Mars had an oxygen-rich atmosphere around 4 billion years ago
13
If aliens located 60-65 million light years away from us, looked at earth through a really powerful telescope today, they would see dinosaurs!
18
Sound doesn't travel in space.
255
The Sun and Moon appear to be the same size because the moon is 400 times smaller than the Sun, but 400 times closer to Earth.
13
There are 5 to 10 times more stars in the known Universe than there are grains of sand on all the world's beaches, but a single grain of sand has more atoms than there are stars in the known Universe.
20
It takes a photon 170,000 years to travel from the core of the Sun to the surface, but only 8 minutes to travel the rest of the way to Earth.
6