Search for Extraterrestrial Intelligence

Question 1

What is the reasoning behind Fermi’s paradox?

Answer 1

That the galactic crossing time &laquo_space;age of the earth

• Mean age of terrestrial planets is 1 Gyr older than earth
• Could explore the entire Milky way in 10 million years with current technology

Question 2

What can we assume from Drake’s equation?

Answer 2

That N must be reasonably small and since the left hand values are relatively well understood:
f(l)f(i)f(c)L &laquo_space;1

Question 3

How does overturning the Copernian mindset solve the Fermi paradox?

Answer 3

Maybe we are rare, and many planets may have life but few have intelligence

Question 4

Name 3 other Fermi paradox solutions

Answer 4

1. Civilizations are short lived due to war, catastrophic events or climate change
2. Aliens are here and we can’t see them
3. The sheer size of the galaxy makes a trip to Earth too long and/or too resource intensive for an alien civilization

Question 5

What is Kardashev’s scale?

Answer 5

A scale for civilization

1. Use all the available energy of a planet
2. Use all the available energy (luminosity) of a star
3. Use all the available energy (luminosity) of a galaxy

Question 6

Why is the ‘water hole’ (radio frequencies between H and OH) used to detect extraterrestrial transmissions?

Answer 6

1. It’s a radio quiet frequency window in the earth’s atmosphere
2. If ETI planet environment is similar, likely to be used

Question 7

Why are leaked ratio transmissions from Earth unlikely to be detected by an ETI?

Answer 7

• Frequencies ill suited

- Highly directional, limited to < 100 pc

Question 8

What are the advantages of Optical SETI?

Answer 8

1. Collimated narrowband pulses are energy efficient
2. Can carry more information (high carrier frequency)
3. Pulses can be transmitted 5000* brighter than the Sun

Question 9

What are the limitations of Optical SETI? How could they be overcome?

Answer 9

Drawbacks
- universe is optically noisy with no ‘water hole’
- interstellar dust could obscure beams
- must be in alien laser’s lign of sight
Solution
- transmit at short (nanosecond) eliminating all noise except muons and coronal discharges
- look at wavelengths not affected by interstellar dust
- look at many lines of sight

Question 10

What evidence of ETI intelligence could IR possibly detect?

Answer 10

1. Dyson spheres
   - artifical sphere encircling a star
   - would re-radiate IR
2. Asteroid mining
   - Many planetary systems have debris belts
   - ETI’s could exhaust local precious metals and go out to mine them
   - traces of this would be left in IR studies of debris disks