Thunder is a noise created by lightning. The air around a lightning bolt is superheated to about five times the temperature of the Sun. This sudden heating causes the air to expand faster than the speed of sound, which compresses the air and forms a shock wave which we hear as thunder.

On the subject of lightning... on average about a hundred lightning strikes occur around the world every second. Those are just the ones that hit the ground. During any given minute, there are more than a thousand thunderstorms around the Earth causing some six thousand flashes of lightning. Something to think about while you're on the golf course.

We'll leave the argument about whether Pluto is a planet or a Kuiper Belt object. But the fact remains that the Solar System's most remote member has an extremely strange orbit in which it's distance from the Sun varies by a whopping 25%. On average that distance is 3.67 billion miles (39.5 times further than Earth), and Pluto takes 248 years to orbit the Sun.

A mission (unmanned, for obvious reasons) to Pluto is now back on the cards - but the boffins will have to pull their proverbial fingers out. Pluto reached it's 'perihelion' (closest approach to the Sun) in 1989 and since then has been moving further away. The New Horizons mission is scheduled to reach Pluto in 2015, 9 years after it's 2006 launch. By this time the thin atmosphere, composed mostly of Nitrogen (with a bit of Methane and Carbon Monoxide thrown in), will be getting a lot colder, dropping to around -233° C (that's -390° F).

The problem that faces the boffins is that eventually, soon after 2016, Pluto's atmosphere will literally freeze and start to drop to the planet's surface. By 2020 this strange snowfall will be complete. So if there's any delays, there'll be no atmosphere for New Horizons to examine.

Bats always emerge from a cave and enter a cave by turning left - this prevents mid-air collisions. This behaviour is imitated by a code of conduct among pilots who, when staring down the nose of an oncoming aircraft, will take evasive action by turning left.

Planets... they're the big fellas of the Solar System, right? And the moons, they're the smaller chaps. That's the deal isn't it? Well, actually, no. Believe it or not, there are seven moons in the Solar System which are bigger than the outermost planet, Pluto. This far-flung and diminutive planet, which was discovered in 1930, has a diameter of 2,274 km. That's smaller than:

	Ganymede (Jupiter's largest moon, with a diameter of 5,262 km)
	Callisto (Jupiter's second largest moon)
	Io (Jupiter's third largest moon)
	Europa (Jupiter's fourth largest moon)
	Titan (Saturn's largest moon, with a diameter of 5,150 km)
	Triton (Neptune's largest moon, with a diameter of 2,700 km)
	Our own moon (with a diameter of 3,476 km)

Pluto is not the only midget orbiting the Sun - Mercury, the innermost planet, is smaller than two moons (Ganymede and Titan) and at 4,880 km in diameter is only just bigger than Callisto. Mercury has no moons, but Pluto does - just one, named Charon (diameter 1,172 km) which, by the way, is the largest moon in comparison to it's parent planet.

Bonus fact - Pluto isn't always the furthest planet from the Sun. It's orbit is such that Neptune is sometimes further out - this recently occurred for over 20 years (1979 to 1999).

Having categorised the facts into 'natural world' and 'human world' I wasn't sure where to put this one - as you'll see it's about the geography of the USA (which is natural), but it also discusses the states which are defined by humans. Anyway, here you go...

There are seventeen states of the USA of which the highest point is still lower in elevation than the lowest point of the state of Colorado. For example, Colorado's lowest point is along the Arkansas River and stands at 3,350 feet above sea level. Pennsylvania's highest point is the top of Mt. Davis which is 3,213 feet above sea level. Florida is overall the lowest state, it's highest point in Walton County being just 345 feet. However, Delaware is the state with the lowest average elevation at just 60 feet. Only California (Death Valley) and Louisiana (New Orleans) have areas below sea level.

There are some people who don't believe that mankind actually landed on the moon, and that it was all a fake. Mind you, when you study the evidence of these supposed whackos, it's actually quite compelling (inconsistent direction of shadows, objects in front of camera cross-hairs, that sort of thing). However, for the sake of argument (and this fact) let's suppose it did all happen a quarter of a million miles away and not on a mocked-up lunar landscape in a secret NASA installation...

Neil Armstrong and subsequent astronauts left footprints on the lunar surface and, because there is no wind, precipitation or water on the moon, those footprints should remain intact for approximately 10 million years. The loose layer of lunar dust is approximately 2.6 inches thick. Within a few million years the footprints will lose their definition as ultra-fine cosmic dust settles within the indentations. However, some of the prints will have already been blown away by the blast from the lunar module take-off.

If you think that rabbits can knock out quite a few offspring, how about this...? One female cabbage aphid, given ideal conditions (and presumably a Mister Cabbage Aphid), could potentially produce 15 new generations of offspring weighing in at 250 million tonnes in one year. Before you decide to buy a can of bug spray, consider also that a pair of house-flies could, in one year, produce enough offspring to cover the entire earth to a depth of 15 metres.

Who calculates this stuff...? And haven't they got anything better to do?

Been sprayed with scent from a skunk's arse recently? No, me neither. But if it should happen to you, take a bath in tomato juice - it's the only thing that will get rid of the pong. Alternatively, sit next to a French taxi driver... you'll smell like a bag of pot pourri by comparison.

Giant anteaters consume up to 30,000 ants per day. Their tongues can stretch up to 60 cms, and they can extend and retract them over 100 times per minute.

Next time you're in the supermarket and grab a packet of Saxa, consider this... if the total salt content of all of planet Earth's seas and oceans were dried, it could cover the land to a depth of 5 feet. Although that would be a little bit inconvenient, it would keep the slugs out of my garden.

A slow cascade of cold water beneath the Denmark Strait between Greenland and Iceland sinks 2.2 miles (3.5 km), over three-and-a-half times farther than the tallest waterfall on land, Venezuela's Angel Falls.

Research indicates that mosquitoes are attracted to people who have recently eaten bananas.

The world's termites outweigh humans 10 to 1.

Residents of warm Southern California are moving to the more temperate Alaska whether they like it or not. Thanks to plate tectonics, Southern California is moving north and will collide with Alaska in approximately 150 million years. So they've got plenty of time to pick up some warmer clothes.

When collected, all of the gold suspended in all of the Earth's seawater would yield 9 lbs (or 4 kg) in weight for every member of the human race.

Mako sharks show cannibalistic tendencies while still in their mother's womb; older embryos will eat the younger embryos and eggs.

Bonus shark facts
Sharks never suffer from cancer
Sharks are heavier than water... they will sink if they stop swimming
Sharks can't swim backwards
Female sharks grow to be larger than male sharks