An outstanding researcher once gave an open lecture on astronomy. He depicted how the earth orbits around the sun and how the sun, thus, orbits around the focal point of an immense gathering of stars called our galaxy. At the end of the lecture, a little old woman at the back of the room got up and stated: "What you have let us know is garbage. The world is truly a flat plate bolstered on the back of a mammoth tortoise." The researcher gave a predominant grin before answering, "What is the tortoise standing on." "You're extremely clever, young man, exceptionally clever," said the old woman. "Yet, it's turtles all the way down!"

The vast majority would discover the photo of our universe as an unbounded tower of tortoises rather ludicrous. What do we think about the universe, and how would we know it? Where did the universe originate from, and where is it going? Did the universe have a start, and assuming this is the case, what occurred before at that point? What is the idea of time? Will it at any point arrive at an end? Would we be able to backpedal in time? Late leaps forward in material science, made conceivable to some extent by awesome new innovations, recommend answers to some of these longstanding inquiries.

Some time or another these answers may appear as clear to us as the earth orbiting the sun – or maybe as absurd as a tower of tortoises. The truth will surface eventually. As long prior as 340 BC the Greek philosopher Aristotle, in his book On the Heavens, could advance two great contentions for trusting that the earth was a round sphere as opposed to a Hat plate. In the first place, he understood that eclipses of the moon were caused by the earth dividing the sun and the moon. The earth's shadow on the moon was constantly round, which would be genuine just if the earth was spherical.

In the event that the earth had been a flat disk, the shadow would have been extended and curved, unless the eclipse dependably happened when the sun was straightforwardly under the focal point of the disk. Second, the Greeks knew from their travels that the North Star showed up bring down in the sky when seen in the south than it did in more northerly areas. Since the North Star lies over the North Pole, it gives off an impression of being straightforwardly over a spectator at the North Pole, yet to somebody looking from the equator, it seems to lie exactly at the horizon. From the distinction in the evident position of the North Star in Egypt and Greece, Aristotle even cited a gauge that the separation around the earth was 400,000 stadia.

It is not known precisely what length a stadium was, but rather it might have been around 200 yards, which would make Aristotle's gauge double the right now acknowledged figure. The Greeks even had a third contention that the earth must be round, for why else does one initially observe the sails of a ship coming into the great beyond, and just later observe the hull? Aristotle thought the earth was stationary and that the sun, the moon, the planets, and the stars moved in roundabout orbits about the earth. He trusted this since he felt, for supernatural reasons, that the earth was the focal point of the universe, and that round movement was the absolute best.

This thought was expounded by Ptolemy in the second century AD into an entire cosmological model. The earth remained at the middle, surrounded by eight spheres that conveyed the moon, the sun, the stars, and the five planets known at the time, Mercury, Venus, Mars, Jupiter, and Saturn. The planets themselves proceeded onward smaller circles connected to their separate spheres keeping in mind the end goal to represent their fairly confounded watched ways in the sky. The furthest sphere conveyed the alleged fixed stars, which dependably remain in similar positions with respect to each other yet which turn together over the sky. What lay past the last sphere was never made clear, yet it positively was not some portion of mankind's discernible universe.

Ptolemy's model given a sensibly precise framework to foreseeing the positions of heavenly bodies in the sky. In any case, keeping in mind the end goal to anticipate these positions accurately, Ptolemy needed to make a presumption that the moon took after a way that sometimes conveyed it twice as near the earth as at different times. What's more, that implied that the moon should sometimes to seem twice as large as at different times! Ptolemy perceived this imperfection, however by and by his model was for the most part, in spite of the fact that not all around, acknowledged. It was received by the Christian church as the photo of the universe that was as per Scripture, for it had the immense favorable position that it cleared out loads of room outside the sphere of fixed stars for paradise and hellfire.

A less complex model, be that as it may, was proposed in 1514 by a Polish priest, Nicholas Copernicus. His thought was that the sun was stationary at the inside and that the earth and the planets moved in roundabout orbits around the sun. Almost a century go before this thought was considered important. At that point two space experts – the German, Johannes Kepler, and the Italian, Galileo Galilei – started openly to help the Copernican hypothesis, regardless of the way that the orbits it anticipated did not exactly coordinate the ones watched.

At the point when Galileo started watching the night sky with a telescope, which he had invented. When he took a gander at the planet Jupiter, Galileo found that it was joined by a few little satellites or moons that orbited around it. This suggested that everything did not need to orbit specifically around the earth, as Aristotle and Ptolemy had thought. In the meantime, Johannes Kepler had altered Copernicus' hypothesis, recommending that the planets moved not in circles but rather in ovals. The forecasts now at last coordinated the perceptions.