School Name: Freedom High School
Area of Science: Astro Physics
Project Title: The Mystery of Spiral Galaxies
How and why do galaxies form in spirals? For the last twelve weeks we have been doing further research on spiral galaxies, theories of their formation, and gravity.
Though there may be some interesting “exceptions” in quanta-mechanics, the speed of light still seems to be the limit to how fast information can travel in the universe. Because of this, whenever you look at a star, or a group of stars, you are looking into the past. The farther away the star, the farther back in time you are looking. As far as we can “look into the past,”’ the majority of galaxies have spiral arm structures. If spiral galaxies wrapped in on themselves then we wouldn’t see them as far out into the universe (back in time) as we do. By measure the velocities of stars by their Doppler Shift, scientists have discovered that all the stars in most galaxy move at about the same velocity. It is obvious that the stars closest to the center have a much shorter distance to travel around the core than the stars further out so, if you picture it in your mind, the inner stars with their shorter path should eventually out-lap the outer stars and thus they would destroy the armed structure. Because of this, the arms of galaxies are thought to remain more stationary as the stars and gas clouds move through them. This ideas sees the arms of galaxies like a plug of traffic on a busy highway. Individual cars move through the plug but the plug moves backward along the highway. The problem is, what could cause the stars and gas to “backup and slow down” in this galactic traffic jam?
Some scientists have a theory that Dark Matter has something to do with the galaxies keeping their uniform structure. What we know about Dark Matter is that we cannot detect it, and according to theory, it is spread evenly throughout the galaxies. The even distribution of matter in galaxies would explain the consistent speed of most stars and material in their galactic orbits. Some candidates for Dark Matter are dead stars, single black holes, and other debris with very little radiation. Why we can’t detect this matter is best understood this way. Imagine yourself at a rock concert. Now imagine that someone 3 rows back is whispering when the band is playing, you aren’t going to hear it. This is exactly how it is with all the radiation in the galaxies. How could we detect something with very little radiation when all around everything is bursting with radiation?
Even with the presence of Dark Matter there is still the problem of spiral structures. Dark matter would follow the same rules of orbital mechanics as all the other matter so we are still missing a process to create these structures.
The idea was suggested to us that the answer may lie in the nature of gravity. There are two theories of gravity, Einstein’s Relativity, and a quanta-mechanics model. The first theory works but the second is not well developed and has not yet been shown to make accurate predictions.
In Einstein’s model the definition of space is changed by the presence of matter. This is what is called “curved space/time”. In Einstein’s view gravity is not a force. Gravity happens because the definition of “stationary” gets changed by the nearby matter and so you move toward the presence of matter but don’t feel an acceleration because there isn’t one. This is shown by the fact that the path of light from stars, which travels in a straight line, is bent by gravity around the Sun. Our questions are, how does a location in space “know” about the matter in the Sun? Also, is the information about gravity transmitted to this location instantly or at the speed of light? How do planets and stars in the galaxies gravitationally react to each other? Are the stars reacting instantaneously to the others stars or are they reacting in delay to the movements?
The answer to this question may come from the second quanta-mechanic model. In quanta-mechanics all information about the forces in the universe are communicated by little packets of information called the quanta. The strong and weak nuclear forces and electromagnetism each have their particle and his model does an excellent job of predicting the world around us. In the undeveloped quantum model of gravity, the information of gravity would be communicated by the graviton. If the speed of light is still the “speed limit” of the universe then the answer seems obvious that objects would be acting “in delay” as the graviton “informed” a location in space about the presence of matter. If this is true, why are all the programs we have seen that display galactic movements based on instantaneous reactions? And we still don’t have a process to create structures in galaxies.
It is the duel nature of the packet of information (quanta) that may help us understand spiral arms in galaxies. Each quanta has an energy level and a wave function. It was suggested to us that perhaps the interaction of the wave nature of gravitons could cause harmonic standing waves in Einstein’s “space/time”. This would suggest that the wavelength of the graviton was very very long with the waves being so stretched out that the peaks and valleys only show up in things the size of galaxies.
In the next few weeks our goals are to learn a lot more about wave functions and harmonics, try to simplify our assumptions, and begin to build a model of simple wave functions on the computer. With a simple model we may be able to “scale it up” and see what happens with shapes like galaxies.