The technology of record players is all based on sound vibrations recorded physically into grooves of a vinyl disc. The delicate needle, or stylus, reads these vibrations and translates them into sound through the arm of the player.
Thomas Edison’s 1877 phonograph was the earliest example of this method of recording and reproducing sound. It was the first machine to use flat disc records, initially made of rubber, which could be rotated and played on the device using a hand crank.
Though records were subsequently made from shellac, then polyvinyl chloride, the basic principles remained. The turntable rotates the vinyl with either a belt drive or direct-drive system, reducing the noise of the motor.
The etchings of the vinyl form a gradual spiral in toward the centre, which the stylus follows as the record turns, picking up the thousands of miniscule bumps and translating them into good vibrations. So, the next time you put on a Kool and the Gang record, you’ll literally be hearing something groovy.
Launching a rocket takes years of planning, and the most important element is the launch pad and its attendant facilities. The launch pad cradles, fuels and powers the rocket, before it is unleashed. In the case of NASA’s Space Shuttle, its rocket motors produced 3.2 million kilograms (7 million pounds) of thrust at launch.
The corrosive exhaust and intense flames from the engines were channelled through a horizontal V-shaped flame trench, which consisted of two 453,600-kilogram (1 million-pound) deflectors made from steel coated with 12.7 centimetres (five inches) of heat-resistant Fondu Fyre concrete, which flakes off to disperse the intense heat.
The Space Shuttle was assembled on a moving launch platform (MLP) at the nearby vehicle assembly building (VAB) and taken to the launch pad on top of a crawler transporter. At the pad, a fixed service structure (FSS) has a lift to gain access to any level of the rocket. Anchored to it is the rotating service structure (RSS) that comprises a clean room used to load the rocket’s cargo.
It took at least a month for 170 technicians and specialists to prepare, check and launch the Space Shuttle, though for less complex, unmanned rockets the timescale is a matter of days. During the countdown, all links between the FSS and the rocket were systematically released, and lastly at blast-off explosive bolts free the shuttle from the MLP.
To protect the delicate components of the vehicle and the pad itself, the MLP is flooded with water at a rate of 3.4 million litres (900,000 gallons) per minute to suppress the damaging sound waves and heat produced by the engines.
Transmissions play a fundamental role in the process of moving a vehicle. A car’s transmission is connected to the engine and serves to transmit’ the power generated there to the wheels that drive it. Within this, gears reduce the number of revolutions of a crankshaft, ensuring more effective use of the engine’s torque.
When a car is in neutral power from the engine is driving the transmission input shaft, in turn rotating some parts in the transmission on idle. However, once first gear is selected to go forwards or reverse to go backwards, the clutch is depressed, disengaging the input shaft from the engine. Due to inertia, the input shaft could still spin for some time however, meaning certain parts of the transmission will be spinning too fast to interlock with the gears.
A clutch brake works by fixing to the input shaft on a manual gearbox, acting as a source of friction between the release bearing and transmission bearing retainer cap, reducing the input shaft’s rate of rotation and slowing the spinning inside the gearbox. This allows for the gears to ‘mesh’ effectively without any significant grinding or clashing. Clutch brakes are instrumental in avoiding excessive wear of those all-important inner transmission components.
There are three common types of clutch brake found in vehicles: a one-piece clutch brake, a two-piece ‘hinged’ clutch brake and a torque. limiting clutch brake. The one-piece variety can only be installed with the transmission removed from the vehicle, so it can go over the circular input shaft. Its thick plate provides a good friction surface to slow the input shaft when it’s spinning. A two-piece hinged clutch brake on the other hand, can be installed with the transmission in place by hinging and then fixing around the input shaft. Finally, a torque-limiting clutch brake is used for more heavy-duty applications and features a hub with washers that slip under a certain amount of torque, ensuring the smooth engagement of gears in the transmission.
Eclipses are among the most spectacular astronomical events you can see. They occur when the Earth, Moon, and Sun all line up so that the Earth casts a shadow on the Moon or the Moon casts a shadow on the Earth. The Sun or Moon appear to go dark to people standing inside these shadows.
The Moon passes between the Sun and Earth every month at “new Moon,” but because its orbit is slightly tilted it usually does not pass directly in front of the Sun. Occasionally, however, it does move directly in front of the Sun and causes a solar eclipse. Although the Sun is 400 times wider than the Moon, by a curious coincidence it is also 400 times farther away. As a result, when viewed from Earth the Moon’s disk fits exactly over the Sun’s disk during a total solar eclipse.
Shadow play A total solar eclipse can be seen only from the center of the Moon’s shadow—the umbra. The umbra sweeps across Earth during an eclipse, tracing a path thousands of miles long but no more than 60 miles (100 km) wide. Outside the umbra, the Moon casts a partial shadow causing a partial solar eclipse
LUNAR ECLIPSES Two or three times a year, the Moon passes through Earth’s enormous shadow and a lunar eclipse occurs. Surprisingly, the Moon does not become completely black. Some sunlight is refracted (bent) by Earth’s atmosphere and makes the Moon turn orange-red, like a red sunset. Lunar eclipses are easier and much safer to see than solar eclipses, since anybody with a view of the Moon can see them.
When day becomes night A total solar eclipse occurs about every 18 months. If you are in the right place to see one, it is an amazing experience. As the last rays of sunlight are eclipsed, darkness falls, stars appear, and day turns to twilight. All that can be seen of the Sun is its hazy outer atmosphere.
For millennia, would-be aviators knew bird flight had something to do with wing structure. As it turns out, the shape of a wing is optimised to generate lift, an upward force caused by manipulating airflow. A wing has a rounded leading edge with a slight upward tilt, a curved topside, and a tapered trailing edge pointing downward. This shape alters the flow of air molecules into a downward trajectory. This results in – as Newton put it in his Third Law of Motion – “an equal and opposite reaction.” When the wing pushes the air molecules down, the molecules push the wing up with equal force. The airflow also creates a lower pressure area above the wing, which sucks the wing up.
Constructing wings is the easy part. To fly, you need to generate enough forward force – or thrust – to produce the necessary lift to counteract gravity. The Wright Brothers accomplished this by linking a piston engine to twin propellers. A plane propeller is simply a group of rotating wings shifted 90 degrees, so the direction of lift is forwards rather than upwards. In 1944, engineers upgraded to jet engines, which produce much greater thrust by igniting a mixture of air and fuel, and expelling hot gasses backward
A pilot controls a plane by adjusting movable surfaces on the main wings, as well as smaller surfaces and a wing-like rudder on the tail. By changing the shape and position of these structures, the pilot varies the lift force, acting on the different ends of the plane to essentially pivot the plane along three axes: its pitch (up or down tilt of the nose), roll (side to side rotation), and yaw (turn to the left or right).
Engineers keep planes as light and aerodynamic as possible. Modern fighter jets are manufactured from super-strong, lightweight composite material, applied in layers to form precise, aerodynamic shapes.