Spontaneous particle creation is the phenomenon of particles appearing from apparently nothing (i.e., a vacuum), hence their name “virtual particles.” However, they appear real, and cause real changes to their environment. What is a virtual particle? It is a particle that only exists for a limited time. The virtual particle obeys some of the laws of real particles, but it violates other laws. What laws do virtual particles obey? They obey two of the most critical laws of physics, the Heisenberg uncertainty principle (it is not possible to know both the position and velocity of a particle simultaneously), and the conservation energy (energy cannot be created or destroyed). What laws do they violate? Their kinetic energy, which is the energy related to their motion, may be negative. A real particle’s kinetic energy is always positive. Do virtual particles come from nothing? Apparently, but to a physicist, empty space is not nothing. Said more positively, physicists consider empty space something.

Before we proceed, it is essential to understand a little more about the physical laws mentioned in the above paragraph.

First, we will discuss the Heisenberg uncertainty principle. Most physics professors teach it in the context of attempting to simultaneously measure a particle’s velocity and position. It goes something like this:

• When we attempt to measure a particle’s velocity, the measurement interferes with the particle’s position.
• If we attempt to measure the particle’s position, the measurement interferes with the particles velocity.
• Thus, we can be certain of either the particle’s velocity or the particle’s position, but not both simultaneously.

This makes sense to most people. However, it is an over simplification. The Heisenberg uncertainty principle has greater implications. It embodies the statistical nature of quantum mechanics. Quantum mechanics is a set of laws and principles that describes the behavior and energy of atoms and subatomic particles. This is often termed the “micro level” or “quantum level.” Therefore, you can conclude that the Heisenberg uncertainty principle embodies the statistical behavior of matter and energy at the quantum level. In our everyday world, which science terms the macro level, it is possible to know both the velocity and position of larger objects. We generally do not talk in terms of probabilities. For example, we can predict the exact location and orbital velocity of a planet. Unfortunately, we are not able to make similar predictions about an electron as it obits the nucleus of an atom. We can only talk in probabilities regarding the electron’s position and energy. Thus, most scientists will say that macro-level phenomena are deterministic, which means that a unique solution describes their state of being, including position, velocity, size, and other physical attributes. On the other hand, most physics will argue that micro level (quantum level) phenomena are probabilistic, which means that their state of being is described via probabilities, and we cannot simultaneously determine, for example, the position and velocity of a subatomic particle.

The second fundamental law to understand is the conservation of energy law that states we cannot create or destroy energy. However, we can transform energy. For example, when we light a match, the mass and chemicals in the match transform into heat. The total energy of the match still exists, but it now exists as heat.

Lastly, the kinetic energy of an object is a measure of its energy due to its motion. For example, when a baseball traveling at high velocity hits a thin glass window, it is likely to break the glass. This is due to the kinetic energy of the baseball. When the window starts to absorb the ball’s kinetic energy, the glass breaks. Obviously, the thin glass is unable to absorb all of the ball’s kinetic energy, and the ball continues its flight after breaking the glass. However, the ball will be going slower, since it has used some of its kinetic energy to break the glass.

With the above understandings, we can again address the question: where do these virtual particles come from? The answer we discussed above makes no sense. It is counter intuitive. However, to the best of science’s knowledge, virtual particles come from empty space. How can this be true?

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. This may appear highly confusing. A few paragraphs back we said that 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.