Believe it or not, this seemingly simple question does not have an easy answer.

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,” said Dave Reneke from Australasian Science Magazine. “It’s 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 5 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.

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,” Dave said.  “US authorities 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. 

Here’s a few big numbers to contemplate.

More than 3,600 small satellites are expected to be launched over the next ten years, a significant increase from the previous decade. The total market value of these satellites is anticipated to be $22 billion (manufacture and launch), a 76 per cent increase over 2006-2015.

This rate of growth is unprecedented for the space sector and will bring about fundamental changes as both new and established industry players attempt to increase their capabilities in order to gain market share.

 Four companies plan to launch more than 1,400 satellites during this period alone: Planet, Spire, BlackSky Global and Satellogic.