Drake’s Equation is an equation used to estimate the number of detectable extraterrestrial civilizations in the Milky Way galaxy. Invented by Frank Drake, the founder of SETI.
Ns
- 1011 Stars discovered so far
Fp (0.5) Half the planets in the Milky Way galaxy have stars around them
Ways to detect planets
- Transit Method: Diming of star due to planet revolving around it
- Astrometry/ Doppler Spectrometry: Wobbling of star due to planet revolving around it
- Direct Imaging: Using optical telescope to directly see massive planets around parent stars
***Thanks to Kepler telescope; we can detect smaller planets; earth-like size
Ne (2.0) Based on the distance from the parent star
- Each star has a particular distance you can be away from it to develop life
- Called the Habitable Zone (Defined by present of LIQUID WATER) MUST BE LIQUID
- Based on molar mass (H20) should be a gas at 25C but remains a liquid due to: 1) COHESION (hydrogen bonds-stick together) 2) HIGH HEAT CAPACITY 3) HIGH HEAT OF VAPORIZATION
- Increase star size= move habitable zone BACK
- Decrease star size= move habitable zone FORWARD
Fl (1.0)
- Because all planets capable of forming life will eventually develop life
Fi/Fc (10% for both)
- Only applicable to planets in habitable zone
- NOT EASY TO ESTIMATE (This valve is greatly debated)
L
- Longer civilization is around, increased likelihood of finding them
- BUT not how old civilization is; its age is determined by when they first evolved communication
- We are about 100 years old with communication / (Age of the Universe (10 bya))
Fermi Paradox
The Drake Equation predicts a large amount of intelligent civilizations, however we have found NONE!
Why haven’t we found anyone?
- Maybe distance is too great
- Maybe Our technology could be incompatible; we can’t detect each other
- Maybe NO other civilizations exist
