It’s reasonable to expect there to be someone out there if you consider the astronomical (pun intended) numbers involved when we talk about space and the heavenly bodies hurtling through it.

NASA scientists estimate that there may be tens of billions of solar systems in The Milky Way, perhaps even as many as 100 billion.

The Milky Way in turn is one of an estimated two trillion galaxies in the observable universe each one with tens of billions of solar systems and trillions of planets in them.

Just on the numbers alone, the probability of intelligent life should be very high, yet, so far our search for evidence of intelligent life out there has only yielded a deafening silence.

This inexplicable situation is expressed in the Fermi paradox which originated from the Nobel Prize-winning physicist, Enrico Fermi who, in the face of no signs of extra-terrestrial life asked: “Where are they?”

Business Insider reports one hypothesis is that before intelligent life manages to spread beyond its original planet to other nearby planets, it runs into a sort of “Great Filter.”

This idea suggests there are several “evolutionary transitions or steps” that a planet like ours would have to achieve before it can communicate with civilizations in other star systems. An obstacle or barrier may make it impossible for an intelligent species like ours to get through all those steps. That would explain why we haven’t heard from or seen any other life.

In Earth’s case, climate change may be that filter preventing us from exploring nearby planets in our galaxy.

Business Insider quotes David Wallace-Wells who wrote in a recent feature for New York magazine:

“In a universe that is many billions of years old, with star systems separated as much by time as by space, civilizations might emerge and develop and burn themselves up simply too fast to ever find one another.

“Peter Ward, a charismatic paleontologist among those responsible for discovering that the planet’s mass extinctions were caused by greenhouse gas, calls this the ‘Great Filter’: ‘Civilizations rise, but there’s an environmental filter that causes them to die off again and disappear fairly quickly,’ he told me. ‘If you look at planet Earth, the filtering we’ve had in the past has been in these mass extinctions.’

“The mass extinction we are now living through has only just begun; so much more dying is coming.”

Scientists have already warned that Earth’s sixth mass extinction is on the horizon. Rising temperatures are already causing havoc and displacing communities. Extreme weather incidents are more frequent, droughts are intensifying, rising sea levels are threatening coastal areas and rising ocean temperatures are killing fish and coral reefs.

If we are unable to halt these conditions, we won’t survive to be able to look for our fellow cosmic brothers.