On July 11, 70-year-old British billionaire Richard Branson created history by reaching the edge of space before his rival Jeff Bezos, giving space tourism an official kickstart.
While the achievement is significant for the commercialisation of space travel, it has put many experts and space enthusiasts in doubt over his reaching space.
Many experts including scientist Neil deGrasse Tyson, a student of Carl Sagan, and space enthusiasts are in doubt whether the height to which he travelled can be termed 'space'.
Richard Branson did not go on space flight, said astrophysicist and director of the Hayden Planetarium deGrasse in an interview with CNN.
But whether or not Branson has technically been to 'space', his achievement ushering in a new age in space tourism. Now lets understand why this question arose at the first place.
Why the controversy
The most widely accepted boundary of space is known as the Kármán line, 100 km above mean sea level.
However, the United States uses 80 km above mean sea level as the cutoff point.
The Kármán line has been compared to international waters, as there are no national boundaries and human laws in force beyond the line.
The Kármán line has been named after aerospace pioneer Theodore von Kármán.
Richard Branson's Virgin Galactic flight reached a height of 86 km while Jeff Bezos' Blue Origin flight is expected to go about 106 km high.
Defining space
In 2009, researchers from the University of Calgary measured the winds of Earth's atmosphere and the flow of charged particles in space.
The researchers from University of Calgary wrote that the edge of space begins at 118 km above sea level.
Jonathan C McDowell from Harvard-Smithsonian Center for Astrophysics published a paper in 2018.
He noted that the Kármán line or 'boundary was chosen as a nice round figure', but it needs more studies from 'a physical point of view'.
Dr McDowell studied the different layers of the atmosphere and proposed that 80 km was a more appropriate boundary.
Atmospheric layers
The Earth's atmosphere has been divided into various layers, with the troposphere starting at the Earth's surface and extending about 14.5 km high.
The stratosphere extending to 50 km, mesosphere to 85 km, thermosphere to 600 kilometers and exosphere to 10,000 km.
Dr McDowell noted that the chemical composition of the atmosphere was largely constant up to the mesopause, or the boundary between the mesosphere and the thermosphere.
Can Branson be termed astronaut?
While there is still confusion regarding whether Branson went to space or to edge of space, largely people agree to the fact that he can be termed as an astronaut.
It has been accepted by former commander of ISS Terry Virts who spent over 213 days in orbit and by NASA astronaut Mike Massimino.
