ALL
TIME KEEPING DEVICES depend on counting a regularly -repeated
.phenomenon .The earliest devices were based on daily ,monthly,
or yearly cycles of the sun and moon .Most modern clocks are
based on repeated mechanical or electronic oscillations
(vibrations). The more frequent the vibrations, the greater the
potential accuracy of the clock.The crystal in the quartz watch
typically vibrates at 32,768 hertz.(32,768 times a second), so
it keeps better time than a pendulum clock ,whose pendulum
typically swings twice a second .
The most accurate timekeeping devices are atomic fountains ,which are based on oscillations of caesium atoms .Global communication technologies , such as computer networks and broadcasting, rely on the world using one accurate time standard.This is called UCT.(UNIVERSAL COORDINATE TIME),and is based on the average time signal received from over 200 atomic clocks worldwide .The more we rely on high technologies for precise timekeeping ,the more vulnerable we become to problems with that technology.
THE ATOMIC FOUNTAIN.
At present ,the most accurate timekeeping device ,is the atomic fountain.It was developed by Nobel Prize-winning scientists in the early 1990s and is far more accurate than a standard atomic clock.The atomic fountain enable us to measure time with greater accuracy , mainly because it uses cooler ,slower-moving atoms than an atomic clock.Atomic fountain devices are accurate to within one ten-billionth of a second per day.
PENDULUM CLOCK.
In the 16th century , the Italian scientist Galileo Galilei used the regular swing of a pendulum to measure periods of time .He suggested that a pendulum could be connected to the hands of a clock to turn them in WE CAN NOT SEE AIR, BUT it is not just empty space .Air is a mixture of many gases.Air exerts pressure on us,but does not crush us .In principle ,we are living on the floor of a kilometer -thick ocean of air known as the air cover or the atmosphere of the Earth.Since ,air is a matter ,it can also carry things ;leaves, in autumn ,birds,aircraft,hot air balloons,and many more things .However ,all objects need propulsion to lift from the ground-birds beat their wings, Aircraft depends on propellers or jet engines. FLYING OF AIRCRAFT- Air crafts need a combination of procedures to fly in the air .They need a propulsion system- a propeller or jet engine .They also need a lift , which comes from wings .While flying , the forward thrust causes the air to flow at great speeds along the wings.The curved shape of the wings and their slightly tilted position give rise to a low pressure above the aircraft and high pressure below it ..This is how the aircraft is pushed upwards .The pressure difference thus generates a buoyancy ,which is greater than the weight of the aircraft ,which pulls it down .The aircraft will fall if the buoyancy is less. HOT AIR BALLOON FLOATS IN THE AIR.- Air at 90 degree centigrade filled in the hot air balloon .The hot air keeps the balloon in the air because its density is lower than that of the surrounding cold air .Before starting the balloon , a gas burner is ignited below the opening of the huge balloon cover and the flames heats up the air in the balloon .When the balloon is rises to the desired height , the burner is switched off, if one wants to the further , it is started again .The balloon must have a minimum size so that it can over come the force of gravitational attraction of the Earth.Thus hot air balloon are able to float in air . PROPELLER WORKS BY SCOOPING AIR. A PROPELLER, IN an aircraft scoops air , as it scoop water in a ship., as in a wind mill,the blades of a propeller are arranged in the form of a star around a rotating shaft..They are shaped and aligned in such a way that the air falls diagonally on them and flows along them .This create a strong air flow that gives the aircraft the required thrust..This principle is used not just by smaller aircraft but also by hovercrafts which can travel over meadows or frozen water. CANDIES ARE SERVED BEFORE AN AIRCRAFT TAKES OFF.-This is because when an aircraft takes off ,some passengers experience a crackling sound in the Ears or get earache .The reason is that the inner ear does not adapt itself quickly to the lower air pressure caused by the take off.A simple candy helps in avoiding this discomfort because while sucking a candy , we need to swallow often .This helps the small muscles to expand the connection between the ear and the nose .In a way , they are ventilated. This leads to a quicker adaption of the inner ear to the outer air pressure and reduce the pain. WE ARE NOT CRUSHED BY THE AIR PRESSURE.-The air exerts pressure on us .The reason why we are not crushed by the air pressure is that the same air pressure is also present in the hollow cavities of our body :in the lungs and in the tiny chambers of our bones.With the same pressure in and around us , we do not feel the weight of the air at all. FACTS- The normal aircraft cannot fly in outer space .Because there is no air in space to generate lift on the wings there will be no buoyancy to overcome the force of gravity acting downwards. HOT AIR BALLOONS PROPELLER AIR CRAFT FUNCTION regular steps.
MEASURING TIME
The most accurate timekeeping devices are atomic fountains ,which are based on oscillations of caesium atoms .Global communication technologies , such as computer networks and broadcasting, rely on the world using one accurate time standard.This is called UCT.(UNIVERSAL COORDINATE TIME),and is based on the average time signal received from over 200 atomic clocks worldwide .The more we rely on high technologies for precise timekeeping ,the more vulnerable we become to problems with that technology.
THE ATOMIC FOUNTAIN.
At present ,the most accurate timekeeping device ,is the atomic fountain.It was developed by Nobel Prize-winning scientists in the early 1990s and is far more accurate than a standard atomic clock.The atomic fountain enable us to measure time with greater accuracy , mainly because it uses cooler ,slower-moving atoms than an atomic clock.Atomic fountain devices are accurate to within one ten-billionth of a second per day.
PENDULUM CLOCK.
In the 16th century , the Italian scientist Galileo Galilei used the regular swing of a pendulum to measure periods of time .He suggested that a pendulum could be connected to the hands of a clock to turn them in WE CAN NOT SEE AIR, BUT it is not just empty space .Air is a mixture of many gases.Air exerts pressure on us,but does not crush us .In principle ,we are living on the floor of a kilometer -thick ocean of air known as the air cover or the atmosphere of the Earth.Since ,air is a matter ,it can also carry things ;leaves, in autumn ,birds,aircraft,hot air balloons,and many more things .However ,all objects need propulsion to lift from the ground-birds beat their wings, Aircraft depends on propellers or jet engines. FLYING OF AIRCRAFT- Air crafts need a combination of procedures to fly in the air .They need a propulsion system- a propeller or jet engine .They also need a lift , which comes from wings .While flying , the forward thrust causes the air to flow at great speeds along the wings.The curved shape of the wings and their slightly tilted position give rise to a low pressure above the aircraft and high pressure below it ..This is how the aircraft is pushed upwards .The pressure difference thus generates a buoyancy ,which is greater than the weight of the aircraft ,which pulls it down .The aircraft will fall if the buoyancy is less. HOT AIR BALLOON FLOATS IN THE AIR.- Air at 90 degree centigrade filled in the hot air balloon .The hot air keeps the balloon in the air because its density is lower than that of the surrounding cold air .Before starting the balloon , a gas burner is ignited below the opening of the huge balloon cover and the flames heats up the air in the balloon .When the balloon is rises to the desired height , the burner is switched off, if one wants to the further , it is started again .The balloon must have a minimum size so that it can over come the force of gravitational attraction of the Earth.Thus hot air balloon are able to float in air . PROPELLER WORKS BY SCOOPING AIR. A PROPELLER, IN an aircraft scoops air , as it scoop water in a ship., as in a wind mill,the blades of a propeller are arranged in the form of a star around a rotating shaft..They are shaped and aligned in such a way that the air falls diagonally on them and flows along them .This create a strong air flow that gives the aircraft the required thrust..This principle is used not just by smaller aircraft but also by hovercrafts which can travel over meadows or frozen water. CANDIES ARE SERVED BEFORE AN AIRCRAFT TAKES OFF.-This is because when an aircraft takes off ,some passengers experience a crackling sound in the Ears or get earache .The reason is that the inner ear does not adapt itself quickly to the lower air pressure caused by the take off.A simple candy helps in avoiding this discomfort because while sucking a candy , we need to swallow often .This helps the small muscles to expand the connection between the ear and the nose .In a way , they are ventilated. This leads to a quicker adaption of the inner ear to the outer air pressure and reduce the pain. WE ARE NOT CRUSHED BY THE AIR PRESSURE.-The air exerts pressure on us .The reason why we are not crushed by the air pressure is that the same air pressure is also present in the hollow cavities of our body :in the lungs and in the tiny chambers of our bones.With the same pressure in and around us , we do not feel the weight of the air at all. FACTS- The normal aircraft cannot fly in outer space .Because there is no air in space to generate lift on the wings there will be no buoyancy to overcome the force of gravity acting downwards. HOT AIR BALLOONS PROPELLER AIR CRAFT FUNCTION regular steps.
MEASURING TIME
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