[yk]

That paper is bizarre.

> In this article an attempt is made to create a list of the possible sources of the signal assuming that, if it was produced by an extraterrestrial civilization, their exoplanet could be similar to Earth.

Citation needed. Quite simply there is no reason given, or obvious, that the exoplanet should be similar to Earth. (Though many Star Trek alien worlds look a lot like California.)

[gfodor]

A stated assumption doesn’t require a citation, it’s an assumption, not a claim.

[blululu]

Why would you even bother searching for extraterrestrial works that are not as nice as California? Nobody is going to travel 50,000 light years to get to a colder, drier Saskatchewan. In some seriousness though, the total range of possibilities is almost endless. You have to start somewhere. Best to start with things you might actually understand.

[goatlover]

It's because Earth is the only planet we know of with life. In particular, the environment to support complex life long enough for an intelligent civilization to emerge. There could be other kinds of planets where this occurs, but of course we don't know about them. It could be that the conditions on Earth are a rare combination needed for intelligent civilizations. Or at least, one of the few ones.

[dylan604]

I've been to a couple of the planets in the Star Trek world. In fact, there's a portal right off a California highway that will transport you directly to one of these worlds if you can park your car.

[astrange]

A lot of them look like California in fire season.