Humans have always sought ‘heaven’ – a celestial world of imagination, that exists beyond the boundaries of their knowledge, and is much more beautiful than this world. However, how much do we know about the world we inhabit and the physical universe beyond the Earth’s atmosphere?The universe encompasses billions of galaxies. Our solar system is located in one of those galaxies called the Milky Way. The Earth is just one of the planets that exist in our solar system. The universe has many secrets and mysteries, and the humans have only discovered a small fraction of those. Let us take a look at some of them.
Empty space & nothingness
If you are asked to explain what planet Earth is, then it can be said that the Earth is a place where living and non-living things co-exist with natural and human-made things. If they all disappeared, then what would be left? If the Earth, planets, stars, galaxies, and even the tiny things down to the last gas and dust were taken away, then what will be left? There would be nothing left, right? One would think that empty space is the same as nothingness.
However, science says that ‘nothingness’ is not the same as empty space. Brian Greene, a professor at Columbia University, says that empty space is a very real physical entity with characteristics unknown to us that can bend, twist, and ripple. Thus empty space helps shape everything in the world around us and forms the very fabric of the cosmos.
The universe cannot exist without space. Space is everywhere; it is the most abundant thing in the universe. Even the atom, which is the basis of all matter, has empty space. However, if we take a picture of empty space, we will see nothing in it. So it can be said that empty space is something that looks like nothingness. Why space is omnipresent, three-dimensional, so vast, and akin to nothingness has yet to be definitively answered.
Outer space
When asked where outer space is, most people point to the sky, but they may not have an answer to the question as to where exactly outer space is. It is generally accepted that space begins where the Earth’s atmosphere ends. International law states that outer space is not the property of anyone in particular, but is a place open to all for exploration. Even then, the law does not specify where each country’s rightful airspace ends. The Karman Line is considered to be the boundary between outer space and the Earth’s atmosphere.
The International Astronomical Union (IAU) ruled that planets are space objects that orbit the Sun, are large enough to be spherical and have regular, undisturbed orbits.
According to National Geographic, the Karman Line is an imaginary line 100 kilometres above sea level. At that altitude, the atmosphere becomes very thin and the intense radiation pressure from the Sun and the dynamic pressure of the solar wind begin to be felt. Therefore, we call outer space the area beyond an altitude of 100 kilometres above sea level. In outer space, there is not enough air to breathe and scatter sunlight. The sky looks blue from the Earth, but once we pass through the atmosphere, the oxygen molecules that scatter the blue light decrease. So, in outer space, the sky loses its blue hue and becomes black.
Outer space is the expanse that exists beyond the Earth and between celestial bodies Even though it is called empty space, like we saw earlier, space is not really empty. A variety of gases, dust, and other particles of matter reside in the voids of the universe. Planets, stars, and celestial bodies are located in non-empty spaces. . As we all know, sound needs a medium to travel. Space is silent because the distance between molecules is too great for sound waves to pass through.
No one has an exact idea of how big space is. To what extent can human-made instruments measure the universe? We measure great distances in space using light years. A light year is the distance light can travel in one year (that is, about 9.3 trillion kilometres).
From the light seen through telescopes, astronomers have discovered galaxies dating back to the Big Bang, the genesis of the universe, which occurred 13.7 billion years ago. However, the astronomical community is not sure whether there are other universes in space besides the one we know about. This means that space may be much bigger than what we can see.
Cosmic rays
Only dust and gases can be found in most parts of outer space. Though it may seem empty, researchers say that there are cosmic rays that are radiating throughout the universe. Our own solar system is permeated by the solar wind, which is made up of plasma and other molecules emanating from the Sun.
Particles emitted from supernovae outside the solar system, called cosmic rays, also pass by the Earth. According to Space.com, The cosmic microwave background (CMB) permeates the entire universe. The CMB, said to be the remnant of the thermal energy produced during the Big Bang, appears as microscopic waves.
Dark matter, dark energy
Dark matter and dark energy remain features of space that are incomprehensible and invisible to humans. Dark matter and dark energy can only be detected through their effects on other matter. Astrophysicists think that the biggest evidence for the existence of dark matter is that the universe is expanding. They says that dark matter is also what causes light from distant objects in space to bend.
Black holes
Black holes are vortexes in space that experience such extreme gravity that even light cannot escape. Gravity is very strong here as matter is drawn into a very small area. A black hole is formed when a star dies. Black holes cannot be seen with the naked eye because the light that goes into them cannot come back out. Telescopes with special systems can detect black holes.
Stars, planets, asteroids, comets
Stars are self-luminous giant balls of fuel. An example is our Sun. Constellations range from giant stars that burn red to cool white ones. Stars burn on the power of fuels. They will die when they run out of fuel, but this is an evolutionary process that takes place over a long period of time. Stars explode when they run out of fuel to burn. Such explosions result in supernovae and white dwarfs. Sometimes, massive objects are formed by starbursts. These are called neutron stars.
In 2006, a debate broke out in the scientific world regarding the then-existing definition of planets. The debate started with the question of whether or not Pluto could be considered as a planet. The International Astronomical Union (IAU) ruled that planets are space objects that orbit the Sun, are large enough to be spherical and have regular, undisturbed orbits. Pluto and other smaller objects would be dwarf planets by this criteria. Meanwhile, the IAU have not given a precise definition of extrasolar planets.
According to NASA, asteroids are rocks that are not large enough to become dwarf planets. It was discovered that asteroids can have ring systems. Asteroids, sometimes called minor planets, are rocky, airless remnants left over from the early formation of the solar system. Most asteroids are found in the region between Mars and Jupiter.
Comets are giant clouds of dust in the solar system. Most comets originate in the Oort Cloud region, which is filled with icy objects. As comets approach the Sun, the heat melts the ice and mixes with dust to form a tail.
Galaxies
Galaxies can be called the largest structures in space. Each galaxy is a large collection of stars. The galaxy which includes our solar system is known as the Milky Way. Galaxies come in many sizes and shapes. Galaxies can change shape as they approach other objects in space or as their stars age.
Human space explorations helped to answer the questions that we had been asking since we first looked up at the sky. These explorations have expanded our knowledge of the universe by using various technologies. But even after decades of studies and research, mysteries of universe continues to baffle us.
Now put on your thinking hats and think about the following questions for a couple of minutes.
How would you describe the term “Karman Line” to your students?
Can you think of how space explorations helped in expanding our knowledge about the mysteries of universe?
Write down your thoughts and discuss them with your students, children and your colleagues. Listen to their views and compare them with your own. As you listen to others, note how similar or different your views are to others’.
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Happy Teaching!
Mysteries of space that continue to baffle us