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Space: Why do we say looking at the sky is a bit like looking back?

Space: Why do we say looking at the sky is a bit like looking back?

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The universe is full of surprises. (© NASA/STScI Webb Images)

Space is full of surprises and strange things. Recently we filmed a question mark in the sky. We also discovered an ocean planet, and another in the shape of a rugby ball.

What if we told you that looking into space is like looking far into the past? It sounds crazy, but it’s true. Good to know as you observe Perseids 2023, which is expected to peak on Saturday night.

Obviously, it is difficult to distinguish with the naked eye. But with the right hardware, you can. explanations.

When we look at the moon, we see it late

This phenomenon is due to the huge distance between us and the components of the universe. Jean-Pierre Martin, a nuclear physicist by profession, chairman of the Cosmology Committee of the Astronomical Society of France, sums up, “The more we look into the universe, the more we look back into the past.”

As a reminder, the only source of information we have about distant galaxies and other stellar objects is the light they reflect.

Light travels at a speed of more or less 300,000 km/s. It’s pretty fast, but not much by such measures.

Take, for example, the Andromeda Galaxy. It is located 2.537 million light-years from Earth. Therefore, it takes 2.537 million years for its light to reach us.

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We’re looking at Andromeda as it was 2.537 million years ago.

Jean Pierre MartinNuclear physicist by profession, Chairman of the Commission on Cosmology of the Astronomical Society of France.

In the same direction, the Moon is just over 300,000 km away from us. So, in a narrow sense, we have moreOne second behind the moon fact.

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Same for our Sun, which is on average 149 million km away. Its light takes about eight minutes to reach us. Also, if it explodes for x or y reasons (this is not planned at all at the moment, don’t worry), we earthlings will continue to light up for eight minutes. Before plunging into a moonless night (it does not emit light and only reflects sunlight).

Do we see stars that are already dead?

This physical phenomenon means that sometimes we notice stars that are already dead. Some are so far away that their light takes billions of years to reach us. Also, in the meantime, something might have happened to them.

As it appears to us at the moment T, we do not see it. “We can only guess,” says the physicist.

On the other hand, for the star Eärendel, which is 28 billion light-years away from us (the farthest thing ever observed by man), we are fairly sure that today it is not more or more. However, we see it!

Seeing the sky is traveling in time. Incredible, right?

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