Since the birth of civilisation, the open sky with its stars, planets, and whizzing asteroids has always amazed mankind. The same question in different forms and degrees has crossed people’s minds across generations – ‘What is out there in the universe’?

Over the years, to seek a better understanding of the universe, we set up astronomical towers, studied stars, and even sent people to space! This led to discovery of new planets and galaxies and the quest to find signs of alien life, or its hope, grew in its intensity.

But has there been any sign that, in a basic form, validated the fact that we are not alone? Perhaps, or perhaps not. Read on to decide for yourself.

1. The WOW Signal

The ‘WOW’ signal was detected on 15 August 1977, at the Big Ear Radio Observatory in Ohio, U.S.A., during a routine search for signs of extra-terrestrial intelligence. The signal lasted for 72 seconds and was reviewed by astronomer Jerry Ehman. He wrote the word ‘Wow!’ on the paper which printed the signal.

Ever since, the signal has been a cause for debate. Some claim that the signal was made by an alien life form, while others contend that a star had caused it. Though many tried to theorise the cause of the signal, there has been no agreed-upon explanation.

2. FRB

FRBs, also known as ‘fast radio bursts’, are sudden, rapid chirps of radio waves originating from space that last only a few milliseconds. The first one was picked up by our radio telescopes in 2007. Ever since, scientists have been scrambling to try and explain their occurrence.

These FRBs appear to be coming from outside the Milky Way, often from millions of light years away. Explanations behind these radio bursts range from colliding black holes to signals from extraterrestrial civilisations.

3. Meteorite ALH84001

Discovered in 1984, this rock is believed to have blasted off the Martian surface because of a collision. It had wandered around the solar system for 15 odd million years before plummeting on Earth.

Upon careful analysis, the rock was found to contain organic molecules and tiny specs of the mineral magnetite, which is sometimes found in Earth’s bacteria. Under the electron microscope, NASA researchers also claimed to have spotted signs of ‘nanobacteria’.

It is speculated that the rock could have been contaminated by Earth's bacteria, while others believe that the bacteria must have been on the rock long before it blasted off the Martian surface.

4. Oumuamua

When the solar system's first interstellar visitor was spotted on 19 October 2017, scientists dashed to observe the strange object.

Some theories suggested that this oddly shaped, rapidly moving traveller had been ejected from its home system and was perhaps a comet or an asteroid. But another interesting theory was also put forward, which suggested that it could have been an alien aircraft!

5. Comet C/2019 Q4 Borisov

C/2019 Q4 Borisov is only the second interstellar (something located between stars) object ever identified, after 'Oumuamua’, which was spotted in 2017.

It was detected floating through the solar system in 2019. Scientists are yet to study the object in detail, but they believe the object could hold the key towards a better understanding of alien life. They are currently assessing the options of sending a mission to study the object using existing technology. So, whether it is a comet or a flying alien ship, we are yet to find out!