If you remove everything from part of the universe, what is left? You might think that "nothing", but it is not. You can remove all particles and antiparticles away, all possible types of radiation, all curvature of space and ripples of gravitational waves - and remain in a completely empty space, where there is nothing to deal with. Will there really be "nothing" in front of you? Or will there be something?
This state is usually referred to as a quantum vacuum. This is the lowest energetic state of empty space. And surprisingly, quantum physics teaches us that zero energy, or the baseline state of the universe, is not actually zero. On the contrary, it is a final, positive value that:
- it was measured observationally - thanks to the effects of dark energy - and was approximately the equivalent of the rest mass of the energy of one proton per cubic meter;
- and it is theoretically calculated, to the best of our abilities, that it should be 10,120 times higher than this value.
It is no exaggeration to say that we understand the physics of "nothing" well enough and that we have no good explanation of why this zero energy does not decrease or evaporate (and does not change at all) over time.
In the next few decades, space observatories - like ESA's Euclid space observatories and NASA's upcoming WFIRST mission - will be able to limit the error in this zero-energy constant in spacetime to 1%. (While this is 8%). By measuring how the universe has expanded throughout its history in many different places and at very different distances from us, we can confirm that the zero energy of the universe is the same everywhere.
But would that be the equivalent of "nothing"? And what is more important is our understanding and perception of the nature of "nothing": an illusion or a key to understanding the most important secrets of the universe?
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Physicists Laura Mersini-Houghton and John Ellis, as well as philosopher James Leydimen, recently discussed this topic at a meeting of the Institute of Art and Ideas in the United States. The problem is that although this is not an illusion, we cannot agree on what is meant by "nothingness" (meaning "nothing", "emptiness"). Namely:
- Is this a baseline energy state that could have been in the past (for example, much higher)? During cosmic inflation, for example.
- Is this a state outside of space and time, from which, in fact, space-time arises (from the true state of emptiness)? Does such a state exist at all and will its existence be meaningful?
- Is this a state of emptiness in the universe, which may be different from a similar state in another pocket of the multiverse?
- Or is it a cosmic vacuum, with all its virtual energy and which can change depending on what is in it?
It is somehow strange to believe that "our emptiness" may not be such a "emptiness" anywhere else, in other places.
But we think that this is where the Big Bang started! In the transition from a higher zero energy to a lower one, the expanding universe, filled with the energy inherent in space itself, went into a lower state, and this transition led to the creation of all matter, antimatter and radiation in our universe. It is even possible that another similar transition awaits us in the future, with a different, colder, Big Bang.
True, such reasoning pleases us little. This "physics of nothing" sounds like the physics of something. When we want to understand nothing, our ideas take us out of space, even before the birth of the Universe, otherwise what is the point? How can you talk about something “for” when you have no space? How can you understand what is "before" if there is no time?
And whatever this "nothing" may be, it contains the whole universe.
Many physicists argue that it is impossible to understand anything thoroughly until we understand what "nothing" is. Because we don't understand where fundamental laws come from if we don't understand which fundamental laws govern the nature of empty space.
Thus, we can say that our Universe really came from nothingness, from emptiness, from nothing, and its final state can asymptotically tend to non-existence after a long period of time. But only if we accept our description of the physical "nothing" as true nothing. This definition of "nothing" by itself cannot depend on our definition of space, time and the "rules" of the universe; physicists, philosophers and others do not have to agree on this matter. There just isn't a physical experiment that lets us say, heh, it looks like we've finally turned this into nothing.
But there are things we are sure of for sure: we have not always existed; we will not always exist; we exist now. Regardless of what "nothing" is, we are all something. And everything, to one degree or another, came out of nothing, whatever that nothing was. And as far as we understand the Universe, one day it will return to a state of endless physical emptiness. But what will be the nature of this final "emptiness" - we have not yet answered this question.
ILYA KHEL
