Introduction and important events:
How big is this universe? This is the question that mankind has been pondering upon since the dawn of the 6th century A.D. Claudius Ptolemy was a Greco-Roman mathematician, astronomer, geographer and astrologer who first attempted to answer that question. According to Ptolemy, the Earth was at the center of the universe and all the other heavenly bodies including the stars and the planets revolved around it. The earth was also flat according to Ptolemy. He stated that the planets and stars revolve around the Earth in paths called epicycles. Using this concept, he was able to accurately predict the position of Venus from time to time. He even recorded his observations in clay tablets, which are well preserved today. Ptolemy’s theory of the universe was widely accepted by the people and got immense support from the Catholic churches around the world at that time. Joshua chapter 10, verse 13 in the Catholic bible supported the idea of a geocentric universe as well as simple observations with the naked eye. So strong was the support from Catholic churches that the idea of a geocentric universe stuck around for ten centuries! Anyone opposing that idea was burnt alive on the stages of the Catholic churches.
Figure 1: Geo Centric model of the solar system according to Ptolemy. Source: Redbubble
Copernicus and modern astronomy: During the mid-16th century, Mikolaj Kopernick, today well known as Nicolaus Copernicus, was the first mathematician and astronomer to propose a Helio-Centric universe model. He made two major and contradictory claims. One is that the Earth is a sphere and not flat as proposed by Ptolemy. Copernicus was able to explain successfully why we have seasons on the Earth and why we can’t see all of the earth at once using the concept of a spherical Earth. Other explorers like Ferdinand Magellan sailed around the Earth in three years (1519 to 1522) and proved that the Earth is spherical. However, Copernicus’s theory on the Sun being at the center of the universe and the planets revolving around it was met with severe opposition from Catholic churches around the world because it defied beliefs in the Catholic bible. Copernicus was only able to preserve his work in a book titled, ‘Revolutions of the Heavenly Spheres’ at the year of his death in 1543. Copernicus’s work laid the foundation stones for modern astronomy
Figure 2: Helio Centric model of the solar system as proposed by Copernicus. Source: cK-12
Johannes Kepler: During the late 16th century, Copernicus’s idea of a Helio-Centric universe model began to gain traction among the mathematicians and astronomers of that time. Astronomers were able to predict the positions of planets like Mars and Jupiter more accurately with the Helio-Centric model rather than the Geo-Centric model. During 1571, the German astronomer and mathematician, Johannes Kepler took Copernicus’s Helio-Centric model one step further. He observed the positions of the planets in the night sky and found that the planets were not where they were supposed to be if they had a perfectly circular orbit. He proposed that planets have elliptical orbits which brought them closer to and farther away from the Sun at different times of the year. This along with the Earth’s spherical shape and axis tilt, contributed to the seasons on the Earth. Like Copernicus, Kepler’s theory again faced stiff opposition from Catholic churches around the world.
Figure 3: Elliptical orbit of a planet as proposed by Johannes Kepler. Source: Ancient World Mysteries.
Galileo Galilei: During 1609, the dawn of the 17th century, the Italian astronomer and mathematician, Galileo Galilei, invented the telescope, giving the science of astronomy another huge leap. Galileo was able to observe the four moons (Io, Europa, Ganymede and Callisto) of Jupiter using his telescope. He recorded the positions of the four moons for three months and found that their paths always circled around Jupiter. This observation further disproved the idea of a Geo-Centric universe. Nevertheless the Catholic Church sentenced Galileo to a life-time of house arrest for his “crime”! Galileo was the first astronomer and mathematician to have discovered natural satellites around other planets apart from the Earth. During the mid-eighteenth century (during 1742) the Catholic Church’s opposition to the Helio-Centric model began to fade when two Catholic mathematicians discovered the planet Saturn by applying Sir Isaac Newton’s gravitational laws. Deviations in the orbit of Jupiter (the last known planet then) led to the discovery of Saturn. Suddenly, the known solar system became twice as big! Finally, the ban on Copernicus’s theory was lifted in 1758 and publication of his book, Revolutions of the Heavenly Spheres, was allowed in 1822. The common folk now had access to the right information which was not obscured by religious beliefs.
Figure 4: Galileo Galilei using his telescope in 1609. Source: YouTube.com
Albert Einstein: During the late-19th century, a German clerk (who later on became a scientist) named Albert Einstein observed deviations in the perihelion of the planet, Mercury. Newton’s gravitational laws could not account for this. He then suggested in his General Theory of Relativity (1916) that space is like a soft fabric. It is bent by ordinary matter and that this bending of space is what causes deviations in the perihelion of the planet, Mercury. His theory on General Relativity was proved correct to the last decimal point during a solar eclipse that happened in 1919. It was a huge leap for science and astronomy. He was awarded the Nobel Prize in Physics in 1921 for his theory on General Relativity.
Figure 5: Bending of space-time by our Sun. Source: Medium
Frederick William Herschel: (1738 to 1822) was a German born British astronomer, music composer and mathematician. Due to his passion for astronomy, he quit his musical career in the late 18th century. He constructed his first large metal refractive telescope in 1774. This was again another huge leap for astronomy. Using his giant telescope, Herschel discovered the planet Uranus along with large number (2,500) of nebulae. Nebulae are hot clouds of dust and gas (Hydrogen) from where stars are born. Gravity contracts the gas and enables nuclear fusion to take place, thus giving birth to stars of all sizes and colours. Some nebulae and stars that he observed were 46 light years away, making the known universe exponentially bigger. After this discovery, huge grants were provided by various European governments for the construction of large telescopes. It made us ask new questions. How big is the universe? Are we alone in this universe? Is the universe expanding or contracting?
Figure 6: William Herschel’s metal refractive telescope. Source: The Book Palace!
Invention of the Radio Telescope and the Big Bang theory: During 1930, a US astronomer and scientist named Carol Jansky used the massive radio telescope in Bell Laboratories in New Jersey, USA. He discovered a constant radio signal coming from a source beyond our Sun. The radio signal’s origin was traced to a super massive black hole at the center of our galaxy, the Milky Way. The black hole was later named Sagittarius A after the constellation Sagittarius in which it was found. It was another huge leap in astronomy because black holes had never been discovered before. During 1964, two US scientists, Arnold Penzias and Robert Wilson used the same massive radio telescope in New Jersey, USA. They were observing the temperature of space where there were no stars. Ideally the temperature of that region of space should have been 0 Kelvin (Absolute zero in which matter has no energy whatsoever. The atoms do not vibrate at this temperature. It is equal to -273 degrees Celsius) but the temperature of that region of space was 4 degrees Kelvin higher than absolute zero! This observation supported the theory of the Big Bang, a time when all the matter in the universe was compressed to a very small region which suddenly exploded (Big Bang), giving rise to the universe. It also supported the theory that the universe is expanding. Then two new questions arose. Will the universe continue to expand indefinitely or will it stop at some point of time and shrink back again (The Big Crunch)?
Figure 7: Gian Radio Telescope in New Jersey, USA. Source: Dark Roasted Blend.
The Hubble Space Telescope: To answer that question, during April 1990, the US government launched the Hubble Space Telescope. It is perhaps the most important space telescope in the world. Since its launch, Hubble has discovered Neptune, Pluto and exo planets, orbiting other stars. It has discovered nebulae like the Eagle nebulae, Ant nebulae, Butterfly nebulae, Orion nebulae and countless others. It has discovered more black holes, neutron stars, magnetars, pulsars and white dwarfs, all so many light years away. During 1995 it took an image called The Hubble Deep Space image and revealed galaxies that were 93 billion light years away! Our universe suddenly seemed to have no boundaries.
The Hubble has also discovered planets that have no stars. These planets are called Planemos or orphaned planets in Greek. Most important of all, the Hubble has been able to measure the wavelength of light coming from distant galaxies. In these observations we found that the light coming from almost all galaxies was shifting towards the red end of the visible spectrum of light. This observation confirmed the theory that the universe is indeed expanding and that the rate of expansion of the universe is also on the rise. This observation led to the discovery of Dark Energy and Dark Matter in 2011. Dark Energy is an invisible force that acts against gravity and pushes galaxies apart or rather it expands the space between the galaxies. It is responsible for the continued expansion of the universe. The Big Crunch theory failed when Dark Energy was discovered in 2011. Nobody knows the origin of or how Dark Energy works. An astonishing 73% of the universe consists of Dark Energy. 23% consists of Dark Matter and only 4% is ordinary visible matter.
Figure 8: The Hubble Space Telescope. Source: Astronomy Now.
Conclusion: The observable universe (beyond which there is plasma, obscuring light) is 93 billion light years in diameter and is 13.7 billion years old. Since the 6th century A.D., mankind has come a long way in knowing the universe but our exploration of space has produced more questions than answers. The latest question on the universe is, When Dark Energy wins the battle over Dark Matter, will the universe continue to expand in its present state (The Great Chill) or will everything in the universe rip apart (The Great Rip) until only indivisible sub-atomic particles like quarks and gluons remain? We have no option but to wait and find out (if we can last that long)
Figure 9: The observable universe. Source: Science.