Where did the sea go? It was here this morning
It was taken away by the tide – a simple word of the amazingly complex combined effect of the gravitational pulls of the Moon and Sun, together with the Earth’s rotation. Put simply, the Moon and Sun pull the sea closet to them up in a bulge, draining it from elsewhere. As the bulge moves around the Earth, the tide in any one place rises and falls. When the Sun and Moon are aligned in a straight line with the Earth, their pull combines and we get a bigger tide (called a spring tide). The height of the tide in any given place depends on a number of factors, including the depth of the sea and the shape of the coastline. The Bristol Channel has one of the biggest tidal ranges in the world because the rising water from the Atlantic is funnelled into a narrow estuary. The sheltered Baltic and Mediterranean seas, by contrast, have small tides.
Why don’t we feel the Earth spinning?
At the latitude of Britain, the ground under your feet is moving at about 600mph, so you might think it’s a wonder we don’t all feel permanently queasy. Yet we only feel motion through accelerations and decelerations – that is, when the speed or direction of movement changes. Standing on the spinning Earth, our speed is pretty high, but constant; and, while our direction does change, it does so slowly, at just one complete turn every 24 hours. That means the overall acceleration is too low to notice.
Why is the sky blue?
Some people think it’s because the sky is reflecting the blue of the sea, but that doesn’t make sense, because the sea has many colours – including white when it’s frozen over. The real explanation is that sunlight is made up of all the colours of the rainbow, from red to blue to violet. Each colour represents a wavelength of light, with red being the longest and violet the shortest. While red light can easily glide over tiny particles in its path, blue and violet light has more energy, and is seriously affected by them. Our atmosphere is packed with these particles, in the form of nitrogen and oxygen molecules, which scatter the blue-violet part of the sun’s light over the sky. Add in the fact that our eyes are more sensitive to blue light than to violet, and that’s why we see the sky as blue.
Why do cats purr?
Nobody knows for sure. It’s not simply because they’re contented. Cats sometimes purr while giving birth, or while recovering from serious injury. Studies have revealed an odd fact that might help explain it. Recordings of purrs have shown that they typically have a frequency of about 20-40 cycles per second – half of frequency of mains electricity ‘hum’. That just happens to be the frequency of vibration that appears to promote bone healing. Which might be why your gran always seems to have the cat sat on her knee.
Can you ever get to the end of the rainbow?
No chance, which means that pot of gold remains elusive. That’s because a rainbow is not a physical object, but simply the result of two refractions (where light bends as it hits water from air or vice versa). Its appearance depends on rays of sunlight striking raindrops at the right angle to enter the drops, reflect off their internal surfaces. Then re-emerge on the right path to enter our eyes. The colours come from the raindrop surface separating out the different hues that go to make up white sunlight, from red at one end of the spectrum to violet at the other. So we only see a rainbow where the sun, the raindrops and our eyes are in just the right relative positions. If we move towards a rainbow, that relationship changes – keeping its end forever out of reach.
Why do things look smaller when they’re further away?
It’s a matter of visual perspective, which depends on how much of our field of view an object takes up. Imagine lines drawn from your eye to the head and feet of a person standing nearby. Now imagine similar lines drawn to the same person, standing twice as far away: the lines form a narrower angle at your eye, so the person takes up less of your field of view. This change in apparent size is one of the clues our brains use to work out how far away things are.
Why do explosives explode?
Explosives such as nitro-glycerine and TNT (trinitrotoluene) are notorious for their devastating power, but the way they work is simple. When they detonate, their constituent chemicals produce gas clouds that expand at incredible speed, blasting anything in their path. The speed – several thousand miles per hour – is due to the high temperatures of the chemical reactions that propel the expansion of the gas cloud.
What’s the deadliest creature in the world?
That depends on what you mean by deadly. If you mean responsible for killing the greatest number of humans, a good case could be made for humans themselves, who murder about 500,000 of their own kind globally each year. But if deadly means most likely to lead to death if you mess with it, then it’s probably the golden poison frog, from the rainforests of Colombia. This beautiful but tiny creature – bright yellow and barely 1.5in long – oozes an astonishingly lethal poison known as a batrachotoxin from its skin. Just 100 micrograms of the poison, which amounts to a barely visible speck, is enough to kill you.
How do camels survive without drinking?
Camels can go for more than a month without drinking, but not by storing water in their humps – that’s a myth. The humps store fat. Camels do without water by conserving every last drop of it and having bodies adapted to dehydration. They barely lose any water through excretion or sweating, having evolved to cope with large changes in body temperature, and even have oval red blood cells, rather than round ones like other mammals, which helps them to keep flowing even when the blood is thicker due to dehydration.
London lad, loving life and all that it has to offer.