In the early 1920s, Edwin Hubble (in whose honor the Hubble Space Telescope was named) was peering through his telescope. As he examined many of the points of light that astronomers had thought were stars or “spiral nebulae” in our galaxy, he realized that they are much more than that. He discovered that they are other galaxies!
By the mid-1920s, everyone knew that our Milky Way is only one of a myriad of other galaxies. Since then, we have learned many things about our galaxy, but we still have much to learn. The Milky Way is a spiral galaxy in the shape of a large saucer. Other types of galaxies–which are the majority–cannot support planets and therefore are not suitable for life.
We are spinning around our spiral galaxy at about 120 miles (200 kilometers) per second. At that rate, it will take us 250,000,000 years to make one complete orbit of the galaxy. We can’t take a picture of the entire Milky Way because to travel outside of our galaxy would take many thousands of years–even at the speed of light. We can take pictures of other galaxies, and this one is another spiral galaxy named M74.
The Milky Way’s disk is about 100,000 light-years across, and we are about 27,200 light-years from the center. It’s good that we are not near the center because that is the location of a giant black hole. It is also fortunate that we live in an area of the galaxy that is not crowded with quasars, black holes, and other major hazards. The galaxy area with the most gas and dust is less than 500 light-years from the central plane–far away from us. That means we are in an area relatively free of debris, so this is an excellent spot to get a good view of our galaxy as well as other galaxies and stars.
Is it just a coincidence that we are in the right kind of galaxy and in the best position in that galaxy to be safe and to be able to study and observe the universe? We think God wanted us to be in a hospitable place where we could see the majesty of His creation.
As we have explained before, scientists understand that a vast percentage of the matter in the creation is something they call dark matter. The simplest way to understand dark matter is to realize that when something is spinning around a core, there must be a force to keep the spinning mass from flying away because of centrifugal force. The dark matter mystery is the unknown quantity preventing spiral galaxies like the Milky Way from flying apart.
If you spin a child around so fast that their feet come off the ground, you must hold their hands tightly. If you let go, they would fly off away from you. Stars going around the center of a galaxy also have to be held by some force. The stars move so quickly that no known force could keep them where they are. That means there is a gravitational force we can’t see holding the stars in their position. We refer to the mass that exerts that gravitational force as dark matter.
Astrophysicist Peter van Dokkum of Yale University has announced the discovery of a galaxy known as DF2, which has stars and star clusters moving at a very slow pace around the core of the galaxy. In all other galaxies having stars at the same distance as stars in DF2, the stars are moving three times as fast as the stars in DF2. That can only mean that there is less dark matter in DF2.
This discovery increases the dark matter mystery because it appears that dark matter is not constant in the cosmos. The amount of dark matter in a galaxy depends on what is needed to keep everything moving at a speed that produces stability in the galactic system. There is a great deal of debate about this discovery, but it appears that the design of galaxies has a new variable that is critical to their existence. That critical factor is how much dark matter has been supplied to keep the system stable. God has tools affecting the creation that we are just beginning to understand. The role of dark matter is only one of those.
On a clear, moonless night, you can look up and see the Milky Way. Actually, we are in the Milky Way, a spiral galaxy of 200 billion stars one of which is our Sun. We are located in a spiral arm of that galaxy 26,000 light-years from its center. Our location seems to indicate many galactic coincidences.
At the center of the Milky Way (and perhaps all galaxies), there’s a black hole sending out lethal radiation to a distance of 20,000 light-years. Farther out than 26,000 light-years from the center, heavy elements that are vital to our existence and survival are scarce. We are in what astronomers call the “galactic habitable zone.”
Spiral galaxies rotate, and we are near the co-rotation spot where our solar system moves at almost the same rate as the spiral arm we are in. If we were in precisely the co-rotation spot, we would experience gravitational “kicks” which could send us out of the habitable zone. If we were far away from the co-rotation spot, we would fall out of the arm and be subjected to deadly radiation.
In the vast majority of spiral galaxies, the habitable zone and co-rotation spot do not overlap. Most other spiral galaxies are not as stable as ours. Most galaxies are not spiral galaxies and would not have a stable location for advanced life.
Furthermore, galaxies exist in clusters, and our cluster called the “Local Group” has fewer, smaller, and more spread-out galaxies than nearly all other clusters. Most galaxies are in dense clusters with giant or supergiant galaxies which create deadly radiation and gravitational distortion making advanced life impossible.
At a June 7 meeting of the American Astronomical Society, Benjamin Hoscheit presented information gained from studying 120,000 galaxies. The study agreed with earlier findings that our Milky Way galaxy is located in the largest cosmic void that we can observe. When scientists look one billion light-years out into the universe, they find that the cosmic density becomes much greater. The conclusion they have reached is that the Milky Way is in a relatively open area of space about two billion light-years across. We live in a quiet neighborhood.
The computer image from the Millennium Simulation Project illustrates the dense filaments of dark matter stretching through space. Galaxies are mostly clumped along the filaments. The Milky Way resides in one of the voids between those strands. What are the implications of that? Galaxies tend to be in clusters, and our cluster is called the Local Group. A typical galaxy cluster will have 10,000 galaxies close together. (Close by cosmic standards.) The Local Group has only forty galaxies, and all of them are dwarf galaxies except the Milky Way and Andromeda which are medium-sized. If there were large galaxies close to us, their gravity could distort the spiral structure of the Milky Way making advanced life on Earth impossible.
The Milky Way is a spiral galaxy—the only kind of galaxy capable of supporting advanced life. Star formation drives the spiral motion. Star formation requires the infusion of gas and dust which the small galaxies provide. Clusters of galaxies reside inside superclusters. Our Local Group cluster is on the outer fringe of the Virgo supercluster. If it were near the center of Virgo, the massive clusters there would absorb the Local Group and make life impossible.
Also, our solar system is located in the best position within our galaxy at about two-thirds of the distance from the center. In the center of the Milky Way (and most galaxies), there is a massive black hole that would swallow our solar system if we were anywhere near it. If we were farther out in the spiral, the solar system would be subject to massive instability, again making life impossible.
Of course, Earth is also located in the solar habitable zone where we are not too close or too far from the Sun. One final thing to note is that in this cosmic void and the position in our galaxy, we are at the optimum location for observing all of the things I mentioned. We have an excellent view of the universe. We are in more than a quiet neighborhood. We are in the “Goldilocks Zone” where everything is “just right.”
One of the most interesting areas of scientific research today is the study of dark matter. We have known for more than half a century that galaxies are groups of billions of stars revolving around a core. Science had assumed that the glue holding galaxies together was the gravitational force produced by the mass of the stars in the galaxy. The problem with this explanation was that the stars were spiraling too fast for the gravity produced by their mass to hold the galaxy together.
If you stand in the center of a circle and spin a bucket of water on a rope, you have to spin it at a certain speed to keep the water in the bucket. If you go too slow, the bucket will hit the ground, and if you go too fast, it will break the rope. In the case of galaxies, the stars were going so fast for the gravity of the stars to hold the system together. Some other gravitational force must be the glue doing the job. The discovery of black holes in the center of galaxies was thought to be a possible answer, but the speed was much too fast for even that source. The amount of mass it would take to hold some of the galaxies together is as much as 85% higher than what we can observe.
This problem led to the proposal that there is a missing mass. Scientists suggested particles called WIMPS, which is an acronym for “weakly interacting massive particles.” For some time now, experiments have been conducted to find evidence for WIMPS. The Large Hadron Collider near Geneva, Switzerland, has been smashing protons together in hopes of detecting the particle. The Large Underground Xenon experiment in South Dakota has been looking for traces of them as well. So far neither attempt has been successful. In an article in Scientific American (October 2016, page 16) Edward Kolb, who was involved in proposing the existence of WIMPS, said: “We are more in the dark about dark matter than we were five years ago.” David Spergel who is an astrophysicist at Princeton says, “…we now need more hints from nature about where to go next.”
It seems that God has already taught us quite a bit about the complexity of creation. Thanks to Isaac Newton we know that mass has a connection to gravity. Thanks to Albert Einstein we know that the shape of space has something to do with it as well. Making a galaxy is not a simple task. Just like the making of electric charge, the process involves understandings that science is just beginning to comprehend. Quantum mechanics has taught us that a whole new set of laws governs what happens in forming these building blocks of what we see.