3:32 PM LINK
How to Cook the Earth
This is an interesting article, about a physicist at University of Houston Institute for Space Systems who has proposed a solution to the world's energy supply problems.
The basic idea is to collect solar energy on the surface of the moon, then beam it to earth in the form of microwave radiation, which is collected on the ground for conversion into electricity. Criswell, the physicist, estimates that 100 terrawatts of power (enough to supply all the earth's power needs) could be harvested by several dozen stations, with the panels fabricated on the moon out of mostly lunar minerals.
Let me get this straight. He's saying we should use the Moon to microwave the Earth? Well, that will certainly help alleviate global warming.
What, you say, can I be serious that sending microwaves beams from the moon onto the earth is the same thing as putting the earth in a microwave oven? Yes, it's pretty much the same thing.
There is a deep issue at work here, something to be decided in this century. Should we collect solar radiation that wouldn't otherwise fall upon the earth, and redirect it into the earth's atmosphere, in order to serve our energy needs?
From the persepctive of the earth, the redirection of sunshine, in whatever wavelength, from space into the earth's atmosphere is basically the same as if the sun were shining slightly harder than it actually is upon the earth. Or, equivalently, it is as if the earth were slightly closer to the sun than it actually is, not anywhere near the orbit of Venus perhaps, but effectively closer, nonetheless.
Of course, we are already doing this very thing. The burning of fuels on earth, for whatever purpose, helps keep the atmosphere slightly heated up, more than it would have been if the sun were the only source of heat. The fact that the fuel was originally created by solar energy can be immaterial, so long as this energy fell on the earth a long time ago, and has been stored as chemical fuel since then. This is because of the fact that the earth is, from thermodynamic perspective, in quasi-equilibrium.
What if the stored fuel is burned to create motion? Does this result in heat? Of course. Have you felt the radiator of a car? All that heat, as well as the air resistance, road friction, and brake friction that eventually brings a car to a half, is dumped into the reservoir of the atmosphere as heat. The roughly 125,000 BTU of chemical potential energy in a gallon of gasoline will eventually be manifest as 125,000 BTU of heat in the atmosphere.
To keep cool, the earth radiates some of its atmospheric heat into space, mostly on its night side. This is what keeps the earth from experiencing a runaway temperature increase from the sunlight it receives. The question is: how much more can the earth take before it undergoes what's known in the thermodynamics trade as a "phase change."
We know the sun experiences periodic fluctuations in its energy output, one cycle of which lasts about eleven years. Yet the earth's climate remains fairly constant over each eleven-year period. Thus the atmosphere is stable enough to endure this fluctuation without the climate patterns going haywire. But the long-term patterns of solar energy pattern are not yet known. Also there is evidence to support the idea that if the thermal conditions in the atmosphere reach a tipping point, climate patterns can be altered quite rapidly, on a human scale. This kind of behavior is typical for complex systems.
By the way, there are certain forms of energy that indeed require no net addition of heat to the atmosphere. Wind power, for example, is the extraction of heat from the atmosphere (yes, in this sense, you can think of wind as heat energy), and the transformation of this energy into electricity, which is then converted back to heat, once it's done "doing its work" of, say, moving a train. There is no net increase. That is, in harvesting wind power, you actually "cool" the atmosphere, and then heat it back up by the same amount when you use the electricity you have harvested.
Likewise there is no net change if terrestrial solar energy is harnessed for any purpose, including to distill hydrogen from water. The burning of that hydrogen would result in no net heat increase to the atmosphere (hydrogen mined from rocks is a different story).
The moral of this story: before embarking on any venture to bring extraterrestrial solar radiation to the earth's atmosphere, we should make sure we have our ducks in a row.
12:41 PM LINK
How to Burn Hydrogen
In 1766 in England, Henry Cavendish separated and experimented with a gas he called "flammable air." He reported that upon burning, the gas left a dewy residue, which he suspected was ordinary water. Lavoisier of France independently discovered this property and gave the gas the name "hydrogen," which stuck.
Hydrogen turns out to be an element, the lightest one in the Periodic Table. Hydrogen gas (the substance distilled by Cavendish and Lavoisier) is actually two hydrogen atoms bonded together into a molecule.
The sun, like most stars, is almost entirely elemental hydrogen, i.e., not bonded into a molecule as hydrogen gas. The shining of the sun is therefore not due to ordinary burning of hydrogen gas. Rather the sun shines due to the separate physical process of hydrogen fusion.
On the other hand, Jupiter is made up largely of molecular hydrogen gas, yet it also does not burn, at least on any planetary scale. This is despite the observed presence in its atmosphere of electromagnetic storms, which could ignite large-scale combustion.
Why doesn't Jupiter's atmospheric hydrogen gas burn? Because in order to combust by an ordinary chemical reaction, hydrogen also requires the presence of oxygen gas, such as that widely found in the atmosphere of Earth (but not Jupiter).
In the presence of enough heat, the hydrogen and oxygen gas molecules will chemically react to form a more stable compound, consisting of water molecules, as well as heat.
From a burning perspective, all hydrogen gas, no matter its origin, is the same. You could have scooped it out of the atmosphere of Jupiter, squeezed in from the lunar soil, or distilled from rain water by solar-powered electrolysis. It all burns the same.
When many people think of hydrogen combustion, they erroneously assume it must be undergoing an uncontrolled explosion. Like natural gas, propane gas, or gasoline, hydrogen gas can either burn or explode, depending on the conditions. With internal combustion engines, it is very desirable not only to store the gasoline property, but also to control the rate of burning of gasoline in the piston, to yield the greatest horsepower per engine cycle. The same is true of burning hydrogen gas. If you want to use it as fuel, you must not only store it properly, but you must also control the rate and conditions of its burning.
