An unqualified summary of alternative energy

Hey guys! I'm no Energician or anything, but I do have some BS degree from this one school in the south, so I'm going to just go ahead and offer my (in)expert opinion on alternative energy.

When you come right down to it, most of our energy sources are solar energy in disguise. Coal, oil, and natural gas were formed when plants stored the sun's energy in their biomass and then decomposed. Hydroelectricity is available when water is flowing downhill, and we force it to turn our turbines; but that water was transported to the top of the hill when it was evaporated by sunlight, and fell back down from the sky. Wind exists on Earth only because of local variations in temperature, caused (for the most part) by sunlight. And, of course, solar panels directly harvest the sun's energy. In fact, the only sources of power I can think of that don't originate from the sun are nuclear power and (arguably) geothermal.

One very interesting energy harvesting scheme is called "Ocean Thermal Energy Conversion". Essentially you have a huge pipe that goes down into the ocean to a depth of about 1,000 m, where the water is colder, about 5 C. At the same time you use water from the surface, which will be around 22 C. The laws of thermodynamics dictate that the heat will flow from hot to cold, but we put our devices in the way so that, like water falling down a hill, the whole process powers our machinations. And they say that the oceans provide a "limitless" supply of cold and hot water (maybe a dangerous idea).

Direct solar energy has a lot of promise. The above map shows the average intensity of sunlight. The blue dots represent the total area required, with current technology, to completely provide the current global demand for electricity. I think the map looks pretty neat.

However, as time wears on, our energy demands will tend to grow exponentially. Some guy made what's called the Kardashev Scale, which classifies how "advanced" a civilization is based on how much energy it can produce. To quote wikipedia, "a Type I civilization has achieved mastery of the resources of its home planet, Type II of its solar system, and Type III of its galaxy." We are estimated to have a rating of 0.72. Looking at the plot, which is on a logarithmic scale, our energy development over time is a straight line, which indicates exponential growth. Extrapolating from the data in just the last 110 years, it will take another 200 years or more to reach a rating of 1. Let's work on that, everybody.

EDIT: So on the Kardashev Scale, a Type 2 civilization will use roughly the energy output of an entire star. Freeman Dyson imagined what is now called a Dyson Sphere, a shell around a star that collects all the energy from that star. Dyson spheres have a few problems, though: If you build a solid shell around the star, then it wouldn't interact gravitationally with the star, and the two would slowly drift apart until they collided. If, instead, you build a swarm of space ships that orbits the star, then occasionally one would block the sun from the other. As you increase the number of spaceships, this happens more and more, until it becomes almost impossible to harvest all the star's energy.

Apocalypse hypothetical

Imagine the following scenario: Astronomers have found an asteroid on a collision course with earth. It will destroy out civilization and kill all humans on the planet. However, that won't happen for another ten years. A large number of the world's top scientists have come together to try and solve the problem, and they have concluded that we will not be able to deflect the object from hitting Earth. The only chance for the continued survival of humanity is to send a spacecraft full of people, which might survive in space for the several thousand years necessary for the earth to become habitable. Each person in the world is given a choice: If you dedicate the next ten years of your life to helping build the space station, you will be entered into the lottery for a ticket onto the space station. You can give the ticket to whomever you want. Otherwise, you can just relax for ten years, and join the biggest party of mass hedonism since Caligula. What would you choose?

So the scenario doesn't say what your chances of getting a ticket are. Most likely, that would be determined by how much work the people get done in ten years. How many people are necessary to repopulate the world? Preliminary research (i.e. google search) points to somewhere around 1,000, to avoid inbreeding. So probably the best strategy is to have as many self-contained satellite habitats orbiting the earth, each with 1,000 people. And then hopefully at least one of these will survive. Another strategy is to have just one massive space ship, but that's a bad idea since then it only takes one big mistake or accident (or crazy person) to destroy it.

So I'm looking at the situation where for two to three years, the scientists perfect a few models of space ship, then every factory in the world starts making as many of them as they can. Wikipedia says that in the last 50 years or so, only about 550 people have been launched into space. But our technology has grown exponentially (even though we are no longer capable of going to the moon) If we can devote a significant fraction of the world's GDP to this project, then we might be able to produce a few dozen of these space stations. . If we devote all our time and money to this problem, maybe we will be able to launch a few dozen of them before time runs out. So that's about 12,000 people who will be saved. At the same time, I would estimate that about half of the world's population would support this effort, that's about 3,000,000. That's a 1/25,000 chance for each person. A tiny chance, but perhaps worth it, if you know that you did your part in helping humanity avoid extinction?

Over several thousand years, each space station will undoubtedly develop its own culture and civilization, even if there is constant communication between space ships. Will they attack each other? If our space station's air filter breaks, will we raid another's, dooming them and saving ourselves? More likely, all space stations will work together, helping each other

Next is the problem of recolonization. When all the surviving space ships land, there might be some hostility between them. One issue is when, exactly, to land. If our space ship lands earlier than the others, we will have more time to set up a prosperous city and multiply. Later than the others, and we will have a more hospitable Earth to greet us. However, most likely there will be more than enough Earth for everybody, so this hostility probably won't cause human extinction.

A different possibility is to make a space craft that is capable of building more copies of itself from raw materials (moon rocks? asteroids?). That way we just launch a few "seed ships" and in a few millennia there will be hundreds or thousands ready to land. And in that case some may not want to land, but instead might move to other parts of the solar system (or to different stars!). This actually seems to me like a necessary step in the development of our civilization. With space stations that are not only self-reliant but also are capable of reproducing, we change all of space into a possible habitat for humanity. And in that case there's no need ever to return to Earth. We might just send it a post-card, though.