[ur-whale]

>I never understood why colonizing Mars is needed.

Correct, but short-sighted.

However much Earth has, we'll quickly gobble it all up.

To quote Bartlett : "The greatest shortcoming of the human race is our inability to understand the exponential function."

(https://en.wikipedia.org/wiki/Albert_Allen_Bartlett)

The only way out is up, and the first stepping stone is the Moon, next is Mars.

[adrianN]

Neverending exponential growth is not possible through space colonization. We can grow at most as the surface area of a sphere that expands at the speed of light, realistically much slower.

[pferde]

In sufficiently long term, it is not entirely correct, because colonized planets will eventually start sending out colonizers themselves.

[adrianN]

That doesn't work. They'll only reach places already colonized.

[dagw]

"The greatest shortcoming of the human race is our inability to understand the exponential function."

In which case the second greatest must be to assume that all growth is exponential.