Our Picture of The Universe Eng. Mohamed Salah Ebeida Teaching Training Course for Future Professors Alexandria University 9 / 26 / 2002

Important Questions!! What do we know about the universe? Where did the universe come from, and where is it going? Did the universe have a beginning, and if so what happened before then? What is the nature of time? Will it ever come to an end?

Development of Human Thoughts Toward Universe! 340 BC, the Greek philosopher, Aristotle put two arguments that the earth was rather a round sphere rather than a flat plate: 1. The Earth Shadow on the Moon was always round during its eclipse 2. The North Star appeared lower in the sky when viewed in the south than it did in more northerly region The Greeks had a third argument that one first see the sails of a ship coming over the horizon, and only later see the hull

In the 2nd Century A.D. “Anno Domini” Ptolemy elaborated the idea of Aristotle that the earth was the center of the Universe into a complete cosmological model

Lots of Room for Heaven & Hell!! Ptolemy Model provided accurate system for predicting the positions of heavenly bodies in the sky. What lay beyond the last sphere was Never made Clear!! This Model was Adopted by the Christian Church as the picture of the Universe, Guess Why?!! Lots of Room for Heaven & Hell!!

The Earth is not the center! In 1514, Nicholas Copernicus proposed that the sun was stationary and all planets move in circular orbits around it. But he didn’t say a word about that! In 1609, Death blow to the old theory came as Galileo started observing the night sky with a telescope, he found that there are several moon that orbit around the planet Jupiter. At the same time, Kepler modified Copernicus’s theory into elliptical orbit, finally the prediction matched the Observation!!

Newton Enters the Race! In 1687, Sir Isaac Newton postulated a law of universal gravitation. Earth M Moon m r

Object Should Rotate To avoid Collapse! Earth M Moon m Centrifugal Force

So What about Fixed Stars! Newton said, that would happen only in a finite world which is now obvious to be infinite!! Others tried to make the gravitational force repulsive at very large distances!! It has been generally accepted that either: The universe had existed forever unchanged, or It has been created at a finite time in the past.

The Universe Can’t be Static! In 1823, Heinrich Olbers noticed that in an infinite static universe the sky would be as bright as the sun Since that doesn’t happen, he deduced that not all stars went on together. What did God do before he created the Universe?!

The Universe is Expanding! In 1929, Edwin Hubble made the landmark observation that wherever you look, distant galaxies are moving rapidly away from us. And that brings us to the Big Bang! An expanding universe does not preclude a creator! Working to find out the unified theory!

(وما خلقت الجن و الإنس إلا ليعبدون) One Question remains! Why are we here? (وما خلقت الجن و الإنس إلا ليعبدون) الآية 56 من سورة الذاريات

Thank you for your time 