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A buzzer is often constructed by running string through two of the holes on a large button and is a common and easily made toy. A buzzer (buzz, bullroarer, button-on-a-string) is an ancient mechanical device used for ceremonial purposes and as a toy. It is constructed by centering an object at the midpoint of a cord or thong and winding the ...
A buzzer or beeper is an audio signaling device, [1] which may be mechanical, electromechanical, or piezoelectric (piezo for short). Typical uses of buzzers and beepers include alarm devices , timers , train and confirmation of user input such as a mouse click or keystroke.
260 BC: Aristarchus of Samos proposes a basic heliocentric model of the universe. [61] 200 BC: Apollonius of Perga discovers Apollonius's theorem. 200 BC: Apollonius of Perga assigns equations to curves. 200 BC: Apollonius of Perga develops epicycles. While an incorrect model, it was a precursor to the development of Fourier series.
First signs of teeth in fish. Earliest Nautilida, lycophytes, and trimerophytes. 488–400 Ma First cephalopods [78] and chitons. [79] 395 Ma First lichens, stoneworts. Earliest harvestmen, mites, hexapods (springtails) and ammonoids. The earliest known tracks on land named the Zachelmie trackways which are possibly related to icthyostegalians.
This is an accepted version of this page This is the latest accepted revision, reviewed on 23 January 2025. Type of clock A traditional wind-up (key-wound), mechanical spring-powered alarm clock An alarm clock or alarm is a clock that is designed to alert an individual or group of people at a specified time. The primary function of these clocks is to awaken people from their night's sleep or ...
The Berlin Archaeopteryx, one of the earliest known birds. Around 350 BCE, Aristotle and other philosophers of the time attempted to explain the aerodynamics of avian flight . Even after the discovery of the ancestral bird Archaeopteryx which lived over 150 million years ago, debates still persist regarding the evolution of flight.
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The funnel model is the hypothesis that the most conserved stage of development (the phylotypic period) occurs at the beginning of embryogenesis, with increasing divergence as development progresses. This is also known as the early conservation model of development.