30 AMAZING ANSWERS TO THE BIGGEST QUESTIONS IN THE UNIVERSE
1 WHERE DOES SPACE START?
There’s an easy answer to this question: space starts at the top of Earth’s atmosphere. The hard part is saying just where that ‘top’ is. The fact that the atmosphere doesn’t end abruptly, but just gets thinner and thinner, means there’s no hard and fast upper bound you can put on it. To some extent, it’s simply a question of coming up with an easily memorable number that’s in the right ballpark. To NASA and the US military, for example, space starts at an altitude of 50 miles. To the international community, on the other hand, it starts at 100 kilometres, which at 62 miles is a little higher. In the middle of the 20th century, a Hungarian-American aerospace engineer named Theodore von Kármán asked a simple question: At what altitude does the speed needed to keep an aircraft aloft through aerodynamic lift become so high that it exceeds orbital velocity? He did the necessary calculations, then rounded the answer to that memorable figure of 100 kilometres, or 62 miles. This altitude is now known as the ‘Kármán line’ in his honour.
LAYERS OF THE ATMOSPHERE
Earth’s atmosphere, though it gets very thin, extends a surprisingly long way
TROPOSPHERE
Extending up to around 12 miles altitude, this is where most aircraft fly – and where most weather happens.
STRATOSPHERE
This intermediate layer, up to 31 miles altitude, accounts for around a fifth of the atmosphere’s gas content.
MESOSPHERE
This atmospheric layer, up to 53 miles altitude, is still dense enough to cause falling meteors to burn up.
THERMOSPHERE
Extending from about 53 miles up to 375 miles, this layer includes the Kármán line and many satellite orbits.
EXOSPHERE
The outermost layer of the atmosphere, the exosphere reaches as far as 6,200 miles from Earth’s surface.
2 WHAT IF EARTH STOPPED SPINNING?
Earth has so much rotational energy – over 200 quintillion gigajoules – that it will take billions of years to lose it all. If it slowed to the point where it was tidally locked to the Sun, one side would be in perpetual daylight and the other side in perpetual night.
3 WHERE ARE THE WORLD’S SPACEPORTS?
Spaceports are dotted all over the world in locations where you’re most likely to find functioning private or state-run space programs. Since they were first developed, 28 spaceports have been used to launch satellites into orbit, with 22 active today.
The Kennedy Space Center at Cape Canaveral in Florida, is probably the world’s best known spaceport, The privately operated Rocket Lab Launch Complex One in New Zealand serves as a commercial launch site. The European Space Agency’s Guiana Space Centre in French Guiana, The Jiu Quan Satellite Launch Center, China, and the Baikonur Cosmodrome in Kazakhstan
