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2 He helium-4; Hoffer et al. 0.19085 g/cm 3 (from 20.9730 cm 3 /mole; hcp crystal melting to He-II superfluid at 0 K, 25.00 atm) : 0.19083 g/cm 3 (from 20.9749 cm 3 /mole; at local min. density, hcp melting to He-II: 0.884 K, 25.00 atm)
Some versions may be plated with other metals. Lead shot was originally made by pouring molten lead through screens into water, forming what was known as "swan shot", and, later, more economically mass-produced at higher quality using a shot tower. The Bliemeister method has supplanted the shot tower method since the early 1960s.
One improvised method for achieving the same effect involves pouring molten wax or tar into the mass of shot. [18] Another is a partial ring cut around the case intended to ensure the shot comes out tightly bunched along with the portion of the case forward of the cut, creating a 'cut-shell'. [ 19 ]
The Mach number (M or Ma), often only Mach, (/ m ɑː k /; German:) is a dimensionless quantity in fluid dynamics representing the ratio of flow velocity past a boundary to the local speed of sound.
The Space Shuttle Solid Rocket Booster (SRB) was the first solid-propellant rocket to be used for primary propulsion on a vehicle used for human spaceflight. [1] A pair of them provided 85% of the Space Shuttle's thrust at liftoff and for the first two minutes of ascent.
The first is the appearance of the hominin Australopithecus anamensis in the early Pliocene, around 4.2 million years ago. [58] [59] [60] The second is the appearance of Homo, the genus that includes modern humans and their closest extinct relatives, near the end of the Pliocene at 2.6 million years ago. [61]
These maria were formed when molten lava flowed into ancient impact basins. The Moon is, except when passing through Earth's shadow during a lunar eclipse, always illuminated by the Sun, but from Earth the visible illumination shifts during its orbit, producing the lunar phases. [18] The Moon is the brightest celestial object in Earth's night sky.
The 2020 Atlantic hurricane season was the most active Atlantic hurricane season on record, in terms of the number of systems. It featured a total of 31 tropical and subtropical cyclones, with all but one cyclone becoming a named storm.