1656-1742


English astronomer who was the first to accurately calculate the elliptical orbits of comets and to predict the returm of one, now called Halley's Comet.

In 1683, Halley published his theory of the variation of the magnet. In his three voyages during 1698-1701, Halley was to test his magnetic variation theory, after which he was to become a professor of Geometry at Oxford. At the age of 64, he invented the diving bell.
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Harvey, William

1578-1657


English physician, doctor to King Charles I of England. Famous as the discoverer of the circulation of the blood and the function of the heart as a pump.

Before Harvey the general assumption was that the movement of the blood was by ebb and flow derived from contracting of the arterial system. Harvey not only gave a correct explanation of the functioning of the heart but also estimated the total amount of blood in the body.

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Werner Karl
Heisenberg

1901-1976



German physicist who found a new way to formulate quantum mechanics.

His theory was based only on what can be observed, for example, on the radiation emitted by the atom. He maintained that we cannot always know the position of an electron in space at a given time. Mechanical quantities, such as position, velocity, etc. should be represented, not by ordinary numbers, but by abstract mathematical structures, or matrix equations.

Later Heisenberg stated his famous 'principle of uncertainty' - for that see Biography below.

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Hertz, Heinrich

1857-1894


German physicist who was the first to broadcast and receive radio waves.

Hertz expanded the electromagnetic theory of light developed by the British physicist Maxwell in 1884; Hertz proved that electricity can be transmitted in electromagnetic waves, which travel at the speed of light and which possess many other properties of light.

His experiments with these electromagnetic waves led to the development of the wireless telegraph and the radio. The unit of frequency that is measured in cycles per second was renamed the hertz.

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Zacharias
Janssen

1580-1638



Dutch maker of spectacles who invented the first compound microscope in 1590 (a compound microscope is one which has more than one lens).

The lens in the eyepiece was bi-convex (bulging outwards on both sides), and the lens of the far end (the objective lens) was plano-convex (flat on one side and bulging outwards on the other side). This advanced microscope had a 3 to 9 times power of magnification.

In 1608 he made the first telescope together with Hans Lippershey.

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Biography