In 1916 Brown University announced that it would soon offer a course teaching students about a new technology: practical and experimental wireless telegraphy. It was more common during this era to transmit messages by radio waves using Morse code. Voice communication and broadcast radio did not become common until the 1920s. Continue reading A fine aerial→
“In addition to helping the crew organize its time, the second HP-41 computer was kept ready for flight-critical, deorbit-burn calculations. Once during each orbit around the Earth, the shuttle has an opportunity to land at one of six contingency locations. During a routine flight, Mission Control supplies the shuttle crew with deorbit-burn information. Should the shuttle encounter an emergency, however, the astronauts would rely on the HP-41 for these calculations.”
– “HP-41’s Again Aboard Columbia.” HP Key Notes, March-May 1982.
To prepare an orbiting Space Shuttle for re-entry through the Earth’s atmosphere it is critical that the spacecraft be “balanced” by taking into account the mass of the fuel left in the tanks at the end of a mission. An astronaut would use a handheld computer or programmable calculator to determine how many minutes and seconds of fuel to burn to get the center of gravity correct for a smooth descent and landing. The “personal computing system” used for this was made by Hewlett Packard in the 1980s. NASA donated one of these, a model HP-41CV, to Ladd Observatory after the retirement of the Shuttle program. Continue reading Flight-critical calculator→
“This is truly scientific magic. Just think of it! You want to know the true time to the fraction of a second, and all you have to do in order to get it is to open your electric ear to these sounds, which seem to drop out of the sky, as if Old Time himself were speaking to you!”
During 1913 the Washington Naval Observatory and the Observatoire de Paris attempted to exchange wireless time signals. The experiment was used to calculate the difference in longitude between the two locations more accurately than was possible with other techniques. They were also trying to measure the velocity of radio waves through space. The goal was to improve communication with ships at sea which used the time signals to calibrate the chronometers used for celestial navigation. For most of the year atmospheric conditions prevented the reception of the signals sent across the ocean. The conditions improved in November and the two observatories were then in regular contact by radio. Prof. Winslow Upton of Ladd Observatory was listening in on the transmissions.
Prof. Winslow Upton tapped a telegraph key as he watched the planet Mercury transit the Sun. The signal was sent to a chart recorder where an electromagnet moved a pen on a slowing turning drum of paper to record the observation. The instrument is called a chronograph. This one was made by the Warner and Swasey Company of Cleveland in 1890. Primarily it was used for calibrating the astronomical regulators (precision pendulum clocks) to set the time accurately. It was also used for timing events such as lunar occultations of stars. Continue reading Timing the transit of Mercury, 1907→