Four times scientists believe we were visited by aliens

Some scientists believe we've actually been visited multiple times by aliens, and if that's the case it'd be really nice if somebody could let the rest of us know they've popped round.

To quote a wise man: "Two possibilities exist: either we are alone in the Universe or we are not. Both are equally terrifying."

We occasionally get odd signals which we think could be aliens trying to contact us but turn out to be something else, and from time to time the occasional person claiming to be a time traveller puts a date on first contact.

However, right now there's no concrete evidence that there is intelligent life somewhere else in the universe and the search for new life and new civilisations goes on.

Some potential good news on that front is that as time goes on our ability to observe space and discover what's out there improves, so perhaps we'll live to see a definitive answer in our lifetimes.

Then there are the scientists who reckon we've possibly already been contacted and there are a few moments where we might have had a genuine connection with aliens.

One such instance was a spot in the galaxy which appeared to be sending us radio signals at incredibly consistent intervals, with a new signal every 18.18 minutes.

Sadly, it's probably not aliens and scientists now reckon it's coming from a neutron star.

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Then there was the Oumuamua, a long cigar shaped object that we spotted flying through our solar system for a few years, which had experts wondering whether it was an asteroid or possibly an alien spaceship of some kind.

If there were aliens aboard they could have at least stopped by to say hello, but maybe it's a good thing they didn't since they were so rude to fly so close and not even say anything.

Scientists also got excited over Tabby's Star after it was spotted giving off some abnormal light fluctuations, which some suggested could be evidence that it was part of a hyper-advanced megastructure like a Dyson Sphere, a structure build around a star to get the energy from the light it gives off.

Again, this one is probably sadly not evidence of aliens, though there's always hope in the form of clues such as the infamous 'wow' message which might have been broadcast from some other world.

On the other hand, if aliens haven't actually visited us then it's probably for the best as we don't really have our act together at the moment.

One expert suggested we'd probably react like a bunch of 'headless chickens' if aliens did show up and ask if they could pop in for a chat and it's hard to argue with any certainty that we'd handle it in a mature and rational manner.

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Earth and humanity are in that 'we need to go away and work on ourselves for a bit' stage so if there are any aliens waiting to announce your existence and change our perceptions of the universe and our place in it we'd really appreciate it if you came back later.

Then of course we've cluttered our orbit with a bunch of noisy satellites, which could mean that we actually miss some sort of extra-terrestrial message being beamed our way.

Even more depressing is the possibility that any alien civilisation with the spacefaring technology capable of visiting us can't because such an advanced place has probably already wiped itself out.

Still, if the aliens won't come to us then in a few billion years we can go to them, largely because by then our Milky Way galaxy is going to collide with the neighbouring Andromeda galaxy.

Sadly, unless we can all live to a very ripe old age we'll miss out on still being around to witness it.