Hipparchus of Nicaea was a Greek astronomer who lived in the 2nd century BC, dying in 127Bc.
The foundations of astronomy were laid down by Hipparchus and survived 1500 years, until they were overthrown by the ideas of Copernicus.
Ancient Babylonian records brought back by Alexander the Great from his conquests helped Hipparchus to make his observations of the stars.
Hipparchus was the first astronomer to try to work out how far away the Sun is.
The first star catalogue, listing 850 stars, was put together by Hipparchus.
Hipparchus was also the first to identify the constellations systematically and to assess stars in terms of magnitude (see star brightness).
Hipparchus also discovered that the relative positions of the stars on the equinoxes (21 March and 21 December) slowly shift round, taking 26,000 years to return to their original place. This is called the ‘precession of the equinoxes’.
The mathematics of trigonometry is also thought to have been invented by Hipparchus.
Hipparchus carried out his observations at Rhodes. He was the first to pinpoint the geographical position of places by latitude and longitude.
When you remember something, your brain probably stores it by creating new nerve connections.
You have three types of memory – sensory, short-term and long-term.
Sensory memory is when you go on feeling a sensation for a moment after it stops.
Short-term memory is when the brain stores things for a few seconds, like a phone number you remember long enough to press the buttons.
Long-term memory is memory that can last for months or maybe even your whole life.
Your brain seems to have two ways of remembering things for the long term. Scientists call these two different ways declarative and non-declarative memories.
Non-declarative memories are skills you teach yourself by practicing, such as playing badminton or the flute. Repetition establishes nerve pathways.
Declarative memories are either episodic or semantic. Each may be sent by the hippocampus region of the brain to the correct place in the cortex, the brain’s wrinkly outer layer where you do most of your thinking.
Episodic memories are memories of striking events in your life, such as breaking your leg or your first day at a new school. You not only recall facts, but sensations too.
Semantic memories are facts such as dates. Scientists think these are stored in he left temporal lobe, at the front left-hand side of your brain.
About 730 million people live in Europe – about 12 percent of the world’s population.
Europe is one of the most densely populated continents averaging 70 people per square kilometer.
Most Europeans are descended from tribes who migrated into Europe more than 1500 years ago.
Most British people are descended from a mix of Celts, Angles, Saxons, Danes and others. Most French people are descended from Gauls and Franks. Most Eastern Europeans are Slavic.
North Europeans such as Scandinavians often have fair skin and blonde hair. South Europeans such as Italians often have olive skin and dark hair. Most European countries have a mix of people from all parts of the world, including former European colonies in Africa and Asia.
Most Europeans are Christians.
Most Europeans speak an Indo-European language, such as English, French or Russian.
Languages like French, Spanish and Italian are romance languages that come from Latin, language of the Romans.
Basque people in Spain speak a language related to no other language. Hungarians, Finns and Estonians speak a Uralic- Altaic language like those of Turkey and Mongolia.
The nervous system is your body’s control and communication system, made up of nerves and the brain. Nerves are your body’s hot-lines, carrying instant messages from the brain to every organ and muscle – and sending back an endless stream of data to the brain about what is going on both inside and outside your body.
The central nervous system (CNS) is the brain and spinal cord.
The peripheral nervous system (PNS) is made up of the nerves that branch out from the CNS to the rest of the body.
The main branches of the PNS are the 12 cranial nerves located in the head, and the 31 pairs of spinal nerves that branch off the spinal cord.
The nerves of the PNS are made up of long bundles of nerve fibres, which in turn are made from the long axons (tails) of nerve cells, bound together like the wires in a telephone cable.
In many places, sensory nerves (which carry sense – signals from the body to the brain) run alongside motor nerves (which carry the brain’s commands telling muscles to move).
Some PNS nerves are as wide as your thumb. The longest is the sciatic, which runs from the base of the spine to the knee.
The autonomic nervous system (ANS) is the body’s third nervous system. It controls all internal body processes such as breathing automatically, without you even being aware of it.
The ANS is split into two complementary (balancing) parts – the sympathetic and the parasympathetic. The sympathetic system speeds up body processes when they need to be more active, such as when the body is exercising or under stress. The parasympathetic slows them down.
Nerves are made of very specialized cells called neurons.
Neurons are shaped like a spider, with a nucleus at the centre, lots of branching threads called dendrites, and a winding tail called an axon which can be up to 1 m long. 336
Axon terminals on the axons of one neuron link to the dendrites or body cell of another neuron.
Neurons link up like beads on a string to make your nervous system.
Most cells are short-lived and are constantly being replaced by new ones. Neurons, however, arc very long-lived – some are never actually replaced after you are born.
Nerve signals travel as electrical pulses, each pulse lasting about 0.001 seconds.
When nerves are resting there are extra sodium ions with a positive electrical charge on the outside of the nerve cell, and extra negative ions inside.
When a nerve fires, gates open in the cell wall all along the nerve, and positive ions rush in to join the negative ions. This makes an electrical pulse.
Long-distance nerves are insulated (covered) by a sheath of a fatty substance, myelin, to keep the signal strong.
Myelinated (myelin-sheathed) nerves shoot signals through very fast – at more than 100 metres per second.
Ordinary nerves send signals at about 1 to 2 metres per second.
Motor nerves are connected to your muscles and tell your muscles to move.
Each major muscle has many motor nerve-endings that instruct it to contract (tighten).
Motor nerves cross over from one side of your body to the other at the top of your spinal cord. This means that signals from the right side of your brain go to the left side of your body, and vice versa.
Each motor nerve is paired to a proprioceptor on the muscle and its tendons (see co-ordination). This sends signals to the brain to say whether the muscle is tensed or relaxed.
If the strain on a tendon increases, the proprioceptor sends a signal to the brain. The brain adjusts the motor signals to the muscle so it contracts more or less.
Motor nerve signals originate in a part of the brain called the motor cortex (see the cortex).
All the motor nerves (apart from those in the head) branch out from the spinal cord.
The gut has no motor nerve-endings but plenty of sense endings, so you can feel it but cannot move it consciously.
The throat has motor nerve-endings but few sense endings, so you move it but not feel it.
Motor neuron disease attacks motor nerves within the central nervous system.
Flowers have both male parts, called stamens, and female parts, called carpels. Seeds for new plants are made when pollen from the stamens meets the flower’s eggs inside the carpels.
The carpel contains the ovaries, where the flower’s eggs are made. It is typically a short thick stalk in the centre of the flower.
A flower may have just one carpel or several joined together. When together, they are called the pistil.
The stamens make pollen. Typically they are spindly stalks surrounding the carpels.
Pollen is made in the anthers which are found on top of the stamens.
Pollen is trapped on the top of the ovary by sticky stigma.
Pollen is carried down to the ovary from the stigma via a structure called the style. In the ovary it meets the eggs and fertilizes them to create seeds.
Before the flower opens, the bud is enclosed in a tight green ball called the calyx. This is made up of tiny green flaps called sepals.
The colorful part of the flower is made from groups of petals. The petals make up what is called the corolla. Together the calyx and the corolla comprise the whole flower head, which is known as the perianth. If petals and sepals are the same color, they are said to be tepals. 1. The fully formed flower is packed away inside a bud. Green flaps called sepals wrap tightly round it 3. The sepals open wider and the petals grow outwards and backwards to create the flower’s beautiful corolla 4 At the right time of year, buds begin to open to reveal flowers’ blooms so that the reproductive process can begin. Some flowers last just a day or so. Others stay blooming for months on end before the eggs are fertilized, and grow into seeds. 2. When the weather is warm enough, the bud begins to open. The sepals curl back to reveal the colorful petals How plants live ,
A ‘perfect’ flower is one which has both stamens and carpels; many have one missing.
Flowers like this orchid have developed vivid colors to attract pollinating insects. 4. The flower opens fully to reveal its bright array of pollen sacs or
Cut flowers are flowers that are sold by the bunch in florists.
The cut flower trade began in the Netherlands with tulips in the 1600s.
In 1995 60% of the world’s cut flowers were grown in Holland.
Latin American countries like Colombia, Ecuador, Guatemala and Costa Rica are now major flower-growers. So too are African countries like Kenya, Zimbabwe, South Africa, Zambia and Tanzania.
In China the growing popularity of St Valentine’s day has meant huge areas of China are now planted with flowers.
After cutting, flowers are sent by air to places like Europe and North America. During the journey they are chilled so they will arrive fresh.
Most of the world’s cut flowers are sold through the huge flower market in Rotterdam in Holland.
Garden flowers, when cut and put into water, are ideal for adding a touch of color and freshness to people’s homes.
By encouraging certain flowers, flower-growers have made cut flowers last longer in the vase they have lost the —but rich scents they once had. Scientists are now trying to reintroduce scent genes to flowers.
A corsage is a small bouquet women began to wear on their bodices in the 18th century.
A nosegay was a small hot tiet Victorian ladies carried in their hinds. If a man gave a lady a red tulip it meant ht . loved her. If she gave him hack a sprig of ilogwood it mean she didn’t care. Various ;link ‘lowers meant ‘no.
Dandelions and daisies are both members of a vast family called Asteraceae.
All Asteraceae have flower heads with many small flowers called florets, which are surrounded by leaf-like structures called bracts.
There are over 20,000 different Asteraceae.
Garden Asteraceae include asters, dahlias and chrysanthemums.
Wild Asteraceae include burdock, butterbur and ragweed, thistles and sagebrush.
When dandelions mature, they form feathery seeds which are blown away like parachutes by the wind. Daisies look like a single bloom, but they actually consist of many small flowers. Those around the edge each have a single petal.
Lettuces, artichokes and sunflowers are all varieties of Asteraceae.
The thistle is the national emblem of Scotland.
Dandelions are bright yellow flowers that came originally from Europe, and were taken to America by colonists. Unusually, their ovaries form fertile seeds without having to be pollinated, so they spread rapidly.
The name dandelion comes from the French dent de lion, which means lion’s tooth, because its leaves have edges that look like sharp teeth.
The daisy gets its name from the Old English words ‘clay’s eye’ – because like an eye its blooms open in the day and close at night.
In meadow grass flowers like buttercups, daisies, clover, forget-me-nots and ragged robin often grow.
In deciduous woodlands flowers like bluebells, primroses, daffodils and celandines grow.
By the sea among the rocks, sea tampion and pink thrift may bloom, while up on the cliffs, there may be birdsfoot trefoil among the grasses.
As humans take over larger and larger areas of the world, and as farmers use more and more weedkillers on the land, many wildflowers are becoming very rare. Some are so rare that they are protected by law.
The lady’s slipper orchid grows only in one secret place in Yorkshire, in the north of England.
I he rare lady’s slipper orchid is also known as the moccasin flower. Its enlarged labellum (hp) makes it resemble a slipper or moccasin.
All flowers were originally wild. Garden flowers have been bred over the centuries to be very different from their wild originals.
Wildflowers are flowers that have developed naturally.
Most wildflowers are smaller and more delicate than their garden cousins.
Each kind of place has its own special range of wildflowers, although many wildflowers have now been spread to different places by humans.
Heathlands may have purple blooms of heathers, prickly yellow gorse and scarlet pimpernel.
When distant galaxies are moving away from us, the very, very, fast light waves they give off are stretched out behind them — since each bit of the light wave is being sent from a little bit further away.
When the light waves from distant galaxies are stretched out in this way, they look redder. This is called red shift.
Red shift was first described by Czech mathematician Christian Doppler in 1842.
Edwin Hubble showed that a galaxy’s red shift is proportional to its distance. So the further away a galaxy is, the greater its red shift — and the faster it must be zooming away from us. This is Hubble’s Law.
The increase of red shift with distance proved that the Universe is growing bigger.
Only nearby galaxies show no red shift at all.
The record red shift is 4.25, from the quasar 8C 1435 + 63. It is 96% of the speed of light.
Red shift can be caused by the expansion of the Universe, gravity or the effect of relativity (see Einstein).
Black holes may create large red shifts.
Red Shift occurs as distant galaxies red shifts so big that they must be moving move away from us. The further away a away from us at speeds approaching the speed of light!
Only 12 percent of the Earth’s ice-free land surface is suitable for growing crops – that is, about 13 billion hectares. The rest is either too wet, too dry, too cold or too steep. Or the soil is too shallow or poor in nutrients.
A much higher proportion of Europe has fertile soil (36 percent) than any other continent. About 31 percent is cultivated.
In North America 22 percent of the land is fertile but only 13 percent is cultivated, partly because much land is lost under concrete. Surprisingly, 16 percent of Africa is potentially fertile, yet only 6 percent is cultivated.
Southern Asia is so crowded that even though less than 20 percent of the land is fertile, over 24 percent is cultivated.
Dairy farms produce milk, butter and cheese from cows in green pastures in fairly moist parts of the world.
Mixed farming involves both crops and livestock as in the USA’s Corn Belt, where farmers grow corn to feed pigs and cattle.
Mediterranean farming is in areas with mild, moist winters and warm, dry summers – like California, parts of South Africa and the Mediterranean. Winter crops include wheat and broccoli. Summer crops include grapes and olives.
Shifting cultivation involves growing crops like corn, rice, manioc, and millet in one place for a short while, then moving on before the soil loses goodness.
Shifting cultivation occurs in forests in Latin America and Africa.
There are now over twice as many farm animals in the world as humans – over 14 billion.