I attended a lecture by Jayant Narlikar in IIT in late December. Narlikar spoke about how our understanding of the cosmos has evolved over the last several centuries, and what the state of affairs is today. I found the talk very brilliant and candid, besides being very accessible to the lay public.
One of the interesting things Narlikar spoke about was that even amongst Western scientists and philosophers, Copernicus wasn’t the first person to postulate that the Earth is not the center of the solar system. That honor goes to Pythagoras. The Pythagoreans believed the earth was only a satellite revolving around another celestial body. However, this other celestial body was not the Sun; the Sun was elsewhere in the cosmos, also revolving around the central point, which was a large fire.
Posed with this theory, the Greeks asked the perfectly natural question: why is it that we can’t see the fire? And the Pythagoreans replied: you would have been able to, but between the earth and the fire is another planet which revolves exactly in sync with the earth so that it always comes between the fire and the earth. This body is called the Shadow-Earth.
Thinking this through, the Greeks thought of the next perfectly logical question: so why can’t we see the Shadow-Earth, then?
And the ingenious Pythagorean explanation was, well, you could, if you lived on the other side of the earth, but you see, Greece, where we all live, is on the opposite side.
Narlikar’s point was that if you had to accept Pythagoras’ hypothesis, you had to believe, not just in the Fire, but also in the Shadow Earth.
In his ingenious lecture, Narlikar then went on to talk about how the modern state of understanding of the Universe is shaped by two distinct theories of Physics – the Big Bang theory, which postulates how the universe was just a few moments after it was created, and particle physics, which describes the behavior of various high energy particles.
The problem is that we do not have a way of directly observing the Big Bang, so we make various energy calculations and we extrapolate from particle physics how various elementary particles that formed the infant universe must have behaved under those conditions of intense energy. So many of the Big Bang publications assume, in some sense, the ‘truth’ of modern particle physics.
On the other hand, particle physicists are limited in their experiments by colliders like the LHC, which, though capable of producing very high energy collisions, are nonetheless unable to produce energies anywhere close to cosmic scales. So to describe the nature of particles with much higher energy, the particle physicists borrow the ‘experimental setup’ of the Big Bang scientists, and explain the nature of these particles assuming that during the Big Bang, states of very high energy existed, during which time such and such particles were formed. And in order to explain more and more complex behaviors, a number of other theories were postulated – very few of which can be actually tested in a scientific setup, and which must be accepted only on the basis of ‘circumstantial evidence’.
And what I thought was a very nice twist, Narlikar made the analogy again – that the current acceptance of the Big Bang theory, and the various theories of particle physics, are interdependent and must be accepted all at once, just like, to believe the Pythagoreans, you need to accept, not only the centrality of the Fire, but also the Shadow Earth and the relative location of Greece.