In light of the discovery of Kepler 452b in July (or at least its announcement then), I thought I would repost an article I wrote a year ago about the search for life, and the possibility of another habitable planets. It’s interesting to see how things change in the space of a year. Also it means I don’t have to write anything new.

“I would venture to say that most of my colleagues here today say it is improbable that in the limitless vastness of the universe we humans stand alone.”

This was said by NASA administrator Charles Bolden during a panel discussion on the search for other forms of life in the universe, about a year ago.

There was a claim at the time that NASA had said they would prove extraterrestrial life within twenty years, but where the twenty years part came from was associate administrator John Grunsfeld saying that scientists are closer to finding another Earth-like planet than people realise. Apparently, with the telescopes we have now, and those we’ll have in the future, we may be able to find life on other planets in as little as twenty years.

The agency has plans to launch the Transisting Exoplanet Surveying Satellite in 2017 and the James Webb Space Telescope in 2018. These will be used – as the former’s name suggests – to find and study new planets and determine if they are capable of harbouring life. Or if they already do!

Thanks to our existing technology, we already know of at least one potentially habitable planet. Considered a prime candidate for life, Gliese 832-c is a super-Earth. The term sounds pretty promising, but in fact a super-Earth is only defined by its mass, which is higher than Earth’s but no more than 10 Earth masses.

Gliese 832-c – a very catchy name – is about five times the size of Earth and closely orbits a red dwarf star. It’s thought to have Earth-like temperatures and is one of the closest potential habitable worlds to us, at about 16 light-years away [Edit: Kepler 452b is actually only 1,400 light-years away]. But we don’t really know much more about it. Because of its orbit, the planet could suffer from drastic seasonal shifts. It could be a gas or water planet. Its atmosphere could preclude life. We don’t know.

In fact, because it’s so massive, Gliese 832-c quite likely possesses a massive atmosphere too. If so, that may well render the planet inhospitable. Such a dense atmosphere would trap heat and make it far too hot for life – more like Venus than Earth. So while it’s potentially habitable, it probably isn’t.

But let’s put things in perspective. Go to Google Sky and start zooming in. How many stars can you count? Perhaps I’ll save you some time and tell you that there are around about 300 billion stars in the Milky Way galaxy alone. Astronomers estimate that there actually are up to 400 billion. And that’s our galaxy alone.

How many stars are there in the universe? Well, there are some galaxies out there with up to 100 trillion stars. Others are smaller than ours. There are an estimated 170 billion galaxies in the observable universe. Again, that’s just the part of the universe that we can see.

So if we use our galaxy as an average, and we multiply the number of stars in the Milky Way by the number of galaxies in the observable universe we get something around a septillion.

That’s 10²⁴­­. That’s a 1 with twenty-four zeroes. That’s 1,000,000,000,000,000,000,000,000 stars.

So how many planets are there? That’s a bit tougher. The Kepler Space Telescope, between 2007 and 2013, found that there may be an average of about three planets orbiting each star in our own galaxy. So to make an unscientific estimate, that’s a potential of over a trillion planets. The lowest scientific estimation is between 100-200 billion. And that’s conservative. Others think up to 10 trillion. That might be a little on the high side.

But let’s forget that average of three and imagine for a moment that every star has one planet. That’s still a septillion planets in the observable universe alone. Or perhaps three septillion? Let’s not even touch on the theory that ours isn’t the only universe…

Consider now that in May 2014, Dan Werthimer and Seth Shostak, respectively director of and astrobiologist at the SETI (Search for Extraterrestrial Intelligence) Institute, told congress that billions of the planets inside our galaxy are Earth-sized and within the ‘Goldilocks’, or habitable, zone. That is, not too close to and not too far from their sun – not too hot and not too cold. Of course, that doesn’t automatically mean those planets are habitable, simply that they are a lot more likely to support life than those not in the Goldilocks zone.

Shostak apparently also said that he believes we’ll detect alien life within twenty years.

So what do we think? What do you think? I think it’s incredibly foolish to think that, in all that space, among all those stars and all those planets, there’s no life but our own. Foolish and arrogant. What kind of life that may be, though, is another matter. Bacterial, perhaps. Sentient life like our own is a bigger leap.

Of course, what we’re talking about is life as we know it – carbon-based. It’s entirely possible that there are life forms with another chemical basis, such as silicon. When we talk about whether life is possible elsewhere, we can’t really be too sure what other kinds of life there may be. We may say that planets are inhospitable to life, but again, it’s only life as we know it. Even on Earth, we have found life in places we previously thought it wasn’t possible to survive.

I would say if we’re here, then perhaps somewhere else there are similar life forms, cutting down their own rainforests and killing each other. There is a theory that our life here was seeded from elsewhere; that Earth’s organisms and whatnot came here via an asteroid, perhaps. If this is the case, then it would make sense that those same organisms would have hitched a ride to other planets. Whether or not those planets were conducive to that life is another matter. We already know there are plenty of planets out there in their star’s Goldilocks zone, and so are potentially habitable, but the ratio of those to uninhabitable ones lowers the odds somewhat.

How life may have come to be on Earth is a fairly interesting topic in its own right, but it isn’t this one.

So we’re perhaps more confident now in the possibility of life elsewhere. But what about sentient life?

We think of intelligent life as a natural stage of evolution, but that’s not necessarily the case. Life elsewhere might be mostly bacteria and plants. Stephen Hawking posits that intelligence may very well be just one of a large number of possible outcomes of a largely random evolutionary process. He says it’s not clear that intelligence actually has any long-term survival value.

Let’s stick with Stephen Hawking. He likes the idea of there being life out there. He supported SETI, until it lost its funding. However, he seems to be of the opinion that, should we receive any radio signals from space, we should be very wary of answering back. It seems he thinks that any intelligent alien beings who have developed enough to be able to communicate with us, or indeed travel to Earth, could very well be hostile. In fact, I seem to recall him saying this last bit was more than possible: it was likely. Don’t quote me on that, though.

I can kind of see why he would say that, as we ourselves have developed to be quite an aggressive and unpleasant species. If we were to encounter alien life less advanced than us, we would almost certainly exploit it. I don’t entirely agree with this theory, but nor do I entirely agree with the idea that a species more advanced than us must also have evolved into wise, benevolent beings. Quite probably, they’d be like us: nice and complete ass****s, all in one.

Hawking says that to meet an advanced civilisation while at our stage of development might be like the Native Americans meeting Columbus. This makes more than a little sense and does make me stop to consider how wise it is to be looking for life. But that’s just one of many possibilities.

As for whether aliens have already visited Earth, there’s interesting evidence (or ‘evidence’, perhaps), but who knows? That’s a whole other topic, too, and one more suited to conspiracy theory forums.

So, in the end, I think we’ll find life at some point. Perhaps it will be fish in the oceans of Europa, bacteria on an asteroid, or Asgardians patrolling the outer reaches of the universe. But we are not alone, and the truth is out there!