In 1929, Edwin Hubble discovered that the universe was expanding, and the velocity of expansion was a function of the distance from the Earth. For example, galaxies at a “proper distance” D from the Earth were moving away from the Earth at a velocity v, according to the following equation: v = H0D, where H0 is the constant of proportionality (the Hubble constant). In this context, the phrase “proper distance” means a distance (D) measured at a specific time. Obviously, since the galaxies are moving away from the Earth, the distance D will change (i.e. increase) with time.

Until 1998, most physicists and cosmologists believed that the expansion would eventually be slowed by gravity and be reversed (i.e. all matter in the universe would eventually be pulled by gravity to a common point resulting in the “Big Crunch”).

In 1998, three physicists (Saul Perlmutter, Brian P. Schmidt, and Adam G. Riess) decided to measure the expansion and expected to confirm that it was slowing down. To their surprise, and the scientific community’s surprise, they discovered that the universe’s expansion was accelerating. In 2011, they received the Nobel Prize in Physics for their discovery.

The accelerated expansion of the universe is one of the great mysteries in science. Since the vast majority of scientists believe in the principle of cause and effect, the scientific community postulated that something was causing the accelerated expansion. They named the cause “dark energy,” which they believed was some kind of vacuum force.

Today we know that extremely distant galaxies are actually moving away from the Earth with a velocity that exceeds the speed of light. This serves to deepen the mystery.

Let us turn our attention to what is causing the accelerated expansion of the universe.

First, let us understand that the extremely distant galaxies themselves are not moving away from the Earth faster than the speed of light. A mass, including a galaxy, cannot obtain a velocity greater than the speed of light, according to Einstein’s special theory of relativity. Any theory that attempts to explain the faster than light velocity of extremely distant galaxies via any type of force acting on the galaxies would contradict Einstein’s special theory of relativity. Therefore, we must conclude the galaxies themselves are not moving faster than the speed of light. However, no law of physics prohibits the expansion of space faster than the speed of light. With this understanding, it is reasonable to conclude the space between extremely distant galaxies is expanding faster than the speed of light, which accounts for our observation that the galaxies are moving away from Earth at a velocity faster than the speed of light.

What is causing the space between extremely distant galaxies to expand faster than the speed of light?

To address this question, let us discuss what we know about space and, more specifically, about vacuums. In my book, Unraveling the Universe’s Mysteries, I explain that vacuums are actually a reservoir for virtual particles. This is not a new theory. Paul Dirac, the famous British physicist and Nobel Laureate, asserted in 1930 that vacuums contain electrons and positrons (i.e. a positron is the antimatter counterpart of an electron). This is termed the Dirac sea. Asserting that vacuums contain matter-antimatter particles is equivalent to asserting that vacuums contain positive and negative energy, based on Einstein’s famous mass-energy equivalence equation, E = mc2 (where E stands for energy, m is the rest mass of an object, and c is the speed of light in a vacuum).

Do vacuum really contain particles or energy? Our experimentation with laboratory vacuums proves they do. However, we have no way to directly measure the energy of a vacuum or directly observe virtual particles within the vacuum. As much as we physicists talk about energy, we are unable to measure it directly. Instead, we measure it indirectly via its effects. For example, we are able to measure the Casimir-Polder force, which is an attraction between a pair of closely spaced electrically neutral metal plates in a vacuum. In effect, virtual particles pop in and out of existence, in accordance with the Heisenberg Uncertainty Principle, at a higher density on the outside surfaces of the plates. The density of virtual particles between the plates is less due to their close spacing. The higher density of virtual particles on the outside surfaces of the plates acts to push the plates together. This well-known effect is experimental evidence that virtual particles exist in a vacuum. This is just one effect regarding the way virtual particles affect their environment. There is a laundry list of other effects that prove virtual particles are real and exist in a vacuum.

I previously mentioned the Heisenberg Uncertainty Principle. I will now explain it, as well as the role it plays in the spontaneous creation of virtual particles. The Heisenberg Uncertainty Principle describes the statistical behavior of mass and energy at the level of atoms and subatomic particles. Here is a simple analogy. When you heat a house, it is not possible to heat every room uniformly. The rooms themselves and places within each room will vary in temperature. The Heisenberg Uncertainty Principle says the same about the energy distribution within a vacuum. It will vary from point to point. When energy accumulates at a point in a vacuum, virtual particle pairs (matter and antimatter) are forced to pop into existence. The accumulation of energy and the resulting virtual particle pairs are termed a quantum fluctuation.

Clearly, vacuums contain energy in the form of virtual particle pairs (matter-antimatter). By extension, we can also argue that the vacuums between galaxies contain energy. Unfortunately, with today’s technology, we are unable to measure the amount of energy or the virtual particle pairs directly.

Why are we unable to measure the virtual particle pairs in a vacuum directly? Two answers are likely. First, they may not exist as particles in a vacuum, but rather as energy. As stated previously, we are unable to measure energy directly. Second, if they exist as particles, they may be extremely small, perhaps having a diameter in the order of a Planck length. In physics, the smallest length believed to exist is the Planck length, which science defines via fundamental physical constants. We have no scientific equipment capable of measuring anything close to a Planck length.

For our purposes here, it suffices to assert that vacuums contain energy. We are unable to measure the amount of energy directly, but we are able to measure the effects the energy has on its environment.

Next, let us consider existence. Any mass requires energy to exist (move forward in time). In my book, Unraveling the Universe’s Mysteries, the Existence Equation Conjecture is derived, discussed, and shown to be consistent with particle acceleration data. The equation is: KEX4 = – .3 mc2, where KEX4 is the kinetic energy associated with moving in the fourth dimension (X4) of Minkowski space, m is the rest mass of an object, and c is the speed of light in a vacuum.

This asserts that for a mass to exist (defined as movement in time), it requires energy, as described by the Existence Equation Conjecture. (For simplicity, from this point forward I will omit the word “conjecture” and refer to the equation as the “Existence Equation.”) Due to the enormous negative energy implied by the Existence Equation, in my book, Unraveling the Universe’s Mysteries, I theorized that any mass draws the energy required for its existence from the universe, more specifically from the vacuum of space. Below, I will demonstrate that this gives rise to what science terms dark energy and causes the accelerated expansion of space.

At this point, let us address two questions:

1. Is the Existence Equation correct? I demonstrated quantitatively in Appendix 2, Unraveling the Universe’s Mysteries, that the equation accurately predicts a muon’s existence (within 2%), when the muon is accelerated close to the speed of light. Based on this demonstration, there is a high probability that the Existence Equation is correct.

2. What is the space between galaxies? The space between galaxies is a vacuum. For purposes here, I am ignoring celestial objects that pass through the vacuum between galaxies. I am only focusing on the vacuum itself. From this standpoint, based on Dirac’s assertion and our laboratory experiments, we can conclude that vacuums contain matter-antimatter (i.e. the Dirac sea), or equivalently (from Einstein’s famous mass-energy equivalence equation, E = mc2) positive-negative energy.

Given that a vacuum contains mass, we can postulate that each mass within a vacuum exerts a gravitational pull on every other mass within the vacuum. This concept is based on Newton’s classical law of gravity, F = G (m1 m2)/r2, where m1 is one mass (i.e. virtual particle) and m2 is another mass (i.e. virtual particle), r is the distance between the two masses, G is constant of proportionality (i.e. the gravitational constant), and F is the force of attraction between the masses.

If we think of a vacuum as a collection of virtual particles, it appears reasonable to assume the gravitational force will define the size of the vacuum. This is similar to the way the size of a planet is determined by the amount of mass that makes up the planet and the gravitational force holding the mass together. This is a crucial point. The density of virtual particles defines the size of the vacuum.

However, we have shown that existence requires energy (via the Existence Equation). A simple review of the Existence Equation delineates that the amount of energy a mass requires to exist is enormous. The energy of existence is directly proportional to the mass. Therefore, a galaxy, which includes stars, planets, dark matter, and celestial objects, would require an enormous amount of energy to exist. In effect, to sustain its existence, the galaxy must continually consume energy in accordance with the Existence Equation.

Using the above information, let us address three key questions:

1. What is causing the vacuum of space between galaxies to expand? To sustain their existence, galaxies remove energy from the vacuum (i.e. space) that borders the galaxies. The removal of energy occurs in accordance with the Existence Equation. The removal of energy results in the gravitational force defining the vacuum to weaken. This causes the vacuum (space) to expand.

2. Why are the distant galaxies expanding at a greater rate than those galaxies closer to the Earth? The galaxies that are extremely distant from the Earth have existed longer than those have closer to the Earth. Therefore, distant galaxies have consumed more energy from the vacuums of space that surround them than galaxies closer to the Earth.

3. Why is the space within a galaxy not expanding? A typical galaxy is a collection of stars, planets, celestial objects, and dark matter. We know from observational measurements that dark matter only exists within a galaxy and not between galaxies. I believe the dark matter essentially allows the galaxy to act as if it were one large mass. From this perspective, it appears that the dark matter blocks any removal of energy from the vacuum (i.e. space) within a galaxy.

Dose this solve the profound mystery regarding the accelerated expansion of the universe? To my mind, it does. I leave it to you, my colleagues, to draw your own conclusions.