The classical... problem... asks: is this the greatest density..? an unsolved problem, one of the most famous...

Matter is actually distributed very unevenly... conglomerated into stars and galactic systems. The average density is the density that we should get if all... could be evaporated into atoms of hydrogen, or protons, and... distributed evenly over the whole of space. ...three or four protons in every cubic foot. ...a million million times less than that of the most perfect vacuum that we can produce... The universe thus consists mostly of emptiness... consider a universe without any matter at all, an empty universe, as a good approximation. But we may also take as our first approximation a universe containing... three or four protons per cubic foot. The local deviations from the average, caused by the conglomeration of matter into stars and stellar systems, are then disregarded in the grand scale model, and are only taken into account when we come to study details.

There is a very stunning range of studies... of interstellar organic matter... the cold, dark spaces between the stars are also loaded with organic matter. ...complex organic materials are everywhere.

Carbonaceous meteorites that fall to the Earth... have several percent to as much as 10 percent of complex organic matter in them.

To me, dark matter is matter. It looks like matter, it quacks like matter, it waddles like matter. It has many, many properties that indicate it's matter. And I think I know what matter it is!

Do you know what this is?
"The floor, Miss?"
"Dust! I read about it—tiny particles of matter.

They had better luck with the seashell. Exobiology suddenly found itself standing on unnervingly solid ground: one and seven-tenths grams of highly organized biological information, definitely extraterrestrial. Olga's seashell generated an entire subbranch of the science, devoted exclusively to the study of...Olga's seashell.

Let us suppose that this ounce of mud is left in perfect rest, and that its elements gather together, like to like, so that their atoms may get into the closest relations possible.

Let the clay begin. Ridding itself of all foreign substance, it gradually becomes a white earth, already very beautiful; and fit, with help of congealing fire, to be made into finest porcelain, and painted on, and be kept in kings’ palaces. But such artificial consistence is not its best. Leave it still quiet to follow its own instinct of unity, and it becomes not only white, but clear; not only clear, but hard; not only clear and hard, but so set that it can deal with light in a wonderful way, and gather out of it the loveliest blue rays only, refusing the rest. We call it then a sapphire.

Such being the consummation of the clay, we give similar permission of quiet to the sand. It also becomes, first, a white earth, then proceeds to grow clear and hard, and at last arranges itself in mysterious, infinitely fine, parallel lines, which have the power of reflecting not merely the blue rays, but the blue, green, purple, and red rays in the greatest beauty in which they can be seen through any hard material whatsoever. We call it then an opal.

In next order the soot sets to work; it cannot make itself white at first, but instead of being discouraged, tries harder and harder, and comes out clear at last, and the hardest thing in the world; and for the blackness that it had, obtains in exchange the power of reflecting all the rays of the sun at once in the vividest blaze that any solid thing can shoot. We call it then a diamond.

Last of all the water purifies or unites itself, contented enough if it only reach the form of a dew-drop; but if we insist on its proceeding to a more perfect consistence, it crystallizes into the shape of a star.

And for the ounce of slime which we had by political economy of competition, we have by political economy of co-operation, a sapphire, an opal, and a di

The Pythagoreans were fascinated by the regular solids, symmetrical three-dimensional objects all of whose sides are the same regular polygon. The cube is the simplest example, having six squares as sides. There are an infinite number of regular polygons, but only five regular solids. (The proof of this statement, a famous example of mathematical reasoning, is given in Appendix 2.) For some reason, knowledge of a solid called the dodecahedron having twelve pentagons as sides seemed to them dangerous. It was mystically associated with the Cosmos. The other four regular solids were identified, somehow, with the four “elements” then imagined to constitute the world; earth, fire, air and water. The fifth regular solid must then, they thought, correspond to some fifth element that could only be the substance of the heavenly bodies. (This notion of a fifth essence is the origin of our word quintessence.) Ordinary people were to be kept ignorant of the dodecahedron.

The abundance of organic matter is why the planet has so much fossil fuel deposits and a rich soil.

What is [life] it? Would we even recognize it. What I imagine we would find would be cell-like things. Not a million miles away from bacteria, using , probably in water, not because it's the only way of organizing. It's just that carbon is very good at that kind of chemistry. It's very common in the universe. Water is ubiquitous. We know, from the principles of life on earth, that all this stuff works and we know that it's thermodynamically favored. ...[J]ust statistically, I would expect, maybe 900 times out of a thousand that life would be organized in a similar way to life here. That's not to say it can't be different. It's just probably... going to be similar.

Dark matter is what my research team is looking for. No one knows what it is. There's more stuff out there in the universe than we can see, that's the point. We can see the stars and the galaxies and the things that shine, but for it all to hang together and not fly apart, there needs to be a lot more of it — to make gravity work, you see. But no one can detect it. So there are lots of different research projects trying to find out what it is, and this is one of them. ... We think it's some kind of elementary particle. Something quite different from anything discovered so far. But the particles are very hard to detect.

Nobody knows what dark matter is. It is another deep mystery waiting to be explored. We know only that it is there, and that it weighs more than the stuff that we can see.

Is it not reasonable to think that by far the greater part is solid and dark, and that this immense globe is encompassed with a thin covering of that resplendent substance from which the sun would seem to derive the whole of his vivifying heat and energy?