It is one of the great mysteries of science. In the same way that we often ask ourselves what will come next, the circle closes with a what was there before? In particular before the Big Bang, just one hundredth of a second before everything began. And now, for the first time, We could have an answer thanks to the superorders and a team of Oxford scientists.
The study, published in Living Reviews in relativity and led by Eugene Lim, of the King’s College in London and Josu Aurrekoetxea, of the University of Oxford (United Kingdom), proposes an answer: Use complex computer simulations to solve numerically (instead of exactly) Einstein’s equations for gravity in extreme situations.
The authors argue that numerical relativity should be applied more and more in cosmology to investigate some of the most important questions in the universe, such as what happened before the Big Bang, if we live in a multiverse, if our universe collided with a neighboring cosmos or if our universe experienced cycles of explosions and crunch.
But we go for steps. Einstein’s equations of general relativity describe the severity and movement of cosmic objects. But if we go back enough time, we will normally find a uniqueness (an infinite state of density and temperature) where the laws of physics collapse. Cosmologists simply They cannot solve Einstein’s equations in so extreme environments; Its usual simplifying assumptions are no longer valid. And this extends to objects that involve singularities or extreme gravity, such as black holes.
A problem could be what cosmologists take for granted. Normally, they assume that the universe is “isotropic” and “homogeneous”, that is, that looks the same in all directions for any observer. This is a very good approach to the universe that we see around us and that allows Einstein’s equations to easily solve in most cosmic scenarios. But is this a good approach to the universe during the Big Bang?
“You can search around the lamppost, but you can’t go further, where it is dark; You simply cannot solve those equations -Lim points out in a statement -. Numerical relativity allows exploring regions away from the lamppost. ”
Numerical relativity was first suggested in the 1960s and 1970s to try to determine what types of gravitational waves (undulations in space-time fabric) They would be emitted if the black holes collided and merge. This is an extreme scenario for which it is impossible to solve Einstein’s equations only with paper and pencil; Sophisticated computer code and numerical approaches are required.
Its development received a renewed interest when the LIGO experiment (an initiative to discover precisely gravitational waves) in the 1980s was proposed, although the problem was not solved in this way until 2005, which generated hope that the method could also be successfully applied to other problems.
A problem that has been “tormenting” scientists for years is cosmic inflation, An extremely rapid expansion period in the primitive universe. Inflation was initially proposed to explain why the universe looks as seen today, extending from a small initial portion.
“If there is no inflation, many things fall apart -add lim -but although inflation helps to explain the state of the current universe, no one has been able to explain how or why the young universe had this sudden and brief accelerated growth. The problem is that, to check it through Einstein’s equations, Cosmologists must assume that the universe was homogeneous and isotropic from the beginningsomething that inflation intended to explain. If, on the other hand, it is assumed that it began in another state, then you do not have the symmetry necessary to write the equations easily. ”
But Numerical relativity could help us overcome this problemholds the study, allowing radically different initial conditions. However, it is not a simple puzzle to solve, since there are infinite ways in which space-time could have been before inflation.
Interestingly, numerical relativity I could also help reveal if there was a universe before the Big Bang. Perhaps, the speculation of the Lim team is that the cosmos is cyclical and experienced “rebounds” of ancient to new universes, experiencing repeated rebirths, Big Bangs and Big Crunchs. But this is a very difficult problem to solve analytically.
“The universes that bounce are an excellent example, since They reach such a strong gravity that you cannot trust symmetries -Add lim -. Several groups are already working on them; Before no one did. ”
This is because numerical relativity simulations are so complex that they require supercomputers for its operation. As the technology of these machines improves, we could expect a better understanding of the universe.
“We hope Develop this overlap between cosmology and numerical relativity so that interested numerical relativists in using your tandCnices to explore cosmol problemseitherGicos can do it -concludes lim -. And the cosmeitherinterested logos In solving some of the questions that cannot be solved, they can use Num relativityandrich ”.