Our Universe as a Laboratory for Understanding Physical Laws

must be multiplied by the object's distance from earth. The apparent brightness of the object must then me compared to a local "standard" of the same class of object. When the red shift and brightness of the distant object is recorded, we can see the expansion of the universe since the time the light was emitted (California Academy of Sciences online) In cosmology, Type 1a supernovae are the standard candle of choice because they have a very well determined maximum absolute magnitude as a function of the shape of their light curve. A light curve as defined by the Cyprus Astronomical Society is: "Brightness or intensity of light plotted against time on a graph. Astronomers discover dark stellar companions using the light curve of the star. As a dark orbiting object eclipses the star, the brightness falls, producing a dip on the light curve. Careful analysis of the light curve reveals the masses of the star and dark companion plus the distance to this eclipsing binary system" (Cyprus Astronomical Society online) Using very distant supernovae as standard candles, one can trace the history of cosmic expansion and try to find out what's currently speeding it up. In Edwin Hubble's discovery of cosmic expansion in the 1920's, he used entire galaxies as standard candles. But galaxies are hard to match against standard brightness since they come in many shapes and sizes. They can grow fainter with time or brighter if merged with other galaxies. In the 1970's it was suggested that the brightest member of a galaxy cluster could be used as a standard candle, but in the end it was realized that all of the proposed galactic candidates were too susceptible to evolutionary change (Perlmutter 53) A supernova with no hydrogen features in its spectra had always been classified as Type 1. If a silicon absorption feature was present, it determined if the supernova would be further subdivided into 1a or 1b. When the Type 1a supernovae were studied in greater detail, their light curves and spectra matched. Also, astronomers could tell that the same physical processes were occurring in all of the massive explosions. The type 1a supernovae were studied when they brightened and faded. (Burrows 727 EBSCOhost) With this breakthrough, there was an immediate interest in trying to use them to determine the Hubble constant, which measures the present expansion rate of the universe. This could be done by finding and measuring type 1a supernovae that occurred 100 million years ago just beyond the nearest cluster of galaxies. If a standard candle supernova could be found 10 times further away, we could sample the expansion of the universe several billion years ago and possibly see the expected slowing of the expansion rate from gravity. We would be, in effect, weighing the universe because the deceleration rate would depend on the cosmic mean mass density. The changing expansion rate would also determine the curvature of space and determine if the universe is finite or infinite and if mass density is the primary energy force of the universe as was generally assumed a decade ago. (Perlmutter 53) After many measurements were made and compared of type 1a supernovae, it was evident that there were some major errors in our understanding of the universe. Dozens of distant supernovae appeared surprisingly faint leading to the conclusion that the universe is accelerating disproving the belief that "gravity always wins." We could only do this by making direct measurements on the universe itself. If the universe is in fact accelerating, there has to be some mysterious force causing this. This force has been labelled dark energy by physicists and astronomers. Dark energy would be almost impossible to detect in a local laboratory because of its tiny density and its very weak interactions. The best way to try to understand dark energy would be to thousands of type 1a supernovae. This is exactly what the SuperNova/Acceleration Probe (SNAP) is going to do. SNAP is going to orbit a 3-mirror, 2-meter telescope circling the globe every 14 days. It will discover and accurately measure over 2,000 type 1a supernovae a year. This would be 20 times the amount that was found in a decade of ground-based research. It will have a very wide-field camera with a billion pixels that will collect images hundreds of times larger than its predecessors. Measuring spurts or slowdowns in the expansion history of supernovae will provide an excellent way in understanding dark energy (Preuss online). While using the universe to measure such forces as dark energy may be the best laboratory, at the same time it demonstrates how our understanding of the universe is not perfect. What if we created dark energy so we would not have to face the slight chance that gravity may behave differently on large scales? Gravity is arguably the most important of the 4 known fundamental forces. If we don't even fully understand gravity, how can we justify saying that the universe itself is the best laboratory in understanding and determining fundamental physical laws. Maybe on a large scale structure, gravity acts in a completely opposite way as currently understood by repelling instead of attracting. According to recent results from NASA's Wilkinson Microwave Anisotropy Probe 73% of the universe consists of a mysterious dark energy. Because it seems to be a property of space itself, dark energy will grow along with space. When the universe is twice its present age dark energy will comprise 97 percent of the total, rendering matter insignificant. It is believed that "dark energy will ultimately expand our universe, but not our horizons. Due to the fact that light travels at a finite speed, only the light from galaxies within a certain range will have enough time to travel to us. As space grows faster and faster, what we will be able to see of the universe will only be a diminishing fraction of the large whole." (Nadi Diagram 2 EBSCOhost) When the universe is about 10 times its current age, we will only be able to observe objects within a 40 billion light year radius. University of Pennsylvania cosmologist, Max Tegmark theorizes that after about 100 billion years dark energy may decay causing the universe to contract again into a "Big Crunch" (Nadi 42 EBSCOhost) we may not be absolutely certain about the true nature of dark energy, but it proves one thing. We do not understand the fundamental forces of nature as well as we would like. If dark energy is evolving, couldn't the other 4 forces be evolving as well which could possibly give us false measurements when we apply them to large scale structure such as the universe as a whole. Dark matter is another topic which we still are very unclear on even though it is believed to make up 90% of the mass in the universe. Scientists can tell that the matter is there, but they can't see it. Bruce H. Margon, chairman of the astronomy department at the University of Washington, told the New York Times, "It's a fairly embarrassing situation to admit that we can't find 90 percent of the universe." Dark matter has never been directly measured. It has been detected numerous times mainly through gravitational lensing, galaxy rotation, gravitational bonding of clusters of galaxies, and the fact that large scale structures of the universe require a certain amount of mass which is vastly more than we can see from luminous matter. The two main categories that scientists consider as possible candidates for dark matter have been named MACHOs or Massive Astrophysical Compact Halo Objects, and WIMPs or Weakly Interacting Massive Particles. MACHOs are the big, strong dark matter objects ranging in size from small stars to super massive black holes called baryonic matter. They are searched for by astronomers. The two main ways that MACHOs can be detected are through gravitational lensing and circling stars. Gravitational lensing occurs when a massive object such as a galaxy bends light from a more distant object behind it, creating multiple images of the farther object. If the object is heavy enough, the star or galaxy will become measurably brighter. Another way to detect a black hole is to notice the gravitational effect that it has on objects around it. If stars are observed to be circling around something that can't be seen, astronomers will assume there is a black hole causing the circling motion. Particle Physicists search for WIMPs, which are tiny non-baryonic particles that are smaller than atoms. The physicists are trying to directly detect WIMPs by detecting them in a medium that is almost absolute zero. The physicists will be able to detect the WIMP energy by measuring any registered heat. Particle physicists have a chance of directly measuring dark matter unlike the astronomers who can only detect it. If our universe is dominated by matter that we have never measured and we don't even have a true name for, how can the universe itself be the best laboratory in understanding and determining fundamental laws? We are very fortunate to be living in this epoch of a rapid accelerating universe. I think with the proper funding and technology, we will have the capacity to understand our universe much better. Our universe has the capacity to be the best laboratory in understanding and determining fundamental laws, but until we can fully understand darkness of the universe I don't think we can say it is. I agree with the many scientists, astronomers, and physicists, who believe that type 1a supernovae hold the key to understanding our universe. I think our outlook on the universe should be "Carpe Diem," seize the day, or in a cosmologist's term, seize the epoch because if our universe is truly accelerating exponentially then this is our only chance as humans in understanding and determining the fundamental physical laws of the universe.