Use of the Drake Equation - Assignment Example

1. In the class notes we make use of the Drake equation as providing a statistical estimate of the number of civilizations that might exist in our Galaxy and are capable of communication. Recently, however, some scientists have argued that the Drake equation is an inaccurate description. This new theory is known as the "Rare Earth Theory" (by Ward and Brownless). Do some research on this new theory and identify what the key components of this theory are that suggest planets like the Earth are much rarer than we think they are.

The rare earth theory argues that for complex extra-terrestrial life to exist they require conditions that are similar to those found on earth. However, the conditions found on earth to come into existence required an improbable combination of astrophysical and geological events to take place. The chances of such events taking place are close to zero and, therefore, the probability of an Earth-like planet with extraterrestrial life is also very low.
Let’s look at some of these events required to understand just how rare a planet like the earth is:
1. The planet must orbit the right kind of star at the right distance. This is also known as the Goldilocks principle. For a planet to sustain life water on it must be in liquid form. Being too far or too close to the sun makes the planet’s surface temperature to be incompatible with liquid water.
2. The planets in the system must be rightly arranged. Take our solar system for example the rocky inner planets are surrounded by massive gas giants on the outer parts with a great gravitational pull that protects the inner planets from bombardment by asteroids.
3. The planet must occupy the right location in the right kind of galaxy. Much of the universe is inhabitable. These are referred to as ‘dead zones’. The habitable zone is determined by the distance from the center of the galaxy. The farther away from the center, the less metallic it is (planets far away tend to have only helium and hydrogen and are not solid. )
As we can see, these occurrences all at the same time and in the same place are highly improbable. Thus the rare earth theory suggests that earth-like planets, if any, are very few in the universe.

2. Consider our galaxy to be a very thin circular disk of stars of a radius of approximately 50,000 light years. If there are currently 2500 civilizations in our galaxy capable of communication, what is the approximate separation of these civilizations (in units of light years) if they are uniformly (e.g. equally spaced) distributed within this circular disk of stars?

3. Based on the responses you got from your circle of friends summarize what you think the relationship between humans and nature must be and whether or not that relationship has played out in the real world. Your generation is all about "sustainability" - based on your responses do you think that humans have the right characteristics to foster sustainability? If so, what are those characteristics, if not, how do you instill the needed characteristics? Read More