In 1950, physicist Enrico Fermi asked a very important question over lunch at the Los Alamos National Laboratory. Based on the number of galaxies we know exist, how many stars are inside those galaxies, and how many planets potentially orbit those stars, probability states that there should be alien life.

So, where is everybody?

This question - known as the Fermi Paradox - raised a lot of eyebrows, because it's a logical thought when considering just how vast our Universe is. While there are many different hypotheses out there that attempt to concoct an answer, one of the best and most thought-provoking is the zoo hypothesis.

The zoo hypothesis was thought up in 1973 by MIT radio astronomer John Ball. He posited that, yes, there might well be intelligent aliens out there, but maybe they are simply ignoring us, forcing us to live in a cosmic 'zoo' or wildlife sanctuary where they can monitor our activity without disturbing it.

In other words, the hypothesis assumes that alien life is out there, but it's so advanced, it either does not want to influence our primitive society, or it knows not to get involved with other intelligent lifeforms.

This makes sense when you consider that life might have evolved and progressed at a much quicker pace on other planets in our galaxy.

The rate at which humanity has progressed over the last 100 years alone sheds a bit of light on how much further along a civilisation that has lasted 100 million years longer than us might be.

"An OC [other civilisation] that is, say, a century younger than we are might not be able to communicate over interstellar distances; a century ago we couldn't," Ball explains.

"And an OC a millennium older than we are would probably be using a technology for interstellar communications, such as modulated gamma rays, that we humans haven't yet learned how to do."

If correct - and it's important to note that this is all extremely hypothetical - there might be a civilisation out there that is so much more advanced than ours on Earth, we would be worth nothing to them.

Ball explains this by comparing how we feel about non-intelligent creatures here on Earth.

As he puts it:

"An argument based on relative time scales suggests that the appropriate PEL [primitive Earth life] is an animal such as those in our Ordovician geological epoch, namely mollusks and trilobites.

Now I can imagine talking with mammals and birds; indeed I've done it, although the conversation was on a pretty low intellectual level. But oysters?"

This notion also harkens back to statements from famed physicist Stephen Hawking who thinks we shouldn't broadcast ourselves out into the Universe just in case an advanced - and unfriendly - civilisation might be lurking in the shadows, looking for some primitive life ripe for conquering.

Ball also notes that there are other hypotheses surrounding the Fermi Paradox too, with some being far more popular than others. One of the most popular is that alien life does exist, but is very primitive, or maybe it's already come and gone?

The fact of the matter here is that no one really knows. The only way any of these hypotheses can be proven is with scientific evidence, and we're working on it.

So, where is everyone? At this stage, your guess is as good as any.