Spark and Perl go looking
Why do people go to space at all?
It started with lights in the sky that would not stay put.
Most stars keep their places. A few wander among them. The Greeks called them wanderers: planets.
What did people think they were?
They told stories about them.
The Romans named the brightest Venus, after their goddess of love. The next brightest, most nights, they named Jupiter, after the king of their gods.
But did anybody measure anything?
Eratosthenes did, more than two thousand years ago.
He worked out how big the Earth is from the shadows of sticks in two towns.
So he flew round it to check.
He could not. Nobody could leave the Earth.
Then he just worked it out, from the shadows.
Yes. For a very long time nobody could check it — and when they could, he turned out to be very close.
And why do we still go now?
To learn about our own planet, by looking at others.
Venus is wrapped in clouds of acid and in air so thick that it traps the heat. Watching it teaches us how our own air works.
And to look for life?
Yes. On the Earth, tiny living things live deep underground, in rock where sunlight never reaches.
So we want to look under the ice of Europa and Enceladus too.
Will we ever know everything?
No. There will always be something left to find out — and that is the best part.
Yes. Venus shines bright after sunset or before sunrise, and Jupiter high at night for months at a time.
Watch one against the stars for a few weeks, and you will see it wander.
Back to the story: The International Space Station
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