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00:00The Universe. Our universe is a large and unimaginable expanse of atomic dust, gas,
00:13stars, dust clouds, galaxies, planets and all living creatures including us. Stars
00:32and galaxies are just a tiny part of the total mass of the universe. Although nobody knows
00:41for sure how the universe began, evidence suggests that it started with an explosion
00:48of energy known as Big Bang.
00:56Galaxy Galaxies are huge star systems made up of
01:03stars and large amounts of gas and dust held together by gravitational attraction. Our
01:13solar system comprising the 8 planets including planet earth, their moons, asteroids, comets
01:23and meteoroids orbiting the sun is a part of the Milky Way galaxy. There are millions
01:32of such planetary systems in our Milky Way. There are millions of such galaxies in the
01:40universe. Do you know? Scientists keep observing, researching and guessing based on the clues
01:51left behind from the birth of our universe.
01:58Stars The skies overhead are filled with stars,
02:05some near and bright, others further away and dim. Stars are gigantic glowing balls
02:14of gases, mostly hydrogen and helium. They have a lot of energy that heats them up and
02:25this is what we see as light from the stars. Since they are very very far from us, light
02:34from them takes a long time to travel, ranging from a few years to a million years. The colour
02:43of a star's light indicates how hot it is, with blue being the hottest.
02:55We know that the solar system consists of 8 planets, their moons and other heavenly
03:04bodies such as asteroids, comets, meteors, planetoids etc. The sun with all the heavenly
03:17bodies that revolve around it form the solar system.
03:24Nearest to the sun are four fairly small rocky planets, Mercury, Venus, Earth and Mars. Beyond
03:38Mars is the asteroid belt with millions of rocky objects. On the far side of the asteroid
03:47belt are the four gas giants, Jupiter, Saturn, Uranus and Neptune. Even though these planets
04:01are much bigger than our earth, they are extremely light in weight for their size.
04:08Until recently the furthest known planet was an icy world called Pluto. Many scientists
04:18have argued that it is too small to be called a true planet. It is now called a dwarf planet.
04:29The Sun The sun is a huge ball of gas and fire which
04:36gives us heat and light. As it is a part of our solar system, it is also the nearest star.
04:47The gravitational force of the sun holds all the objects of the solar system together and
04:53makes them orbit around itself. It is the center of our solar system.
05:03Planets Each planet in our solar system has its own
05:09features which includes the distance from the sun, the number of moons etc. Even the
05:17year and the day are different. Here are some features of each planet in our solar
05:25system. Mercury is the closest to the sun. It is
05:33also the smallest planet of the solar system. Venus is the hottest planet as its atmosphere
05:44retains all the heat of the sun. Next is the planet earth which has water
05:54and an atmosphere which supports life. Mars the red planet lies forth from the sun.
06:07It gets its red color from the mineral iron that is present in abundance on its surface.
06:18Next four planets Jupiter, Saturn, Uranus and Neptune comprise more of gaseous matter
06:29than solid rocks and are thus called the gas giants.
06:37Jupiter is the largest planet in the solar system. Saturn is the second largest planet
06:47after Jupiter and has rings around it that are composed of ice, rocks and dust. Some
06:59of the rings can be seen from the earth through a telescope. Uranus and Neptune are much smaller
07:10than the other two gas giants. Uranus is the third largest planet. Approximately four times
07:22the size of the earth. Neptune is the farthest from the sun.
07:32Let us look at the number of moons each planet has. Mercury and Venus have no moons. Earth
07:46has one and Mars has two. Among the outer planets Jupiter has 79, Saturn has 53, Uranus
07:59has 27 and Neptune has 13.
08:11Planets closer to the sun have shorter years as their orbit is shorter. Planets away from
08:19the sun take longer to orbit so they have longer years. Based on earth�s day and year,
08:28a day and year of other planets are estimated as shown here.
08:40Asteroids are smaller rocky bodies that are present in the asteroid belt between Mars
08:46and Jupiter. They are sometimes also called �minor planets� as they are smaller than
08:55the planets. Due to their size, they do not have enough gravity to pull themselves together
09:04to form a planet. Scientists believe that these are either remains of a planet between
09:12Mars and Jupiter which for some reason exploded or these are materials left over when the
09:22planets were formed around 4.5 billion years ago.
09:32The small bodies made of frozen gases, rock and dust are called comets. When a comet passes
09:45close to the sun, the intense heat of the sun heats up the comet and gases are released.
09:57These gases form a tail that points in the direction away from the sun. The Halley�s
10:08comet is visible from the earth every 75 to 76 years. It was last observed in 1986.
10:26Meteoroid is a small chunk of rock or iron that travels through space. When a meteoroid
10:40heats up in earth�s atmosphere, it makes a bright trail. Then it is called a meteor.
10:48It is also known as a shooting star. Sometimes a meteor does not burn up completely
10:55and lands on surface of the earth. It is called as a meteorite.
11:08Space is what separates one thing from another. When objects are close together, there is
11:16little space between them. When objects are far apart, there is more space between them.
11:26There is unimaginable space in the universe. There is space between stars, there is space
11:34between galaxies, there is space between planets. The space between planets is called interplanetary
11:44space.
11:48Facts about the Earth and the Moon
11:52Our planet earth. It is the third planet from the sun and the fifth largest in our solar
12:00system. It takes 365 days to revolve around the sun. It has an atmosphere which supports
12:11life. It has liquid water on its surface. Gravity on earth is 6 times stronger than
12:22moon. It is nearly 4 times bigger than the moon.
12:29Our satellite moon. It is the only natural satellite orbiting the earth. It takes 28
12:38days to revolve around the earth. There is no atmosphere on the moon. It has no water
12:49on its surface. There is only ice under its surface. It has a very big gravitational pull.
13:02It is about a quarter of the earth's size.
13:09Movement of the Earth
13:12The earth shows two types of movements, rotation and revolution. Both rotation and revolution
13:23play a very important part in our lives.
13:31When an object spins around itself on an imaginary line passing through its center, it is said
13:39to be rotating around its axis. The earth is spherical like a ball and spins around
13:52an imaginary tilted axis and this spinning movement is called rotation of the earth.
14:01The earth completes one rotation in 24 hours.
14:10Different regions on the planet get varied amounts of heat and light from the sun.
14:21Effects of the Earth's Rotation
14:25The part of the earth which faces the sun receives sunlight and experiences daytime.
14:35The other side of the earth that does not face the sun experiences darkness and so it
14:42is night there. Thus, day and night on the earth occur because of its rotation.
14:52As the direction of the rotation is from west to the east, it appears that the sun rises
15:03in the east. It is only because of rotation that almost all parts of the earth receive
15:14sunlight once every 24 hours.
15:21Equator
15:22The equator is an imaginary line that divides the earth horizontally in two equal parts.
15:32It is halfway between the north pole and the south pole.
15:37The two equal parts are called the hemispheres. Hemi means half, sphere means round.
15:49The upper half is referred to as the north hemisphere and the lower half is referred
15:57to as the south hemisphere.
16:02Revolution
16:03As the earth rotates on its axis, it moves around the sun in a particular path or orbit.
16:13This movement of the earth is called revolution.
16:19The earth completes one revolution around the sun in 365 and a quarter days. This period
16:30is called a year.
16:33Seasons
16:35The earth has seasons because its axis is inclined. As the earth orbits round the sun,
16:46its tilted axis always points in the same direction.
16:53So, throughout the year, some parts of the earth always get direct sun rays.
17:00The north pole tilts towards the sun around June.
17:07After 6 months, when the earth is on the other side of the orbit, it is the south pole that
17:19tilts towards the sun around December.
17:25Thus, the different seasons on the earth are caused due to the axial tilt and the rotation
17:34of the axis.
17:38Thus, the different seasons on the earth are caused due to the axial tilt and positional
17:49change of the earth at different points on its orbit of revolution around the sun.
18:01Dramatic Representation Showing Occurrence of Seasons
18:06December
18:09Direct rays of the sun fall on the southern hemisphere while on the northern hemisphere
18:17they are more slanted and mild.
18:22The southern hemisphere thus experiences summer while it is winter in the northern hemisphere.
18:41March
18:43Both the northern as well as southern hemispheres receive equal amounts of the sun's light and
18:53warmth around this time.
18:56Thus, the northern hemisphere experiences the spring season while the southern hemisphere
19:04experiences autumn.
19:09June
19:12The direct rays of the sun fall on the northern hemisphere whereas they are slanting and mild
19:21on the southern hemisphere.
19:24This causes summer in the northern and winter in the southern hemisphere.
19:34September
19:36The sun shines equally on the northern and southern hemispheres thereby causing autumn
19:46in the northern hemisphere and spring in the southern hemisphere.
19:55Man and the Space
19:58Since ancient times, we have been studying the stars and tracking the movements of heavenly
20:05bodies across the night sky.
20:09The first telescopes were developed in the early 17th century and scientists were able
20:19to observe much more than what they could see when they only used their naked eyes.
20:27Through the ages, we have had many theories about the space and the universe.
20:34From the time when we believed that the earth is the center of the entire universe until
20:41now when science has helped us reach and study objects in distant space, the relationship
20:48between man and space has come a long way.
20:54In 1543, Nicholas Copernicus published his theory that the sun was at the center and
21:04the planets revolved around it in perfect circles.
21:10People refused to accept this theory even after Galileo confirmed it in 1609.
21:20Galileo Galilei, an Italian physicist, mathematician, engineer, astronomer, played a major role
21:30in the world of science.
21:33His achievements include improvements in the telescope and the consequent astronomical
21:42observations.
21:43He also said that earth rotates on its own axis once every 24 hours.
21:51Sir Isaac Newton built the first reflecting telescope, a technology which is still used
21:59these days.
22:01He also developed the theory of gravity that extended far beyond earth to space.
22:10Albert Einstein showed the relationship between space and time and matter and energy.
22:18Edwin Hubble concluded that there were other galaxies outside our own Milky Way and that
22:26the universe is expanding.
22:29The Hubble Space Telescope, launched in 1990, has helped us study distant objects in space
22:37far beyond our Milky Way galaxy.
22:40This telescope was named after him.
22:44Sir Stephen Hawking, born in 1942, further continued Einstein's theory of time.
22:53He is known for his theory on the black holes and origin of the universe.
23:01A Soviet cosmonaut, Yuri Gagarin, was the first man to go into space.
23:07He orbited the earth on 12 April 1961.
23:13A few weeks later, Alan Shepard, in a 15-minute suborbital flight, became the second person
23:22and first American to travel into space.
23:27Eight years later, thanks to technological progress, man was able to walk on the moon.
23:35On 20 July 1969, US astronaut Neil Armstrong became the first man to step on the moon.
23:46He was accompanied by astronauts Edwin E. Aldrin Jr. and Michael Collins.
23:56Nowadays, manned spacecrafts stay in space for long periods and conduct useful experiments
24:05and carry out repair works of satellites.
24:11Russian cosmonaut Valentina Tereshkova was the first woman to visit space in the year 1963.
24:20Alexei Leonov, also a Russian cosmonaut, was the first person to walk in space in March 1965.
24:38Rakesh Sharma was the first Indian to travel in space.
24:44On 2 April 1984, he went into space with two Soviet cosmonauts in a spacecraft called Soyuz T-11.
24:57Dr. Kalpana Chawla was the first Indian woman to go into space.
25:04She was born in 1961 in Karnal, Haryana.
25:10Her first space mission was a 16-day mission which began on 19 November 1997.
25:20She was part of a six-member crew of Columbia STS-87.
25:27In January 2003, she went into space for the second time but this was to be her last flight.
25:37On 1 February 2003, at 7 pm Indian Standard Time, the space shuttle Columbia STS-107 exploded on re-entry into the Earth's atmosphere.
25:53All seven astronauts on board died in the explosion.
25:59Sunita Williams went aboard the space shuttle Discovery on 10 December 2006.
26:08She returned to Earth in June 2007 after spending 195 days in space.