Is the Earth big?
It's all relative! The Earth is 8000 miles across, and that is
big, compared to us anyway. Let's put it into perspective, and take
a look at how we compare as a planet. To start with, our Moon is
250,000 miles away from the Earth. That means that there is
enough space in between the Earth and the Moon to fit in an extra
30 planets the same size as Earth!
Most planets in our solar system are much bigger than us.
Recently a meteorite crashed into Jupiter. Scientists estimate that
the mark that it left is the same size as the Earth. Take a look at
the video of the meteorite crashing. Look carefully because it is
hard to spot.
But if you thought Earth is big, our Sun is 850,000 miles
across. That's over 100 times bigger than the Earth.
Did you know?
- It would take 109 duplicate Earths to match the diameter of the
- It would take 340 earths to fit around the Sun
- It would take 1,300,000 Earths to fill the Sun
Have a look at this video to see how small the Earth is compared
with all the other stuff in the universe:
What do you know about the universe? Well, it's sort of big
right? It's not just big - it's really, really BIG. The
reason why it's hard to see how big stuff is, is because it is so
far away. Everything looks small to us because its millions and
billions and trillions of miles away.
The problem scientists have is that describing distances in
miles or kilometres becomes meaningless - there are just too many
00000000000000's. We need a much bigger unit. This is called
the light year.
A light year is how far light can travel in a year. Light
travels at 186,000 miles per second, the speed limit for the
universe. So in a year a ray of light covers about 6 trillion
miles. Think about it this way - in one second light can
travel round earth 7 times! Imagine how far it gets in a
The nearest star to our Sun is Proxima Centauri. This star
is four light years away - about 24 trillion miles.
Starting to see how big everything is? Our Galaxy, the Milky
Way, is about 100,000 light years across. Even travelling at the
speed of light it would take 100,000 years to fly from one side to
Scientists think there might be as many as 500 billion galaxies
and that is just too big to think about. The most distant
galaxy scientists have ever seen is 13,000,000,000 light years
So the furthest away visible galaxy is
78,000,000,000,000,000,000,000 miles away!
Does your head hurt too? When you see stars and galaxies in the
sky, you are seeing what they looked like billions of years
ago. In fact, when you look up at the stars, some of them
actually no longer exist. They will have disappeared
centuries ago, but their light is still travelling to us.
There's a lot of space out there!