September 8, 2006

Astronomers Derive Universal History From Light

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“A long time ago, in a galaxy far, far away” opens the famous fantasy epic, but George Lucas wasn’t just trying to blow his audience’s minds; that line was inspired by real science. This line rests on the same logic that serves as a foundation for modern science and as definitive evidence that this universe existed long before man. I’m speaking of course about the speed of light, a fundamental constant in physics. Visible light is just one form of electromagnetic radiation, all kinds of which travel at the same speed.
So, what does this have to do with Luke Skywalker? Light (Lucas’ motion picture) from “a galaxy far, far away” travels across the universe at a constant speed, and when it shines on Earth, it displays a snapshot of when the light was originally created (i.e. Star Wars) “a long time ago.” This concept isn’t just for science fiction buffs; astronomers rely on this idea to examine the early years of the universe. The famous Cosmic Microwave Background, which provides some of the best evidence for the Big Bang theory, is also some of the oldest light in the universe.
Wait, microwaves are light? Microwaves, just like those generated in a microwave oven, are a type of electromagnetic radiation, the same as visible light. In fact, microwaves, radio signals, infrared and ultraviolet radiation, and X-rays are practically identical. They all travel at the speed of light and share similar properties. Their defining difference is the length of their waves. This wavelength explains why visible light can’t travel through buildings but radio signals often can. Since heat emits infrared light, night vision goggles are designed to transform that light into visible light allowing warm objects (such as body heat) to be seen in the dark.
Seeing in the dark is what astronomy is really all about. For thousands of years, astronomers relied on the naked eye. Even after the development of the optical telescope, there was little scientific understanding of the processes that take place outside of the solar system, where dust often obscures visible light. It wasn’t until the mid-20th century that astronomers began taking advantage of the full electromagnetic spectrum (radio signals through the ultraviolet). This first breakthrough examining these different wavelengths is often referred to as the “Golden Age” of astronomy because it allowed a tremendous amount of scientific progress in a short period of time.
In the decades since, astronomers have mapped the universe in millions of colors, most of which aren’t even on the visible rainbow. One small chunk of the rainbow has noticeably been left out. This area represents wavelengths between a tenth and one millimeter and thus is often referred to as part of the study of submillimeter astronomy. This wavelength is difficult to observe and few have ventured to do so. It’s made difficult by water in the atmosphere, which absorbs this light and so observations must been done in space, which is very expensive, or in very dry areas on the Earth, which are just difficult places to work. Submillimeter telescopes are often built in deserts, the tops of very high mountains, or even worse, desert mountains. One telescope is at the South Pole because it happens to be one of the driest atmospheres in the world, despite all the snow on the ground. It’s once again not a very comfortable place to work; just ask Prof. Gordon Stacey, astronomy, and his team. They are the cutting edge of building and observing with submillimeter detectors.
But now, the missing knowledge has become too valuable. A decade ago, there were no submillimeter galaxies; today their number keeps growing and theorists predict many more. Submillimeter light contains information from an early, relatively unknown age of the universe. Prof. Jason Glenn, of the University of Colorado at Boulder, spoke yesterday at the astronomy colloquium about his efforts in the field. Since the field is relatively new, much of his energy is devoted to developing better submillimeter detectors. In fact, he plans on working closely with Cornell on a new proposed telescope. Cornell and California Institute of Technology have proposed building what would be the most advanced single dish submillimeter telescope in the world. However, Cornell astronomers shouldn’t plan on being that comfortable: they plan on building it high up in the Chilean mountains in the middle of a desert.