Are Aliens Already Watching us?
Imagine an alien civilisation is
looking up at the night sky, scanning the heavens, trying to detect signs of
life. We as a species have been sending out radio signals for about a hundred
years and we have followed that up with television signals. Those signals have
gone into space and travelled at the speed of light and by now have reached
hundreds of stars and hundreds of planets around them.
So if there was an alien
civilisation in that distance and they were pointing their detectors roughly in
our direction, they would have heard the first BBC Broadcasts and by now they
would have seen many many years of Coronation Street and have a rough idea of
how our humanity works. Some very prominent scientists think it’s quite silly that
we’re sharing quite so much about ourselves to the galaxy. Aliens may not be
very kind and maybe we shouldn’t be giving away our position and our entertainment
choices. Maybe we should all just collectively stop advertising ourselves to
the galaxy. So let’s say we do go quiet. Could aliens still find us?
So imagine that same alien civilisation
looking at the night sky, but now there are no radio signals, no television
signals, just three hundred billion beautiful white lights quietly shining
away. But it is that white light, seemingly so fundamental and pure, that holds
the key to unlocking the secrets of all those planets around all those stars. White
light is only pure until you crack it open. With a prism or a drop of water,
white light shows what really is within it – the rainbow. And the rainbow isn’t
just made up of seven colours. With a powerful enough prism, you can get all of
the reds and all of the violets, all of the infinite colours between them and
beyond them in the infra-red and the ultra-violet. So if that alien
civilisation pointed a very expensive prism at our sun, they’d be able to see
our sun’s rainbow. And if they were very patient and looked carefully, they
would notice that every year a few new shadows would appear and disappear. And they
would appear and disappear. And those shadows are caused by the molecules in
our atmosphere. And they’ll be able to look at those shadows in the rainbow and
know that we have an extremely lively planet, that we have vast inhabited
oceans, that we are oxygen reliant life forms, that we have at least one
technological species and also that we pollute a lot.
The earth has a living atmosphere. We
call that a biosphere. And that biosphere is a planet-sized unintentional
message to any aliens out there who care to listen. It tells the story of who
lives on this planet and what we do with it. So we could stop sending messages
into space, but even if we do go quiet, they can still tell that we’re here. It’s
the galactic equivalent of thinking I’m invisible now.
And can we do the same to them?
Could we detect aliens even if they have no radio or television? Well we can
already look at some alien atmospheres, although we can’t quite look at a full
terrestrial atmosphere yet. But we’re very close, we are developing tools to
try to decipher these potential alien biospheres. Those tools are how we will
be listening into alien messages. And of course, we would love to receive the
alien version of The Simpsons coming done from the heavens. Until them, we’ll be
looking for the signs of life that the aliens didn’t even mean to create.