Scientists indicate that only 4% of the mass and energy in the universe is visible. They infer the other 96% based on gravitational influence on the visible universe. In other words, they calculate its existence using math to fill in the gaps.
What is this missing 96%? Well, typically about 73% of the missing universe is called dark energy and about 23% of the universe is called dark matter.
Richard Panek’s new book, “The 4 Percent Universe,” explains how dark matter and dark energy were discovered. Logically, the outermost stars of a galaxy would orbit more slowly than those stars closer to the center. However, all the stars in a galaxy, no matter where they were located, circled the super massive black hole in the center of the galaxy at roughly the same speed. If there were no dark matter and dark energy, the galaxies would be breaking apart.
Using models, scientists proved that a galaxy including only the visible portion (stars, planets, comets, asteroids, gas clouds, etc.) would disintegrate very quickly. It takes a mass and energy force of about six times that of the visible portion to keep it intact. That would match the approximate 23% deemed to be dark matter.
But what is dark matter? A popular theory is that dark matter consists of exotic particles that don’t interact with regular matter, or even light, and so are invisible. Yet their mass exerts a gravitational pull, just like normal matter, which is why they affect the velocities of stars and other phenomena in the universe. However, try as hard as they might, scientists have yet to detect any of these particles, even with tests designed specifically to target their predicted properties. Still, some scientists hope that experiments conducted at the Large Hadron Collider particle accelerator in Geneva may solve the riddle.
But what is dark energy? Dark energy appears to be even more elusive than dark matter. It was discovered about 20 years ago when two teams of researchers were trying to figure out if the universe would keep spreading out forever or if it would eventually turn on itself in a “Big Crunch.” Scientists measured the velocities of supernovas to determine how fast they were moving away from us. They found out that the universe was accelerating its expansion. This didn’t make sense since the gravity of the visible mass should have been slowing down the expansion. There was a powerful force at work that was counteracting the force of gravity and was causing the visible universe to accelerate. They called this force dark energy.
You might imagine that galaxies, galaxy clusters, and dust clouds look like filaments strung together like nerves inside the muscle mass of our bodies. The 3% visible universe added to the 23%, consisting of black holes and a supermassive black hole in the center of the galaxy might form the structure of those filaments, while the muscle mass could be equated to the dark energy that holds the nerves in place. In other words, dark energy could be all around us and perhaps inside us, holding everything that we know together like universal glue. It may be similar to Einstein’s space-time fabric, except it might be considered to be the dark-light fabric, including dark energy, dark matter, and our visible universe all locked together in one universal fabric.
If most galaxies are rapidly moving away from each other, then are they expanding or contracting? This is a fair question because either expansion or shrinking would cause the galaxies to appear to be moving away from each other. If the galaxies were uniformly impacted by a dark energy that caused them to decrease in size, they would appear to be distancing themselves from each other just the same as if they were moving away from each other.
So, which is more likely? If expansion were going on, it would be similar to inflating a balloon and watching the galaxies move away from each other. But an increasing rate of expansion would be likely only if the majority of the dark energy were in the space uninhabited by our visible universe, drawing it toward it as it got closer to a huge reservoir of that dark energy. Of course, dark energy also could be repelling the visible universe. But whether it is pushing or pulling, it is only movement causing a repositioning of the same 4% of the visible universe.
However, the universe appears to be very consistent. In other words, a rapid acceleration caused either by the push or pull of dark energy would have disrupted the homogeneous universe, stretching everything apart. As the galaxies distanced themselves from each other, the dark energy might fill in the empty space, but this probably would dilute the effect on the expanding galaxies. In effect, if the dark energy were also stretched to fill in the void, there would be less of it to push or pull the visible universe. Our visible universe should be decelerating in speed.
But a contraction of our visible universe would simply make the same consistent universe smaller. In other words, the matrix of the visible universe would remain uniform. As between two galaxies, they would appear to be moving away from each other, but rather instead, they would be decreasing in size.
The law of conservation of mass and energy states that the total amount of mass and energy in the universe must remain constant. So if the visible universe were shrinking, dark energy should be increasing. The reduction in size of galaxies would cause a transformation to increase the percentage of dark energy. In effect, over millions of years, the 4% of our visible universe should be 3% with either dark matter or dark energy gobbling up that 1%. But this does not seem to be the case. The ratio may have been the same since the Big Bang and is not changing.
This is analogous to the ratio of hydrogen, about 75%, to helium, about 23%, and the rest of the elements, about 2%. It may not be a coincidence that it is about the same ratio as dark energy to dark matter to the visible universe. As hydrogen burns, it is fused into helium, and subsequently into other elements. However, many scientists believe that this ratio has remained constant since the Big Bang.
So what is going on that these ratios do not change? That is a question for another article. But there may be localized transformations of mass to energy, so that our sun is definitely losing its supply of hydrogen, turning it into helium, energy, and other elements. And local galaxies may well be losing their mass, turning it into dark matter or dark energy.
As the dark matter and dark energy increased proportionately to these galaxies, this would have a more powerful impact. In effect, there should be an acceleration of the shrinking of local galaxies, which is exactly what we see in the red shift among galaxies.