The Aliens Are Coming!
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19 It keeps you sane in a crazy world, thereby enabling you to avoid traffic and eventually go to bed with someone.
20 Human population is estimated to have been less than ten million at the beginning of the Holocene. In 1804 it reached one billion, and two billion in 1925.
21 In broad strokes, cellular life emerged from the vent around four billion years ago, evolved oxygenic photosynthesis around three billion years ago, evolved the eukaryotic cell around two billion years ago, multicellularity around 1.5 billion years ago, then complex multicellularity around 575 million years ago. Plants moved on to land in the Ordovician roughly 480 million years ago, amphibians followed them in the Devonian 375 million years ago, and 2009 saw the release of the alpha version of Minecraft.
22 There might be a way around this. Since red dwarves are relatively lower in mass, a rocky planet in the habitable zone may well be in tidal lock with the parent star. If one hemisphere is always facing away from the star, it would be shielded from radiation doom, and could have energy transferred to its radiation-shielded night side via the atmosphere. Alternatively, a giant planet might generate a large protective magnetic field that could shield itself or its moons from the worst effects.
23 It was a while ago, so here’s a brief reminder that we label the hydrogen-burning stars as follows, brightest to dimmest; O, B, A, F (yellow/white dwarf), G (yellow dwarf), K (orange dwarf), and M (red dwarf).
24 Of course, in terms of complexity, plants are streets ahead of algae and fungi, and animals are light-years ahead of plants.
25 Not 6.5 billion years, remember, because of GRBs. Anything older than five billion years will be toast.
26 Nevertheless, Fermilab runs a program on the IRAS infrared satellite which attempts to do just this. So far they have identified seventeen “ambiguous” candidates, four of which they class as “amusing but still questionable.”
27 Planned for 2022.
28 The Galileo spacecraft was launched in 1989, arrived in 1995, and spent eight years in the Jovian system. It was deliberately crashed into Jupiter to avoid contaminating its moons with Earth life.
29 The olive oil may be the crucial ingredient here. Omit it–and fail to stir–and your penne will limpet to the bottom of the pan in a congealed mess.
30 I’m thinking specifically of Jeremy England of MIT and his 2013 paper “Statistical physics of self-replication,” available from all good search engines.
1 $100 million.
2 Green Bank is, of course, the telescope on which Frank Drake conducted the first ever SETI search, when, in 1961, he pointed it at our two nearest Sun-like stars, Tau Ceti and Epsilon Eridani.
3 Kepler 452b makes an orbit every 385 days.
4 Kepler is pointed at a distant but dense portion of the starfield between the constellations of Lyra and Cygnus, where it monitors the brightness of around 150,000 stars, all of which are between several hundred and several thousand light-years away.
5 The website for the Institute for Computational Cosmology at Durham University gives 250,000 stars within 250 light-years, so I’ve assumed even density of stars to get roughly 750,000 stars within 360 light-years.
6 Since the Islamic conquest of Egypt in AD 641, in fact.
7 Precise figures are hard to come by, but, roughly speaking: 30,000 infantry, 3,000 cavalry, and 3,000 artillery and engineers, plus Napoleon’s personal bodyguard of 380. Of the rest, 300 were women and 167 were savants. As well as 400 transport ships, Napoleon had thirteen ships of the line and seven frigates. Nelson had thirteen ships of the line but–following a storm in the Med–no frigates.
8 Whom we last met courtesy of our mutual friend the duck-billed platypus.
9 I’m not saying that building a library is decadent; it’s more the incest that I’m aiming for. That said, the practice of brothers marrying sisters–and worse–was common in the upper echelons of Ancient Egyptian society.
10 Or, rather, les Aiguilles de Cléopâtre. The supine one now resides on the Thames Embankment in London, the other in New York’s Central Park. Both were gifts from the Egyptian government decades after Napoleon’s departure from Egypt. The connection with Cleopatra is that she designed the Caesarium, or “Palace of the Caesars,” at Alexandria, and after her death the Emperor Augustus transported the needles from outside the Temple of the Sun in the city of Heliopolis, near modern Cairo. They were originally commissioned in 1450 BC by Pharaoh Thutmose III to honor the sun god Ra.
11 The 18th Dynasty, by the way, is the one that belongs to another famous pharaoh, Tutankhamun, who reigned from (roughly) 1332 to 1323 BC.
12 The very bay, in other words, where the French had lost the Battle of the Nile in 1798.
13 Young showed that if a light source was obscured but for two parallel slits, the light from those slits would produce an interference pattern. This landmark experiment was subsequently modified by one of my all-time physics heroes, G.I. Taylor, to prove the quantum nature of light. Basically he turned the brightness of the lamp down until there could only be one photon of light in the system at any one time, and went on a sailing holiday. When he returned, there was an interference pattern, just as in Young’s experiment, proving there was no such thing as a “single path” for a quantum object. Small things, in other words, can be in two places at once; in fact they can be in all places at once.
14 There’s an added bit of brilliance here; hieroglyphs don’t usually contain vowel sounds, and neither does Demotic script. Vowel sounds came in with the Egyptian–Greek combo that is Coptic.
15 So what do the sun the gaming board and the scarab mean in the throne name of Thutmose III? The sun meaning “that which is,” is easy enough, and we already know that the scarab denotes “that which will be,” but what about the gaming board? Crucially, it’s not an ideogram, but a phonogram, “mns.” “Menes” was the first pharaoh of Egypt, flipping us back to an ideogram with the meaning “that which was.” Altogether we get “present, past, future,” or “everlasting.” So Thutmose’s throne name is “Son of Ra, He who is everlasting.” Phew.
16 Granted, we are making the assumption that mathematics is universal, and not just something we cooked up to try and make sense of life on Earth. So in a sense we are funneling the number of communicable civilizations down to “those that have radio dishes and share our mathematics.”
17 Pi, like many dimensionless numbers in physics, is irrational, meaning it can’t be neatly expressed as a fraction.
18 Ulysses was serialized from March 1918 to December 1920, then published in book form in Paris in 1922. Its title is the Latin name for Odysseus, the hero of Homer’s epic poem the Odyssey; like his editor Ezra Pound, Joyce wasn’t afraid of an allusion or two.
19 The other, of course, is the Odyssey.
20 OK, this is the most nerdy joke in the entire book but here goes: When we rank the various explanations of Zipf’s law together with the number of academics that subscribe to that explanation, we get the only data set involving human decision-making which isn’t subject to Zipf’s law. Snarckle.
21 You can find a fascinating discussion of all things Zipf in Alex Bellos’ rather brilliant book Alex Through the Looking Glass. Thanks, Alex, for bumping into me in a coffee shop and handing me a copy at the very moment I happened to be writing this chapter.
22 For his work on the Calvin Cycle, the process by which plants photosynthesize sugars using the light energy captured by chlorophyll.
23 I highly recommend that you check out the film of the same title by Chris Riley, he of In the Shadow of the Moon fame, which contains original footage of the experiment and a present-day interview with Margaret Lovatt.
24 Diana Reiss has some extraordinary footage of this in her TEDxBrussels talk entitled “The Dolphin in the Mirror.”
25 Dolphins also make another type of sound called burst-pulses, which are like a rapid series of clicks. Like whistles, there is evidence that these are also social calls.
26 A little brown bat (
Myotis lucifugus) can hear frequencies up to 115KHz; a common bottlenose dolphin (Tursiops truncatus) is good up to 150KHz. Humans hear up to 20KHz.
27 Another way of looking at this is: Thanks to grammar, if you know seven words of a phrase you can have a go at guessing the eighth. Knowing eight words, however, won’t help you with the ninth.
28 For the keeny-beany Shannonites: Zipf’s law gives the distribution of word probabilities in the first-order Shannon entropy. There, I’ve said it.
29 I’m playing fast and loose with the words “letter,” “symbol,” and “word” here, but I’m sure you get the point: Shannon’s formulae apply whether you look at the text at the level of letters, phonemes, words, or phrases, etc. That said, a higher Shannon entropy for letters will correspond to a lower one for words, e.g., first-order entropy for words of English corresponds to somewhere between fifth- and sixth-order entropy for English letters.
30 As a rule of thumb, to calculate the nth-order Shannon entropy, you need 10n letters. In other words, for third-order entropy you need 1,000 letters; for fourth you’d need 10,000. Ulysses is approximately 265,000 words in length, so is capable of revealing anything up to fifth-order Shannon entropy, since log10(265,000) ≈ 5.4
31 Estimated in 2007, by Priscila Lopez of UOC and Martin Hilbert of USC, to be 2.9 × 1020 bytes.
32 Plus one of its best jokes is that it is impossible to understand.