Science — Page 3

Water can boil and freeze at the same time, at the triple point.

The triple point of water occurs at a temperature of about 0.01 degrees Celsius and at very low pressure. At that…

Atoms are almost entirely empty space.

If the nucleus of an atom were the size of a tennis ball, the electrons would be several kilometres away. Matter…

Sound travels faster in water than in air.

In air, sound travels at about 343 metres per second at room temperature. In water, the speed rises to about 1,480…

Hot water can freeze faster than cold water under certain conditions.

This phenomenon, called the Mpemba effect, was observed by a Tanzanian student in 1963. Under certain conditions, hot…

Bananas are slightly radioactive because of potassium.

Bananas contain potassium, and a small fraction of that potassium is the radioactive isotope potassium-40. Therefore…

Glass is not a liquid, it is an amorphous solid.

Contrary to popular belief, glass does not flow over time. It is an amorphous solid, with a disordered but rigid…

Water is called the universal solvent because it dissolves all substances.

Water is called the universal solvent because it dissolves more substances than any other common liquid. However, it…

Water is the only substance that exists naturally on Earth in all three physical states.

Water exists naturally on Earth in solid, liquid and gaseous states. It is the only known substance found in all…

The human body contains about 0.2 milligrams of gold.

The human body contains traces of gold, about 0.2 milligrams, mostly in the blood. Gold has no known biological…

There are more possible chess games than atoms in the observable universe.

The number of possible chess games, known as the Shannon number, is estimated at 10 to the power of 120. The number…

Helium can become solid under very high pressure.

Helium is the only element that does not solidify at normal atmospheric pressure, even near absolute zero. However…

Diamonds are eternal and never degrade.

Contrary to popular belief, diamonds are not eternal. They are only metastable and can turn into graphite over…

The human body contains enough sulphur to make about 200 boxes of matches.

The human body contains about 140 grams of sulphur, present in amino acids such as cysteine and methionine. This…

The human heart has a limited number of beats over a lifetime, about 2.5 billion.

The human heart beats about 2.5 billion times over an average 80-year life. This number is not a fixed limit, but an…

The air we breathe is composed of about 78 percent nitrogen.

Atmospheric air is composed of about 78 percent nitrogen, 21 percent oxygen and 1 percent other gases, such as argon…

The human body contains about 7 billion atoms.

The human body contains about 7 octillion atoms, that is, 7 followed by 27 zeros. Most of these atoms are hydrogen…

Sound does not travel through the vacuum of space.

Sound needs a material medium, such as air, water or metal, to propagate. In the vacuum of space there are not enough…

Liquid oxygen has a pale blue colour.

Unlike oxygen gas, which is colourless, oxygen in the liquid state is pale blue. This colour is due to the absorption…

The human eye can detect a single photon.

Under ideal dark conditions, the human eye can detect a single photon of light. Studies show that the rods in the…

The human nose can detect a drop of perfume in an entire house.

The human sense of smell is extremely sensitive. We can detect the smell of a single drop of perfume dispersed…

Graphene is the strongest known material, 200 times stronger than steel.

Graphene is a sheet of carbon only one atom thick, arranged in a honeycomb pattern. It is the strongest known…

The first email was sent in 1971.

The first email in history was sent in 1971 by Ray Tomlinson, an ARPANET engineer. He chose the at symbol to separate…

Diamond is the hardest known natural material.

Diamond is the hardest known natural material, with a hardness of 10 on the Mohs scale. It is formed from pure carbon…

Plasma is the most common state of matter in the universe.

Plasma is the fourth state of matter, after solid, liquid and gas. It is formed by ionised gas at very high…