Life in the Universe What We Want to Know There is intelligent life on Earth Could it have happened...
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Transcript of Life in the Universe What We Want to Know There is intelligent life on Earth Could it have happened...
![Page 1: Life in the Universe What We Want to Know There is intelligent life on Earth Could it have happened elsewhere? Alien Spacecraft/UFO’s? Evidence is unconvincing.](https://reader036.fdocuments.in/reader036/viewer/2022062314/56649f255503460f94c3c4f8/html5/thumbnails/1.jpg)
Life in the UniverseWhat We Want to Know
•There is intelligent life on Earth•Could it have happened elsewhere?
•Alien Spacecraft/UFO’s?•Evidence is unconvincing
•Can we calculate probabilities?•No•Drake’s Equation is a way to estimate how many intelligent civilizations (besides ours) are in the galaxy
![Page 2: Life in the Universe What We Want to Know There is intelligent life on Earth Could it have happened elsewhere? Alien Spacecraft/UFO’s? Evidence is unconvincing.](https://reader036.fdocuments.in/reader036/viewer/2022062314/56649f255503460f94c3c4f8/html5/thumbnails/2.jpg)
Drake’s Equation
N = number of civilizations in our galaxy
R* = rate at which solar-type stars form
fP = fraction of those stars with planets
nPM= number of suitable planets and moons
fl = probability of getting life
fi = probability of life evolving intelligence
L = lifetime of intelligent species
N = R* fP nPM fl fi L
![Page 3: Life in the Universe What We Want to Know There is intelligent life on Earth Could it have happened elsewhere? Alien Spacecraft/UFO’s? Evidence is unconvincing.](https://reader036.fdocuments.in/reader036/viewer/2022062314/56649f255503460f94c3c4f8/html5/thumbnails/3.jpg)
Stars, Planets, and Moons
N = R* fP nPM fl fi L
R* = rate at which solar-type stars form = 1/year
fP = fraction of those stars with planets = 0.1 – 0.5
![Page 4: Life in the Universe What We Want to Know There is intelligent life on Earth Could it have happened elsewhere? Alien Spacecraft/UFO’s? Evidence is unconvincing.](https://reader036.fdocuments.in/reader036/viewer/2022062314/56649f255503460f94c3c4f8/html5/thumbnails/4.jpg)
The right temperatureN = R* fP nPM fl fi L
nPM = number of suitable planets and moons
= 0.1 - 1 Too hot
Too cold
Just right
![Page 5: Life in the Universe What We Want to Know There is intelligent life on Earth Could it have happened elsewhere? Alien Spacecraft/UFO’s? Evidence is unconvincing.](https://reader036.fdocuments.in/reader036/viewer/2022062314/56649f255503460f94c3c4f8/html5/thumbnails/5.jpg)
Getting Life StartedN = R* fP nPM fl fi L
fl = probability of getting life started = ?? – 1
•The basic building blocks of life (elements, amino acids) are common•Life started fairly quickly on Earth
•But even very simple life is extremely complicated/unlikely
![Page 6: Life in the Universe What We Want to Know There is intelligent life on Earth Could it have happened elsewhere? Alien Spacecraft/UFO’s? Evidence is unconvincing.](https://reader036.fdocuments.in/reader036/viewer/2022062314/56649f255503460f94c3c4f8/html5/thumbnails/6.jpg)
Getting Advanced CivilizationN = R* fP nPM fl fi L
fi = probability of life evolving intelligence = ?? – 0.5
•Evolution follows naturally from physical laws
•Evolution naturally leads to some complexity•Intelligence is a very useful kind of complexity
•Catastrophes could wipe out advanced life•Evolution may sometimes lead to dead ends
![Page 7: Life in the Universe What We Want to Know There is intelligent life on Earth Could it have happened elsewhere? Alien Spacecraft/UFO’s? Evidence is unconvincing.](https://reader036.fdocuments.in/reader036/viewer/2022062314/56649f255503460f94c3c4f8/html5/thumbnails/7.jpg)
Keeping Civilization AliveN = R* fP nPM fl fi L
L = Mean lifetime of intelligent life = 100 – 109 years
•We have the ability to destroy civilization•We are also damaging our environment•We are using up non-renewable resources
•Civilizations may “mature” – some evidence•Sustainable civilizations is technically possible
![Page 8: Life in the Universe What We Want to Know There is intelligent life on Earth Could it have happened elsewhere? Alien Spacecraft/UFO’s? Evidence is unconvincing.](https://reader036.fdocuments.in/reader036/viewer/2022062314/56649f255503460f94c3c4f8/html5/thumbnails/8.jpg)
Are We Alone?N = R* fP nPM fl fi L
•Intelligent life could be rare•Intelligent life could be common
R*= 1/yr fP = 0.1 – 0.5nPM = 0.1 - 1 fl = ?? – 1 fi = ?? – 0.5 L = 100 – 109 yr
= 0 - billions
My opinion:•We are first in the galaxy, and possibly the visible universe•Ultimately, this is an experimental question
![Page 9: Life in the Universe What We Want to Know There is intelligent life on Earth Could it have happened elsewhere? Alien Spacecraft/UFO’s? Evidence is unconvincing.](https://reader036.fdocuments.in/reader036/viewer/2022062314/56649f255503460f94c3c4f8/html5/thumbnails/9.jpg)
Searching Stars for Life
How can we know if intelligent life exists around other stars?•Visitors from outer space?
•Fermi paradox – If they exist, why aren’t they here?•Travel to distant stars?•Search for signals from space?
![Page 10: Life in the Universe What We Want to Know There is intelligent life on Earth Could it have happened elsewhere? Alien Spacecraft/UFO’s? Evidence is unconvincing.](https://reader036.fdocuments.in/reader036/viewer/2022062314/56649f255503460f94c3c4f8/html5/thumbnails/10.jpg)
Traveling Between the Stars
How Best to do it?•Best chemical rockets: 10-4c – 10-3c
•Millenia to nearest star•Nuclear rockets, solar sails, ion engines
•10-2c – 10-1c•Decades – centuries to nearest star
•Solutions:•Unmanned missions•Generation ships – parents have children•Long life span/hibernation
![Page 11: Life in the Universe What We Want to Know There is intelligent life on Earth Could it have happened elsewhere? Alien Spacecraft/UFO’s? Evidence is unconvincing.](https://reader036.fdocuments.in/reader036/viewer/2022062314/56649f255503460f94c3c4f8/html5/thumbnails/11.jpg)
Signals From Space
•We can send/receive electromagnetic signals throughout the universe at c
•The universe is a noisy place•Dust/gas/etc. blocks many wavelengths•Some radiation can penetrate gas and dust•In radio waves, the Earth outshines the Sun
![Page 12: Life in the Universe What We Want to Know There is intelligent life on Earth Could it have happened elsewhere? Alien Spacecraft/UFO’s? Evidence is unconvincing.](https://reader036.fdocuments.in/reader036/viewer/2022062314/56649f255503460f94c3c4f8/html5/thumbnails/12.jpg)
Signals From Space•We send accidental and intentional signals into space•We also look for signals from alien civilizations
•Nothing found so far
![Page 13: Life in the Universe What We Want to Know There is intelligent life on Earth Could it have happened elsewhere? Alien Spacecraft/UFO’s? Evidence is unconvincing.](https://reader036.fdocuments.in/reader036/viewer/2022062314/56649f255503460f94c3c4f8/html5/thumbnails/13.jpg)
Final Exam Equations
sin2 2
l
d
P2 = a3
F = ma
2
GMmF
r
(M + m)P2 = a3 c = f c = m/s
shift rest rad
rest
v
c
E = hfP = knT
maxT = 2900 Km
4 H + 2e - He + 2 neutrino + energy
L = 4d2B
3.26 lyd
p
4 2L T R
L T R
v = H0d H0 = 22 km/s/Mly
![Page 14: Life in the Universe What We Want to Know There is intelligent life on Earth Could it have happened elsewhere? Alien Spacecraft/UFO’s? Evidence is unconvincing.](https://reader036.fdocuments.in/reader036/viewer/2022062314/56649f255503460f94c3c4f8/html5/thumbnails/14.jpg)
End of Material for Test 4
Questions?