A World Record
Jul 10, 2009
|The National Radio Astronomy Observatory, in Green Bank, West Virginia - Friday afternoon, July 10
Seven miles up the road from Cass stands the Robert C. Byrd Green Bank Telescope, the world’s largest fully steerable radio telescope. We first caught sight of it from several miles away, and it is a sight to behold. Standing 485 feet tall, it is taller than the Statue of Liberty and nearly as tall as the Washington Monument, and it towers over the semi wooded fields in which it stands.
The telescope is the property of the National Radio Astronomy Observatory, a facility of the National Science Foundation. The observatory does tours of the telescope, and we made it in time for the 5:00 PM tour. Tours are free and they start with a ten minute video and a short presentation by the tour guide. Digital photography is not allowed inside the gates to the facility, and she demonstrated why that is. She collected three cameras and held them inside a copper box monitored by an oscilloscope. Each time she turned one on it registered a definite electrical interference on the scope, and the radio telescope, huge as it is, is extremely sensitive to such interference - hence the ban on using cameras inside the gates.
Radio telescopes collect radio waves received from space, and transmit them to a control center where they are recorded and evaluated. The images they create differ radically from those received through visual telescopes, and compared to visual images they have an almost cartoon quality, but they contain information impossible to ‘see’ visually and they are invaluable tools for answering science’s biggest questions.
The Green Bank Telescope (GBT) represents a late stage in the development of radio telescopes, and it is likely that it is the final stage in the evolution of large single dish equipment. The dish itself is made up of 2004 metal panels that are each about the size of a queen sized mattress. The total surface area is almost 2.3 acres, or the size of two football fields, and while it can be focused to an accuracy of one arcsecond (equivalent to the width of a human hair seen from a distance of 66 feet away) it weighs 17 million pounds.
How much bigger can you get? And the answer to that question is, “Not much!” The good news is that radio telescopes don’t have to get any larger, and that the same result can be obtained using multiple dishes placed the right distance apart. In fact the latest iteration in radio telescopes, the Very Large Array (VLA) in New Mexico uses dishes that are one sixth the size of the GBT but spread out as much as 27 miles across the desert to see farther and with greater resolution than the GBT can see into space. The future of radio telescopy seems to lie in the development of such arrays, and the abandonment of large and cumbersome equipment like the GBT.
Nevertheless, the GBT is awesome, and it’s still in constant use 24 hours a day - it’s course of study not affected by visible light like conventional telescopes. To minimize electronic interference the government has created a ‘quiet zone’ of thousands of square miles around the GBT where no commercial transmitters of any kind are allowed. The regulation even extends to such things as microwave ovens and even electric blankets for residents in close proximity to the facility. This means no cell phone towers nearby, making our Verizon air card one of the casualties of the regulations.
We boarded a bus and the girl guide took us out to the telescope. She stopped at an observation deck outside the gate to let us take pictures, but inside the gate only conventional film cameras are allowed. On the way out we passed a number of older and smaller radio telescopes, some still in use by organizations like M.I.T. The facility uses only diesel powered vehicles to eliminate spark plug interference, and they have an interesting fleet of old Checker Cabs that have been converted to diesel power.
We ended the day with a tour of their inside exhibits which are very good, but which put us on overload after such a busy day. We scored a nice campsite at an RV park a few miles away, where we downloaded the hundreds of pictures we took during the day. And a rare and memorable day it was!