From antiquity until today, many thinkers have been interested in "nothingness" and "vacuum", (Parmenides, Euripides, Leucippus, Democritus, Plato, Aristotle, Saint Augustine, Pascal, Leibniz, Kant, Heidegger, Bergson, etc.). Countless texts have been written about it, but these metaphysical concepts still remain mysterious and questionable. Can nothingness exist? Nothingness being the absence of "everything", one can only think of nothingness by giving it a form of existence. Indeed, if in our mind something that represents nothingness appears, then it is a paradox since nothingness is neither matter, nor energy, nor information, nor space-time, nor something, nor even nothing. - Leonardo Da Vinci (1452-1519): "Nothing has no center, and its limits are nothingness." - Blaise Pascal (1623 - 1662): "For after all, what is a man in nature? A nothingness with regard to infinity, a whole with regard to nothingness, a middle between nothing and all," - Arthur Schopenhauer (1788-1860): "Nothing after death? Isn't this the state we were used to before life?" - Victor Hugo (1802-1885): "Nihilism has no substance. Nothingness does not exist and zero does not exist. Everything is something. Nothing is nothing." - Friedrich Wilhelm Nietzsche (1844-1900): "I think, therefore it is." - André Malraux (1901-1976): "The greatest mystery is not that we are thrown randomly onto the earth. It is that in this prison, we draw images of ourselves powerful enough to deny our nothingness ." If nothingness could not create anything and cannot be thought of then let us think of the void which is not nothingness.
The absolute "vacuum" is the absence of matter in a certain volume of space. Can vacuum exist? Classical physics tells us that matter and energy are the same thing (E=mc2). In 1900, Max Planck (1858-1947) discovered that radiation is pure energy (e=hν). However, we do not know of a place where there is neither matter nor energy. Quantum physics tells us that particles always have a non-zero momentum (nothing is static in the Universe). Any matter that has momentum has a temperature above absolute zero (0 Kelvin). Any material that has a temperature emits radiation and therefore energy. However, absolute zero is a theoretical temperature inaccessible by matter because of its intrinsic quantum properties. Every system has energy, even when it is very close to absolute zero. Its minimum energy corresponds to the energy of its ground state and the kinetic energy of its ground state cannot decrease. Just as the speed of light cannot be exceeded, absolute zero is unreachable. Thus, the radiation emitted by matter propagates throughout the Universe and fills the "vacuum". It is said that the vacuum is agitated by virtual particles, from which can be born in the light of an excitation the observable matter. In summary, the vacuum always has a minimum energy, this minimum energy will be necessary for the existence of all matter (E=mc2).
Image: At room temperature, the wavelength of the particles is extremely small (≈2x10−11 m). When the temperature decreases, the speed of the particles decreases, the frequency decreases and the wavelength increases until it forms a giant wave. Just as the speed of light cannot be exceeded, absolute zero is unreachable by matter.
And beyond the universe?
Gottfried Wilhelm Leibniz (1646-1716) in "Principles of Nature and Grace" formulates this question, "Why is there something rather than nothing?" Indeed the "nothing" is much simpler than the existence of something, but our Universe is there!!! The question then is: where did it emerge from? This simple question revives in our mind the concepts of nothingness and vacuum. The Big Bang theory tells us that about 13.8 billion years ago, in a fraction of a second, the universe was born. This seems true because we capture everywhere, in all directions of the cosmos, the "fossil radiation" of the first moments. Does this mean that our observable Universe had a beginning? No, within the framework of quantum field theory, our Universe would have sprung from the pre-existing quantum vacuum. Currently we find that our Universe is filling an expanding and cooling space. Its temperature, although very low (2.7 K), is above absolute 0. This low temperature allows us to see the first glimmers of our universe (Planck mission opposite). However, this temperature continues to radiate its vicinity while cooling further, so we cannot say that there is nothing beyond the observable Universe.
This small energy will fade until it reaches a minimum energy. The Universe will then have returned to its initial state, that is to say the fundamental state of the vacuum or in other words, the default state of what we consider to be nothingness. When the matter, space and time of our Universe have disappeared, the energy, always present, will be preserved in the quantum vacuum teeming with fluctuations (in an atom, there are more than quantum fluctuations than of stars in the universe). This minimum energy, below which it is impossible to go, pre-exists and cannot be created ex nihilo. Then, another fluctuation of the quantum vacuum could bring another universe back to life and start another very different story where matter, energy, space and time are reunited again. This bottom of energy which is preserved indefinitely, periodically renews a different history. All metaphysical concepts (nothingness, vacuum, nothing, non-being, era of Planck, etc.) can be unified in the agitated vacuum energy of endlessly appearing and disappearing virtual particles. Vacuum is the origin of everything and what we consider nothingness could be the link between us and infinity.
Image: The first glimmers of the observable universe seen by the Planck mission (March 2013). This embryonic universe already has an incredible amount of detail. The tiny temperature irregularities we see are the scars left by the quantum vacuum on the surface of spacetime. Each small pixel will evolve into clusters of galaxies (at this moment, the Milky Way is only a quantum fluctuation of the vacuum). Credit: ESA and Planck collaboration.