Respect the Earth and the life it nurtures. #EarthDay

#OTD December 31, 1999 Ellie Arroway became the first human to make Contact with an extraterrestrial intelligence. She traveled aboard "The Machine" whose plans were received while she searched for signs of intelligent life by listening to radio static from space for "Patterns in the Chaos" #SciFi

#OTD Dec 29, 1888 the Great Nebula in Andromeda (the Andromeda Galaxy), was photographed by Isaac Roberts with a 20" reflector & 4 hour exposure. It revealed the nebula was a spiral, unexpected at the time. Photos such as this changed astronomy by revealing the form of nebulae and clusters #histsci

#OTD Dec 27, 1831 The HMS Beagle set sail from Plymouth harbor with 22 year-old Charles Darwin as the ship's unpaid naturalist. His 5 year voyage of scientific discovery led him to develop the theory of biological evolution through natural selection #histsci

#OTD December 24, 1968: Apollo 8 astronauts Frank Borman, Jim Lovell, and Bill Anders became the first humans to orbit the Moon, and the first to witness an "Earthrise" #histtech #space

#OTD Dec 23, 1947 the transistor was first demonstrated at Bell Labs by Walter Brattain & John Bardeen. The PNP germanium transistor worked to amplify a microphone & headphones. In 1956 Brattain, Bardeen & William Shockley received the Nobel Prize for discovery of the transistor effect. #histtech

#OTD December 22, 1968. The first US live TV broadcast from a manned spacecraft in space. The crew of Apollo 8 held six live telecasts during the mission to orbit the moon for the first time. #histtech #space www.youtube.com/watch?v=x1F4...

#OTD 50 years ago, the Altair 8800 microcomputer kit went on sale. It was the first commercially successful personal computer and began the 1970s computer revolution. It had no video output and was programed via switches or terminal, later using Micro-soft's first product, Altair BASIC #histtech

#OTD Dec 18, 1958 First communication satellite launched. SCORE Signal Communication by Orbiting Relay Equipment was built in an Atlas B rocket & it's body served as the antenna. It was the 1st successful use of an Atlas as space launch vehicle & 1st broadcast of a human voice from space. #histtech

#OTD Dec 17, 1903, the Wright Flyer built by Orville and Wilbur Wright made the first sustained and controlled heavier-than-air, powered flight. It traveled 120ft/36.6m in 12 seconds with Orville lying down operating a wing-warping mechanism with his hips. #histtech

#OTD Dec 16, 1912 the world's first stamp to depict an airplane was issued in the U.S. It was a 20-cent Parcel Post stamp, with carmine rose red ink, titled “Aeroplane Carrying Mail” with a drawing of a biplane. #histtech

#OTD Dec 14, 1972 the last humans on the moon left the lunar surface to return to the earth aboard Apollo 17. No one has yet returned.

#OTD Dec 13, 1962 Experimental communications satellite Relay 1 launched on a Delta B rocket. It provided communications between North & South America & Europe. It was the first satellite to transmit television across the Pacific. Developed by RCA, it worked till 1965 and remains in orbit #histtech

#OTD Dec 12, 1901 The first transatlantic radio signal was received by Marconi at Signal Hill in Newfoundland, Canada using a wire antenna flown by a kite. Morse code letter "S" was transmitted from 3,500 km away at Poldhu, Cornwall England by a ~12 kW spark gap transmitter on ~500 kHz. #histtech

#OTD December 12, 1961 The first amateur radio satellite OSCAR 1 launched on a Thor-Agena from Vandenberg AFB. It transmitted "HI' in morse code at 140mW on 144.983MHz. First of 164 amateur satellites so far, there are currently 18 operational used to communicate worldwide. #HamRadio #histtech

#OTD Dec 11, 1911 Marie Curie became the first person to receive a 2nd Nobel prize. This prize was for her individual achievements in Chemistry, whereas her first prize in Physics, (shared with Pierre Curie & Henri Becquerel) was for contributions in the discovery of radium & polonium. #histsci

#OTD Dec 10, 1922 Nobel Prize in Physics awarded to Niels Bohr for contributions to understanding atomic structure, radiation & quantum theory. He theorized energy levels of electrons are discrete & revolve in stable orbits around the nucleus, but can jump from one energy level to another. #histsci

#OTD Dec 7, 1972 The Blue Marble photo of Earth was taken by the crew of Apollo 17. The image released during a surge in environmental activism in the 1970s, became a symbol of the environmental movement. A depiction of Earth's fragility, vulnerability, and isolation amid the vast expanse of space.

#OTD December 7, 1934 Wiley Post discovered the jet stream while flying in the stratosphere in an unpressurized plywood plane. He helped B.F. Goodrich develop a pressurized flying suit, forerunner of the space suit, made of rubberized fabric with an aluminum helmet pressurized to 0.5 bar.

#OTD Dec 6, 1882 The transit of Venus across the sun was photographed on a series of glass plates by David Peck Todd using a solar telescope on the summit of Mount Hamilton. Venus transits were predicted by Johannes Kepler in 1627 and occur in eight-year pairs with gaps of 100+ years between pairs.

#OTD Dec 5, 1969 The initial four-node ARPANET network was established. The precursor of the Internet, the network connected four universities: the University of California, Los Angeles, Stanford Research Institute, U.C. Santa Barbara and University of Utah, using 50-kilobit-per-second phone lines.

#OTD Dec 2, 1942 Enrico Fermi and his team demonstrated the first self-sustained nuclear chain reaction. They built a lattice of 57 layers of uranium and uranium oxide embedded in graphite blocks underneath the football stands at the University of Chicago. It ran for 4.5 minutes at about 0.5 watts.

#OTD Nov 30, 1609 Galileo pointed his telescope at the moon and made drawings of the irregularities of the surface. It was the first time the moon had been realistically depicted. He made watercolor sketches from the drawings which were engraved for his revolutionary book "Starry Messenger"

#OTD Nov 29, 1924 100 years ago, the first wireless photograph, a “Radiophoto” was transmitted from New York to London on 1.3 Mhz. A photograph was placed on a rotating drum and a photoelectric cell converted the shades of light and dark into electric signals that could be transmitted via radio.

#OTD November 28, 1929 Commander Richard Byrd began the first flight to reach the South Pole. A four person crew flew a Ford Trimotor aircraft from “Little America” base on the Ross Ice Shelf for an 18hr round trip. They navigated by the sun as magnetic compasses don't work near a Pole.

#OTD Nov 28, 1967 The first pulsating radio source (pulsar) was detected by graduate student Jocelyn Bell, at the Mullard Radio Astronomy Observatory, Cambridge, England. The radio telescope consisted of a rectangular array of 2,048 full-wave dipoles arranged in 16 rows of 128 elements on 4.4 acres.

#OTD November 27, 1885 The first photo of a meteor trail was taken by Austro-Hungarian astronomer Weinek László in Prague, Czechoslovakia. Part of the Andromedids meteor shower, it's also called the Bielids because it was caused by Comet Biela. Observers reported seeing one meteor/second.

#OTD November 26, 1965 France became the third country to launch a satellite on its own rocket. Astérix launched on a Diamant A rocket from CIEES launch site in Algeria to an orbit of 527km/327mi x 1,697km/1,054 mi. Named for a French comics character it still remains in orbit today.

#OTD Nov 25, 1915 Albert Einstein presented his final paper on the theory of general relativity to the Prussian Academy of Sciences.

#OTD Nov 24 1859 The Origin of Species by Charles Darwin, was first published in England. He presented his idea that species are the result of a gradual biological evolution in which nature encourages, through natural selection, the propagation of those species best suited to their environments.

#OTD Nov 22, 1935 Pan American Airways China Clipper began the first commercial aircraft crossing of the Pacific. It took off from San Francisco with 111,000 letters on board and landed in Manila 59 hours, 48 minutes later. Overnight stops included Honolulu, Midway, Wake Island, and Guam.

#OTD November 21, 1877 Thomas Edison announced his invention of the first "talking machine." A needle indented grooves in a foil covered cylinder to record sound. Phonographs and wax coated cylinders of music were mass produced for years until the flat disk record became standard.

#OTD Nov 20, 1998 Zarya the first module of the ISS launched on a Russian Proton rocket. It had a mass of 19,323kg / 42,600lbs, length 12.56m / 41.2ft, diameter 4.11m / 13.5ft, and habitable volume of 46,722 liters / 1,650 cubic feet. It was joined two weeks later by the Unity module from the U.S.

#OTD Nov 18, 1850 US patent was issued to Friedrich Langenheim for Magic Lantern slides made of glass. He and his brother Ernst invented the first photographic lantern slides in 1848. Magic Lanterns were an early type of image projector used for education and entertainment until the mid-20th century

#OTD November 17, 1967 Surveyor 6 became the first spacecraft to launch from the moon. After landing at Sinus Medii on November 10, it's engines were restarted and burned for 2.5 seconds to a height of 12ft/4m, and west 8ft/2.5m. It successfully soft landed again and continued functioning.

#OTD 50 years ago, a message was intentionally sent to space for alien civilizations to receive by the Arecibo radio telescope. Designed by Frank Drake, it took three minutes to send 1,679 bits at a frequency of 2,380 MHz, modulated by shifting the frequency by 10 Hz, with a power of 450 kW.

Searching for signs of intelligent life...