What forces are playing with the universe?


It seems, one might say, a Disturbance in Strength.

A long time ago, when the universe was only about 100,000 years old – it was a bustling mass of radiation and expanding particles – a strange new energy field lit up. This energy filled the space with a kind of cosmic antigravity, which was a rather abrupt stimulus to the expansion of the universe.

After another 100,000 years, more or less, this new field simply disappeared, leaving no more traces than an accelerated universe.

This tells the strange story spread by some astronomers of Johns Hopkins University. In a bold and speculative leap in relation to the past, this team proposed the existence of this field to explain an astronomical enigma: It seems like the universe is expanding faster than it should.

The cosmos is expanding nine percent faster than theory indicates. But this seemingly small discrepancy has fascinated astronomers, who believe this may be revealing something new about the universe.

So they have met in recent years in workshops and conventions to look for some error or deficiency in your previous measurements and calculations, which so far has not borne fruit.

"If we take cosmology seriously, that's the kind of thing we should take seriously"said Lisa Randall, a Harvard University theorist who studies the problem.

Some ideas started to emerge. Researchers point out that the problem could be solved with the assumption that previously unknown subatomic particles. Others, such as the Johns Hopkins group, have new types of energy fields.

Or maybe everything is due to an error. Astronomers have rigorous methods to calculate the effects of statistical noise and other random errors on their results, but not for possible biases not studied or known, called systematic errors.

Several generations of great astronomers have failed to measure the universe. A number is under debate: the so-called Hubble constant, so called by Edwin Hubble, the astronomer who in 1929 discovered that the universe was expanding.

As space expands, it moves away the galaxies from each other as if they were the sparks of a cake that is inflating. The further the two galaxies are, the faster they become distant from each other. Hubble's constant simply tells us how fast.

However, to calibrate the Hubble constant, astronomers rely on objects such as supernova explosions and certain variable stars whose distances can be calculated by brightness or some other characteristic. And then the debate begins.

Until a few decades ago, Astronomers did not agree with the value of the Hubble constant: they calculated 50 or 100 kilometers per second per megaparsec (megaparsec = 3.26 million light-years).

However, in 2001, a team that used the Hubble Space Telescope reported a value of 72: for every megaparsec a galaxy is farthest from us, it is moving 72 kilometers per second faster.

The new precision brought new problems. These results are so good that now differ from the results that the European spacecraft Planck predicted a Hubble constant of 67.

Experts believe that, possibly, the difference of nine percent is only by the way the measurements are made: Planck's Hubble constant is based on an initial image of the cosmos; the classic astronomical value derives from what cosmologists humbly call "local measurements," a few billion light-years later in a middle-aged universe.

What if this initial image omitted or concealed some important feature of the universe?

Thus, cosmologists are trying to adjust the model of the primordial universe so that it understands the expansion a little faster without eliminating what the model actually achieves.

Some astrophysicists suggest that one method is to consider that in the early universe there were more species of lightweight subatomic particles, such as neutrinos. With them, the universe would have more room to store energy, just as more drawers in a dresser would allow more pairs of socks. Then, according to the mathematics used to contemplate the Big Bang or Big Bang, the The revitalized universe would expand faster and, hopefully, the initial image would not be challenged.

A more drastic proposal uses exotic fields of antigravity energy. This idea takes advantage of one aspect of string theory, "theory of everything" (not yet proven), which states that the elementary constituents of reality are twisting little strings.

String theory suggests that space could be filled with exotic energy fields linked to light particles or forces not yet discovered. These fields, called par excellence, could act against gravity and could change over time; arise, deteriorate, or alter their effect, such as moving from repulsion to attraction.

The university team Johns Hopkins focused especially on the effects of hypothetical particle-related fields called axions. In a 2018 paper, the team indicated that if one of these fields appeared when the universe was approximately 100,000 years old, it could have produced the right amount of energy to correct the discrepancy in the Hubble constant. They refer to this theoretical force as "initial dark energy".

"I was surprised how this happened"commented Marc Kamionkowski, a Johns Hopkins cosmologist who participated in the study. "This works".

But a conclusion has not yet been reached. Adam G. Riess, of the Center for Astrophysics at the Space Telescope Science Institute, who oversees Hubble, commented that the idea works, but that does not mean he agrees or is correct. Nature, which will be manifested in future observations, will have the last word.

Michael Turner, a University of Chicago cosmologist, said, "Of course, all of this is beyond our comprehension. We are confused, but we hope the confusion will lead us to find something good! "

The primitive dark energy is appealing to some cosmologists because it suggests connection with two mysterious episodes in the history of the universe, or between them.

The first episode occurred when the universe was less than a trillionth of a trillionth of a second. The cosmologists postulate that, at that time, a violent "inflation" gave rise to the Great Explosion; in a fraction of a trillionth of a second, this event organized and equalized the initial chaos and transformed it into the more orderly universe we observe today. Nobody knows what triggered.

The second episode is unfolding today: the cosmic expansion that is accelerating. But why? The question arose in 1998 when two rival teams of astronomers wondered whether the collective gravity of the galaxies would slow the expansion enough to one day drag everything to one "Great implosion."

Surprisingly, they found the opposite: the expansion was accelerated by the influence of an antigravity force that was later called dark energy. Both teams won the Nobel Prize.

Dark energy comprises 70% of the mass energy of the universe. Under the influence of dark energy, now the cosmos is increasing in size to double every ten billion years. No one knows for what purpose.

Thus, the initial dark energy pointed out by the Johns Hopkins researchers would be only a third antigravity episode. "Maybe the universe only does that once in a while?"said Reiss.

If this dark energy remains constant, whatever is outside our galaxy in the long run will move away from us faster than the speed of light and will no longer be visible. The universe will become inert and completely dark.

But if the dark energy is temporary – if it is possible that one day it will stop inflating the universe – then cosmologists and metaphysicians will be able to contemplate the possibility of tomorrow. "An interesting feature of this is that there may be a future for humanity"said Scott Dodelson, a theorist at Carnegie Mellon University who looked at similar scenarios.

In addition, the future is still uncertain.

Far from disappearing, the dark energy that currently exists in the universe actually increased during cosmic time, according to a recent report from Nature Astronomy. If this continues, the universe could someday end in what astronomers call the Great Trait, in which atoms and elementary particles would tear, perhaps the greatest cosmic catastrophe possible.

This terrible panorama comes from the work of Guido Risaliti, from the University of Florence in Italy, and Elisabeth Lusso from the University of Durham in England. In the last four years, they have elucidated the deep history of the universe using cataclysmic phenomena called quasars as distance markers.

Quasars arise from supermassive black holes in the centers of galaxies; They are the brightest objects in nature and can be clearly seen throughout the universe. Quasars are not ideal as measuring lights for the Hubble constant because their mass varies greatly. However, researchers have identified some regularities in quasar emissions, which allowed us to trace the history of the cosmos to almost 12 billion years ago. The team of Risaliti and Lusso found that the rate of cosmic expansion deviated from expectations over this period of time.

One interpretation of these results is that dark energy is not constant but is changing, becoming denser and therefore stronger throughout cosmic time. It turns out then that this increase in dark energy would also be enough to resolve the discrepancy in the constant measurements of Hubble.

The bad news is that if this model is correct, the dark energy could have a particularly virulent form – and, according to most physicists, unlikely – called ghost energy. Their existence would imply, for example, that things can lose energy by accelerating. Robert Caldwell, Dartmouth physicist, referred to this as "bad omen."

As the universe expands, lunder pressure the ghost energy would grow without limits and eventually overcome gravity; it would rip the Earth first and then the atoms.

Astronomers try to measure this possibly dark ghost energy for two decades. Two space missions were designed – Euclides from the European Space Agency and NASA's Wfirst – to study it, and with luck, definitive answers in the following decade.

Meanwhile, Reiss said, everything – even phantom power – should be considered possible. The future of the universe is at stake.

* Copyright: 2019 The New York Times News Service


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