Science and Technology

The lowest temperature theoretically possible, corresponding to -459.67 degrees on the Fahrenheit scale and -273.15 degrees on the Celsius scale and it is 0 on the Kelvin temperature scale, which uses the same degrees as the Celsius scale.

Although absolute zero has not been reached, yet, the techniques of cryogenics, the technology for creating temperatures below -200 degrees Celsius, have come closer.

1. The rate of change of a moving body's velocity which has two components: speed and direction; so, a body's acceleration is altered by either a change in speed, a change in direction, or both.
2. The acceleration due to gravity, for instance, is 32 feet (9.8 meters) per second per second; means that for every second an object falls, its velocity is increasing, too.

Acceleration is measured by a device called an accelerometer, the basic component of which is usually a heavy mass that moves only in one dimension and is supported by springs.

The simplest accelerometer consists of just one weight and has a sliding electrical contact attached to it. As acceleration increases, the weight slips back and a higher voltage is generated; then, as acceleration decreases, the weight moves forward and a lower voltage is generated.

A storage battery which is, a group of rechargeable secondary cells; for example, the lead-acid car battery.

A Swedish astrophysicist who worked in spectroscopy and solar physics.

His writing titled Recherches sur le spectre solaire (1868) presented an atlas of the solar spectrum with measurements of 1,000 spectral lines expressed in units of one-ten-millionth of a millimeter, the unit which later became the angstrom or ångstrom.

A length equal to 10^-10 meters or one-ten-millionth of a millimeter, used for atomic measurements and the wavelengths of electromagnetic radiation.

A unit that measures the wavelength of light and equals 0.00000001 of a centimeter. Blue light has a wavelength of about 4400 angstroms, yellow light 5500 angstroms, and red light 6500 angstroms.

An English horologist. He first made his name as the maker of a very small half-quarter repeater for King George III, but later became known for his chronometers.

A "repeater" is a clock or watch that can be made to repeat its latest chime when someone presses a spring or it is also defined as a type of timepiece that has the ability, controlled by a button or a pull-cord, to repeat the last chime-hour struck.

An American astronomer, surveyor, and mathematician who published almanacs in 1792-1797.

In 1753, having studied only a pocket watch, Banneker constructed a striking clock, the first of it kind in America.

He took part in the survey that prepared the establishment of the U.S. capital, Washington, D.C.

A Swiss-born clockmaker and mathematician.

He was one of the first clock makers to use second hands, and Bürgi also introduced a mechanism for providing the escapement (a device which converts continuous rotational motion into an oscillating or back and forth motion) with a constant driving force.

In mathematics, he developed a comprehensive system of logarithms (about 30 years before the Scottish mathematician John Napier), but his work has been largely ignored.

His classification as a scholar is controversial because he lacked a formal education and did not know Latin, the only language of scholarly publications at the time, and because he left few written records of his work.

Historians of science claim that Bürgis legacy of many unique and innovative mechanical astronomical models should be considered an unorthodox method of "publishing" astronomical insights.

A Swedish astronomer, physicist, and mathematician who introduced the Celsius temperature scale.

In 1742, he presented a proposal to the Swedish Academy of Sciences that all scientific measurements of temperature should be made on a fixed scale based on two invariable and naturally occurring points.

His scale defined 0° as the temperature at which water boils, and 100° as that at which water freezes. This scale, in an inverted form devised eight years later by his pupil Martin Strömer, has since been used in almost all scientific work.

For more details, see Centigrade as well as this Thermometer and Temperature Scale page.

An instrument for measuring time precisely, originally used at sea.

It is designed to remain accurate through all conditions of temperature and pressure. The first accurate marine chronometer, capable of an accuracy of half a minute a year, was made in 1761 by the English horologist and instrument maker John Harrison.

The study of how systems evolve and learn, as well as how they manage themselves.

An MIT mathematician named Norbert Wiener (1895-1964) coined the term cybernetics defined the word, which he derived from the Greek (from which also comes the English word "govern"), as the science of communication and control in animals and machines.

Cybernetics referred to an understanding of the animal nervous system, suggesting that a person might consider the brain as a collection of individual neurons that behave much like the binary circuits of a digital computer.

Subsequent research showed that this concept was not correct, but the analogy had a strong effect on biologists, driving them toward a more mathematical and rigorous basis for their own work, and on computer engineers, leading them to think of their creations more as information processing machines than as electronic circuits.

In mechanical watches and clocks, a device which converts continuous rotational motion into an oscillating or back and forth motion or a mechanism that permits motion in only one direction, allowing power from a coiled spring or falling weight to turn gears connected to the hands.

Without the escapement, the system would simply unwind uncontrollably, but the escapement regulates this motion, controlled by the periodic swing of the pendulum or balance wheel.

It allows the gears to advance or "to escape" a fixed amount with each swing, moving the timepiece's hands forward at a steady rate.

A second function of the escapement is to keep the pendulum or balance wheel moving by giving it small pushes.

Polish-born Dutch physicist who invented the first accurate thermometer in 1724 and devised the Fahrenheit temperature scale.

Using his thermometer, Fahrenheit was able to determine the boiling points of liquids and found that they vary with atmospheric pressure.

His first thermometers contained a column of alcohol which expanded and contracted directly, as originally devised in 1701 by the Danish astronomer Ole Römer (1644-1710).

Fahrenheit substituted mercury for alcohol because its rate of expansion, although less than that of alcohol, is more constant and could be used over a much wider temperature range.

To reflect the greater sensitivity of his thermometer, Fahrenheit expanded Römer's scale so that blood heat was 90° and an ice-salt mixture was 0°; on this scale the freezing point was 30°.

Fahrenheit later adjusted the scale to ignore body temperature as a fixed point so that the boiling point of water came to 212° and the freezing point was 32°. This is the Fahrenheit scale that is still in use today.

For more details, see Centigrade as well as this Thermometer and Temperature Scale page.

An English horologist and instrument maker.

He made the first chronometers that were accurate enough to allow the precise determination of longitude at sea, and so permit reliable and safe navigation over long distances.