode 4. Now this episode is brought to you by Squarespace.
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