It's a question many of us have asked ourselves: are we alone in the universe?
From flying saucers to balls of light rocketing through the sky, South Australia has had its fair share of reported UFO encounters.
One avid ABC reader has asked us to delve into the history of the state's major cases, as part of our Curious Adelaide campaign.
So we dusted off some of South Australia's oldest X-Files to find answers.
Nightmare on the Nullarbor
We'll start in the outback, where a traumatised family was allegedly lifted off the ground by aliens.
It was still dark in the early hours of January 20, 1988, when the Knowles family was driving along the remote Nullarbor Plain.
The seemingly mundane trip from Perth to Melbourne quickly turned to terror when they encountered an unidentified flying object that tormented them for 90 minutes.
A large glowing object "like a big ball" chased Faye Knowles and her adult sons Patrick, Wayne and Sean down the highway, before landing on their roof and plucking them into the air.
"It apparently picked the car up off the road, shook it quite violently and forced the car back down on the road with such pressure that one of the tyres was blown," a police spokesman told media at the time.
In a state of shock, Sean Knowles put his foot on the accelerator as his mother screamed but, according to reports, their voices distorted like time was slowing down.
"I wound down the window and I felt this thing on the roof... all of this smoke stuff started coming into the car, the car was covered in black stuff," Faye Knowles told reporters after the incident.
"It was a small light and all of a sudden it became big like this, like a big ball.
"We thought we were dying, then we got out the car and we hid behind a little tree and the bushes and it couldn't find us."
The family eventually made it to Ceduna and reported the bizarre events to police who took the report seriously, given the state of the car, which was dented and had dust over it.
The story made headlines around the world with sceptics and believers alike trying to make sense of what happened on that lonely stretch of road.
Flying saucers and lights in the sky
UFO reports in the state can be traced back to the beginning of the twentieth century but it wasn't until the early Cold War that they started appearing all over the place.
Rockets were a new invention, originally for military purposes, that made the stars seem closer than ever before.
It seems that, in an atmosphere of heightened political tension, people became spooked by strange lights in the sky.
UFO researcher Keith Basterfield said Port Augusta was home to one of the state's first sightings.
"Even in the beginning of the flying saucer era in 1947 when the whole thing took off, we had one of the earliest sightings in Port Augusta," Mr Basterfield said.
"Five metallic objects were seen by three people working at the Commonwealth railways there.
"Even the government astronomer — we had such a person at the time — couldn't explain that sighting."
Reports made the front pages of newspapers of strange objects sighted from Eyre Peninsula to the outskirts of Adelaide.
On January 22, 1954, The Bunyip newspaper reported three people had sighted a flying saucer over Gawler.
"As the object approached at terrific speed they could make out the perfect shape of a saucer — pure white," the report stated.
"It looked no bigger than an ordinary saucer because of its great height."
One case that still stumps Mr Basterfield took place outside the remote community of Kimba on the Eyre Highway on the night of February 4, 1973.
Four people in three separate cars all spotted it in a clearing they passed — an orange rectangle similar to an illuminated door in the scrub, with a strange figure standing inside.
Police were baffled, so Mr Basterfield and his team drove out to investigate.
"We had a look at the site, we took soil samples from the area, we had the samples analysed looking for something unusual there," he said.
"That's not your typical flying metallic saucer but it's a very, very strange set of observations by a group of independent people.
"And we never did get to the bottom of it."
Another strange happening, in South Australia's Flinders Ranges in 2006, was witnessed by scores of people many kilometres apart.
Service station owner John Teague was outside pumping tyres when something plummeted through the sky.
"For some reason I glanced up and I yelled, 'look at that Lloyd', and this thing was hurtling through the air," he said.
"Looked like [it was] about the size of a baseball just flying through the air rapidly."
Mr Teague made such a noise that a group across the street looked up and saw the same thing.
"Then all of a sudden, and this was quite some time later, a huge sonic boom rattled through the air," he said.
"I thought it might have been a meteor going through the air in daylight, I didn't know what it was, maybe space junk coming back.
"But it would have had to be pretty big for space junk for it to be that size way up in the air."
To this day, what it was remains a mystery.
So how common are UFO sightings in South Australia?
South Australia's Astronomical Society's Paul Curnow said it's pretty common.
"The average city person doesn't look at the sky very often and sometimes when they do look up and see something strange, they can't really explain it," Mr Curnow said.
Late last year, the Pentagon admitted that up until 2012, it had been running a secret investigation into UFOs, but it seems that Australia's aerospace and security agencies don't keep detailed records or data on UFO sightings — at least, that's what they told us.
When Curious Adelaide phoned SA Police to check whether it could shed some light on the matter there was a moment of silence, before some laughter.
Senior constable Mick Abbott did however make the following comment:
"If you stay on the line, I'll transfer you to agents Mulder and Scully from our X-Files division."
When the ABC contacted the CSIRO there was a similar reponse.
According to Paul Curnow, it's still common to get several dozen to hundreds of UFO reports each year in South Australia alone.
But what's being reported is changing, he told us, with fewer sightings of flying saucers hovering over the land.
"Probably for every 10 cases you get, nine can be explained in mundane terms," Mr Curnow said.
The majority of cases, unfortunately for those hoping for an encounter with the extra-terrestrial, have a logical explanation.
"Quite often people report a little silver dot in the sky [and it] turned out to be an aircraft," he said.
"A lot of these things like planes, satellites, planets, even searchlights sometimes, can all add to what people are reporting."
So is the truth really out there?
UFO researcher Keith Basterfield was based in Adelaide when the Knowles family incident occurred.
"My first thought was 'here is a very interesting story that we can carry out some hard science on'," he said.
"We've got a vehicle, we've got reported unusual dust on a vehicle, we've got a number of witnesses.
"If we could document all that we'd have a very strong case for saying something unusual occurred."
However, the conclusion he reached was far from the extra-terrestrial encounter portrayed by the media.
The car had been forensically tested with nothing unusual found, and Mr Basterfield had a more ordinary explanation for the bright light.
"We figured it was potentially a mirage caused by a temperature inversion that night," he said.
That kind of mirage can make lights a long way in the distance curve over the Earth's horizon and appear to be much closer than they actually are.
"Although they saw the light approaching them, they never saw the [source of the] light reach them, so it never actually got to them," Mr Basterfield said.
"It disappeared at that point in front of them so we figured a mirage of a track light several kilometres away could explain that."
He also had a simple explanation for the car jumping and vibrating.
"If a tyre explodes under your car going at really high speed you're going to get vibrations, you're going to get brake dust entering the vehicle," Mr Basterfield said.
"It was simply a case of misunderstanding, of seeing a light in the distance, a tyre bursting and those things had built up into a story."
While it seems science offers an explanation for many of the sightings in the state, you'll need to decide for yourself whether it's more tale than truth.