Most people think that a vacuum is empty, but it is not. It is filled with energy. This may be hard to believe, but it is a scientific fact.
According to Paul Dirac, a British physicist and Nobel Prize Laureate, who first postulated virtual particles, empty space (a vacuum) consists of a sea of virtual electron-positron pairs, known as the Dirac sea. This is not a historical footnote. Modern-day physicists, familiar with the Dirac-sea theory of virtual particles, claim there is no such thing as empty space. They argue it contains virtual particles.
This raises yet another question. What is a positron? A positron is the mirror image of an electron. It has the same mass as an electron, but the opposite charge. The electron is negatively charged, and the positron is positively charged. If we consider the electron matter, the positron is antimatter. For his theoretical work in this area, science recognizes Paul Dirac for discovering the “antiparticle.” Positrons and antiparticles are all considered antimatter.
Virtual particle-antiparticle pairs pop into existence in empty space for brief periods, in agreement with the Heisenberg uncertainty principle, which gives rise to quantum fluctuations. Let’s understand these points.
- What is the Heisenberg uncertainty principle? The Heisenberg uncertainty principle embodies the statistical nature of energy at the quantum level, which implies that energy at the quantum level can vary. Another way to say this is to state the Heisenberg uncertainty principle gives rise to quantum fluctuations.
- What is a quantum fluctuation? It is a theory in quantum mechanics that argues there are certain conditions where a point in space can experience a temporary change in energy. Again, this is in accordance with the statistical nature of energy implied by the Heisenberg uncertainty principle. This temporary change in energy gives rise to virtual particles. This may appear to violate the conservation of energy law, arguably the most revered law in physics. It appears that we are getting something from nothing. However, if the virtual particles appear as a matter-antimatter pair, the system remains energy neutral. Therefore, the net increase in the energy of the system is zero, which would argue that the conservation of energy law remains in force.
No consensus exists that virtual particles always appear as a matter-antimatter pair. However, this view is commonly held in quantum mechanics, and this creation state of virtual particles maintains the conservation of energy. Therefore, it is consistent with Occam’s razor, which states that the simplest explanation is the most plausible one, until new data to the contrary becomes available. The lack of consensus about the exact nature of virtual particles arises because we cannot measure them directly. We detect their effects, and infer their existence. For example, they produce the Lamb shift, which is a small difference in energy between two energy levels of the hydrogen atom in a vacuum. They produce the Casimir-Polder force, which is an attraction between a pair of electrically neutral metal plates in a vacuum. These are two well-known effects caused by virtual particles. A laundry list of effects demonstrates that virtual particles are real.
Therefore, a vacuum is not empty. It is filled with energy.
Please excuse my ignorance but I was aware that from 1925 to 1958 Paul Dirac made many superb contributions to scientific knowledge, but I must admit that I’ve been ignorant of his work regarding virtual particles as such. In 1935 in Japan Hideki Yukawa, worked out properties strong nuclear force particles would need using Einstein’s brief non-conservation and that large particles later called ‘mesons’ would be needed. He also postulated virtual particles. Also in 1935, the second edition of Dirac’s book, “The Principles of Quantum Mechanics” was published, the first edition most folk didn’t understand having been published in 1930. He’d completely rewritten it and this time it became a classic work, and I gather is still read by many students. Did he include Yukawa’s virtual particles concept in this, or when?
Dirac did not discuss “virtual particles” in his books, but he did postulate the Dirac sea. The Dirac sea theory hold that a vacuum is filled with an infinite number of electrons and positrons (i.e., the antimatter counterpart of an electron). Dirac is widely recognized for his work leading to the discovery of antimatter. Dirac postulated a Dirac sea in 1930 to explain the anomalous negative-energy quantum states predicted by the Dirac equation for relativistic electrons. Later work, by others, in quantum field theory surfaced the concept of “virtual particles” to explain, for example, the Casimir effect. Virtual particles are widely accepted to exist by the scientific community.