Is solar energy clean?

For decades we have been sold the idea that when we fully harness solar energy, all our problems of getting cheap and abundant energy, air pollution, and global warming will be solved.

For decades I have been warning that this optimistic approach is not true. If we were able to completely replace energy from fossil fuels (coal, oil and natural gas) by solar energy, some of our problems will not go away, they will just take longer to become unsustainable, especially the problem of global warming.

Why do I think this? Because the Earth receives a certain amount of solar energy. A part is used by plants to carry out the chlorophyll function, which transforms inorganic matter into organic matter, thus making life possible for all animals, including us, humans. Another part heats the oceans and the continents, allowing the Earth to maintain an almost constant temperature, despite the heat losses it suffers every day from the side opposite the sun. Finally, another part of the solar energy is reflected or diverted, in the atmosphere or on the surface, and is lost in outer space.

Superluminal interstellar travel

James H. Schmitz

The human imagination knows no limits. Einstein can tell us that the speed of light sets an insurmountable limit for objects with mass, but deep down we don't believe it. There has to be a way to break that limit! Otherwise, how could we reach the stars during the short span of our lives, return to Earth and tell here what we have seen?

People in our time, especially our civilization, are determined that we must get everything we want. I want to be immortal, so I must be; if I can't, at least my children or my grandchildren. (We don’t usually go beyond our grandchildren…) I want to travel to the center of the galaxy; if I can't, someone will. I want to do whatever I want with my life, so I will… no matter what!

Traveling at the speed of light

Image of
"2001, a Space Odyssey"

Actually, the title of this post is wrong. Traveling at the speed of light is impossible, because it would take infinite energy to accelerate to that speed a body with rest mass greater than zero. What I am going to talk about here is travel at relativistic speeds (close to the speed of light), which means more than 10% of the speed of light (i.e. 30,000 kilometer per second).

Interstellar travel in suspended animation

Most of the problems mentioned at the end of the previous post would disappear if the generational journey were combined with another scientific advance that does not seem, at first glance, impossible: the conservation of human beings in a state of latent life for very long periods of time. This state, which resembles what many living beings do when environmental conditions are unfavorable, is called hibernation when it is a response to cold, and aestivation when it is used as a defense against heat and dry seasons.

Under the current conditions of science, human hibernation is not feasible. It is true that it is possible to reduce the vital rhythm through the application of low temperatures, a technique that is being used in surgery to carry out complex or delicate operations, but the total suspension of vital activities is always transitory and limited to a short period of time, usually measured in hours.

Generational interstellar travel

In a subset of science fiction novels and stories, the journey to the stars is longer than a human lifetime. The space vehicles are huge, as they must be to house many cosmonauts during thousands of years. The speeds of these spacecraft are not very high, on the order of a few million kilometers per day. At that rate it takes thousands of years to cross the interstellar chasms.

The cosmonauts who reach the end of the journey are not the same ones who started: hundreds or even thousands of generations have passed their entire lives aboard a spaceship and don’t know the Sun, or life in the open air. The vehicle where they travel is a small planet: a closed entity, in perfect ecological balance. Nothing is wasted. Wastes from normal activity are recycled and reused. The cycles of water, oxygen, carbon, nitrogen and other essential elements of life must be perfectly controlled. They only eat hydroponic vegetables.

Will traveling to the stars be possible?

Will interstellar travel be possible? At the current level of our technology, the answer is clearly no. Will it be possible in the future? It is always dangerous to make predictions: reality often strays from what was supposed to happen. But it doesn't look like interstellar travel is going to become feasible anytime soon. Of course, in the scientific literature, both serious and imaginative, various methods have been proposed, some of which we’ll review in this and future posts, by analyzing the relative probabilities of each one.

Many writers consider interstellar travel the next frontier of human spread, and the only guarantee to avoid our extinction, either accidental, if a cosmic catastrophe occurs, or caused by ourselves with a nuclear war. The problem is, a trip to the stars would be much more difficult than planet exploration in the solar system. Apart from the sun, the closest star to us is 4.27 light-years away, just over 40 trillion kilometers. With our current technique, speeds of the order of one million kilometers per day can be reached, so a trip to that star would last more than one hundred thousand years. Taking advantage of the gravitational pull of giant planets, like Jupiter, it would be possible to triple the speed, but even so we are talking about tens of thousand years.

Super-accurate Innumeracy

A.K. Dewdney

Between 1984 and 1991, A.K. Dewdney authored numerous articles in the section on Mathematical Games of Scientific American. He was one of the successors to Martin Gardner, most famous contributor of that section. Dewdney is also the author of an amazing book, The Planiverse (1984), which belongs to the same genre of mathematical fantasy as Edwin Abbott's Flatland, published just a century earlier.

In the previous post I offered a few examples of innumeracy taken from A.K. Dewdney’s book 200% of Nothing. In this book, Dewdney points out, among many others, two very frequent mathematical mistakes. The first consists in giving so few digits of a number that it loses all usefulness (he calls those numbers nums, to indicate that they are not full numbers, as they are not complete). The second mistake is the opposite: giving too many digits of a number, beyond what is necessary or makes sense. He calls unnecessary digits dramadigits, as they only serve to give the particular number a more dramatic look.

Let's look at an example from Dewdney's book: