PASSION FOR SCIENCE
As I’ve already intimated, my other great passion, apart from Sherlock Holmes, is
Science. I like to think that the Great Detective would be as passionate as I am about the subject, if he had lived in our era. His analytical and logical mind would surely cause him to question the same things that fascinate us today.
‘There’s no such thing as a dumb question!’ So argued one of the most eminent American scientists, the late Carl Sagan, though there are dumb answers. When he was a young boy, filled with curiosity about the world, Carl asked an adult, ‘What are the stars?’ He was told, ‘Why, they’re just lights in the sky, kid! ‘ So he went to the library and asked the librarian for a book about the stars. She gave him a book with pictures of Hollywood movie actors and actresses.
I can empathise with Professor Sagan because I too was filled with curiosity about the world and nature when I was a boy (and I still am filled with curiosity!) I asked, ‘What causes lightning and the thunder that follows a lightning strike’? I was told it was the clouds bumping together! Even to my childish mind I knew that had to be wrong because clouds are just water vapour and very soft so how could they ‘bump’ together making huge sparks and a loud noise? Some of the other questions I asked, and received no answers to, were: What causes a magnet to attract other metal? Why is the sky blue? Is water compressible like air? How does a vacuum flask keep things hot? How can aeroplanes, weighing many tons, fly? Why does salt, which is at the same temperature as the air around it, make ice melt? What makes a rainbow? I was so disappointed that my parents and other adults did not know the answers to these basic questions, but what staggered me most was that it didn’t seem to bother them that they didn’t know! Why didn’t they try to find out? Why were they content in not knowing? They were well versed in the pseudo-sciences such as astrology, faith healing, UFO’s etc. but knew virtually nothing about real science.
As I grew older and found answers to the questions of my childhood I was faced with yet more questions. Now I wanted to know, for example, What is relativity? What is gravity? Is the universe infinitely large and how old is it? What is the smallest particle? How did life begin on earth? If you or your children have ever asked such questions then you are on the first rungs of the ladder of scientific enlightenment and the journey upwards is stimulating, rewarding, intriguing and virtually unending, though it is never dull!
In what follows I shall try to answer some of the questions raised, starting with the simpler ones that puzzled me when I was young.
1) Why is the sky blue? Daylight is made up of all the colours of the rainbow and the dust particles in our atmosphere and the molecules of the air itself, reflect the blue part of the spectrum. As the sun sets, the light passes through the atmosphere at a low angle, i.e. a thicker volume of air, so the colour changes. That’s why sunsets are red and orange rather than blue. On Mars, which has a much thinner atmosphere than the earth, the sky is pink and the sunsets purple!
2) What (really) causes thunder and lightning? In a storm cloud, ice crystals form and circulate inside the cloud on convection currents, increasing in size as they do so. Friction between these hailstones generates static electricity with opposite charges at the highest and lowest levels of the cloud. When this charge has built up to an incredibly high voltage, a huge spark jumps the gap. Many of these find the shortest path down to the ground, these are lightning bolts. The spark, which is as hot as the surface of the sun, heats the air explosively, causing the initial ‘crack’ and creating a partial vacuum in the atmosphere. The surrounding air rushes in to fill this ‘hole’ causing the rumble we recognise as thunder. Without lightning there would be no life on earth because the chemistry of primitive life was triggered by lightning! There is still a great deal regarding lightning that we know nothing about. There are phenomena called Red Sprites and Blue Jets that are enormous bursts of electrical discharge, above the clouds, that shoot up to the fringes of space itself.
3) Why does salt melt ice? When salt is sprinkled onto an icy surface it mixes with the ice and since salt water has a much lower freezing point than fresh water, the ice melts! Only very rarely does the sea itself freeze, except at the Poles where it is really cold.
4) Why is seawater salty? Because billions of years ago when the earth was very young, torrential rain (that lasted for thousands of years) leached the water-soluble minerals and salts from the land and into the sea!
5) Is water compressible like air? No. I actually found this out for myself, when I was still a young boy, by conducting an experiment of my own. I drew some water up into my bicycle pump and, covering the hole with my finger, tried to compress the water by operating the pump. It locked solid, unlike the air, which could be compressed quite a lot! It’s fortunate that liquids aren’t compressible otherwise car’s brakes wouldn’t work because the brake fluid would be compressed.
6) How does a vacuum flask keep things hot? The heart of the flask is a glass vessel with a double skin. All the air is sucked out of the space between the walls of the vessel, creating a good (though not perfect) vacuum. Heat needs a medium to travel through, like air or water, and does not travel well through a vacuum. Also the inside of the vessel is highly polished, which reflects the heat back rather than letting it escape!
7) How does a heavy aeroplane fly? The only parts of the plane that actually fly are the wings! Everything else, including you and your luggage is dead weight, which must be carried by the wings. The secret is in their shape. A wing is curved over its top surface, whereas the underside is flat. As the plane moves forward, under the thrust from the propellers or jet engines, the flow of air around the wing increases. As the air passes over the top surface it has to travel faster to cover the longer distance of this curvature, which causes a drop in air pressure. The air pressure on the underside is now greater than on top and this creates the lift that makes the plane fly!
8) What causes a magnet to attract other metal? Magnetism is still not completely understood (especially by me), but is intimately linked with electric fields. In a magnet all the molecules lie in an aligned lattice each with a North Pole and a South Pole. ‘Like’ poles repel each other and ‘unlike’ poles attract. If you cut a bar magnet in half you don’t get a North Pole magnet and a South Pole magnet you get two normal, but smaller magnets! If you move a magnet inside a metal coil an electric current will be generated in the wire. Conversely if you pass an electric current through a coil a magnetic field will be created, demonstrating the inseparable link between them. To really understand magnetism you need to know about quantum mechanics and relativistic invariance, which is a little beyond the scope of this treatise (and my intelligence, though I am still trying to understand it!). Electricity and magnetism resonate together to make Electromagnetism, which includes light itself!
9) What makes a rainbow? As we already know, sunlight is made up of all the colours in the spectrum and the water droplets in the air, during a shower, refracts or splits the sunlight up into its constituent colours creating a rainbow. A glass prism can do the same thing. Even a soap bubble can form a rainbow as the light is reflected simultaneously from both the outer surface and the inner surface of the ‘skin’ of the bubble!
10) What are the stars? They really are more than just lights in the sky! They are; of course, other suns like our own, but so far away that they look like pinpoints of light in the night sky. They consist of great concentrations of gas undergoing nuclear reactions called atomic fusion. Unlike atomic fission, as in a bomb, where the atoms are split releasing their binding energy. Fusion, as its name implies, is a process that fuses atoms together creating new elements and releasing vast amounts of energy. Hydrogen is fused into helium, helium into lithium, lithium into beryllium and so on through the elements. This process can only create the elements up to the density of iron. After that it needs a supernova to make the heavier elements and the gold in the ring on your finger was made billions of years ago in a huge stellar explosion! Super-novae have seeded the universe with these elements and the carbon in your cells, the iron in your blood and the calcium in your bones were all ‘cooked’ in earlier generations of stars. All of us truly are made from stardust!
Look for more questions and answers on future posts!