The first person to propose that everything is made of atoms was the Greek philosopher Democritus, around 440 B.C. He reasoned that, if he were to attempt to cut an object in half over and over again, he would eventually reach a tiny grain of matter that could not be cut in half. Democritus called these hypothetical building blocks of matter "atoms", after the Greek atomos, "uncuttable". (source)

Phytoplankton are tiny little plants that drift with the currents throughout the ocean. A teaspoon of sea water can contain as many as a million one-celled phytoplankton. (source)

Saturn's beautiful rings are not solid. They are made up of particles of ice, dust and rock—some as tiny as grains of sand, some much larger than skyscrapers. (source)

Soviet Life once ran a feature article on Nikolai Syadristy, a craftsman from Uzhgorod, who carved a set of chess figures by hand that were so small that they could only be distinguished when magnified two thousand times with a microscope. (source)

One of the most interesting demonstrations of the quantum mechanical nature of light is the double-slit experiment. In this experiment, light is shone through two slits on an opaque plate onto a screen. If one slit is open, the light impacts the screen with greatest intensity at the centre, fading as one moves away from the centre. One might think that, if both slits are open, the result would be the sum of the intensities from the individual slits, but what actually occurs is that an interference pattern is produced, showing that light has wave properties. Even more unusual, if you only fire one photon at the apparatus at a time (and replace the screen with a photographic plate), an interference pattern is still produced, so it would appear as if an individual photon is able to travel through both slits and interfere with itself. If you place a detector at each slit, you will observe that each photon only goes through one slit—but the pattern is now just the sum of the intensities from the individual slits, without any interference pattern.

There are roughly 100 trillion bacteria and archaea found in the human stomach, a number that is about 10 times the entire number of cells in the human body.

A teaspoon of good-quality soil contains billions of microbes.

Perhaps the most successful organisms on Earth are a lineage of species called the Group I marine archaea. These organisms are found at concentrations of 10,000 to 100,000 individuals per millilitre of seawater at a depth between 200 to over 4,000 metres below the surface, in most oceans. This lineage was only described in the early 1990s.

In terms of the total volume of living material on Earth, the dominant life-forms are bacteria and archaea. The total number of individual bacteria and archaea alive today is estimated at 5 × 10³⁰. If they were lined up end-to-end, they would make a chain longer than the Milky Way.

There is an organism, a member of the domain Archaea, that lives in surroundings of 121°C. Its habitat is within hot springs at the bottom of the ocean, where water up to 300°C emerges, mixing with 4°C seawater.

The oxygen in Earth's atmosphere is entirely a product of life on Earth. There was no oxygen in the Earth's atmosphere before cyanobacteria evolved around 2.8 billion years ago.

The Roman poet Lucretius (ca. 94–ca. 55 B.C.) wrote a poem in 56 B.C. describing the views of Greek philosophers who, like him, thought the universe to be composed of atoms. This poem is the only record of the beliefs of these early atomists, whose works were lost due to their unpopular views. Lucretius' poem was lost as well, but in 1417, however, a copy was discovered. Its views helped to persuade chemists to consider the atomic theory of matter, a theory that won out eventually.

In 1624, three scholars advertised that they would give lectures in support of the idea that matter is made of atoms. The authorities replied by ordering the audience dispersed, confiscating the scholars' writings, and prohibiting any teaching about atoms under penalty of death.

The size of Earth is roughly the geometric mean of the size of the universe and the size of an atom, and the mass of a human is roughly the geometric mean of the mass of Earth and the mass of the proton. (source)

There is sound in space. Sound is a pressure wave, and as long as there is some kind of gaseous medium, there is the possibility of forming pressure waves in it. In space, the interplanetary medium is a very dilute gas at a density of about 10 atoms per cubic centimeter, and the speed of sound in this medium is about 300 kilometers per second. Typical disturbances due to solar storms and "magneto-sonic turbulence" at the Earth's magnetopause have scales of hundreds of kilometers, so the acoustic wavelengths are enormous. Human ears would never hear them, but we can technologically detect these pressure changes and play them back for our ears to hear by electronically compressing them. (source)

The last person to contract smallpox through natural transmission was Ali Maow Maalin, a hospital cook in Somalia who contracted it after coming into contact with an infected child in 1977. Maalin survived. In 1978, Janet Parker, an English medical photographer, was exposed to smallpox through a laboratory accident, and subsequently died. The laboratory's virologist felt so guilty that he later committed suicide. On May 8^th, 1980, the World Health Organization declared smallpox eradicated, although some samples remain in laboratories in Atlanta and Moscow. (source)

A giant sequoia tree will bear millions of seeds over its lifetime, but each seed is so small that it takes 3,000 of them to weigh one ounce.

In 1974, Stephen Hawking showed that black holes evaporate. According to quantum mechanics, pairs of virtual particles are constantly being created and then annihilating each other near black holes (as well as everywhere else in the universe). On occasion, one of the pair of particles ends up inside the black hole's event horizon, and so cannot annihilate its pair, which is forced to become a real particle. This results in a slight increase in the total mass-energy of the outside universe, and that mass-energy has to come from the black hole, whose mass-energy is slightly decreased. Eventually (after an incredibly long time for normal-sized black holes) the black hole would disappear in an explosion of particles and energy. (source)

About 25% of the universe consists of "dark matter", and about 70% consists of "dark energy", leaving only about 5% of the universe visible to us. (source)

Ordinary matter consists almost entirely (99.9999999999999%) of empty space. (source)

Bell's Theorem states that certain measurements made on one particle can instantaneously affect the measurements made on a second particle that, in theory, could have been removed to the opposite side of the galaxy, with no physical connection between the two. (source)

The largest known bacterium is Thiomargarita namibiensis, a bacterium found in sediments off the coast of Namibia in 1997. Specimens have been found that are up to 0.75 millimetres long, large enough to be seen with the naked eye. (source)