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The idea of using atomic transitions to measure time was first suggested by the British scientist Lord Kelvin in 1879, [204] although it was only in the 1930s with the development of magnetic resonance that there was a practical method for measuring time in this way. [205] A prototype ammonia maser device was built in 1948 at NIST. Although ...
Unlike most other methods of measuring time, the hourglass concretely represents the present as being between the past and the future, and this has made it an enduring symbol of time as a concept. The hourglass, sometimes with the addition of metaphorical wings, is often used as a symbol that human existence is fleeting, and that the " sands of ...
The prehistory of Australia is the period between the first human habitation of the Australian continent and the colonisation of Australia in 1788, which marks the start of consistent written documentation of Australia. This period has been variously estimated, with most evidence suggesting that it goes back between 50,000 and 65,000 years.
This timeline of time measurement inventions is a chronological list of particularly important or significant technological inventions relating to timekeeping devices and their inventors, where known. Note: Dates for inventions are often controversial. Sometimes inventions are invented by several inventors around the same time, or may be ...
Before the coming of the railways in the 1840s, local time was displayed on a sundial and was used by the government and commerce. Before the invention of the clock the sundial was the only way to measure time. After the invention of the clock, the sundial maintained its importance, as clocks needed to be reset regularly from a sundial, because ...
There’s something almost magical about the way boomerangs arc through the air and return to the hand of the thrower. Watching them cut through the sky on their wide trajectories can provide ...
Australian-Aboriginal man David Unaipon is known as "Australia's Leonardo" for his contributions to science and the Aboriginal people. [1] His inventions include a tool for sheep-shearing, a centrifugal motor, a multi-radial wheel and mechanical propulsion device. Unaipon appears on Australia's $50 note.
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