On November 18, 1989, NASA launched the cosmic background explorer COBE (Cosmic Background Explorer), which made the first measurements about the big bang and the origin of the universe. COBE dated its age to 13.8 billion years and obtained an echo image of that first explosion, shortly after it formed (300,000 years). The idea of the project had been had in 1974 by John Mather (Virginia, 1946), a physicist then twenty-eight years old who was doing his doctoral thesis. For his studies he won the Nobel Prize in Physics in 2006. There was already a theoretical precedent in 1948, when the physicist George Gamow and the cosmologist Ralph Alpher predicted in an article that the big bang would have left a radiation in the matter that could be detected and measured . Then, in the 1960s, physicists Arno Penzias and Robert Wilson measured the cosmic microwave background radiation from the big bang in a laboratory in New Jersey, earning them the Nobel Prize in Physics in 1978.
But the measurement of the cosmos from the Earth has many interferences. It was necessary to go further, and then Mather had his crazy idea: to place an eye in space, the COBE satellite, which operated between 1989 and 1993. Since 1995, Mather works as the scientific director of an heir to the COBE space telescopes, WMAP and Hubble (this one is still active): the James Webb Space Telescope (JWST), a technological marvel destined to revolutionize the science of the universe, whose launch, after successive delays, is scheduled for October 31 of this year. Mather welcomes us in his office at NASA’s Goddard Space Flight Center outside of Washington.
He is a smiling man, tall and thin, with very large glasses. On the table, some papers, the computer and several copies of the book The Very First Light (1996), in which he told the story of COBE and its research.
In November of last year, COBE was thirty-two years old, an idea that you raised in your thesis and that you described as crazy. How do you remember it?
It was a proposal between crazy and necessary [smiles]. You have to imagine what could happen instead of what seems like it could happen. I raised the proposal with my boss, he talked to other people and it prospered.
Have the results obtained with COBE changed the universe described by Einstein in the same way that it changed Newton’s?
No. Einstein gave us the descriptive tools of the cosmos as we see it now. I was not wrong. His general theory of relativity has been tested in many ways, and it fits. The only thing he did not foresee was that the universe could be expanding. He believed it had to be static. His theory is true, but he made that mistake.
You have said that the term big bang to illustrate that first moment is not very accurate. Why?
Big bang sounds like a firecracker has just exploded. An explosion is an event that happens in a specific place and time, but that did not happen, but the entire universe began to expand and also very quietly. Something almost the opposite of what people imagine when they hear the expression big bang happened.
Is there room for a god out there, a deity that shaped everything we contemplate by looking at the sky?
A believer would say that we are contemplating what He did. But what the Bible says is not what we see in space. Science cannot explain everything, but it can explain many things. Of course the general principles in which we operate seem to be true, only that it is not possible to use those principles to predict and describe all the details of reality. The idea that two human beings like you and I are having this conversation could not have been predicted from the laws of nature.
The idea of an infinite universe, that there may not be a beginning, seems shocking and counterintuitive. It takes a lot of imagination to try to understand that.
It’s true. In the image of an expanding universe there is no first moment, just as there is no positive number that is the smallest, the first number. When we try to get to those early moments of the big bang, to those fractions of fractions of a second, the imagination is not enough. As the temperature and the density were very high, we ventured that the rules of nature did not operate the same as now. But the big question is: what happens when gravity is as strong as the other natural forces?
If gravity affects space and time, the latter may become meaningless. They are mysterious questions, we do not know the answer and we could never know it, because how would we test it? When someone says: “Maybe there was something before, that there were previous universes that collapsed and that gave rise to the expanding universe that we have.” Maybe, but we can only frame it as assumptions.
Could there be a universe before the expansion of the big bang?
Maybe yes. Mathematicians also say that there could be other cosmos besides this one. We cannot know. In addition, the idea of the universe already includes everything! Mind you, we are lucky to have found evidence to support many theories and concepts. Now, for example, we want to know what dark matter and energy are, but it is very possible that they will never be measured in a laboratory, since they are extremely weak. We have not seen them – by definition they cannot be seen – but we can measure their effects. When you say dark matter, people imagine that it is black, like a black sweater, but it is not like that: dark matter is transparent. 75% of the universe is made up of dark energy, 21% of dark matter, and the rest of the ordinary matter that we see.
If what we know about the universe comes from measurements made from a ridiculous planet around a common star in another galaxy, can we be sure of something?
In science one can never be sure of anything. It’s hard to come up with a story that fits everything. It is possible to think that we do not observe things directly, so we cannot know if reality adapts to the idea we had of it. There is also the possibility that there are other true explanations that have not yet been discovered. It is a question almost of pure imagination. There will always be areas that we cannot reach. You cannot measure every moment of the universe. We cannot describe them directly. We can only come up with an idea and check whether the predictions made from that idea match what can be seen. It is not possible to definitively prove that something is true. Just prove it to be false.
For theoretical physics, is time travel possible?
We don’t know enough to say that they are impossible, but we also don’t know how they could be done. There is a concept called wormholes – wormholes, in English – hypothetical structures of space-time. If they existed, perhaps they could be used to go from one part of the universe to another. But we do not know if they exist, and, according to the calculations made, if they did exist they would be unstable, so they would disappear, so we could not use them. At the moment we only know how to go forward, but we can travel back in time with our imagination. This quality is wonderful for science. Go to the big bang and imagine what it was like. When we observe space we also travel in time: we see things as they were.
Because of the light, but has there always been light in the universe?
As far as we know, yes . We do not know if it was the first thing to be created, but probably in the early universe there were light waves at the very beginning. Light is one of the most important things in life. The universe is full of matter, protons, electrons and neutrons as we see them today, and they were all here from the beginning, such as antimatter [a less common form of matter that is made up of antiparticles], which was abundant, and gravity , which is a very powerful force. We wouldn’t be here without them. a less frequent form of matter that is made up of antiparticles.
When you talk about those first moments, do you mean a few million years, thousands, hundreds, how long?
At a fraction of a tiny fraction of a second.
What is antimatter?
It was predicted a century ago from the idea that in addition to particles there should be antiparticles, and that when they collide, huge amounts of energy would be released in the form of light. Matter and antimatter are opposites and would deny each other. We know that we can create antimatter by colliding two elements, but we don’t start with antimatter. If you collide two electrons, enough energy is produced to create particles from it and you end up obtaining new particles that are equal parts matter and antimatter. This is extraordinary: matter can be converted into energy and vice versa.
Could there be areas of the universe made up of antimatter, such that there would be antiplanets and antigalaxies?
No. If there were a part with antimatter it would collide with another with matter and the contact would cause the annihilation of both and a huge release of energy. Nothing is seen in space to express that. It is not logically impossible, but it is unlikely.
Why are there laws of physics?
The evidence says that there are and that they work everywhere. Science studies those that rule on Earth and then looks to see if they operate elsewhere. Like when we use a spectrometer to do a chemical analysis of fireworks, which produce different colors according to different chemical elements. Well, the same happens with the stars and planets that we discover, and we see that everything works in a similar way. All the atoms in the universe appear to be the same.
A distant galaxy is like ours in the elements that compose it. It seems that there are only a few physical laws and they operate everywhere: the law of gravity, Einstein’s relativity, the speed of light, which is constant, or the cosmic microwave background radiation. Then there are things that change because the universe is expanding and cooling, but natural laws do not change. It is the content of the cosmos that is transformed.
Why do we see the universe as mysterious and beautiful as a painting by Leonardo da Vinci or a cathedral?
Because the story it tells is extraordinary. Hubble photos tell where we come from: we see examples of how stars were born, how planets arose, galaxies like ours, and we think: “This is my story, that’s where I come from.”
How and when did your vocation arise?
Coming Soon. In elementary school, I heard about infinity and picked up all the science books I could find. At the age of eight I was reading about great scientists and I thought I wanted to imitate them, although I did not know in what field. Astronomy was exciting in 1954. Today it is even more so because there are many discoveries thanks to space telescopes. From Earth, the atmosphere makes it difficult to see well. Much information from space comes in the form of waves, and the atmosphere clouds them. But a space telescope can see galaxies formed billions of years after the big bang with just an 85 cm diameter mirror.
You are the scientific director of the James Webb Space Telescope (JWST). What goals do you set for yourself?
We have delayed the launch because it has been difficult to build. The problem is that it is very large and will have to live in cold outer space. It has to be tested in a similar environment, created at the Johnson Space Center in Houston: a large tank 20 m in diameter by 4 m high that was erected for astronauts going to the moon. Testing the JWST in the tank is time consuming and expensive.
What do you hope to find with him?
We want to observe nearby objects and also the first galaxies, stars and black holes that were generated after the big bang. We are going to study the gravitational processes that gave rise to the Milky Way, to photograph the history of the universe and to trace the zones of stellar birth. Around the nebulae there is an accumulation of gases and stars; some of them are barely three million years old, and we know where they are being created. Stars are born in very cold regions of cosmic dust. The lower the temperature, the lower the pressure. Gravity can overcome it and knead the materials and gases into a compact object that ends up being a star.
Why are stars so important?
In the big bang there were only hydrogen and helium, two gases. The other elements were later manufactured in the stars. We are made from materials that were generated within you, we are stellar recycling. Gold, for example, arose from the collision of stellar neutrons. They generated, together with the stars and gravity, all the elements. And we are paleontologists of the universe.
Space projects generate new technologies and inventions that we later use in everyday life. What will the JWST leave us?
One team member devised a system to correct telescope mirror errors and realized that he could apply it to calculate vision failures in the human eye lens. So if you go to the eye doctor, you may see better thanks to the JWST.
How long will the James Webb be in operation?
Ten years. Six months after launch, it will start collecting data. It will be located 1.5 million kilometers away, at a point where the Sun, the Earth and the telescope will be aligned and we will be able to deploy its parasol so that it is cold and protected from the solar heat.
Where do you think surprises could come from?
There are many mysterious objects and phenomena in space, such as fast radio bursts, discovered in 2007, that come from very remote places, but we do not know what produces them. Maybe with the telescope we’ll find out. We also want to study exoplanets. We know that most stars have them and that some may be the right temperature to support life.
Do you think there could be life in other parts of the universe?
Yes, the cosmos is huge, so chances are high. If a planet is the right size and temperature and contains water, there is likely to be some kind of life on it. As for intelligent life, having two people elsewhere having a conversation similar to this is perhaps more unlikely.
How did the Earth come about?
According to recent data, the Sun was created from gases and matter in a very cold region where gravity was able to amalgamate them. The Earth would have emerged from the remains of those materials. There are similar events in the universe, but we have not been able to see planets form, although there are images of the formation of solar systems.
On the one hand it seems that the universe is chaotic but at the same time the image of a stable and orderly entity emerges. What is it really like?
Both. Stability is time dependent. For us, the Solar System is very stable. The sun invariably rises every twenty-four hours. But if you handle a timescale of ten million years, you see that the climate has changed and many species have also changed, and after a hundred million years you find that the continents have moved. As for the universe, it is highly structured hierarchically: there are huge elements, galaxies, which in turn are gathered in groups and contain other smaller elements, which are stars, which are surrounded by planets. And everything is influenced by gravity, which acts on all elements and orders the structure. And in places in the universe where there are no galaxies, there is cosmic dust.
Did the big bang have to happen or did it happen because something went wrong?
We have no other universe to compare with. According to Alan Guth’s theory of the inflationary universe, it was formed by an instability that led to the big bang and everything that followed. But in the long run everything is unstable. Gravity makes things so.
Is the expansion that unleashed the big bang accelerating?
The cosmos is accelerating. Galaxies are moving away from each other due to dark energy. In the first 9 billion years, gravity offered resistance and was able to reduce the speed of cosmic expansion. However, in the last 5 billion years, it is going faster and faster due to dark energy.
Will it expand forever?
Yes, because of the dark energy it contains. Could the expansion be stopped? We do not have a reason to justify it, so it will most likely continue to expand forever. Although if the dark energy disappeared, the universe would stop its expansion.
Would it contract again and then expand again?
Apparently not, but there is no way of knowing. The big bounce theory defends that the universe contracts and compresses cyclically. There are scientists who think it is possible.
Does nothing exist for a physicist?
We can’t say much. We can talk about how one thing becomes another, but there is no way to explain that at some point there was absolute nothingness and then something emerged. For me, that concept of nothing has no meaning, it does not mean anything.
