What is the oldest light we have observed (and does it ever go out?)

There are phrases that we have become so accustomed to that our astonishment has worn off a little, but that if we rethink them, they can awaken curiosity.

Described as a “cosmic miracle” by the team of scientists who detected it with the James Webb Space Telescope, its discovery is awaiting peer review to be confirmed as the point detected by the most distant and, at the same time, oldest scientific instrument of all.

An echo of a very remote past, because we cannot forget that, since the Universe is so colossal, by the time those lights arrive, the objects that emitted them are no longer the same.

What astronomers observe is what it was: a point that indicates that a galaxy existed, which may now be a gigantic galaxy… or who knows what.

When we look at the lights in the sky, we travel through time.

But what about the future? Will the light have an expiration date?

If scientists have detected light that began its journey almost since the dawn of time, does that mean it never goes out?

“Photons are complicated,” answers astronomer Matthew Middleton.

“But you don’t have to go very deep to appreciate that energy is conserved in any closed system: that’s the first law of thermodynamics. So energy doesn’t disappear, it just changes form.

“A photon is a form of energy, and that energy will always exist in some form. Photons can change, but the energy remains.”

How can a photon transform into something else?

“You can get photons that produce matter and antimatter particles. So you can literally see light turning into matter. By the way, that’s why we exist.

“But photons can also be absorbed.”

When a photon hits an atom, its energy can be absorbed and cause an electron to rise to a higher energy level, Matthew explains.

In that case, the photon ceases to exist as an independent particle and the electron “jumps” to an excited state, taking with it the energy that the photon delivered. If the photon has enough energy, it can even completely knock the electron out of the atom (ionization).

“That energy is no longer in the form of a photon, but temporarily stored in the electron and the nucleus, but it still exists and can later be re-emitted as light, perhaps with a slightly different energy.

“It changes, it moves, but it is never completely destroyed.

“This is another way of looking at it: if I created something that released a photon into the Universe and it never interacted with anything, it would forever be a photon.

“It never turns off suddenly… if it did, it would drive many physicists crazy.

“So yes, in principle, light lasts forever.”

In conclusion: light has no expiration date.

If it traveled through empty space, it would continue to shine forever.

And even if it interacted with something, it wouldn’t be destroyed, it would just become a different form of energy.