Alex McColgan

Letting other races know that you are there would simply place a target on your back.

After all, if you could both do this, and they wouldn't see it coming, could they really trust you not to strike first?

They could see us as a risk that they are not willing to take.

Known as the Dark Forest Theory, this possible answer to the Fermi Paradox says that the only aliens out there are silent simply because they don't wish to be on the possible receiving end of these kind of planet buster weapons.

Like hunters travelling cautiously through a dark forest, they are all either quiet or dead.

They have been subject to this selective pressure.

However, this is not the only plausible model of behaviour that might still prevent us from seeing aliens.

The second option is simply indifference.

With billions of years of history at play, it might not be the case that we are on technological parity with all the other forms of life that might be out there.

Alien life might simply be so far beyond us, they simply regard us as dispassionately as we might an ant.

They might not be talking to us because we have nothing interesting to say.

Why do you not talk to insects in your garden?

The gap is too great.

You understand what they want perfectly, and they have no hope of understanding you.

Communication would be frankly pointless.

That said, life might be rare in the universe.

If they desire resources, and are that far beyond us, they probably wouldn't need to mine our planet specifically.

We might have value as a curiosity, something to be left alone to flourish simply because they have decided that we have some value as a specimen in some kind of grand cosmic zoo.

And as any zookeeper would tell you, the closer you get an enclosure to look like an animal's natural habitat, the happier that animal normally is.

While they might not care about us, perhaps they do not wish to alarm us by stepping into our natural habitat.