Here is the full transcript of Indian theoretical physicist Dr. Spenta Wadia’s TEDx Talk: String Theory and the Hidden Structure of Space-Time at TEDxStXaviersMumbai conference.
Dr. Spenta Wadia – Physicist
I am going to tell you a story. It’s about our bigger home, the Universe. It’s about the force of gravity that shapes our Universe more than any other force that we know. And yet, it is the least understood of all the forces of nature and presents the greatest challenge for those of us who are in search of the fundamental laws of nature.
So very briefly and very quickly, I will take you from the time of Galileo to Newton, to Maxwell, Einstein, and to the present-day work in string theory. Let me just mention to you that we are all celebrating in the scientific world 100 years of Einstein’s Theory of General Relativity this year.
Galileo discovered a new law of nature which still holds. You all know about this experiment from the Leaning Tower of Pisa, where he took two objects, one very heavy one and one light one, and let it go, and both of them actually under good conditions of weather, basically hit the ground at the same time. So they fall in the same way, independent of their mass. That’s a great law of nature. It’s still valid. To one part in 10^10 actually. Experimentally verified.
So the next big step, actually, in the formulation of theory in science is of course Isaac Newton; and this is his famous law of gravitation that how two masses, actually, two objects, interact with each other. The force goes as the product of the masses divided by the square of the distance by which they are separated; and you notice that this force is actually very weak because I am not really attracted to anyone of you. I am not falling towards you, right? It’s very weak, but when the distance between the two objects becomes very, very small, you see this force is huge and uncontrolled. And in fact, in a sense, defines the rest of our story.
But it is also very large when the masses are very huge, you see? And the important thing is that this force cannot be screened like the force of electromagnetism, because charges come in different signs. I put plus charge, minus charge together; it’s neutral, no force outside.