Lecture 14

Question 1

The Borongs, a technological civilization not unlike ours, lives on a planet orbiting a star 25 light years from the Sun. Would Borongian radio astronomers have detected our presence?

Answer 1

Yes, the Borongs would have noticed the artificial nature of the radio emission of the solar system decades ago

Question 2

The range of frequencies that are contained in a particular radio signal is referred to as its

Answer 2

bandwidth

Question 3

Which of the following signals from an advanced civilization would be easiest to detect?

Answer 3

high intensity, narrow bandwidth

Question 4

What is the “Wow!” signal?

Answer 4

It is a strong radio signal from space of unknown origin that did not repeat

Question 5

What really is SETI?

Answer 5

SETI is concerned with searches for signals from extraterrestrial civilizations, not spectral “biomarkers”we discussed earlier in course, or actual travel to other star
systems

Question 6

Why is SETI done most in radio range?

Answer 6

1. Interstellar dust selectively blocks shorter wavelengths (higher frequencies) strongly suggests we use the IR or radio parts of the spectrum (long wavelengths or small frequencies)
2. Radio photons are cheaper to send than optical photons (because energies are ~ 100,000 times smaller for radio)
3. The main consideration is noise: Here “noise”means anything that is not an alien signal–any kind of interference.

SO NOISE IS MOST IMPORTANT

Question 7

What did the Ohio State University SETI detect?

Answer 7

Detected a strong narrow-band signal for 72 seconds (Signal was also short-lived as it was detected only by
one of the telescopes detectors).
Is also the origin of the Wow! signal

Question 8

The Eerie Silence

Answer 8

• SETI has been on-going for about 50 years andNOTHING compelling has been detected….
• Conclusion: are we alone? Are there no ETIs in our galaxy? Is there a fundamental issue that limits L? = The Great Filter hypothesis….
• No, not yet. But they are probably no nearby ETIs similar to us, nor a nearby strong radio beacon intended to notify us of an advanced ETI’s presence.