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big bang origin of universe: How could the Big Bang arise from nothing Know what experts say

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‘The last star will gradually cool and fade. With its passing, the universe will once again become void, without light or life or meaning.’ In the recent BBC series Universe, physicist Brian Cox made a similar warning. The disappearance of that last star would only be the beginning of an eternally long, dark age. Eventually all matter will collapse into monstrous black holes, which in turn will vanish into the faintest flashes of light.

Space will expand until even that dim light has spread beyond the range of contact. Activity will stop. Or will it happen? Oddly, some cosmologists believe that the former, cold dark empty universe, as enshrined in our distant future, may be the source of our own Big Bang. First Matter But before we get to that, let’s look at how ‘matter’ – physical matter – came about in the first place. If we want to explain the origin of stable matter made of atoms or molecules, there certainly was nothing like it around the Big Bang – nor after hundreds of thousands of years.

Really no content in any familiar sense of the word
We actually have a very detailed understanding of how the first atoms made up of simple particles once cooled enough for complex matter to be stable, and how these atoms were later added to the heavier elements inside stars. But that understanding does not address the question of whether something came from nothing. So let’s think back. The first long-lived matter particles of any type were protons and neutrons, which together make up the atomic nucleus. They came into existence around ten thousandths of a second after the Big Bang.

Before that point, there was really no content in any familiar sense of the word. But physics lets us look at the back of the timeline – to the physical processes that precede any stable matter. This takes us into the so-called ‘Grand Unified Era’. By now, we have entered the realm of hypothetical physics, because we cannot produce enough energy in our experiments to investigate the processes going on at that time. But a plausible hypothesis is that the physical world was made up of a sum of short-lived elementary particles—including the building blocks of quarks, protons, and neutrons.

like a mathematical weirdness instead of real physics
There was almost equal amounts of both matter and ‘antimatter’. However, matter and antimatter are annihilated in a flash of energy when they meet, meaning that these particles were constantly created and destroyed. But how did these particles first come into existence? Quantum field theory tells us that a vacuum, too, is filled with physical activity in the form of energy fluctuations. These fluctuations can help the particles move out, which only disappear after a short time. This may sound like a mathematical strangeness rather than actual physics, but such particles have been observed in countless experiments.

The spacetime vacuum state is constantly emerging with particles being created and destroyed, apparently ‘out of nothing’. But perhaps all this really tells us is that the quantum vacuum (despite its name) is nothing but something. Philosopher David Albert has strongly criticized Big Bang claims that promise something like this from nothing. Suppose we ask: Where did spacetime itself originate? Then we can turn the clock even further back, in a truly ancient ‘Planck era’ – a period so early in the history of the universe that our best principles of physics break down. This epoch occurred after the Big Bang to only one millionth of a trillionth to a trillionth of a trillionth of a second.

At this point, space and time themselves became subject to quantum fluctuations. Physicists typically work separately with quantum mechanics, which governs the microcosm of particles, and with general relativity, which applies to larger, cosmic scales. But to truly understand the Planck era, we need a complete theory of quantum gravity that combines the two. We still don’t have a perfect theory of quantum gravity, but there are attempts – such as string theory and loop quantum gravity. In these endeavors, normal space and time are usually seen as incidental, like waves on the surface of a deep ocean.

even the best physics utterly failed to answer
What we perceive as space and time are the products of quantum processes operating on a deeper, microscopic level – processes that don’t mean much to us as beings contained in the macroscopic world. In the Planck era, our common understanding of space and time breaks down, so we can no longer rely on our common understanding of cause and effect. Despite this, all theories of quantum gravity describe something physical that was going on in the Planck era – some quantum precursor of ordinary space and time.

But where did it come from? Even if causality does not apply in any general way, it may still be possible to explain one component of the Planck-era universe in terms of another. Unfortunately, even our best physics so far have completely failed to answer. Unless we move in the direction of the ‘theory of everything’, we will not be able to give a definite answer. At this stage we can say with the most confidence that physics has not yet been confirmed to arise from nothing.

Alastair Wilson, University of Birmingham

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