Universal FAQ

 kw: book reviews, nonfiction, science, cosmology, ultimate questions, humor

I was thinking of titling this post "The FAQ to end all FAQ's", but realized that's too much hubris. I like answer lists (and many kinds of lists). Frequently Asked Questions About the Universe, by Jorge Cham and Daniel Whiteson, serves up question-answering essays on twenty big questions. One could say they have really put the universe under a microscope.

Both authors are PhD scientists, and Jorge Cham is also a cartoonist (see Piled Higher and Deeper – this links to the archive; it ran 20 years). Nearly every page of the book has at least one of his little illustrations. Here are a couple of them, picked at random.

The first question: "Why Can't I Travel Back in Time?" The answer isn't simple, though the authors simplify things as much as they can, so the essay takes up about 14 pages. It ends with a technical dichotomy, that time reversal doesn't violate any laws of physics, but getting the engineering expertise to carry it off is far, far from us. Put simply, you can't unmake an omelette, a practical expression of the term "entropy".

Another question that is currently on the minds of many is "How Long Will Humanity Survive?" Here the dichotomy is between doomsayers and Pollyanna's, which make up only a few percent of humanity, but between them they make nearly all the noise. Things that might doom us include asteroids, "gray goo" (runaway nanotech), and too much CO₂. I have to quibble about the comparison of Earth and Venus in this chapter. The surface temperature of Venus is 800°+ F, and the description goes into a runaway greenhouse as the oceans boiled off. However, Venus is presently water-free. It is the CO₂ that is keeping it that hot. Furthermore, the amount of CO₂ in its atmosphere is about 2 million times the amount in Earth's atmosphere. Clearly, the relationship between the amount of CO₂ and the temperature isn't a simple straight line, otherwise Venus would be hotter than the hottest known star (I plan to go into this principle in a future post...how far in the future is not settled). Also, something that isn't mentioned, probably because the authors are into robotics and physics, and not biology, is that few species remain unchanged for more than one or two million years. To speculate about what humans might be doing a billion years from now, by which time the Sun will be 40% hotter and our oceans will have long since boiled off, has to include being somewhere else.

By the way, the chapter "Can We Turn Mars into Earth?" mentions that Mars is so cold because there's no greenhouse effect, because its atmosphere is less than 1/100th as dense as Earth's. But I realized that nearly all of that is CO₂. Earth's atmosphere is only 0.04% CO₂. So Mars has 25 times as much greenhouse gas per square meter! What gives? Water, that's what. Nearly all the greenhouse effect on Earth is from water vapor, 60° worth. The CO₂ just adds another couple of degrees. And the amount of water vapor in Earth's atmosphere is 1-2% (up to 3% in the Tropics). It would take a lot of water to bring the temperature of Mars up by 60°, and it would still be colder than winter in Montana. The water would immediately freeze back out, so terraforming Mars is rather out of the question.

Being somewhere else is taken up in "What's Stopping Us From Traveling to the Stars?" and a later chapter, "Can We Build a Warp Drive?" We have about 200 million years to figure these out...at most. Basic parameters of what the Sun will do to us, if nothing else really bad happens (like a Moon-size asteroid smacking into Central Park):

• A quarter to half a billion years from now, whether CO₂ is under control or not, it's too hot for terrestrial animals and plants to live.
• A billion years from now, the oceans have finished boiling away, so marine life is also caput.
• 4 billion years along, the Sun expands into a red giant. It may or may not reach Earth, but with at least 30% of the sky toasting at a temperature of 5,000°F or more, the planet will be liquified.

There are more stages to the Sun's evolution into a white dwarf, but that's enough to ruin the entire solar system. If we move to Enceladus, under the ice, by that time, the oceans of Enceladus will also boil off. So, how do we "go elsewhere"? Slowly, by galactic standards. If we want to push a 190,000 ton (170,000 metric Tons) spaceship to half the speed of light, its kinetic energy becomes immense. BTW, that is the supposed weight of the Enterprise in Star Trek, which is powered by antimatter-matter annihilation. Each kg of the spaceship has a kinetic energy of 3x10¹⁶ Joules, which you could obtain by annihilating 1/6 of a kg of matter with 1/6 of a kg of antimatter…if the conversion of energy to motion is 100% efficient. To go more like 90% the speed of light more than doubles the energy required. Basically, to send a fleet of spaceships "nearly as fast as light" (NAFAL) would require annihilating the entire mass of, say, Jupiter. And then you have to slow them down when they reach their destination. Thus the question about warp drives. Again, we find the answer is dichotomous: possible in two or three ways according to the laws of physics, but an engineering "challenge."

The last chapter is "Why Do We Ask Questions?" I'm a simpleton; my answer is, "Because we don't know everything yet, and we are driven to do so," some of us, at least. The authors get more philosophical than that. In the end they point out that we can answer questions of What and How, usually, but never Why. It occurs to me that when a little kid asks, "Why is the sky blue?" we should answer, "I can tell you how" (well, I can, but perhaps not every Dad can), and then proceed to do so, at the kid's level.

OK, for those who aren't sure how the sky is blue, it's because light scatters off molecules, but it scatters better and better the closer the size of the molecules are to the wavelength of the light. Molecules are a lot smaller than the wavelength of visible light, so the shorter wavelengths, which look blue, get scattered more. So sunlight is scattered, and more blue scatters than other colors. Bonus point: The light that comes straight to us from the Sun is thus a bit more yellow, because some of the blue has been scattered away. It's the reason the Sun is thought of as a yellow star, when actually, if you get above the atmosphere, it is pure white.

So this is a very enjoyable book, with a great lot of humor in the answers (one author likes banana smoothies and the other likes peach smoothies, so there are digs back and forth, for example). We get multiple answers to a bunch of interesting questions. We may not like all the answers (I'd really like to be able to get to another star system, for example), but we get a better understanding of what's involved in real answers.