My Science School

Not all the planets move at the same speed. The earth spins on its axis once every twenty-four hours. At the same time it moves round the sun, taking 365 days, or thereabouts, to complete a year’s full circuit. Mercury is the planet nearest to the sun. It revolves round the sun in only eighty-eight earth days. So its year is much shorter than ours. On the other hand, each day on Mercury is incredibly long because the planet spins very slowly on its axis. In fact, for anyone standing on a fixed place on the surface of Mercury, the gap between one sunrise and the next would be 176 days, or two Mercurian years.

 

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Greenhouses help gardeners grow plants they would not normally be able to grow in their gardens and plants they could not grow outside during the colder times of the year. This is certainly true in northern countries where there are often frosts at night.

The glass in a greenhouse is the secret of its success. This takes in light and warmth from the sun, providing energy for plants to grow. The glass keeps out cold winds too. And if a greenhouse is heated, it is possible to grow warmth-loving plants like grapes in countries where they would not usually survive.

 

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You can fill a balloon with hot air or with has. Whichever you use, the air or gas inside the balloon has to be lighter than the air outside it. That is the basic rule of balloon flight.

Modern hot-air balloons are inflated with air heated by a gas burner. Since hot air rises, the balloon lifts off the ground as soon as there is enough hot air to lift the canopy, basket, gas bottles and passengers. The air does not stay hot forever. As it cools, the balloon begins to lose height. So the pilot needs to heat it again, using the gas burner every time he or she wants to go higher.

The gas generally used to fill balloons is helium. This is also lighter than air and does away with the need for a burner to produce hot air. Airships are filled with helium too. When an airship pilot wants to come in to land, he or she has to let air into the canopy to make the airship descend.

 

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From time to time dark spots appear on the surface of the sun. Some are quite small, around 2000 kilometres across, while others can stretch for over 100,000 kilometres over the sun’s surface. They appear dark because they are cooler than the surrounding gas – about 1700ºC cooler. Sunspots can last from a day or two to a month longer. And they are probably caused by strong magnetic fields which stop the flow of heat to the sun’s surface for a time. You can’t see them with the naked eye so don’t try looking for them – anyway you should NEVER stare directly at the sun. You might damage your eyes really badly.

 

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A number of things have to happen if you want to see a rainbow. It has to be raining. The sun has to be shinning. And you have to have your back to the sun. The rainbow you will then see is formed by raindrops breaking up the sunlight into its various colours; red, orange, yellow, green, blue, indigo and violet. Disappointingly, the one colour you will not find is gold. There never has been a crock of gold at the end of the rainbow.

Something that you often see with a rainbow is a paler ‘secondary rainbow’. In the brighter one, red is on the outer edge and violet on the inner. In the secondary rainbow the colours are reversed.

 

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Pictures of the moon’s surface show that it is pockmarked with round walled shapes known as craters. What caused them is a bit of a mystery. Men have landed on the moon several times. A lot of satellites have been sent to look at it. Yet scientists still cannot say for certain what caused the craters. The moon does not have an atmosphere like the earths. This makes it easier for meteorites to smash into its surface. Meteorites heading towards earth often break up as they pass through the atmosphere. So meteorites probably caused a good many of the moon’s craters.

A lot of the craters are huge. Some measure over 150 kilometres across. Others are so tiny they cannot be seen from earth. So another theory is that some craters may have been formed by volcanic activity bubbling up from inside the moon.

Most likely both meteorites and internal eruptions were responsible. But we still do not know for certain.

 

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Appearances can sometimes be deceptive. This simple experiment is a good example. Put a pencil into a glass of water and you will notice that it appears to bend. Take it out again and of course it is perfectly straight – as it always was. But back in the water it bends again. So what is going on?

Scientifically is caused by a change in the speed at Refraction is caused by a change in the speed at which light travels through different transparent substances. Light travels more slowly through water than it does through air. Because of this it changes direction slightly. Objects like the pencil, part of which is in the air and part of which is in the water, appear to bend.

Refraction also makes us miss things we try to pick up underwater. Again it is the ‘bending’ of the light which appears to do this. Objects appear slightly to one side of where they really are. We aim for where they appear to be and are a little off target.

 

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The next time you are trudging towards the North Pole remember to make the right adjustment to your compass reading. If you do not you will end up in the wrong place – and the North Pole is not the easiest part of the world to get to at the best of times.

Having two north poles is confusing, but there it is. One is the magnetic north pole. The other is the true North Pole, the one that everyone tries to reach at the top of the world. This lies at the northern end of the imaginary line drawn through the centre of the earth, around which it is supposed to spin. At the other end is the South Pole.

As the earth spins, movements in its outer core of molten rock set up a magnetic field which is concentrated at the north and south magnetic poles. Because the earth actually spins on a slightly different axis to the imaginary north-south one, magnetic north is somewhere in northern Canada, about 2570 kilometres from the North Pole. Magnetic south is the same distance from the true South Pole.

The position of the two magnetic poles varies a little each year as the earth shifts slightly on its axis. By taking this small change into account, navigators can find their way around the world with their compasses, because a compass needle always point towards the magnetic north pole.

 

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How many days are there in a normal year? The answer’s 365 – or is it? That is the number that we conveniently use even though it is not strictly accurate. It really takes the earth 365¼ days to go round the sun. So every fourth year an extra day is added to February to make up the difference. This keeps our calendar in time with the astronomical calendar – the one the earth and sun work by.

Why a leap year? Assume a given date in a month falls on Monday the first year. The next year it will be Tuesday. The year after, it will be Wednesday. When it comes to the fourth year, it is time to add the extra day. So the date leaps over Thursday to Friday.

 

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If you hold a magnifying glass so that it concentrates a beam of sunlight on to a piece of paper – and hold it steady for a few minutes – the paper will start to smoke and then catch fire. That is one way of cutting through things with light. But paper is rather different from steel. Yet laser beams can cut through steel faster than you can burn paper with a magnifying glass. The secret is that they use a different sort of light.

Light waves usually overlap as they pass through the air. When this happens, the energy in one wave cancels out the energy in another. In a laser the light waves work together. Therefore all the energy can be channeled into a very narrow, powerful beam of light. This is powerful enough to cut through steel, or send a pencil-thin beam of light over great distances on earth and far out into space. In America, military scientists are trying to develop lasers that can even knowck out nuclear missiles.

 

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It may sound silly, but imagine what would happen if a rocket sent up to the moon missed its target. The moon may be pretty big. But so in space. Missing something even as big as that could easily happen, without careful control of the spacecraft. That’s why each moon shot takes months of planning and complicated calculations.

The rocket must be programmed so that soon after take-off it reaches almost 42,000 kilometres per hour. This is the speed necessary for it to break free of the earth’s gravity. After that, its speed has to be carefully controlled so that when it reaches the moon it will be travelling at about 1250 kilometres per hour.

Of course, while a rocket is flying to the moon, the moon is on the move as well. It is whizzing round the earth at an average speed of 3836 kilometres per hour. Just to complicate things further, it does not stick to a regular path. The distance between the earth and the moon can vary by as much as 52,800 kilometres! The flight controllers have to work out where the moon is going to be all through the flight, to be certain that the rocket reaches the right place at the right time. Then there is the moon’s gravity to be taken into consideration. The closer a rocket gets to the moon, the more it is affected by this gravitational pull. So for the last 3000 kilometres the scientists have to watch the rocket’s speed very closely as it becomes more and more affected by the moon’s gravity.

You can see that controlling the speed and navigation of a spacecraft is anything but easy. The speed has only got to be a couple of kilometres an hour either side of the right speed to miss the moon completely. And one degree off course could throw the rocket’s timing out by as much as seven hours.

 

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Some people might answer: when it blows the roof off your house. The weather men see it differently. ‘Hurricane’ is one of the names given to violent tropical storms. These develop over warm tropical seas and blow up into huge spinning storms of clouds and rain. Hurricanes can be driven by winds reaching speeds of 300 kilometres per hour and can cause terrible damage.

The system used to measure wind speed is called the Beaufort scale. Hurricane is at the top of the scale and is known as force 12. When the wind reaches 122 kilometres an hour, a violent storm of force 11 becomes a hurricane of force 12.

 

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The universe is so enormous it is hard for us to imagine the distance in it. Trying to measure them in kilometres would be almost meaningless as well, because the numbers would be incredibly long with strings of noughts on the end. Instead, distances in the universe are measured in light-years. One light-year is the distance that light travels in a year. Since light travels at 299, 792.5 kilometres per second, in one year it travels an amazing 9,460,528,405,000 kilometres. That’s what a light-year represents.

To get an idea why such measurement is necessary, think about these statistics. It takes 75,000 light-years for light to reach earth from the most distant star in the Milky Way. Light from the most distant star we can see with the naked eye takes even longer. We have to wait 2,200,000 years for light to come from anything as far away in the universe as that.

Closer to home, it takes just under eight and a half minutes for light to reach us from the sun. The moon’s closer still. Light reflected off the moon comes to earth in only one and a quarter seconds.

Yes – the universe is a big place!

 

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If you take your temperature when you are feeling healthy and normal, the thermometer will read around 37ºC. That is the temperature we regard as being normal. When the air temperature gets that hot, it feels anything but normal. We soon get hot and uncomfortable and try to find somewhere cool. Of we were not wearing any clothes, and just relaxed and did nothing too active, we would probably feel all right at that temperature. But modern life is not like that,

Any uncovered part of our body radiates heat. So we soon feel cold if we go out in shorts and T-shirts and the temperature drops. If we sat still in a garden, wearing juts a swimming costume, then an air temperature of 37ºC would not feel too bad. The heat we radiated would be the same temperature as the air around us and a balance would be struck. Things would start getting uncomfortable, however, if we moved into a confined space in that temperature. The heat from our bodies would gradually warm up the air around us. And that would make us hotter still. In the same way, if we did any physical activity, we would get warmer, and again we would begin to radiate more heat.

The story is the same when we wear clothes. These stop us radiating heat as efficiently as we would without them, and consequently we feel hot. That is why we generally feel more comfortable at air temperatures lower than our body temperature.

 

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The LHCb (Large Hadron Collider beauty) experiment is one of eight particle physics detector experiments collecting data at the Large Hadron Collider at CERN. LHCb is a specialized b-physics experiment, designed primarily to measure the parameters of CP violation in the interactions of b-hadrons (heavy particles containing a bottom quark). Such studies can help to explain the matter-antimatter asymmetry of the Universe. The detector is also able to perform measurements of production cross sections, exotic hadron spectroscopy, charm physics and electroweak physics in the forward region. The LHCb collaboration, who built, operate and analyse data from the experiment, is composed of approximately 1260 people from 74 scientific institutes, representing 16 countries.

The fact that the two b-hadrons are predominantly produced in the same forward cone is exploited in the layout of the LHCb detector. The LHCb detector is a single arm forward spectrometer with a polar angular coverage from 10 to 300 milliradians (mrad) in the horizontal and 250 mrad in the vertical plane. The asymmetry between the horizontal and vertical plane is determined by a large dipole magnet with the main field component in the vertical direction.

 

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