• The Astronomical Part: Basically, observations suggest that planetary formation is a natural consequence of star formation. Nearby stars exhibit dusty disks in orbit about them which are likely solar systems in the process of formation. For every star of some temperature, there is a zone around it called the habitable zone in which the temperature is right for the condensation of water vapor. The width of the habitable zone depends on the temperature of the star. If you make planets via the acretion of small grains then it is likely that one of the acreting planets will land in this habitable zone. In our case, if the sun were a cooler star we would have this class on the second planet from the sun, if it were hotter, we would be Martians. Hence, I regard the formation of planets with a liquid surface as ubiquitous.

• The Biological Part: I believe that given enough time, chemistry, mixing in the liquid surface, local concentration of organic molecules, etc, will eventually lead to a self-replicating system. That process took a billion years to happen on the earth so maybe all you need is time. But, since the planet is subject to random catastrophe, there are all kinds of problems that species have to overcome, I rate the probability of reaching intelligence as only 10% (of course it could be much smaller!).

• The Socio-Economic Part: Okay, does intelligence begat Technology? Is it the manifestation or the asshole of Intelligence? Does the capacity to destroy our planet mean that we can never really be Intelligent? And what about our lifetime as a technical civilization, will it be short or long? I assume again only a 10% probability of intelligent civilizations becoming technological (maybe most are smarter than US?). So overall, I have assumed that on only 1% of all planets with a liquid surface does a civilization which builds radio telescopes arise.

  For the lifetime I adopt the following argument:

  • 99% of all technological civilizations extinct themselves after 100 years
  • The remaining 1% survive, in harmony with their planetary resources for 1 billion years.
  • This leads to an average lifetime of 10 million years (1% of 1 billion)

• Notice, that the number of civilizations which currently exist is strongly correlated with your estimate of the average lifetime.

• Multiply it all together to get one million civilizations which now exist. This is actually a small number.

Why one million is a small number

What is the Moral: Life, All Life is Rare whether its yours, your neighbors or your neighbors pet slug.

Our Place in the Cosmos

But Who are We?

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In the model presented in this class, a connected pathway of events (schematically illustrated above) have lead to the situation where the Universe can ask itself a question.

The fate of question marks on this planet is unclear.

Can we preserve the question mark through the colonization of other worlds? Is this even an appropriate way to do that? (morality vs. economics again).

What about Colonization of Space ?

Why would we colonize other worlds?:

• Too many people on the earth
• Earth has become unliveable
• No more resources left for N billion year people
• Manifest Destiny (growth of the Red Dot)

The above reasons would all exist if your species is unable to engage in multi-generational thinking and planning. Colonization requires this.

To move several (hundred) thousand individuals off this planet towards another world is a serious effort and a serious use of planetary resources.

Such large scale colonization requires a 50-200 year planning and implementation effort. Our technological culture has repeatedly demonstrated an inability to do this kind of long range planning.

This might be a form of self-censoring. Non-equilibrium cultures can't colonize because, when they feel the need, it will be too late (resources will be gone).

Why would equilibrium cultures colonize then when they would have no reason to?

• CURIOSITY what's out there. That's a powerful stimulus for space exploration

• Planetary Instability For instance, the earth has periodic ice ages which may be a severe threat 10,000 years from now.

• Avoiding the next asteroid impact that causes mass extinctions?

• Global warming? a threat 2-300 years from now? (of course, this wouldn't be a problem for equilibrium cultures)

A colonization scheme: The argument why N must be one:

Implications of the above argument:

• We are it we are suppose to colonize
• Multi-generational committment to this scheme is impossible and therefore it is always doomed to failure
• Why would the blue dots choose to colonize?