A rap about the table of elements

October 2, 2008 - Leave a Response

British hip-hop duo dan le sac Vs Scroobius Pip rapped about the periodic table of elements in their song “Development.” It’s not the most helpful take on the subject, but at least somebody is teaching science to our kids.

Hydrogen is number one
Cause hydrogen is what puts the shine in the sun
Through nuclear fusion and when it’s done
It leaves element number two: Helium
Helium is the second lightest gas that there is
So we use it in balloons we give to little kids
Then there’s lithium often used to treat mental problems
Beryllium don’t conduct electric currents, it stops them
Boron can be used to make things harden
And that smoke that’s coming out of your exhaust, carbon
Carbon is arguably the most important element
And nitrogen in the air is almost eighty percent
The rest of the air is mainly oxygen
And fluorine is the lightest of the halogens

See here for the full song lyrics.

A Galactic Internet

September 26, 2008 - Leave a Response

Timothy Ferris is a popular science writer. In Interstellar Spaceflight: Can We Travel to Other Stars?, he starts writing about space travel but ends up speculating about an interstellar internet.

Living as we do in technologically triumphant times, we are inclined to view interstellar spaceflight as a technical challenge, like breaking the sound barrier or climbing Mount Everest – something that will no doubt be difficult but feasible, given the right resources and resourcefulness.

…[But] the technical problems involved in traveling to the stars need not be regarded solely as obstacles to be overcome but can instead be viewed as clues… that point through other ways to explore the universe.

The high cost of interstellar spaceflight suggests that the payloads carried between the stars… are most likely, as a rule, to be small. It is much more affordable to send a grapefruit-sized probe than the starship Enterprise. Consider spacecraft equipped with laser-light sails, which could be pushed through interstellar space by the beams of powerful lasers based in our solar system. To propel a manned spacecraft to Proxima Centauri, the nearest star, in 40 years, the laser system would need thousands of gigawatts of power, more than the output of all the electricity-generating plants on Earth. But sending a 10-kilogram unmanned payload on teh same voyage would require only about 50 gigawatts – still a tremendous amount of power but less than 15 percent of the total U.S. output.

What can be accomplished by a grapefruit-sized probe? Quite a lot, actually, especially if such probes have the capacity to replicate themselves, using materials garnered at their landing sites… The probe would mine [an] asteroid and use the ore to construct a base of operations, including a radio transmitter to relay its data back to Earth. The probe could also fashion other probes, which would in turn be sent to other stars. Such a strategy can eventually yield an enormous payoff from a relatively modest investment by providing eyes and ears on an ever increasing number of outposts.

[Another] clue – that radio can convey information much faster and more cheaply than starships can carry cargo – has become well known thanks to SETI, the search for extraterrestrial intelligence. SETI researches use radio telescopes to listen for signals broadcast by alien civilizations…

When SETI was first proposed… in 1959… the object most frequently raised to the idea of interstellar conversation was that it would take too long. A single exchange – “How are you?” “Fine.” – would consume 2,000 years if conducted between planets 1,000 light-years apart. But… conversation is not essential to communication; one can also learn from a monologue… We learn from Socrates and Herodotus, although we cannot speak with them…

In 1975, when I first proposed that long-term interstellar communications traffic among advanced civilizations would best be handled by an automated network, there was no model of such a system that was familiar to the public. But today the Internet provides a good example of what a monologue-dominated interstellar network might be like and helps us appreciate why extraterrestrials might prefer it to the arduous and expensive business of actually traveling to other stars.

The most profound gulf separating intelligent species on various star systems is not space but time, and the best way to bridge that gulf is not with starships but with networked interstellar communications.

The gulf of time is of two kinds. The first is the amount of time it takes a signal to travel between [civilizations]. Therefore, it makes sense of send long, fact-filled messages rather than “How are you?”

The other gulf arises if… communicative civilizations generally have lifetimes that are brief by comparison with the age of the universe… Even if we manage to survive for a robust 10 million years to come, that is still less than a tenth of 1 percent of the age of the galaxy.

Any other intelligent species that learns how to determine the age of stars and galaxies will come to the same sobering conclusion – that even if communicative civilizations typically stay on the air for fully 10 millions years, only one in 1,000 of all that have inhabited our galaxy is still in existence. The vast majority belong to the past. Is theirs a silent majority, or have they found a way to leave a record of themselves, their thoughts and their achievements?

That is where an interstellar Internet comes into play. Such a network could be deployed by small robotic probes like the ones described earlier, each of which would set up antennae that connect it to the civilizations of nearby stars and to other network nodes… one could get in touch with many civilizations, without the need to establish contact with each individually. More important, each node would keep and distribute a record of the data it handled. Those records would vastly enrich the network’s value to every civilization that uses it.

If there were any truth in this fancy, what would our galaxy look like? Well, we would find that interstellar voyages by starships of the Enterprise class would be rare, because most intelligent beings would prefer to explore the galaxy and to plumb its long history through the more efficient method of cruising the Net. When interstellar travel did occur, it would usually take the form of small, inconspicuous probes, designed to expand the network, quietly conduct research and seed infertile planets. Radio traffic on the Net would be difficult for technologically emerging worlds to intercept, because nearly all of it would be locked into high-bandwidth, pencil-thin beams linking established planets with automated nodes. Our hopes for SETI would rest principally on the extent to which the Net bothers to maintain omnidirectional broadcast antennae, which are economically draining but could from time to time bring in a fresh, naive species – perhaps even one way out here beyond the Milky Way’s Sagittarius Arm. The galaxy would look quiet and serene, although in fact it would be alive with thought.

In short, it would look just as it does.

Here is a PDF of the full essay.

Cosmic Gall

September 25, 2008 - Leave a Response

John Updike was a novelist, poet, short story writer and literary critic. His careful wordcraft was just as powerful when he made science his subject. Here is his 1960 poem Cosmic Gall.

Neutrinos, they are very small.
They have no charge and have no mass
And do not interact at all.
The earth is just a silly ball
To them, through which they simply pass,
Like dustmaids down a drafty hall
Or photons through a sheet of glass.
They snub the most exquisite gas,
Ignore the most substantial wall,
Cold shoulder steel and sounding brass,
Insult the stallion in his stall,
And, scorning barriers of class,
Infiltrate you and me. Like tall
And painless guillotines they fall
Down through our heads into the grass.
At night, they enter at Nepal
And pierce the lover and his lass
From underneath the bed – you call
It wonderful; I call it crass.

Note: It turns out some neutrinos do have mass, but we didn’t know this in 1960.

Why are Bugs Attracted to Light?

September 19, 2008 - Leave a Response

Mark Leyner and Billy Goldberg wrote Why Do Men Fall Asleep After Sex?, a collection of “questions you’d only ask your doctor after your third whiskey sour.” Many of them are potentially embarrassing: What does a chimpanzee do with the umbilical cord after it has a baby? Can you breast-feed wih fake boobs? Is douching dangerous? Is there such a thing as a death erection? And some, like this one, respond to an everyday curiosity:

Why are bugs attracted to light?

Phototaxis is an organism’s automatic movement toward or away from light. Cockroaches are negatively phototactic. Turn on that kitchen light and off they scurry to their dark little holes. But many insects are positively phototactic – as evidenced by teh mass bug graves in your light fixtures. Many people are also phototactic, especially for the “limelight” – those of us who secretly crave the strobe fusillade of paparazzi flashbulbs and murmer, “Mr. DeMille, I’m ready for my close-up” in our dreams… But, back to bugs. There are a variety of reasons that various insects are positively phototactic. Many insects, including bees, orient themselves in relation to the sun. Certain nocturnal bugs – moths, for instance – use moonlight to navigate, flying at a certain angle to the moon’s light rays to maintain a straight trajectory. When it approaches a source closer than the moon – say, a lightbulb – a moth perceives the light as stronger in one eye than the other, causing one wing to beat faster, so it flies in a tightening spiral, ever closer the the light. Some bugs are sensitive to ultraviolet light reflected by flowers at night. Artificial lights that emit UV rays will also be attractive to these guys. Other bugs are drawn to the heat that incandescent bulbs produce at night. Fireflies are bugs and bulbs all in one. They use their bioluminescence to attract each other.

Buy Why Do Men Fall Sleep After Sex?

Good and Bad Science

September 11, 2008 - Leave a Response

Richard Feynman was a well-known physicist. Surely You’re Joking, Mr. Feynman! is one of his memoirs. He ends it with an essay about some differences between good and bad science.

During the Middle Ages there were all kinds of crazy ideas, such as that a piece of rhinoceros horn would increase potency. Then a method was discovered for separating the ideas – which was to try one to see if it worked, and if it didn’t work, to eliminate it. This method became organized, of course, into science. And it developed very well, so that we are now in the scientific age. It is such a scientific age, in fact, that we have difficulty in understanding how witch doctors could ever have existed, when nothing that they proposed ever really worked – or very little of it did.

But even today I meet lots of people who sooner or later get me into a conversation about UFO’s, or astrology, or some form of mysticism, expanded consciousness, new types of awareness, ESP, and so forth. And I’ve concluded that it’s not a scientific world.

Most people believe so many wonderful things that I decided to investigate why they did… First I started out by investigating various ideas of mysticism and mystic experiences. I went into isolation tanks and got many hours of hallucinations, so I know something about that… I became overwhelmed. I didn’t realize how MUCH there was.

I found things that even more people believe, such as that we have some knowledge of how to educate. There are big schools of reading methods and mathematics methods, and so forth, but if you notice, you’ll see the reading scores keep going down – or hardly going up – in spite of the fact that we continually use these same people to improve the methods. There’s a witch doctor remedy that doesn’t work. It ought to be looked into; how do they know that their method should work? Another example is how to treat criminals. We obviously have made no progress – lots of theory, but no progress – in decreasing the amount of crime by the method that we use to handle criminals.

So we really ought to look into theories that don’t work, and science that isn’t science.

…there have been many experiments running rats through all kinds of mazes, and so on – with little clear result. But in 1937 a man named Young did a very interesting one. He had a long corridor with doors all along one side where the rats came in, and doors along the other side where the food was. He wanted to see if he could train the rats to go in at the third door down from wherever he started them off. No. The rats went immediately to the door where the food had been the time before.

The question was, how did the rats know, because the corridor was so beautifully built and so uniform, that this was the same door as before? Obviously there was something about the door that was different from the other doors. So he painted the doors very carefully, arranging the textures on the faces of the doors exactly the same. Still the rats could tell. Then he thought maybe the rats were smelling the food, so he used chemicals to change the smell after each run. Still the rats could tell. Then he realized the rats might be able to tell by seeing the lights and the arrangement in the laboratory like any commonsense person. So he covered the corridor, and still the rats could tell.

He finally found that they could tell by the way the floor sounded when they ran over it. And he could only fix that by putting his corridor in sand. So he covered one after another of all possible clues and finally was able to fool the rats so that they had to learn to go in the third door. If he relaxed any of his conditions, the rats could tell.

Now, from a scientific standpoint, that is an A-number-one experiment. That is the experiment that makes rat-running experiments sensible, because it uncovers that clues that the rat is really using – not what you think it’s using. And that is the experiment that tells exactly what conditions you have to use in order to be careful and control everything in an experiment with rat-running.

I looked up the subsequent history of this research. The next experiment, and the one after that, never referred to Mr. Young. They never used any of his criteria of putting the corridor on sand, or being very careful. They just went right on running the rats in the same old way, and paid no attention to the great discoveries of Mr. Young, and his papers are not referred to, because he didn’t discover anything about the rats. In fact, he discovered all the things you have to do to discover something about rats. But not paying attention to experiments like that is a characteristic example of [bad] science.

Buy Surely You’re Joking, Mr. Feynman!

Revolutionary New Insoles Combine Five Forms of Pseudoscience

September 10, 2008 - Leave a Response

As The Daily Show proves, sometimes fake news gets at the truth better than real news. This article, from fake newspaper The Onion, is a perfect mockery of common pseudoscience and superstition.

Stressed and sore-footed Americans everywhere are clamoring for the exciting new MagnaSoles shoe inserts, which stimulate and soothe the wearer’s feet using no fewer than five forms of pseudoscience.

“What makes MagnaSoles different from other insoles is the way it harnesses the power of magnetism to properly align the biomagnetic field around your foot,” said Dr. Arthur Bluni, the pseudoscientist who developed the product for Massillon-based Integrated Products. “Its patented Magna-Grid design, which features more than 200 isometrically aligned Contour Points™, actually soothes while it heals, restoring the foot’s natural bio-flow.”

“MagnaSoles is not just a shoe insert,” Bluni continued, “it’s a total foot-rejuvenation system.”

According to scientific-sounding literature trumpeting the new insoles, the Contour Points™ also take advantage of the semi-plausible medical technique known as reflexology. Practiced in the Occident for over 11 years, reflexology, the literature explains, establishes a correspondence between every point on the human foot and another part of the body, enabling your soles to heal your entire body as you walk.

But while other insoles have used magnets and reflexology as keys to their appearance of usefulness, MagnaSoles go several steps further. According to the product’s website, “Only MagnaSoles utilize the healing power of crystals to re-stimulate dead foot cells with vibrational biofeedback… a process similar to that by which medicine makes people better.”

In addition, MagnaSoles employ a brand-new, cutting-edge form of pseudoscience known as Terranometry, developed specially for Integrated Products by some of the nation’s top pseudoscientists.

“The principles of Terranometry state that the Earth resonates on a very precise frequency, which it imparts to the surfaces it touches,” said Dr. Wayne Frankel, the California State University biotrician who discovered Terranometry. “If the frequency of one’s foot is out of alignment with the Earth, the entire body will suffer. Special resonator nodules implanted at key spots in MagnaSoles convert the wearer’s own energy to match the Earth’s natural vibrational rate of 32.805 kilofrankels. The resultant harmonic energy field rearranges the foot’s naturally occurring atoms, converting the pain-nuclei into pleasing comfortrons.”

Released less than a week ago, the $19.95 insoles are already proving popular among consumers, who are hailing them as a welcome alternative to expensive, effective forms of traditional medicine.

“I twisted my ankle something awful a few months ago, and the pain was so bad, I could barely walk a single step,” said Helene Kuhn of Edison, NJ. “But after wearing MagnaSoles for seven weeks, I’ve noticed a significant decrease in pain and can now walk comfortably. Just try to prove that MagnaSoles didn’t heal me!”

Equally impressed was chronic back-pain sufferer Geoff DeAngelis of Tacoma, WA.

“Why should I pay thousands of dollars to have my spine realigned with physical therapy when I can pay $20 for insoles clearly endorsed by an intelligent-looking man in a white lab coat?” DeAngelis asked. “MagnaSoles really seem like they’re working.”

Read the original article here.

Folding Paper

September 6, 2008 - Leave a Response

ABC’s Dr. Karl recounts how a high school student overturned the old myth that it is impossible to fold a piece of paper – no matter how big – 10 times.

When my son was near the end of his primary school years, I thought that it was time that I should impart some of my Weird Freaky Science Wisdom – and have a little bit of fun as well. I told him that I would give him a million dollars if he could fold a piece of paper in half, and in half again, and so on for a total of 10 times. Of course he tried, and of course he failed.

I knew that this would happen, because it was “accepted wisdom” that it was impossible to fold a piece of paper in half 10 times (or seven, or nine, for that matter.). I told him that it couldn’t be done, even if he used paper the size of a football field. But I now know that I was wrong.

Suppose that you start with an standard A4 sheet of paper – about 300 mm long, and about 0.05 mm thick.

The first time you fold it in half, it becomes 150 mm long and 0.1 mm thick. The second fold takes it to 75 mm long and 0.2 mm thick. By the 8th fold (if you can get there), you have a blob of paper 1.25 mm long, but 12.8 mm thick. It’s now thicker than it is long, and, if you’re trying to bend it, seems to have the structural integrity of steel.

…if you had a sheet of paper, and folded it in half 50 times, how thick would it be?The answer is about 100 million kilometres, which is about two thirds of the distance between the Sun and the Earth.

And so Accepted Wisdom on Paper-Folding ruled, until 2001.

That was when a high school student, Britney Gallivan (of Pomona, California) was given a maths problem. She would get an extra maths credit, if she took up the option of solving the problem of folding a sheet in half 12 times. She tried and failed with reasonably-sized sheets of paper.

So she got smart, and used something incredibly thin – gold foil, only 0.28 of millionth of a metre thick. She started with a square sheet, 10 cm by 10 cm. It took lots of determination and practice, as well as rulers, soft paint brushes and tweezers, but she finally succeeded in folding her gold foil in half 12 times. She ended up with a microscopic square sheet of gold foil.

But her maths teacher said that ultra-thin gold foil was too easy – she had to fold paper 12 times.

When she looked closely [at the math of paper folding], she found that if you are trying to fold the sheet as many times as possible, there are advantages in using a long narrow sheet of paper.

Her formula told her that to successfully fold paper 12 times, she would need about 1.2 km of paper.

After some searching she found a roll of special toilet paper that would suit her needs – and that cost US $85. In January 2002, she went to the local shopping mall in Pomona. With her parents, she rolled out the jumbo toilet paper, marked the halfway point, and folded it the first time. It took a while, because it was a long way to the end of the paper. Then she folded the paper the second time, and then again and again.

After seven hours, she folded her paper for the 11th time into a skinny slab, about 80 cm wide and 40 cm high, and posed for photos. She then folded it another time (to get that 12th fold essential for her extra maths credit), and wrote up her achievement for the Historical Society of Pomona in her 40 page pamphlet, How to Fold Paper in Half Twelve Times: An “Impossible Challenge” Solved and Explained. She wrote in her pamphlet, “The world was a great place when I made the twelfth fold.

Britney Gallivan succeeded because she was as contrary and determined as Juan Ramon Jiminez, the Spanish poet and winner of the 1956 Nobel Prize for Literature. He wrote, in a metaphor for the questioning and resilient human spirit, “If they give you ruled paper, write the other way.”

Read the full article here.

Bob Evans, Supernova Hunter

September 1, 2008 - Leave a Response

Bill Bryson knows how to tell a good story. He always loved science, and he wanted to know “Wait, how did we figure that out?” His A Short History of Nearly Everything is the story of how we figured things out. Here Bryson recounts his meeting with Bob Evans, amateur scientist extraordinaire.

By day, Evans is a kindly and now semiretired minister in the Uniting Church in Australia… But by night he is, in his unassuming way, a titan of the skies. He hunts supernovae.

Supernovae occur when a giant star, one much bigger than our own Sun, collapses and then spectacularly explodes, releasing in an instant the energy of a hundred billion suns, burning for a time brighter than all the stars in its galaxy. “It’s like a trillion hydrogen bombs going off at once,” says Evans.  [But] most are so unimaginably distant that their light reaches us as no more than the faintest twinkle.. It is these anomalous, very occasional pricks in the crowded dome of the night sky that the Reverend Evans finds.

To understand what a feat this is, imagine a standard dining room table covered in a black tablecloth and someone throwing a handful of salt across it. The scattered grains can be thought of as a galaxy. Now imagine fifteen hundred more tables like the first one — enough to fill a Wal-Mart parking lot, say, or to make a single line two miles long — each with a random array of salt across it. Now add one grain of salt to any table and let Bob Evans walk among them. At a glance he will spot it. That grain of salt is the supernova.

[When Bob asked the astronomical community] if they had any usable field charts for hunting supernovae, [they] thought he was out of his mind. At the time Evans had a ten-inch telescope — a very respectable size for amateur stargazing but hardly the sort of thing with which to do serious cosmology — and he was proposing to find one of the universe’s rarer phenomena. In the whole of astronomical history before Evans started looking in 1980, fewer than sixty supernovae had been found. (At the time I visited him, in August of 2001, he had just recorded his thirty-fourth visual discovery; a thirty-fifth followed three months later and a thirty-sixth in early 2003.)

Evans, however, had certain advantages. Most observers, like most people generally, are in the northern hemisphere, so he had a lot of sky largely to himself, especially at first. He also had speed and his uncanny memory. Large telescopes are cumbersome things, and much of their operational time is consumed with being maneuvered into position. Evans could swing his little sixteen-inch telescope around like a tail gunner in a dogfight, spending no more than a couple of seconds on any particular point in the sky. In consequence, he could observe perhaps four hundred galaxies in an evening while a large professional telescope would be lucky to do fifty or sixty.

Looking for supernovae is mostly a matter of not finding them. From 1980 to 1996 he averaged two discoveries a year—not a huge payoff for hundreds of nights of peering and peering. Once he found three in fifteen days, but another time he went three years without finding any at all.

“There’s  something  satisfying,  I  think,” Evans said, “about the idea of light traveling for millions of years through space and just at the right moment as it reaches Earth someone looks at the right bit of sky and sees it. It just seems right that an event of that magnitude should be witnessed.”

Buy A Short History of Nearly Everything.

The Rarity of Old Fossils

August 29, 2008 - Leave a Response

Don Lindsay is a computer scientist who likes to debate creationists and Scientologists. He has a knack for saying things in the simplest possible way. Here he explains why we don’t have many really old fossils.

We have lots of seashells. We’re very short of jellyfish fossils. That’s not too surprising.

We have a few T. Rex fossils, but we’re short on small, fragile creatures. This is easy to explain. First, it’s just easier to find the great big fossils. Second, fragile skeletons are, well, fragile. They are more likely to be scavenged or crushed before they can form a fossil.

But there is another pattern, which is that there just aren’t very many really old fossils. Why?

There are at least four reasons. For one, the earth’s surface has been rebuilt many times. Regions have been uplifted and then eroded away. Erosion destroys rock, and destroys any fossils in that rock. The new rock that forms contains new fossils. So, much of the earth’s surface is recent, compared to the age of the planet itself. Old rocks are rare, so of course old fossils are rare too.

The second reason is that many old rocks have spent time buried. While buried, they experienced great heat and/or pressure, and are now metamorphic rocks. Their fossils have turned to smudges.

Worse again is that the best fossils are found in ocean-bottom sediments. But as the continents move, they ride over the ocean floor. Old floor is sucked down towards the center of the earth at subduction zones, never to be seen again. (Places like the North Atlantic Ridge are creating new ocean floor to replace the old.)

Continents travel at about an inch a year. So, if you look at the size of an ocean, and do some simple arithmetic, you will see that most of the world’s ocean floor should be less than 200-300 million years old. But dating methods say that animal life arose 800 million to 1000 million years ago, and it moved onto the land about 400 million years ago. So, this is a frustrating situation. The oceans have been repaved since the really interesting stuff happened. We have to make do with the very few old ocean rockbeds that escaped destruction.

And the fourth reason is that the first creatures didn’t have skeletons, and they were tiny, too. We can tell in two ways. First, we’ve been lucky, and found a few very old deposits that preserved soft things. And secondly, we’ve found tracks.

Why didn’t they have skeletons? Well, because skeletons had to be invented at some point, and that point was about 600 million years ago.

Visit Don’s website.

What If Gravity Was Weaker or Stronger?

August 26, 2008 - Leave a Response

Martin Rees is an astrophysicist famous for his work on Big Bang theory and galaxy formation. In Just Six Numbers, he explains what the universe would be like if gravity was a bit stronger or weaker compared to other forces.

Despite its importance for us… gravity is actually amazingly feeble compared with the other forces that affect atoms… The gravitational attraction between [two] protons is thirty-six powers of ten feebler than the electrical forces, and quite unmeasurable. Gravity can safely be ignored by chemists when they study how groups of atoms bond together to form molecules.

How, then, can gravity nonetheless be dominant, pinning us to the ground and holding the moon and planets in their courses? It’s because gravity is always an attraction… On the other hand, electric charges can repel each other as well as attract… But any everyday object is made up of huge numbers of atoms (each made up of a positively charged nucleus surrounded by negative electrons), and the positive and negative charges almost exactly cancel out. Even when we are ‘charged up’ so that our hair stands on end, the imbalance is less than one charge in a billion billion. But everything has the same sign of gravitational ‘charge’, and so gravity ‘gains’ relative to electrical forces in larger objects… An apple falls only when the combined gravity of all the atoms in the Earth can defeat the electrical stresses in the stalk holding it to the tree. Gravity is important to us because we live on the heavy Earth.

Sand grains and sugar lumps are, like us, affected by the gravity of the massive Earth. But their self-gravity — the gravitational pull that their constituent atoms exert on each other, rather than on the entire Earth — is negligible. Self-gravity is not important in asteroids, nor in Mars’s two small potato-shaped moons, Phobos and Deimos. But bodies as large as planets (and even our own large Moon) are not rigid enough to maintain an irregular shape: gravity makes them nearly round. And masses above that of Jupiter get crushed by their own gravity to extraordinary densities (unless the centre gets hot enough to supply a balancing pressure, which is what happens in the Sun and other stars like it). It is because gravity is so weak that a typical star like the Sun is so massive. In any lesser aggregate, gravity could not compete with the pressure, nor squeeze the material hot and dense enough to make it shine.

Gravitation is feebler than the forces governing the microworld by the number N, about 1036. What would happen if it weren’t quite so weak? Imagine, for instance, a universe where gravity was ‘only’ 1030 rather than 1036 feebler than electric forces. Atoms and molecules would behave just as in our actual universe, but objects would not need to be so large before gravity became competitive with the other forces. The number of atoms needed to make a star (a gravitationally bound fusion reactor) would be a billion times less in this imagined universe. Planet masses would also be scaled down by a billion. Irrespective of whether these planets could retain steady orbits, the strength of gravity would stunt the evolutionary potential on them. In an imaginary strong-gravity world, even insects would need thick legs to support them, and no animals could get much larger. Gravity would crush anything as large as ourselves.

Galaxies would form much more quickly in such a universe, and would be miniaturized. Instead of the stars being widely dispersed, they would be so densely packed that close encounters would be frequent. This would in itself preclude stable planetary systems, because the orbits would be disturbed by passing stars — something that (fortunately for our Earth) is unlikely to happen in our own Solar System.

But what would preclude a complex ecosystem even more would be the limited time available for development. Heat would leak more quickly from these ‘mini-stars’: in this hypothetical strong-gravity world, stellar lifetimes would be a million times shorter. Instead of living for ten billion years, a typical star would live for about 10,000 years. A mini-Sun would burn faster, and would have exhausted its energy before even the first steps in organic evolution had got under way. Conditions for complex evolution would undoubtedly be less favourable if (leaving everything else unchanged) gravity were stronger. There wouldn’t be such a huge gulf as there is in our actual universe between the immense timespans of astronomical processes and the basic microphysical timescales for physical or chemical reactions. The converse, however, is that an even weaker gravity could allow even more elaborate and longer-lived structures to develop.

Gravity is the organizing force for the cosmos… [It] is crucial in allowing structure to unfold from a Big Bang that was initially almost featureless. But it is only because it is weak compared with other forces that large and long-lived structures can exist. Paradoxically, the weaker gravity is (provided that it isn’t actually zero), the grander and more complex can be its consequences. We have no theory that tells us the value of N. All we know is that nothing as complex as humankind could have emerged if N were much less than 1,000,000,000,000,000,000,000,000,000,000,000,000.

Buy Just Six Numbers.