- Ruth Lazcuz
Let’s put a strong title, an old question, and a few drops of physics into the cocktail shaker. If we shake it well, all we can do is taste it.
But will you leave a good taste in your mouth knowing what fate has in store for the universe?
We have collected here the testimonies of all the people who have asked this question to themselves since ancient times.
However, we do have one advantage: We can finally provide answers using the latest science, and predictions suggest we may be heading toward a violent end, a major rupture.
The empirical data fit well with the large rupture, indicating that it is very likely to occur.
The bottom line is that the universe has enough dark energy to “stretch” it, expanding faster and faster.
The galaxies will move more and more, and little by little the gravitational pull will become less important until its influence wears off.
Planets and satellites will lose their orbits, and stars will separate from galaxies.
Then will come the great rupture of the universe.
Dark energy is expanding the universe rapidly
The large-scale universe is definitely getting bigger.
Specifically, the pace of its expansion is accelerating.
Einstein’s equations suggest that the reason is that they are mainly composed of dark energy, which produces repulsive gravity.
But can we improve it further?
Let us humbly admit, before moving forward, that our paradigms hide our ignorance by presenting it as wisdom.
In them, we imagine dark energy as a liquid described in a very elementary way. We use inherited variables from thermodynamics for this.
On the one hand, we will have the pressure of this fluid; On the other hand, its density, that is, the amount of energy per unit volume.
If we only had particles with small velocities, then this energy would basically be the energy of their masses.
Thus, it is sufficient to think of gravity in the manner of Newton, without relying on Einstein.
But this is not possible because in our universe very fast particles, such as photons and neutrinos.
Given this, we then suggest that the universe is a soup of different liquids with their different properties.
Thus, we make Einstein’s equations tell us what properties different fluids must have in order to produce accelerated expansion.
And not only that, they tell us in what proportions these components should be.
In addition to photons (neutrinos and other junk), we will have dark matter in the component segment that produces gravitational attraction. They are incompatible with dark energy.
The rate of expansion can become unlimited
The most interesting type of dark energy is the cosmological constant, and it presents a rather unique barrier.
The most common working assumption for describing any of the fluids mentioned is that pressure and energy density are proportional to each other.
But be careful! While the energy density is always positive, dark energy has a negative pressure.
In fact, it should be negative enough.
The number that controls the ratio of pressure to energy density plays a crucial role in solving Einstein’s equations.
This parameter primarily tells us whether or not the universe is expanding rapidly.
In other words, it determines whether the pressure is negative enough to produce the desired repulsion.
But even more negative pressure can lead to dramatic behavior: the rate of expansion can suddenly become unlimited.
In fact, the size of the universe itself (and its scale factor) will be as well.
And this would have disastrous consequences, destroying all known structures.
In fact, all this would be nonsense under the circumstances. Also, change in change will suddenly become limitless.
There is a clue
The possibility of this situation occurring is well known in theory. Surprisingly, the empirical data seems to favor this position. In other words, there is evidence that the universe may end up in a major rupture.
Well, it is useful to go into detail in order to avoid the protests of some colleagues. Depending on the sources consulted, this scenario is not necessarily what the statistics strongly support.
But, interestingly, the consensus suggests that the current margin of uncertainty includes the significant rupture between the most likely final destinations.
Phantom dark energy is to blame
The type of dark energy that causes the end of this violent party is called phantom dark energy.
To give more details, it is necessary to resort to the system of modules selected for this.
Using it, we see that a large rupture will occur if the pressure exceeds the energy density in absolute terms.
If they are equal, then we are faced with a bound state, namely the famous cosmological constant.
Einstein introduced this well-known type of fluid.
Ironically, their goal was to achieve a stationary, unexpanded universe. The genius abandoned him, calling it the biggest mistake of his life when Hubble proved the expansion of the universe.
130 billion years until the Great Rip
But back to what matters.
If the universe were to shatter into a thousand pieces, what things should we stop worrying about? Will anyone with a mortgage to pay another 20 years breathe a sigh of relief?
I’m afraid I’m not the bearer of good news.
The Great Disruption could take about 130 billion years to occur.
This is 10 times the age of the current universe.
This estimate is based on selecting a pair of values within the windows that are statistically valid.
First, we can say that dark energy accounts for 70% of the content of the universe.
And second, we will make the relationship between pressure and energy density only 10% larger than the cosmological constant.
And with that it is over! We anticipate a major rupture that will take a long time to arrive.
To further improve this whole picture, we need large-scale observations of the universe of greater quantity and quality.
Data provided by the James Webb telescopes (underway) and Nancy Grace Roman (planned), along with those from other international efforts, will undoubtedly contribute to this.
Perhaps most interestingly, the mystery of the universe’s ultimate fate has yet to be solved.
Nor is it an opportunity to solve the others that we haven’t talked about.
It would be really interesting the possibility of unknown mysteries emerging.
Because, as physicist and Nobel laureate Kip Thorne said, “The right answer is rarely as important as the right question.”
* Ruth Lazcuz is Professor of Theoretical Physics at the University of the Basque Country / Oscal Herico Universitatia, Spain.
This article was originally published on the academic news site The Conversation and is republished here under a Creative Commons license. Read the original version here (in Spanish).
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