Space theories that may seem fictional but are strong possibilities

The multiverse theory, as the name suggests, claims that ours is not the only universe. There may be countless others out there with their own laws of physics, stars, galaxies, and maybe even their own intelligent civilizations.

The most well-known foundation of the multiverse concept is inflation theory. Inflation theory says that the very early universe (less than a second old) expanded extremely rapidly. This process is thought to have ended about 14 billion years ago. However, as cosmologist Heling Deng told Live Science, "Inflation does not end everywhere at the same time. It is possible that as inflation ends in some region, it continues in others.” This could lead to individual universes arising out of larger expanding universes.

This digital art represents the idea of a parallel universe.

We all know that the Moon currently has no atmosphere. Thus, there is certainly no possibility of life existing there. However, a 2018 study published in the journal Astrobiology suggests that two past incidents might have given the Moon favorable conditions to support life. The first incident happened 4 billion years ago, when Earth’s only natural satellite was forming from a debris disk.

Water vapor and other gases were being released in mass quantities during this time. The other incident took place some 3.5 billion years ago, when the lunar surface saw peak volcanic activity. According to the study, both instances would have created liquid water pools as well as a dense atmosphere that could have lasted millions of years.

This is a stock image of the Moon's surface. In the image, the detailed lunar terrain is marked by rugged grey craters, vast maria, and subtle shadows, set against the dark, star-filled expanse of deep space.

The Big Rip theory suggests that if dark energy becomes too strong, the entire universe will start to expand so vigorously that galaxies, stars, planets, and even atoms will get torn apart.

Dark energy is the mysterious force behind the apparent accelerated expansion of the universe. It permeates all of space-time and remains constant. However, there is a possibility that it could intensify with time, leading to increased acceleration of the universe. This, in turn, could push the velocity between any two points in space beyond the speed of light. If that were to happen, no physical force would be able to hold two points in space together, and so the universe as we know it would be torn apart. Even atomic and nuclear bonds wouldn't be able to hold their own.

The image is an illustration of the Earth burning, depicting the threat that global warming poses to our home planet.

Like other low-mass stars out there, our Sun too will end its life as a white dwarf—an incredibly dense star, roughly the size of Earth, that has exhausted all its nuclear fuel.

But Earth will probably be long gone before the Sun enters its final days. That is because the Sun is slowly expanding, and, before it becomes a white dwarf, it will enter its red giant phase in about 5 billion years. Having lost all its hydrogen, the core of the Sun will begin to collapse during this stage, causing the surrounding shell of plasma to become hot enough to begin fusing hydrogen itself. The extra heat that will be generated because of this will cause the Sun to expand dramatically and eat up some of the inner rocky planets. While Mercury and Venus are almost certain to be eaten up during this expansion, Earth might also become a casualty.

This image is a 3D rendering of the Sun.