How did the very beginning of the universe look like? Today, there is no satisfactory answer to this question. We know what was happening fractions of a second after the explosion, but what was the explosion itself like? Physicists call the “zero point,” which the universe was created from, the “singularity”. It is something that cannot be described by the known laws of physics. So much for the introduction. Since we do not yet know how the very beginning looked like (and perhaps we will never know), maybe it will be easier to answer what is end going to look like?
Everything indicates that it will be cold. Oh, very cold. For many years, basically until the discoveries made in the first decades of the twentieth century by Edwin Hubble, people believed that the universe is stationary, that nothing is changing in it. Obviously, they knew that the planets are moving, but they thought that the range of these changes is very small, that looking at a large area of the universe, they “neutralize each other.” It is a bit like looking at the still surface of a lake, knowing that single molecules of water are not at rest, but are moving in it. This model of the stationary universe was heavily impaired by the observations of galaxies receding from each other, which were made by Edwin Hubble. The model fell entirely upon the experimental confirmation of the existence of the microwave background radiation. The era of a dynamic universe has begun. But what does it mean in practice? There were several concepts. Since the universe is growing wider, it will be doing this infinitely. However, what may happen – it was said – is that it will be growing more and more slowly, until it stops. Or alternatively, after a period of swelling, it will begin to shrink. In the end, it will be at one point, which will be the beginning of a new universe. Neat, is it not?
Each of these concepts had (some still have) its supporters and opponents. Most appealing to the imagination and the most “elegant” concept is the one of the BIG CRUNCH. The end of the universe would be the beginning of a new one at the same time. Is it possible? So far, the galaxies have been moving away from each other. Furthermore, the observations indicate that this process is accelerating. There is nothing to suggest that it would slow down one day. Thus, what seems to be more likely is rather the concept called the BIG RIP. This rip, whose author is a cosmologist, Robert Caldwell, would apply not only to galaxies, but, over time, also atoms. Protons, neutrons and electrons, and later even quarks, would spill in the space like beads from a broken necklace. The third hypothesis is the so-called BIG CHILL. The expansion of the universe will stop, but at some point, when the light elements “burn out,” it will just run out of energy.
Out of the above three, it seems that the most probable is the one which says that the universe will be expanding and expanding and expanding… and the second process related to the burning out of stars will overlap. Less and less of these arise. While analysing the images of the faraway universe made by three huge telescopes, the Japanese Subaru Telescope, the UKIRT (United Kingdom Infrared Telescope) on Mauna Kea in Hawaii and the Very Large Telescope in Chile, the astronomers from the University of Leiden in the Netherlands came to the conclusion that, today, 30 times fewer stars come into being than 11 billion years ago, at the peak of the boom of their birth. This result should not surprise anyone. On the contrary, we should be glad that it was possible to experimentally confirm what, until now, was realized only in theory.
When the universe was very young, when it was only tens of minutes, all the matter accumulated in it consisted of hydrogen and helium. Only these two elements were created during the Big Bang. These two are necessary for “lighting” stars. An active star “converts” light atoms into the atoms of heavier elements. And even though they are essential in the formation of, for example, planets or us, the humans, they cannot be a building material for the next generation of stars.
The star which is closest to the Earth is of course the Sun. It is shining, because a thermonuclear reactor is carousing inside it. Matter is converted into energy, which, in turn, is radiated into outer space. The stars burn out. Every second, our star is losing 4.5 million tons of hydrogen. In about 5 billion years, our star will have run out of fuel. All the stars in the universe will finally run out of fuel. For trillions of trillions of years, the universe will be dark. There will be only the ashes of stars in it. Ashes, which will also slowly disintegrate. Even these small “piles of matter,” like little castles of sand, will be “dispersed”. At the moment when the last sun goes out, the era of stars will end. One of many periods of the evolving universe. The last stars in the universe will be red dwarfs. Tiny stars which, because of their sizes, can use the energy stocks at their disposal for the longest time. In about 100 trillion years, they will have gone out as well. And then, there will be darkness.
dr Tomasz Rożek
A doctor of physics, a science journalist of the Gość Niedzielny weekly and an author of popular science books. Has his vblog “Science. I like that”.