Inflation is Back

My reference here is not to Janet Yellen’s appointment as Chair of the Federal Reserve. Rather it touches on Cosmological Inflation said to have happened immediately after the Big Bang. A group of scientists have reported, in Nature, new evidence that the inflation really did take place. Hence the faith in the Big Bang appears to be justified. The team, headed by John Kovac, used the BICEP2 radio telescope, located at the South Pole, to obtain a new look at the Cosmic Microwave Background radiation (CMB). Kovac is with the Harvard-Smithsonian Center for Astrophysics (CfA) and the leader of the BICEO2 collaboration. A CfA press release it here.

The core of the discovery announced is the first actual detection of gravitational waves. What are these? Well, they are hypothesized by Einstein’s theory of relativity to come about because the density of matter deforms something he called spacetime. The issue is competently summarized in the following three paragraphs from the Reuters report on the discovery (link):

Those curvatures of space are not stationary, Einstein said. Instead, they propagate like water in a lake or seismic waves in Earth's crust and so are "gravitational waves" that "alternately squeeze space in one direction and stretch it in the other direction," Jamie Bock, a physicist at the California Institute of Technology in Pasadena and one of the lead scientists on the collaboration, told Reuters.

The other, much more recent theory that predicted gravitational waves is called cosmic inflation. Developed in the 1980s, it starts with the well-accepted idea that the universe began in a Big Bang, an explosion of space-time, 13.8 billion years ago.

An instant later, according to the theory, the infant cosmos expanded exponentially, inflating in size by 100 trillion times. That made the cosmos remarkably uniform across vast expanses of space and also super-sized tiny fluctuations in gravity, producing gravitational waves.

The waves detected by BICEO2 team are thought to be physically measurable remnants of that inflation’s squeeze-and-stretch of the primordial spacetime—of which the CMB radiation carries an imprint.

Now inflation is based on the theory that the cosmos is expanding. That theory in turn rests on the red-shift of galaxies, and the farther away they are, the more red-shifted their light. The presumption is that, going backward in time, we shall see all of these galaxies converging, joining, and eventually collapsing into an extremely tiny particle, smaller than a proton. Since both space and time, in Einsteinian thought, are the product of matter, both were equally minute. As for what existed before that less-than-proton-sized object exploded, on that we have no theory at all. What the theory of inflation proposes is that the initial expansion of that particle, going forward in time again, exhibited negative (i.e. repulsive) gravity for a fraction of a second. Had such an extremely rapid expansion not occurred, the cosmos would not be as uniform in the distribution of its energy and matter as it is.

Amazing, amazing. Personally I’m sill hung up on spacetime myself, which I take to be a mathematical convenience. As for repulsive gravity, it has much to do with virtual particles, which, per quantum mechanics, are spontaneously formed and destroyed in a vacuum—the modern version of creatio ex nihilo. Such negative energy is also, alas, associated with Dark Energy. And then, remembering Richard Feynman, I recall that time can also run in reverse, at least in Quantum Land. The new discovery published this month, therefore, does not give me what it seems to give to cosmologists, namely closure.

Now if we suppose that the red-shift Hubble observed is not caused by actual motion (or by the expansion of space), or not exclusively caused by it, then, of course, there was no Big Bang and all the vast work that followed to track it has been just for fun. Reversals in science are rare, but they do leave large black eyes. Let us remember that Einstein himself once introduced a cosmological constant, lambda, into his field equations for general relativity (in 1917) because the equations suggested that gravity would cause the cosmos to contract—in an age where the Steady State cosmos was accepted orthodoxy. After Hubble’s finding suggested that the cosmos was expanding, Einstein abandoned his constant (in 1929) and labeled its introduction the greatest blunder of his life. As with that constant so perhaps with the Big Bang. Just give it a little spacetime.