Lecture 31: SETI

Question 1

what are the main methods used in SETI (radio and optical approaches), and the rationale behind them?

Answer 1

optical SETI:
- use optical wavelengths
- modern lasers produce pulse 5000 brighter than sun
- universe noisy in optical as no water hole
- to fix this, look on very short timescales
- see extraterrestrial life

radio:
- looking for narrow-band, artificial radio signals that stand out from natural cosmic noise
- typically focus on frequencies like the water hole where natural noise is low

rationale:
- civilisations might use electromagnetic signals to communicate across space
- radio waves travel long distances
- may use high-powered lasers to send tightly focused, brief pulses of light

Question 2

what is an example of efforts to communicate with extraterrestrial intelligence?

Answer 2

voyager records
-voyager records attached to 2 probes in 20th century
- composed of images, audio messages
- set to reach star gilese in about 40,000 years
- show we are friendly

Question 3

what is the fermi paradox, and what are 2 potential answers to the problem?

Answer 3

with there being 200 billion stars in the galaxy, there are many earth-like planets alongside them

if earth is typical, some may develop intelligent life, and some should be much older

some will develop interstellar travel, a tech earth is investigating now and so the galaxy should be colonised

solutions:
- all civilisations destroy themselves
- there are no other civilisations
- they are observing from a far

Question 4

what is the drake equation, and what do the terms in the equation mean?

Answer 4

estimates the number of civilisations in our galaxy

N= R*.f_p.n_e.f_l.f_i.f_c.L

where:
N is no. of civilisations in galaxy with which communication might be possible

R* is average rate of star formation in our galaxy

L is length of time that civilisations release these signals into space

Question 5

what are some of the general ideas of how people might respond to contact if it ever occurred?

Answer 5

• make sure signal is genuine
• ensure scientistic teams find repeat detection
• inform relevant national authorities
• UN treaty on outer space requires you to inform secretary general
• announce to public