There is no physical place where earth’s atmosphere stops and space begins. The air just gets thinner and thinner and eventually fades away.

On his 108 minute flight in 1961, the Soviet cosmonaut Yuri Gagarin, the first human being in space, went into orbit around the Earth. By all accounts, he crossed the mysterious border between the Earth and space. Or did he?

It’s been more than half a century since Gagarin’s historic journey but only now have we come up with a universally accepted definition of where space begins.

Simply put, space is just above your head, 100 kilometres high – It’s only an hour’s drive away – if your car could go straight up.

Any NASA test pilot or astronaut who crosses this altitude is awarded their astronaut wings.

You know, our atmosphere has as many as five distinct layers. Continue moving upward and you’ll eventually encounter the mesosphere, the section in which meteors generally burn up.  

A little further and the atmosphere ultimately merges with space. It’s basically the city limits. This is where earth stops and the heavens start! Cool huh?

This is the age of spaceflight, it’s also the age of space tourism. In order for Sir Richard Branson to start selling tickets and advertise his upcoming space flights he requested a definite ceiling height.

The US authorities considered, consulted, and then made a ruling that space officially begins at the 100 kilometre mark.

Above earth's atmosphere we welcome true space, outer space if you will! It’s the ‘space’ between the planets. When we leave the solar system we enter ‘interstellar space’– the space between the stars! Easy, isn’t it? 

Dave Reneke from Australasian Science Magazine