Candles in the Sky

The physicist David Bohm used to say that physicist were not physical enough. They relied too much on mathematical equations and had no, as it were, viscerally physical sense of what they were talking about. A variant of this came to mind yesterday as I first heard and then read about the 2011 Nobel Prize for physics awarded to Saul Perlmutter, Adam Riess, and Brian Schmidt. The variant is that we interpret physical observations based on theoretical structures. But the work these gentlemen engaged in was right physical, actually. They used arrays of massively modern telescopes to observe one type of supernova activity, that associated with Ia supernovae.

The terminology here is unfortunate. We have two kinds of supernovae, 1 and 2, but these are rendered in Roman form as i and ii. In the first category, i, interests us here. Type ii are produced by large stars late in their lives. In the first category, we have three subdivisions: 1a, 1b, and 1c; the first is produced by dwarfs, the last two by massive stars. On YouTube videos we hear people talking about “one A,” but in press accounts we see Ia. But never mind. the 1a’s are all white dwarf stars to begin with, and these are always associated with another sun; each dwarf is thus one member of a binary system. Furthermore, each is the collapsed form of the bigger of the two, with immense density. Most white dwarfs are about the size of the earth but have mass equivalent to 0.6 of the sun. The 1a supernova comes into being when the white dwarf sucks the mass of its binary companion to itself. Slowly its mass increases. When it comes very close to having 1.38 solar mass, it produces an enormous nuclear explosion, the supernova of type 1a. That number, 1.38, is called the Chandrasekhar limit, named after Subrahmanyan Chandrasekar who wrote a 1931 paper titled “The Maximum Mass of Ideal White Dwarfs.” The process described above is illustrated by the fabulous graphic authored jointly by NASA, the European Space Agency, and A. Field; I bring it courtesy of Wikipedia Commons (here).

The important point here is that white dwarfs never go into nova unless they reach that mass. And knowing that mass, we can calculate their brightness at peak with great precision. It is always just about the same. For this reason whenever such a supernova appears, we know how bright it must be where it is. Measuring its observed brightness with our by now stupendous instruments, we can therefore calculate how far away it is. 1a supernovae, therefore, act as a pretty reliable standard candles, thus objects of known absolute magnitude (luminosity). Knowing their observed magnitude, we can calculate their distance from us using a simple formula.

Our Nobelists looked for and found many, many supernovae of type 1a and measured their distances from us. In the absence of any kind of theory of the cosmos, this would give us a nice, clean idea how far away the most distant galaxies—those housing the 1a’s—are from us. Instead these men were greatly surprised by their findings. The most distant galaxies turned out to be much dimmer, thus much farther away, than they had expected them to be. I emphasize that word because “the model” now comes into the picture. That model, simply, is that the universe began with a Big Bang and has been expanding for 14 billion years. The expectation was that over time, the expansion would have slowed, decelerated, owing to the gravitational pull of everything on everything. Adam Riess uses the image of throwing your car keys into the air (read Big Bang). You expect the keys eventually to lose their upward energy—and to fall back down again. Instead, these keys just seemingly kept on going up. The following little graphic shows what they expected and what they actually saw.

Not to forget. The Big Bang is behind this expectation, thus a certain energetic, one-time dynamism. The Big Bang itself is based on Edwin Hubble’s observation that the farther galaxies are from us, the more red-shifted their light actually is, thus that the peaks of the light waves are farther apart. This used to be explained by saying that space was expanding and, as it expanded, it stretched the light. Today the explanation is that some kind of energy must be causing the expansion, dark energy, dark because we cannot detect it directly. And the observed red shifts—and now the unexpected dimming out of supernovae at great distances—has been interpreted to mean that the universe is mostly just that, dark energy (as I’ve had occasion to report here).

Alternative models are not even on the back burner these days. One of these might be that light gets tired as it moves, and therefore a red shift simply means tired light; hence there is no expansion. Fritz Zwicky (1898-1974), a physicist associated with supernovae, proposed the tired light hypothesis. Astronomer Halton Arp (1927-) holds “heretical” views on the red shift as well. If the red shift doesn’t always mean what Hubble thought it did, there might never have been a Big Bang. But we like the Big Bang. In the beginning, etc. Let there be Light. And having light, we now complete the picture with energetic Darkness.

Is Ether Back?

A May 19, 2011 story in Science Daily (here) carries this headline: Dark Energy is Driving Universe Apart: NASA’s Galaxy Evolution Explorer Finds Dark Energy Repulsive. Most of the text is quoted directly from NASA’s own site here, a press release also dated 5/19/2011.

Fascinating story. We’re approaching a major redefinition of reality. Herewith some background I’ve extracted from Wikipedia. The notion of dark matter surfaced in 1934 and is attributed to the Swiss astronomer Fritz Zwicky. His calculations suggested that the Coma galaxy cluster had to have considerably more mass than its luminosity indicated. He referred to the invisible mass, necessary for the rotational behavior of the cluster, to be due to “dark matter.” Dark energy got its name in 1998 from the American cosmologist Michael S. Turner. He took his phrasing from Zwicky to give a name to something. That “something” was an even more invisible mass necessary in the cosmos, but present outside of galaxies. This “something” was what caused the observed expansion of the universe; it was some kind of force. Ironically, the theoretical root of this concept dates to 1917 when Einstein introduced a fudge factor into his gravitational field equations; he called it the cosmological constant. Einstein’s equations suggested that gravity would ultimately cause the universe to collapse. A steady-state universe was then the orthodox view; the cosmos was neither growing nor expanding; for this reason Einstein chose a constant that would counteract the gravitational pull suggested by his equations just to the right extent to keep the cosmos in a steady state. When Edwin Hubble’s later observations suggested an expanding universe, Einstein is said to have labeled his constant his biggest blunder; and removed it. Prematurely, it seems. The constant is now back, as dark energy.

Indeed there is, based on calculations of the expansion (now said to be accelerating) and the anomalies observed in galactic rotation (that cannot be explained by gravity working on the visible bodies), far more of it than anything else. Contemplate the picture (from Wikipedia here but downloaded from NASA) of the constitution of the cosmos. Virtually all of the cosmos is dark energy and dark matter, leaving a mere 4 percent for matter; of that 4 percent only 0.4 percent are stars, and the matter of planets is too small to note.

To this I might add that both dark energy and dark matter are based on inferences, not on direct observations, one of cosmic expansion the other of anomalous galactic rotation. I will not be surprised if, in the fullness of time, the two will be found to be the same. It’s all dark energy. And that, folks is the cosmos.

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Now Brigitte (my unfailing muse) pointed me to that story in Science Daily yesterday because of an earlier discussions about David Bohm (see this post). It turns out that Bohm’s own formulation of Quantum Theory in 1993—but already articulated in various forms in 1980 and before—offers a grand theory of the cosmos entirely in consonance with what we are seeing today. Bohm suggests that reality consists of two orders. One he calls the Implicate (enfolded) and the other the Explicate (unfolded) Order. He pictures the first as an “immense ocean of cosmic energy.” A sudden wave pulse within that ocean could create our universe, the Explicate Order, in extent tiny relative to that ocean. “This pulse,” Bohm continues, “would explode outward and break up into smaller ripples that spread yet further outward to constitute our ‘expanding universe’.” These words are from Bohm’s Wholeness and the Implicate Order (1980), p. 192. The scientific presentation of these ideas is in his 1993 The Undivided Universe.

In Wholeness Bohm introduces this subject saying:

What is implied by this proposal is that what we call empty space contains an immense background of energy, and that matter as we know it is a small, ‘quantized’ wavelike excitation on top of this background, rather like a tiny ripple on a vast sea.… In this connection it may be said that space, which has so much energy, is full rather than empty. The two opposing notions of space as empty and space as full have indeed continually alternated with each other in the development of philosophical and physical ideas. Thus, in Ancient Greece, the School of Parmenides and Zeno held that space is a plenum [fullness]. This view was opposed by Democritus, who was perhaps the first seriously to propose a world view that conceived of space as emptiness (i.e., the void), in which material particles (e.g., atoms) are free to move. Modern science has generally favored this latter atomistic view, and yet, during the nineteenth century, the former view was also seriously entertained, through the hypothesis of an ether that fills all space. Matter, thought of as consisting of special recurrent stable and separable forms in the ether (such as ripples or vortices), would be transmitted through this plenum as if the latter were empty. [p. 191]

Well, it seems to me that ether is back once more, but differently named. New names are necessary because reputation is so vital in science, and while it is now fashionable to be darkly energetic, it will not do to be ethereal.

Words, words, words. To see our great universe as a minor bubble deep in an ocean of eternity, a bubble broken up and carried by the ocean’s immense energy towards re-absorption in the whole (read expanding universe), is humbling but has a promising flavor. Indeed, NASA seems to agree. It suggests that as Dark Energy has its way with the universe, time will come when we will no longer see the stars out there. Eventually even our own galaxy will begin to spread apart.