What was before the Big Bang?

Advertisements

It’s the question that always arises when thinking about the origin of the Universe: what happened before?

Advertisements

And if it wasn’t there before, what was the cause of the Big Bang in the first place?

Until a few centuries ago, the answer was easy: an eternal divinity set everything in motion.

Isaac Newton also believed that God created the universe some 6,000 years ago.

Advertisements

Later, many scientists, including the young Albert Einstein, believed that the Universe itself was eternal and eternal.

Albert Einstein writes an equation on a blackboard

Einstein’s theories of spacetime have revolutionized our understanding of the universe. Credit: Bettmann/Getty Images

But when cosmic expansion was discovered, Belgian cosmologist (and Jesuit priest) Georges Lematre realized that there must have been a beginning of a scientific version of Genesis, so to speak.

Not that everyone immediately agreed.

Advertisements

Until the 1960s, Fred Hoyle’s steady-state theory was quite popular among iconoclast scientists and laymen alike.

Hoyle accepted the expansion of the universe, but he didn’t believe in the Big Bang.

Instead, he assumed that a slow and continuous creation of new matter could keep the average density and general properties of the Universe constant over time.

Advertisements

Popular in the 1950s, steady-state theory claimed that matter is continually being created as the Universe expands, a theory superseded by the Big Bang idea that density decreases as galaxies move away from each other. from each other

Popular in the 1950s, steady-state theory claimed that matter is continually being created as the Universe expands, a theory superseded by the Big Bang idea that density decreases as galaxies move away from each other. from each other

The 1964 discovery of the cosmic microwave background was the major nail in the coffin of the steady state theory.

Since then, the evidence supporting the Big Bang origin of our Universe has accumulated to the point where there is almost no doubt left.

However, no one has the definitive answer to the question “what happened before the Big Bang?”.

Advertisements

Could there have been a Universe before the Big Bang?

Most scientists simply ignore the question, as it seems to be too hard a nut to crack.

A snapshot of the cosmic microwave background - the residual heat from the Big Bang - when the Universe was only 380,000 years old, as seen by the Planck telescope.  It shows tiny temperature fluctuations that correspond to regions of different densities – the seeds that would grow in today's stars and galaxies.  Credit: ESA and the Planck collaboration

A snapshot of the cosmic microwave background – the residual heat from the Big Bang – when the Universe was only 380,000 years old. Credit: ESA and the Planck collaboration

Indeed, when astronomers talk about the Big Bang, they are usually not referring to the beginning of the Universe (time zero), but to the incredibly hot and compact state of the Universe in the first two minutes of its existence.

Advertisements

To some extent, this is because no one has a real clue about the true nature of time, let alone the beginning of time.

British physicist Julian Barbour, for example, has argued that time doesn’t even exist, except as an illusion in our minds.

According to others (including Stephen Hawking), time came into existence along with the Universe, making the whole concept of the word before meaningless.

Advertisements

Asking what happened before the Big Bang would be like asking what lies north of the North Pole, or what distance is below zero.

Hubble Ultra-Deep Field 3, June 2014. Virtually every bright spot in this image is a galaxy, each made up of billions of stars.  Credits: NASA, ESA, H. Teplitz and M. Rafelski (IPAC/Caltech), A. Koekemoer (STScI), R. Windhorst (Arizona State University), Z. Levay (STScI)

Will all matter end up folding in on itself? Credits: NASA, ESA, H. Teplitz and M. Rafelski (IPAC/Caltech), A. Koekemoer (STScI), R. Windhorst (Arizona State University), Z. Levay (STScI)

alternative theories

Then again, we just don’t know whether or not there was time before the Big Bang.

According to the once popular idea of ​​the cyclical (or oscillatory) Universe, the current expansion of space could one day turn into a contraction, and the resulting Big Crunch could rebound into a new Big Bang, starting the next cycle of a eternal sequence. .

Advertisements

To find out more, read our interview with Katie Mack on the end of the universe.

It’s just one of many hypotheses where our Universe is not unique, but part of a possibly infinite multiverse, one way or another.

And if the multiverse is also infinite in time, we return to the idea that everything has always existed, conveniently circumnavigating the nagging question of a beginning.

Advertisements

What is Antimatter?  Credit: NASA/JPL

Credit: NASA/JPL

Finally, South African physicist Neil Turok thinks that the Big Bang not only spawned our Universe, but also an anti-Universe, composed of antimatter and running back in time.

Again, an intriguing idea, but there’s also no possibility of confirmation (or rejection!) via observations.

In the end, we have to admit that we were ignorant of the real beginning of the Universe.

Advertisements

And even if we lean towards an eternal multiverse with no real beginning, we don’t know why there is something (or, more accurately, why there is everything) instead of nothing.

This article originally appeared in the June 2023 issue of BBC Sky at Night magazine.

#Big #Bang

Advertisements

Leave a Comment