In the Old Testament, stars have been mentioned, but Claudius Ptolemy (c.100 — c.170 AD) is the first to propose a geocentric model of the universe where the Sun and all the planets in our solar system revolved around the Earth. Copernicus formulated that Sun is the centre of the universe. Galileo is the first to put forward the theory of earth revolving around the sun, which he invented with the help of a telescope. In 1633, the Inquisition of the Roman Catholic Church forced Galileo to recant his theory that the Earth moves around the Sun.
Cosmos is a common term which implies that the universe is in an orderly system. The universe is referred to all space and time and their contents, including planets, stars, galaxies, and all other forms of matter and energy. The Big Bang theory is the prevailing cosmological description of the development of the universe. The universe is believed to be at least 10 billion light years in diameter and contains a vast number of galaxies and it has been expanding since its creation in the Big Bang about 13 billion years ago. Therefore when we gaze stars in other galaxies, we are journeying back in time for 10-13 billion years.
Outer space, commonly known as the space, is the near-vacuum between celestial bodies. It is where everything such as the planets, stars, galaxies and other objects are found. In fact space begins at 63 (100km) miles above sea level. Normally, commercial aircrafts fly in troposphere, the maximum height of which is about 11.80 miles(19 km). Troposphere is expected to increase as the temperature of earth is increasing. Certain military aircrafts fly beyond this into stratosphere. The speed required for an object to go into space and orbit the Earth (orbital velocity) is about 28,000 km/hr (17,500 mph), which should be more than to counteract the gravitational force. The Soviet cosmonaut Yuri Gagarin is the first human being to travel into the space in 1961.
As per the big bang theory, the universe was created 13.8 billion years ago. The big bang is how astronomers explain the way the universe began. It is the idea that the universe began as just a single point, then expanded and stretched to grow as large as it is right now. The origin of universe is still an abstract science. Universe brought the concept of time and all physical matter in it. This consists of the star systems, galaxies, gas and dust, plus all the matter and energy that exists now, and in future.
Galaxies are gravitationally bound group of stars, remnants of stars and gases in the universe. A typical galaxy is spiral in shape and its size is about 55000 light years diameter and 60 million years away from earth. The space between galaxies are filled with tenuous gas. Our galaxy, ‘milky way’ is named after a Greek myth about the goddess Hera who sprayed milk across the sky. Solar system is formed by the collision of Sagittarius dwarf galaxy with milky way, 4.5 billions years ago. Another bigger galaxy Andromeda, is racing towards Milky Way at a velocity of 400000 km per hour (110 km per second) and is expected to collide and merge with Milky Way in another 4.5 billion years. That will be the end of the world we live in with the destruction of all living organisms and our civilisation.
Stellar outcast is the term for stars which are not in galaxies. Hubble space telescope invented them among other celestial bodies. Constellations are defined as group of stars in our galaxy, ‘milky way’ and those stars can be gazed by naked eyes. A nebula is a giant cloud of dust and gas in space, which are visible in a cloud free night sky. Some nebulae come from the gas and dust thrown out by the explosion of a dying star, such as a supernova. The term supernova refers to sudden increase in brightness of a star because of a catastrophic explosion that ejects most of its mass.
Stars are huge celestial bodies made mostly of hydrogen and helium that produce light and heat from the churning nuclear forges inside their cores. The stars we see in the sky as dots are many light-years from Earth. A light year is the distance travelled by light in a year. This is a unit of length used to express astronomical distances and is equivalent to 9.46 trillion kilo meters or 5.88 trillion miles. Stars emit heat and light in a steady fashion, in contrast to planets and other celestial bodies, which only reflect the light. Since stars are many light years away and the refraction of rays through the turbulent media causes the twinkling effect. The celestial bodies which do not twinkle are not stars.
Like in solar system, 50% stars have planets as big or bigger than earth. The eight planets in the solar system are Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, and Neptune. Our next planet, Mars is otherwise called Red Planet. Which contains carbon Dioxide and nitrogen. Since it contains CO2, scientist think, rice and potato can be cultivated there, but since oxygen level is low, human being and animals cannot survive there.
Every planet rotates on its axis clockwise or anticlockwise and revolves around the sun on a specified orbit. The period to rotate or revolve around sun varies significantly from planet to planet. Contrary to what climate change activists formulate, changes in the angle of axis or the change in orbital pattern can cause climate and temperature fluctuations. Most of the planets contain hydrogen and helium, but Venus and Mars contain carbon dioxide. Gravitational force of each planet varies substantially, Pluto has the least while Jupiter got the highest gravitational force. But the gravitational force of sun is 12 times greater than Jupiter.
Mercury and Venus have no moons, while Saturn has 83 moons and Jupiter has 80 moons. Our moon is 27% of the size of earth and it takes roughly 29 days to circle Earth. Moon is 384400 km(238855 miles) away from earth. The first person to set foot on the moon is Neil Armstrong of Apollo 11 in 1969. The moon of earth is seen very bright in a night free of cloud, and poets describe moonlight in a romantic way. Full moon and new moon cause tides. The gravitational pull of the Moon affects fluids within the human body, aggravating conditions such as epilepsy asthma, kidney stones and menstrual cycles.
There are other celestial bodies such as meteors, meteorites, comets and asteroids. They are leftovers from other planets. Meteor is otherwise called a shooting star, which gets burned due to frictional force when it passes through earth’s atmosphere. A meteor that hits the surface of earth without burning down is called meteorites. Asteroid are objects larger than a meteoroid that orbits the sun and is made of rock or metal. Comets are visible to naked eyes, although accidentally seeing a comet is interpreted as bad omen. Most comets have a nucleus that is less than about 6 miles (10 km) wide and a tail. The size of a comet changes depending on how close it is to the sun. A good example of comet is Halley’s Comet which orbits the Sun every 76 years whose next visit of earth will be in 2061.
The concept of universe is evolving, and will need updating from time to time depending upon the discoveries of National Aeronautics and Space Administration(NASA) and other space programmes. A good number of people still do not believe the above scientific facts but are prone to believe in biblical apocalypse, or final destruction of world. They are like those who do not accept pandemics or other scientific realities of life and nature. Nowadays, as reported by media a handful of people have taken up the hobby of gazing at the universe with the help of powerful telescopes and taking photos of galaxies many billions of light years away from earth and selling them on line for a profit!
Dr.C.J.George FRCS
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