The universe may collapse inward

Image: Shutterstock

The Great Collapse is a simple, clear vision of the future of the universe. In 1922, Russian physicist and mathematician Alexander Friedman developed a famous set of equations that showed that the fate of our universe depends on its density. It may expand or contract, but it will not remain unchanged. With enough matter, the expansion of the universe would eventually stop and gravity would cause it to collapse inward.

In the 1960s, scientists calculated that there was enough matter in the known universe that the universe would eventually collapse into an infinitely dense state, or perhaps a supermassive black hole. Once it is compressed to a point of infinite density, another cycle will begin (The Next Big Bang) and the expansion will begin again in what is called the Big Reversal.

In 1969, physicist John Wheeler introduced the term “black hole.” He was a great supporter of the Big Collapse, and in his view, observations of black holes clearly indicated the ultimate fate of the universe. Wheeler viewed each black hole as a “microcosm” of the final state of the universe. Astronomers agreed with this theory and argued for a long time that this is how our universe should end. But this is not the only option.

When the stars burn out

Image: NASA, ESA and HST Frontier Fields Team (STScI), Acknowledgments: Judy Schmidt

In the late 1990s, two groups of scientists studied the distant universe by analyzing Type Ia supernovae, which astronomers use to measure distances in the universe. It was later discovered that distant supernova explosions appeared faint, so they should have been farther away than expected. It has been said that the expansion of the universe is not slowing down at all, but on the contrary, it must be accelerating. It has also been suggested that there must be an unknown form of energy catalyzing this process – so-called dark energy.

Accepting the existence of dark energy means that the universe is unlikely to end in a major collapse. Even all the matter pulling inward in the universe would not be able to overcome the expanding effect of dark energy. Therefore the Big Collapse theory was rejected and it was suggested that the universe must end with heat death.

Wouldn't it be easier to deny the existence of dark energy? Exactly not, because without it there is no mass in the universe. Research conducted in 2011 seems to confirm the existence of dark energy, which makes up to 68.3 percent. In the energy balance in the universe. For comparison, it should be noted that “normal” matter, that is, everything we see, is only 4.9%. (The missing proportions are filled with dark matter.) Dark energy is the real force behind Einstein's cosmological constant, which plays an important role in preventing the Big Collapse.

About a year from now, the last objects in the universe – supermassive black holes – will finish being evaporated by Hawking radiation. After this event, the universe will enter a so-called dark age in which there will be no matter.

According to the second law of thermodynamics, entropy will reach its maximum level. This means that the universe will reach a state in which all energy (including heat) is distributed evenly. The temperature of the entire universe will be slightly above absolute zero (-273.15 degrees Celsius). Everything around you will be empty and dark. The universe will simply “burn up.”