E | F | G | H | I | J | K

E

egg

An egg is the sex cell produced by females. It contains half the full complement of chromosomes and will ultimately combine with a sperm at fertilisation. Females tend to produce only one egg at a time; eggs require a lot of resources because they contain food for the developing embryo.

electromagnetic rotations

An electric current flowing through a wire generates a magnetic field around the wire. When a current-carrying wire is placed between the poles of a magnet the two magnetic fields – one generated by the current and the other from the magnet – interact. At some places around the wire the magnetic fields cancel out, at other places they add up. The result is that the wire feels a force due to the unbalanced magnetic field, and is pushed out from between the magnet's poles.

This motion can be harnessed to form a very basic electric motor by making the wire into a 'C' shape and placing it between the poles of a magnet. As the electric current is passed through the wire, the magnetic fields interact. The bottom of the C is pushed in one direction out of the permanent magnet and the top is pushed in the other direction forcing the C to rotate.

element

An element is a substance that cannot be broken down into different chemicals. Gold, helium and iron are all examples of elements, each contains only one type of atom [see atoms]. There are less than 90 stable elements in the Universe, but by combining together in different ways they form other substances. For example, hydrogen and oxygen, two elements, combine to produce water.

E=mc²

This simple looking equation shows that matter and energy are equivalent – that they can be converted from one to another. The terms in the equation are E for energy, m for mass and c for the speed of light. The small 2 means that the speed of light has to be squared.

The equation tells you that if you had one kilogram of matter (anything will do) and you converted all of that mass into energy, you would end up with 9 x 10^16 (a 9 followed by 16 zeros) Joules of energy. This is enough energy to keep a 100 Watt light bulb burning for about 28 million years!

enzymes

Enzymes are proteins that are produced and used by organisms to change the rate of chemical reactions within the organism. The enzymes are unchanged at the end of the reaction. Different enzymes are specific to particular reactions.

F

fission

In naturally occurring radioactivity, the nucleus of an atom changes of its own accord by small stepwise amounts, either through ejecting small particles or by simply emitting energy. In nuclear fission, the nucleus of a heavy atom is bombarded with neutrons, causing it to become unstable. The unstable nucleus splits, forming two lighter atoms and releasing free neutrons and a vast amount of energy.

If all the atoms in 1kg of uranium²³⁵ [see uranium²³⁵] underwent fission it would release about 1 million times the energy obtained from burning 1kg of oil or coal.

flash photolysis

Flash photolysis is a method of investigating the mechanism of fast chemical reactions. A mixture of chemicals is subjected to a very short, intense burst of light, normally provided by a laser. This light provides enough energy to start the chemicals reacting with each other.

Immediately after the flash, the mixture of reacting chemicals can be studied to see what molecules and molecular intermediates are being produced.

flu

Flu, or influenza, is a viral infection that causes a fever, runny nose, cough, headache, muscle ache and a general feeling of illness or malaise. Whilst the symptoms sound similar to those of the common cold, flu can be a much more serious infection and can be fatal in the elderly, very young or those with compromised immune systems.

Flu can be spread by inhaling infected droplets that have been coughed or sneezed out by an infected person. It can also be caught by handling household items shortly after an infected person.

Since flu is a viral infection, it cannot be treated with antibiotics. The main treatment is to rest and drink plenty of fluids. There are vaccines available for flu and these are normally offered to those people most at risk of contracting flu or those who are at risk of becoming very ill if they are infected.

Fludd, Robert

Robert Fludd (1574-1637) was an English physician and astrologer who developed his own brand of mystic philosophy that opposed the reductive methods of science.

Fludd was deeply interested in the many forms of occult knowledge that existed in the 17th century. From these he synthesised a new philosophy that drew parallels between the workings of the human body and of nature. He emphasised a very holistic approach to treating illnesses, considering far more than just the physical body of the patient.

food poisoning

Food poisoning is a general term used to describe the symptoms of vomiting, diarrhoea, fever, loss of appetite, nausea and cramps that occur after eating contaminated food. Food poisoning can be caused by either bacterial or chemical contamination of food or water. In many cases, toxins produced by the growth of micro-organisms are the cause of the symptoms.

foot and mouth disease

Foot and mouth disease is a highly infectious viral disease which produces a fever and vesicles, or blisters, in the mouth and feet. It can be spread by direct or indirect contact with infected animals and the movement of animals, persons, vehicles and other objects, which have been contaminated by the virus.

The disease is very rare in humans and should not be confused with the unrelated human condition hand, foot and mouth disease.

More information can be found at: www.defra.gov.uk/footandmouth/about/index.htm

fuels the Sun

The Sun is powered by nuclear fusion [see fusion] reactions that take place at its core. The centre of the Sun is extremely hot, over 10,000,000°C. This gives the hydrogen nuclei enough energy to collide with each other and to fuse together.

At its core, the Sun converts hydrogen into helium, releasing stupendous amounts of energy in the process. Every second the Sun converts 4,000,000 tonnes of hydrogen nuclei into helium nuclei producing light and heat energy.

fusion

In a fusion reaction, the nuclei of two lighter atoms fuse together to form a heavier atom, releasing energy. This is in contrast to nuclear fission [see fission] where very heavy nuclei are split in two.

Two nuclei strongly repel each other, so it is very hard to force them close enough together to react. Very high temperatures are needed, such as those found in the centre of the Sun. On Earth, a fusion bomb can be created by initiating the reaction with a small fission bomb. The reaction cannot yet be controlled cheaply enough to provide power in a fusion reactor.

G

Galilei, Galileo

Galileo Galilei (1564-1643) was an Italian astronomer, mathematician and physicist who developed the modern scientific method, uniting experimental evidence with the power of mathematics.

One of the first to view the sky with a telescope, Galileo made many discoveries including the existence of moons around Jupiter and that the Milky Way is composed of a myriad of stars. He also investigated how objects move under the influence of forces and developed mathematical solutions to these problems.

Galileo's heavenly observations and understanding of moving bodies led him to believe in the Copernican model of the Universe [see Nikolai Copernicus] and into conflict with the Church. He spent the last years of his life under house arrest.

genetics

Biology is a large subject that can be divided into a number of specialised topics. Genetics is the part of biology that deals with genes – the unit of heredity information found in our cells. It also deals with how and why living things vary.

genes

Genes are the unit of heredity information found in our cells. They are portions of DNA that contain the information needed to produce proteins, the body's building blocks.

glanders

Glanders is a contagious disease of horses, mules and donkeys caused by the bacterium Actinobacillus mallei. It can also be transmitted to humans who come in to contact with infected animals.

The symptoms of glanders include the formation of lumps or nodules in the Nasal passages, lungs and on the skin which gradually enlarge to form pus filled ulcers.

There is no completely effective treatment for glanders and it often results in death in both horses and humans. To control outbreaks of the disease, infected animals are destroyed.

gynaecology

Gynaecology is the branch of medicine that deals with diseases and conditions specific to women. Doctors who specialise in gynaecology are called gynaecologists.

H

Harvey, William

William Harvey (1578-1657) was an English physician who demonstrated how the blood circulates around the body, and the role of the heart as a pump.

Until the 16th century, most knowledge of how the human body worked was derived from the works of Galen, a Greco-Roman physician from the 2nd century AD. Vesalius [see Andre Vesalius] added new knowledge of anatomy, but many mechanisms of the human body were still unknown.

Harvey studied with Italian anatomists interested in the nature of the heart, blood and veins. By employing a new, rigorous scientific method of experimentation he was able to demonstrate how the blood circulated around the body.

heredity

The biological similarity between parents and their children is due to heredity. It is the transmission of genes which carry information about individual characteristics (eg the shape of your nose) from one generation to the next.

high resolution x-band radar

Radar (radio detection and ranging) systems use pulses of radio waves to measure distance and track moving objects. Amongst other things, radar is routinely used to track weather systems and in air traffic control.

Radio waves have a large spread of frequencies (3kHz-300GHz) and different radar systems use different frequencies depending on what they are tracking and what resolution is needed – the higher the frequency, the greater the resolution. X-band radar uses radio waves in the frequency range 8-12GHz leading to a high resolution. This means it can distinguish between two objects much closer together than a radar system using, for example, 1-2GHz radio waves.

Human Genome Project (HGP)

The Human Genome Project is a 13-year international project which began in October 1990 involving 20 institutions located in France, Germany, Japan, China, UK and USA. The objectives of this project are: to discover all the human genes and make them accessible for subsequent research; to work out the order of the estimated 3.2 billion DNA subunits that make up the genes; and to interpret the function of the human genome by also studying simpler organisms such as the bacterium E. coli.

The Sanger Centre, located near Cambridge and funded by the Wellcome Trust, is providing the UK's contribution to the project.

hydrochloric acid

Hydrochloric acid, known as spiritus salis (spirit of salt), was the last mineral acid the alchemists learned to prepare. It could be obtained by distilling common salt with nitric acid, and dissolving the gases in water.

Today hydrochloric acid has thousands of uses, from cleaning metals surfaces and synthesising plastics, to dissolving bones to make gelatine.

I

impregnated

The term impregnated refers to the transfer of sperm from the male body into the female body, or to a fertilised egg successfully implanted in to the womb of a female.

in vitro fertilisation (IVF)

IVF is a clinical procedure where eggs are removed from a woman's ovaries and fertilised with semen outside the body (in vitro). Contrary to popular belief, this is done in a petri dish rather than a test tube. Once the eggs have successfully been fertilised, one or more of the fertilised eggs are implanted in the woman's womb. Fertilisation normally occurs in the fallopian tube inside the body (in vivo).

K

Kepler, Johannes

Johannes Kepler (1571-1630) was a German astronomer and astrologer. His three laws of planetary motion described how the planets orbit the Sun, recognising that they do not move in perfect circles.

From early in his career Kepler believed in the controversial Copernican model of the Universe [see Nikolai Copernicus]. However, the new system could still not neatly account for all the motions of the planets.

Kepler had access to the superb astronomical observations of Tycho Brahe, which allowed him to show that the planets moved in ellipses rather than in circles. This was a profound leap in thinking, as people believed that all objects in the heavens were perfect, and so moved in perfect circles.

kinetic kill

Kinetic kill devices use their kinetic energy and speed of impact to disable or destroy targets rather than explosives.