The James Webb Observatory, about to ascend to the skies (a kilometer and a half away from Earth), will be able to capture the first “light” of the cosmos. But how is this possible? How can you observe something that happened at the beginning of time?
For starters, if James Webb is to detect a cosmic birth, where should he look? If you’re going to see the origin of everything, the primordial light, the first glimmer behind the eternal darkness, where do you point?
the big bang is deceptive
The answer involves one of the most fascinating stories in science. Let’s accept a dark soup of primordial particles, suddenly an explosion and the universe begins to exist. With the explosion comes space, time, matter and energy.
Until now, we could talk about an exact point where it all started. But this is not exactly the case.
«The name Big Bang gives the idea of a rocket that explodes in a time and place, with a center. But the universe has no center »
“The Big Bang is a really misleading name for the expanding universe we see. We see an infinite universe expanding. The name Big Bang conveys the idea of a rocket that explodes in a time and place, with a center. But the universe has no center. The Big Bang was a process that happened in time, not a point in time. We know this because we see galaxies moving away from each other, not from a central point, and we also see the heat that’s been left over from the early days, and that heat evenly fills the universe,” he explains. John Mather, Principal Scientist of the James Webb Space Telescope Project on NASA’s official website.
Everything that exists today, December 2021, everything from the essential particles that make up a butterfly’s wings or the pen I bite, to the galactic dust beyond Orion, essentially all lived in the Big Bang.
There is no center from which the universe expanded because, among other things, space did not exist, time did not exist. Space is created because matter begins to occupy it. There is a metaphor that may help to understand how the space did not exist until it was occupied. It’s like thinking about the future, which never exists. We occupy the future as we live in the present. So space and time exist as the universe expands. Pretty crazy, right?
Mathematics, that science that says there are infinite dimensions, or defines the rules by which parallel universes work, shows that the universe is isotropic and homogeneous. In other words, it’s the same no matter where you look at it. This principle is actually supported by observations.
So this is the answer to the first question: where do you look James webb see the origin of the cosmos? Whatever.
The journey from the origins
From anywhere in this exotic and convulsive universe, a photo of its origin could be obtained.
It’s easy to forget that light needs time to travel. When we look at the moon, we see what it was like 1.3 seconds ago. So to look ten billion years into the past, you have to look at ten billion light years.
It would be possible that somewhere in the universe someone was looking at our galaxy, the Milky Way, as it was at the beginning, right at birth, at a time when Earth and humans did not exist.
With James Webb we will, in fact, have a picture of how things were at the beginning of time
Now let’s turn this around. By analyzing the spectrum of light that reaches us from an object, we can know how far away it is from us and, therefore, where in the past the photo we received belongs. With James Webb we will, in fact, have a picture of what things were like at the beginning of time.
There is another proven calculation, and that is that the universe is already an age. 13.7 billion years, a million above, a million below. Accepting this, James Webb is so sensitive that he will be able to catch light from the first objects that formed, will be the first stars and galaxies, or whatever it is that formed in the beginning of space and time.
That flash will have spent 13.7 billion years traveling through space to reach the James Webb. It will be very weak infrared radiation, invisible to the human eye. The international team of engineers and scientists who built the Webb had to design the largest, most expensive and most complex telescope in history to capture it.
Why infrared light?
The universe is in permanent expansion. The space between galaxies gets bigger and bigger as it expands. Between Andromeda and the Milky Way we inhabit, there is more and more space. The light we receive from galaxies “extends” as they travel through space.
To understand it, the example of the sound of a siren is often given: we will perceive it louder when it is closer and lower when it moves away. The same is true for the wavelengths of light emitted by objects.
The light is compressed as it gets closer (it turns blue) and stretches as it moves away (becoming redder). This snippet is called the cosmological redshift. And here comes the key to everything: if we observe an object that is moving away from us, the light we perceive will shift towards red proportional to the speed and distance that the object in question is moving.
The signal that will arrive from the first light of the cosmos will be very weak, and will have traveled 13.6 billion light years to reach the James Webb
This light will let us know how fast it is moving and how far away it is. The signal that will come from the first light in the cosmos will be very weak, and you will know it is coming from there because its wavelength will indicate that it is coming from a place 13.6 billion light years away, the moment when the first photon possibly formed. This infrared signal is a heat wire, which can only be recognized if the telescope is, on the contrary, very cold.
James Webb’s Sensitivity
The JWST will be almost as dark and cold as outer space to ensure it will be able to receive signals as far away
On the way to the destination, the telescope slowly unfolds five sheets made of Kapton, the size of a tennis court and thinner than notebook paper. These blades will act as a giant umbrella, protecting the telescope’s body from the light and heat of the sun, moon and Earth. This way, the JWST will be almost as dark and cold as outer space to ensure it can receive these distant signals.
The ‘James Webb’ is the largest telescope ever launched into space. Fruit of collaboration between NASA, ESA and the Canadian space agency.
As soon as the protective umbrella is unfolded, eighteen gold-coated beryllium mirror hexagons will open up like a huge flower. The mirrors will form a reflective surface as tall and wide as a house and will have the ability to detect light that has been traveling for more than thirteen billion years.
The chemistry that gave birth to life
Looking in the infrared, we’ll look further back in time than Hubble achieved, and we’ll see light coming from the first galaxies to form.
James Webb will be able to pick up the faint signals of heat from these objects that are so far away.
JWST was not designed to see the beginnings of the universe, which was a huge soup of particles in absolute darkness, but to see a period in the history of the universe. that we haven’t seen before. Specifically, with James Webb, they hope to see the first objects that formed when the universe cooled after the Big Bang. We don’t know exactly when the universe generated the first stars and galaxies, or how they happened. This is what JWST will help answer.
Where we came from. The GN-z11 galaxy is so far the most distant galaxy detected from us. It’s 13.4 billion light years away. Has been detected by Hubble and it is estimated that it was born when only three percent of the entire universe existed, 400 million years after the Big Bang
“The chemical elements of life were first produced in that first generation of stars after the Big Bang. We are here today because of them and we want to better understand how it happened! We have ideas, we have predictions, but we’re not really sure. One way or another, the first stars must have influenced our own history, starting with shaking everything up and producing the other chemical elements besides hydrogen and helium. If we really want to know where our atoms come from and how small planet Earth came to be able to support life, we need to know what happened in the beginning. That’s what James Webb will achieve,” adds John Mather, lead scientist for the James Webb Space Telescope project.