Janna Levin writes equations at the headquarters of her new project, Pioneerworks, in New York.
Cosmologist Janna Levin has summarized in just over 200 pages an epic that lasted 1.3 billion years. It all started when two black holes in an unknown area of the universe collided violently. They spewed out more energy than a trillion atomic bombs and it began to roam the universe in all directions at the speed of light like the ripples caused by a stone falling into a pond. When one of those waves entered our galaxy, humans were still living in caves. When it reached the closest star cluster to the Sun, as early as the last century, a physicist predicted that the universe could produce gravitational waves, but that we could never detect them. More than a century later the signal from the old black hole collision entered the Solar System, passed Neptune and reached the Sun. There were eight minutes left for one of the most important discoveries of recent science: the detection of the first gravitational wave. , the phenomenon predicted by that brilliant physicist: Albert Einstein . On that day humanity entered a new era of exploration of the universe. It was not only possible to observe it with telescopes, but to listen to it with gravitational wave detectors.
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Within this epic there is a shorter one: that of scientists convinced that it was It is possible to build a detector sensitive enough to pick up gravitational waves, which when they reach Earth only produce oscillations of space-time smaller than an atom.
In his book The Black Hole Blues , published by Captain Swing, Janna Levin (San Antonio, USA, 54 years old) interviews the main protagonists of this discovery, including Rai Weiss, Kip Thorne and Barry Barish , who won the Nobel Prize in Physics in 2017 for their discovery, and many others who dedicated a good part of their lives to devise the LIGO Detection Observatory and fight to get enough money to get it up and running. In this interview Levin explains that this detector and others like it will answer questions that have not even been asked yet.
Capturing gravitational waves is like recording the soundtrack of the cosmos
Question. Why do you think everyone should know the history of gravitational waves?
Answer. The first gravitational wave, produced by the first black hole collision ever detected, was the most energetic, most powerful event ever recorded by humans since the Big Bang. It is amazing because of all the energy that was released, nothing was in the form of light, it was something totally invisible. All the energy was released in gravitational waves, sound after all that deformed space-time, the material of which the universe is made. It's like recording the soundtrack of the cosmos. I was very interested in the obsessive madness of all the scientists involved in this project. Why did they do it?
Q. Since the discovery of the first gravitational wave, LIGO has gone much further and is now capturing black hole mergers that should not exist according to the laws of physics we know. What is the biggest question that Will we be able to respond thanks to gravitational waves?
R. Many people, even within LIGO, thought that signals from black holes could never be captured. There are experts who discarded studies because they were blindly convinced that these types of black holes do not exist. They had decided a priori that they do not exist. It is a limitation of some scientists who are not open minded. This is why the first detection was so important. The book is called The Black Hole Blues because it was a sad story. Even the parents of the experiment feared that they would never get the signal. They were going to fail. These new discoveries are exciting because they contradict the predictions, the models that say they cannot exist. These black holes can reveal the chaotic behavior of their environment and especially their origin. Until now we thought that black holes are super complex and dark and that nature only had one way to create them: by killing a very massive star. This has already changed. Thanks to LIGO we know that there may be alternative ways. Possibly there are black holes that appeared in the young universe and have grown to the sizes we see now. All of these questions are open again and the deniers must step back.
There is much more beauty in science than in religion
Q. Your next book is called Black Hole Survival Guide . What would happen to someone who entered one?
A. In some cases you would not even realize that you have fallen into a black hole
It may seem surprising, but the event horizon of a black hole, that border that if you cross and you can never go back, it is a very benign region. People think it is a solid surface, but in reality there is nothing. For the person who enters, the center of the hole is transformed into a point in time, his future. The same happens with stars when they collapse and create a black hole. They leave the horizon behind and keep falling in on themselves
Q. You explain that the interior of a black hole is luminous and that a person could survive within it for quite a long time
R. The interior of a black hole is an illuminated place because there is a lot of light that comes from outside and falls into the hole. These bodies are more benign than we think. A person could survive for a year or more while falling deeper and deeper into one of them. It all depends on the size. When you stand on the Earth you do not notice that you are stepping on a curved surface, but you are. However, if you try to stand up on a basketball, you will notice the second. The same goes for black holes. The smaller, the more violent the tidal forces, the pull of gravity on the different parts of your body. A very large black hole will not pull much on you, the effects will be much less. In any case, when you get to the center, what we know as singularity, the end is the same: you get to the center, to your future
Q. What happens then?
R. If we only consider the theory of relativity , you will shatter to the point that the atoms in your body will disintegrate and you will become a handful of elementary particles. There comes a point where those particles reach the singularity and cease to exist. But if quantum mechanics comes into play that is impossible. Roger Penrose thought that, that quantum would save us from disappearing completely. That matter ceases to exist, that information is lost, is something unacceptable according to the physics that we accept. We may be wrong, but if quantum mechanics is correct, information cannot be lost
Q Will we ever invent a way to explore the inside of a black hole and study what goes on inside?
A. There are so many theories about how to save information that falls into a black hole. Some say that the matter that falls is expelled and it remains around the horizon of events transformed into a network of quantum particles. Another theory says that there are wormholes that connect the inside and the outside. If any of this is true, and I believe it is, you fall in, but your quantum remains are left out. Then there is the possibility of reconstructing what has happened inside the black hole through the study of these quantum debris. But for now it is as impossible as burning an encyclopedia, whose complete information is still there transformed into heat and ashes, and rebuilding it to recover everything it contained.
All the information accumulated by humans will be lost because the Earth and the rest of the solar system will fall into a black hole, says the author
Q. In The Black Hole Blues you talk about the end of the universe. He says that in the end all the information accumulated by humans will be lost because the Earth and the rest of the solar system will fall into a black hole. Then the rest of the universe will fall into black holes and those black holes will evaporate. What will be left then?
A. If that is correct, and it is a widely accepted theory, the meaning of the passage of time will be lost. It can no longer be measured. Now we know that time has passed because we have changed since we started this conversation, for example. But once this is what you talk about, the universe will remain unchanged forever. If everything evaporates it will be just a great sea of evaporated matter. And it can be much worse. If the universe continues to expand in an accelerated way as before, eventually each particle will be left alone and will be unobservable because it will be so far away that the light will never reach it. It is a kind of event horizon of cosmological dimensions. Nothing can be seen anymore. With which talking about the passage of time will not make sense either. But this will happen on a huge timescale, something like a one followed by a hundred zeros or more. The universe was created 13.7 billion years ago, so it has much more future than past .
Q. What was there before there was a universe?
A. That is the question for which I studied cosmology. There are many ways to answer it. One theory says that the universe was originally very chaotic, with many dimensions, disordered. The idea is that maybe spacetime has always existed. Suddenly a small region of that space-time experiences a quantum fluctuation , as if it were on fire, until it accumulated enough energy to explode. That is the Big Bang . No matter how much we observe the current universe, we will never be able to see beyond that moment.
Q. If this theory is true, there are many other bubbles, many other universes. What was there before?
R. We only know that among a lot of possibilities our region caught fire and it is possible that the same thing has happened with many others. That is the so-called multiverse , a set of slightly different universes. Saying when something happened in another universe from our frame of reference is not a relevant question. Somehow you cannot synchronize the clocks to know what was before our universe. The idea of physicists like Stephen Hawking and Roger Penrose is that before the Big Bang there was nothing. Even nothingness can have quantum fluctuations. In this case only our region catches fire and explodes. There is nothing before the Big Bang because time has no meaning before this point. In relativity you cannot make general statements about time. You always have to know who is keeping time. If there is no clock, if there is no mechanism to record the passage of time because time does not exist, then what was there before time is not a relevant question.
Q. We understand only what 5% of the universe is made of. The rest is dark matter and dark energy What is the possibility that we are wrong and these do not exist?
R. It is possible but it is very unlikely. The evidence for dark matter is overwhelming. For example, let's think about the Bullet Cluster , which are two groups of galaxies in full collision. We see where the light is and where the mass of these galaxies is, and for everything to have that shape there must be dark matter. This component of the universe is not as mysterious as some people think. Neutrinos are a form of dark matter . They do not interact with light. We know that they are particles that have mass but are invisible. The mystery is that neutrinos cannot explain dark matter. That's why many dark matter experiments look for neutrino-like but heavier particles.
Q. What about dark energy?
A. That worries me more. The experiments to show that it exists are much more difficult and there are alternative explanations. I think it exists because many different observations have come up with the same conclusion [that dark energy is the cause that the universe is in constant accelerated expansion].
Q. Do you think it takes a god to explain some of the big questions? of the universe?
A. No, I'm an atheist. There is much more beauty in science, in cosmology, than in religion, in magical answers. I have a lot of respect for the people who are comforted by that way of seeing the world, but it doesn't work for me. I feel much better thinking that we are part of a universe that we can try to understand. The good thing about this vision is that it is universal. Science explains facts that are true for everyone, believe what they believe, wherever they live. I also believe that this way of understanding the universe improves humanity, generates better relations between peoples, less wars and violence.
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