PHY - U4L

P105Unit4LabSetiandYou.pdf

PHYS 105 Unit 4

Application 4 - SETI and You Part 1: The Drake Equation

As our technology and searching got more intense in the 20th Century, Frank Drake designed what became the "Drake Equation" to begin to explore what the odds of discovering alien civilizations might be based on a series of assumptions.

How can we estimate the number of technological civilizations that might exist among the stars? While working as a radio astronomer at the National Radio Astronomy Observatory in Green Bank, West Virginia, Dr. Frank Drake (now Chairman of the Board of the SETI Institute) conceived an approach to bound the terms involved in estimating the number of technological civilizations that may exist in our galaxy. The Drake Equation, as it has become known, was first presented by Drake in 1961 and identifies specific factors thought to play a role in the development of such

civilizations. Although there is no unique solution to this equation, it is a generally accepted tool used by the scientific community to examine these factors.

That these numbers are assumptions and not hard facts is important, because the value that each person receives when they calculate the equation is different. Coming up with numbers for civilizations, especially at different technological stages is extremely dicey. We are the only case we know of - are we typical? Kinda hard to say.

Procedure:

• Watch this video - https://www.youtube.com/watch?v=2s1qTUqOv88 – Carl Sagan explains the Drake Equation and why it is useful.

• Are we alone? Calculate the odds using this Drake Equation applet. The suggested values are listed under the “more” at the end of each sentence.

Questions:

1. Using the calculator above, make 5 different predictions of N. Vary only 2 of the 7 variables (use some of the recommended values for the other 5, either using ones from the book or from another website). Report which variables you changed, why you chose those particular values for them, and your 5 values of N here (a table would be nice).

2. What pattern did you see in the variation of N based on your changing values?

https://www.youtube.com/watch?v=2s1qTUqOv88

http://www.pbs.org/lifebeyondearth/listening/drake.html

3. Can you think of another way to calculate the odds of finding a civilization other than the Drake Equation? Find one on the Net, maybe? How is it different from the Drake Equation? In your opinion, which is more valid?

4. Of the 7 values, which 2 do you think are the most up in the air in terms of what we think they should be? Why?

5. Based on these values for the Drake Equation, do you think it likely that we will find another civilization? Support your argument with data from this calculator.

Part 2: Project Phoenix - Signals From Space

Where would YOU look for signs of extraterrestrial intelligence (SETI)? This is the question astronomers involved in the selection of target stars for Project Phoenix have been asking.

Project Phoenix was the world's most sensitive and comprehensive search for extraterrestrial intelligence. It was an effort to detect extraterrestrial civilizations by listening for radio signals that are either being deliberately beamed our way, or are inadvertently transmitted from another planet. Phoenix is the successor to the ambitious NASA SETI program that was cancelled by a budget- conscious Congress in 1993. Phoenix began observations in February, 1995 using the Parkes 210 foot radio telescope in New South Wales, Australia. This is the largest radio telescope in the Southern Hemisphere.

Following the southern observing campaign, the project turned its attention to northern stars. Appropriately, this phase brought the search back to its roots at the National Radio Astronomy Observatory in Green Bank, West Virginia. The 140 Foot Telescope is only a short distance from the antenna used by Frank Drake in Project Ozma. Project Phoenix operated in Green Bank from September 1996 through April 1998, using the telescope about 50% of the time. As the primary instrument in Green Bank, the antenna was shared with other astronomers.

Phoenix doesn't scan the whole sky. Rather, it scrutinizes the vicinities of nearby, sun-like stars. Such stars are most likely to host long-lived planets capable of supporting life. We naturally include stars that are known to have planets. There are about one thousand stars targeted for observation by Project Phoenix. All are within 200 light-years distance.

Because millions of radio channels are simultaneously monitored by Phoenix, most of the "listening" is done by computers. Nonetheless, astronomers are required to make critical decisions about signals that look intriguing.

Phoenix looks for signals between 1,000 and 3,000 MHz. Signals that are at only one spot on the radio dial (narrow-band signals) are the "signature" of an intelligent transmission. The spectrum searched by Phoenix is broken into very narrow 1 Hz-wide channels, so two billion channels are examined for each target star.

Observations are currently being made during two three-week sessions each year using the 1,000 foot radio telescope at Arecibo, in Puerto Rico. During the observing sessions, the astronomer on duty post reports.

When the project concluded in 2004, Phoenix had examined about all of the stars on its "hit list." So far, no clearly extraterrestrial transmissions have been found. But the faint whine that would betray an alien civilization might be heard tomorrow.