Hubble and the VAR! Plate
Part of a Series on the Philosophy of History
Exactly a century ago, on Saturday 06 October 1923, the astronomer Edwin Hubble dated a photographic plate that showed a Cepheid variable star in Andromeda. Cepheid variable stars exhibit what is known as a period-luminosity relationship, so if their periodicity can be identified, their luminosity can be determined, and, if their luminosity can be determined, the observed luminosity can be compared to the predicted luminosity and the distance to the Cepheid variable star can be calculated. A Cepheid variable star is a “standard candle” on a cosmological scale. In short, with this plate Hubble proved that what was then called the Andromeda nebula was not a cloud of dust and gas within the Milky Way galaxy (as many astronomers believed to be the case), but was, in fact, a galaxy in its own right. The Cepheid variable observed in Andromeda was too distant to be a part of the Milky Way even by the most expansive estimate of the size of the Milky Way. Andromeda was a galaxy, and a galaxy more than a million light years away. If you look carefully at the picture of the plate above, not only will you see the date, you will also see “N” crossed out — the observed bright star was initially thought to be a supernova — and “VAR!” written below it, for “variable.”
A recent book has been written about this discovery, The Day We Found the Universe, by Marcia Bartusiak, in which the author describes the discovery:
“…Hubble went back to his logbook, page 157, and quickly scrawled an added note on the side of the page to amend the report of his October 5 observing run. Customarily reserved, Hubble at this moment is unmistakably restive. He didn’t write his message in black ink, which he regularly did for his records, but instead in pencil. And his handwriting, usually so fluid and precise, was more hurried and askew. He was obviously elated: ‘On this plate (H 335 H), three stars were found, 2 of which were novae, and 1 proved to be a variable, later identified as a Cepheid — the 1st to be recognized in M31.’ To highlight the addition, he drew a big arrow, pointing directly downward at his historic news. In its broad stroke, the arrow makes his excitement visible upon the page. For once Hubble dropped his guard and figuratively clicked his heels at this moment of discovery.”
Up to that moment, there were two reigning theories of the structure of the universe, namely, that it consisted only of the Milky Way galaxy and nothing else, or that the universe consisted of many, many galaxies, set in vast stretches of empty (or nearly empty space). On that Saturday, it was decided, for all practical purposes, that the universe consists of a multiplicity of galaxies, not a single galaxy, and it has been understood as such for the past century. And this was not the first or only time when a single observation shifted the way we understand the universe.
In 1985 the BBC documentary “The Day the Universe Changed” was aired, in which writer and presenter James Burke in ten episodes chronicled scientific discoveries that placed the world entire in a new light, as it were. With such discoveries, the universe changes suddenly, or, at least, our perception of the universe changes suddenly — perhaps it is transformed at the very moment that an observation like the “VAR!” plate is brought to our attention, though I suspect that we could agree that it takes time for such observations, and their consequent transformation of scientific knowledge, to sink it. But for the individual, ontogenically, as it were, the change can be sudden, and it can be accurate to say that there is a day when the universe changes. I watched this series at an impressionable age, and never forgot it. In particular, in an Afterword to each episode James Burke would discuss the content of the episode with Benjamin Dunlop (these afterwords, recorded in 1986, are not included on the DVD I have of the series but they are available on Youtube).
In these afterwords, and in the final episode entirely given over to the interpretation of the history of science, Burke presents a strongly Kuhnian philosophy of the history of science, replete with the paradigm shifts that he called days that the universe changed. These philosophical asides are all the more surprising when contrasted to the implicit philosophy found throughout Burke’s other and earlier science series, “Connections” (1978). Connections is as much about cumulative knowledge as The Day the Universe Changed is about Kuhnian paradigm shifts. Perhaps someone has already done this, but, if it hasn’t been done, I would be interested to read an interview with Burke in which he would give his account of his conversion to Kuhnianism. Clearly, there was a major shift in perspective between Connections and The Day the Universe Changed (sometime between 1978 and 1985). Burke may have had his own day when the universe changed for him.
Burke did not produce an episode of his television series on Hubble and the “VAR!” plate, but he could have, and, arguably, he should have — it is a perfect example of his thesis in that television series, and we can today look back at it, now with a century of perspective, as a day when the universe changed. Over the same century, the Earth also changed dramatically. As the Earth sciences developed at least as rapidly as cosmology, we went from a stable and possibly eternally steady state Earth to a planet constantly changing, often violently. In a strangely similar development, during the same century the universe was transformed from something stable and perhaps eternal, into a cosmos that is constantly changing, often violently. We no longer view black holes and neutron star collisions as bizarre and unlikely, but we recognize them as playing essential roles in shaping the universe that we know. Without these violent events, the elements necessary for life and civilization do not appear, and the universe would be a very different place from that which we know.
It is understandable for writers to use phrases like “the day the universe changed,” even though our usual interpretation of this is that our knowledge of the universe changed, but the universe has remained unchanged, except for that part of the universe that constitutes our knowledge, and our actions that follow from effective knowledge. It is a bit like feeling the need to make a distinction between history as a human discipline and history as past actuality. And indeed, this simple distinction has been woven through the philosophy of history, and continues today to make itself felt, especially when the distinction is conflated. If the universe were so unstable that it changed every time our knowledge of it changed, then we would live in a strange world. Similarly, if history changed every time our knowledge of history changed, the past would be unstable in a way that resembles George Orwell’s political past in 1984, which is a perpetual present in which the party is always right. Instead, with the scientific conflation of the universe and knowledge of the universe, we would live in a perpetual present in which science is always right. And, for some of us, this may well be the case. Our perception of things, when we place ourselves at the center of rapidly changing scientific research, is like William James’ claim that the world of an infant is a “blooming, buzzing confusion.” At times it seems to be, but we can’t live that way.
Further Resources
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