How do we measure the age of the Universe?

How do we measure the age of the Universe?


It is difficult to imagine the immense period of time that has elapsed since the Universe was formed.

When did everything start?

To discover it, the BBC “detectives”, the geneticist Adam Rutherford and the mathematician Hannah Fry, embarked on an epic journey to go back to the beginning of all time .

The question, however, is not long-standing. 100 years ago it was not even a question, nobody thought that the Universe could have some age.

At the beginning of the 20th century it was considered to be eternal.

“In 1915 the physicist Albert Einstein was sure that the Universe had always been there, and that, therefore, it did not have a beginning,” explains physicist Jim Al-Khalili.

But now we know that it is not like that. Who contradicted it?

Albert Einstein in 1921
Copyright of the WIKIMEDIA COMMONS imageImage caption Albert Einstein thought that the Universe had always existed.


Georges Lemaître was a physicist and a Catholic priest of Belgian origin. He was the first to make the observations of the Universe correspond with the theory (Einstein had not succeeded), and thus he realized that he was expanding.

Al-Khalili says that in 1927 Lemaître presented his idea to Einstein, who responded by saying that his mathematical skills were admirable, but the physics were abominable.

The next chapter in the story is that of the American astronomer Edwin Hubble, who showed, once and for all, that the Universe was expanding … after surprising everyone with the discovery that there were galaxies outside the Milky Way.

“He was studying them and he realized that they were moving quickly as far as he could see further and that’s what he found,” says cosmologist Andrew Pontzen.

And he continues: “You know that the galaxy is expanding by measuring the color of the light it emits, if the red color is more intense than what is usually observed, it means that it is moving, and the extension of that modification is what it indicates how fast it moves. “

By calculating the change observed in the light it is possible to know at what speed the galaxy is moving. That, however, does not allow us to calculate how many years the Universe has.

Night landscape
Copyright of the GETTY IMAGES imageImage caption Thereare many mysteries that the Universe hides.


The accounts that Hubble took, however, were incorrect. According to his estimates, the Universe was 2,000 million years old.

It was the decade of the 30, and at that time the scientific community coincided with respect to the age of the Earth: 3,000 million years.

The discrepancy did not make sense. Fortunately, in the following decades, the mechanisms that allowed calculating the distance to which the galaxies were located and the speed at which they moved were perfected.

“But it was not easy to reach an agreement, there were several groups of scientists confronting each other, and everyone was convinced that they were right,” says Pontzen.

The supernova stars , which some describe as cosmic bombs because they are characterized by exploding, made it possible to clarify the diatribe.

Explosion in the Universe
Copyright of the GETTY IMAGES imageImage caption The intense light from the explosion of a supernova star allowed us to understand more about Space.


“The light they emit when this happens is so intense that for a short period of time it can be seen in the depths of Space,” says astrophysicist Jo Dunkley.

And he continues: “Until 20 years ago we believed that although the Universe was expanding, that process was slowing down.”

But scientists who studied supernovas surprised their colleagues with a discovery that was recognized in 2011 with the Nobel Prize.

And is that according to the calculations made, contrary to everything that was believed until then, the expansion process of the Universe was accelerating.

“I thought we had made a mistake in the observations we made, maybe we were wrong in the analysis, so we went back to review our work, but we could not find any mistakes,” said astronomer Alex Filippenko, who received the Nobel Prize.

Interior of the building where the Nobel celebrations are held in Stockholm.
Copyright of the GETTY IMAGES imageImage caption The discovery that the expansion of the Universe accelerated surprised everyone and won the Nobel Prize for the scientists who detected it.

The answer

The demonstration that the speed of expansion is greater today means that, in the past, it was lower, which in turn implies that the Universe is older than previously believed.

This discovery, however, brought other problems: physicists did not know how to explain acceleration.

But they did manage to establish a consensus, which is still valid, with respect to the age of the Universe: a little less than 14,000 million years.

Part of the uncertainty has to do with the “dark energy”, the “antigravity” process that accelerates the expansion of the Universe … Another scientific mystery that awaits to be revealed.

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Rava Desk

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