Did you know?

# Astatine is an element so rare that if you searched the entire planet you’d only find a lump the size of a sugar cube.

# When a flea jumps, the rate of acceleration is 20 times that of the space shuttle during launch.

# The maximum speed that raindrops can fall at is around 18mph, depending on their size.

# If every star in the Milky Way was a grain of salt they would fill an Olympic sized swimming pool.

# 12 Astronauts have walked on the moon, between them bringing back 382 kilograms of rocks, pebbles, sand and dust.

# Whales talk to each other by making a loud clicking noise. The sound waves travel extremely well underwater and they can hear each other from 100 miles away.

# A TV screen shows 24 pictures a second. Because a fly sees 200 images a second, it would see TV as still pictures with darkness in between.

# Cats can see clearly in one-sixth the amount of light we humans would need. This is due to a special layer of cells at the back of their retinas, which acts like a mirror, reflecting light back to the retina's cells.

# In 1936 Professor Alfred Gaydon underwent surgery on his eyes after an accident. When his sight began to return he found that he could see ultra-violet light, which is normally beyond the visible spectrum of humans. This helped in his work as a physicist, but it did distort how he saw other colours!

# Because of thermal expansion the Eiffel Tower is 15cm taller in summer.

# Some people who have two or more different kinds of fillings in their teeth are able to hear high-power AM broadcast stations when located within a few hundred feet of the stations. In such cases, the strong radio waves act upon the teeth fillings in such a way that the electromagnetic oscillations get transformed to mechanical vibrations in the person's head, and these are heard as sound.

# The amount of sunlight reaching the earth's surface is 6,000 times the amount of energy used by all human beings worldwide. The total amount of fossil fuel used by humans since the start of civilization is equivalent to less than 30 days of sunshine.

# Tree crickets are called the poor man's thermometer because temperature directly affects their rate of activity. Count the number of chirps a cricket makes in 15 seconds, then add 37. The sum will be very close to the outside temperature in farenheit!

# The highest temperature ever recorded at the South Pole was minus 13 degrees centigrade.

# If our Sun were just inch in diameter, the nearest star would be 445 miles away.

# If the Sun were the size of a beach ball then Jupiter would be the size of a golf ball and the Earth would be as small as a pea.

# The mass of the Earth increases every year because of 3,000 tonnes of meteorite debris that hits its surface from space.

# The microwave oven was invented by accident, when Percy Spencer found that his chocolate bar had been melted by an experiment he was running on radar systems. He immediately started experimenting successfully on microwaved popcorn.

# A supernova is the most energetic single event known in the Universe. Material is exploded into space at about 10,000 kilometres per second. All the stars in our galaxy (about 100,000,000,000) would have to shine for six months to produce the amount of energy released by just one supernova.

# The planet Venus’s day is longer than its year. It takes 225 ‘Earth’ days to rotate around the Sun (a Venusian year) and 243 ‘Earth’ days to rotate on its axis (a Venusian day).

# It takes the energy output of at least one power station to keep the traffic lights in the British Isles operating.

# One kilogram of butter stores as much energy between its atoms as the same quantity of TNT.

# Men are six times more likely to be struck by lightning than women.

# Do astronauts burp? Because you are weightless in space, the contents of your stomach float and tend to stay at the top of your stomach, under the rib cage and close to the valve at the top of your stomach. Because this valve isn't a complete closure (just a muscle that works with gravity), if you burp, it becomes a wet burp from the contents in your stomach.

# The Moon is gradually moving away from the Earth and the tides are to blame. Every year, the Moon moves a further 3.82cm from the Earth.

# Gold leaf is pure gold, but you can cover large areas with it very cheaply because it is very thin. Gold leaf is less than 0.00008 millimetres thick - which is only about 300 atoms thick.

# Every rainbow is unique - each rainbow is formed from light hitting your eye at a very precise angle. Someone standing next to you will see light coming from a slightly different angle than you and therefore see a different rainbow.

# A bolt of lightning contains enough energy to toast 160,000 pieces of bread. Unfortunately the bolt only takes 1/10,000 of a second – so turning the bread over might prove difficult.

# If 10 kilograms of matter spontaneously turned into energy there would be enough energy to power a 100 Watt light bulb for 300 million years - a harrowing thought for all weight watchers.

# If blood is red, why are veins blue?

Blood is bright red in its oxygenated form and a dark red in deoxygenated form. In simpler terms, it is bright red when it leaves the lungs full of oxygen and dark red when it returns to the lungs for a refill. Veins appear blue because light penetrating the skin is absorbed and reflected in high energy wavelengths back to the eye. Higher energy wavelengths are blue.

# Why is the sky blue?

When sunlight travels through the atmosphere, it collides with gas molecules. These molecules scatter the light. The shorter the wavelength of light, the more it is scattered by the atmosphere. Because it has a shorter wavelength than the other colours, blue light is scattered more, ten times more than red light, for instance. That is why the sky is blue.

# Why does the setting sun look reddish orange?

When the sun is on the horizon, its light takes a longer path through the atmosphere to reach your eyes than when the sun is directly overhead. By the time the light of the setting sun reaches your eyes, most of the blue light has been scattered out. The light you finally see is reddish orange, the colour of white light minus blue.

# Why do onions make you cry?

Onions, like other plants, are made of cells. The cells are divided into two sections separated by a membrane. One side of the membrane contains an enzyme which helps chemical processes occur in your body. The other side of the membrane contains molecules that contain sulfur. When you cut an onion, the contents on each side of the membrane mix and cause a chemical reaction. This reaction produces molecules such as ethylsufine which make your eyes water. To prevent crying when you cut an onion, cut it under a running tap of cold water. The sulfur compounds dissolve in water and are rinsed down the sink before they reach your eyes. You can also put the onion in the freezer for ten minutes before you cut it. Cold temperatures slow down the reaction between the enzyme and the sulfur compounds so fewer of the burning molecules will reach your eyes.

# Why you shouldn't smoke

If you smoke, you're also inhaling arsenic, benzene, cadmium, hydrogen cyanide, lead, mercury and phonol. In all, 4 000 harmful chemicals, including 44 types of poison, of which 43 are proven cancer-causing substances