“I’m going to tell you a story,” John Mather ‘68 began. “It’s the story of the whole universe, from the Big Bang to far in the future. Unfortunately,” he quipped, “I can’t tell you every detail of this story.” He proceeded to give an enlightening lecture on just how we think the Big Bang happened and how his research helped prove that it actually did.
On Thursday night, John Mather, a Swarthmore alum who shared last year’s Nobel Prize in Physics with collaborator George Smoot, gave this year’s McCabe Lecture, entitled “From the Big Bang to the Nobel Prize and on to the James Webb Space Telescope.” He opened with a story about growing up near a Rutgers research laboratory (in a barn), containing everything from Geiger counters to cryogenic experiments, but being afraid of the cows that his father was researching. They were, after all, bigger than he was.
He then returned to his more ambitious story, about the universe, starting with a slide that read “Your Chin is Made of Exploded Stars.” He gave a quick description of how astronomers measure how far away celestial objects are — via trigonometry and the standard candle — and how fast they’re moving — by measuring the red- or blue-shift caused by the Doppler effect.
With those tools, in 1929 Edwin Hubble discovered that the universe was actually expanding, not contracting as one would expect — after all, wouldn’t gravity just pull everything together eventually? So, as Mather said, “In 1929 the world economy collapsed, but the universe expanded.” Meanwhile, Alex Friedman and Georges LemaÃ®tre, among others, were developing various versions of what would later become known as the Big Bang theory. Hubble’s ideas fit well with these theories, one component of which was that
Mather then presented a “brief history of the universe on one chart,” with very small text, “that might even be true.” The chart spanned from the Big Bang through the first production of helium nuclei (about three minutes in), to when the universe became transparent (after about 389,000 years), to the formation of the solar system (nine billion years), to Galileo and Einstein (13.7 billion years), to what might happen in the future: signs of life on other planets (he hopes), the sun’s eventual demise, and after a long time, the “sky going dark” because other stars are receding from us faster than the speed of light.
Now, the Big Bang was a very hot event, and that heat energy had to go somewhere. Theorists predicted a cosmic background radiation of a few degrees Kelvin as early as 1948, though experimental verification would wait until the sixties. In 1965, Penzias and Wilson verified the presence of the cosmic microwave background, but, says Mather, “the data was wrong.” This sparked him in the early seventies (while he was doing graduate studies at Berkeley) to start a project that would measure the background radiation more accurately. To avoid atmospheric interference, he and his collaborators decided the best platform for doing so would be a satellite.
Mather put together a proposition for such a satellite while at Berkeley, and was selected, along with several others who had submitted similar propositions, to design COBE, for Cosmic Background Explorer. Over the course of years, they ran into many engineering hurdles, including the need to switch from being shuttle-delivered to rocket-launched because of the grounding of space shuttles after the Challenger mishap. Finally, in 1989, the satellite was launched.
The COBE mission was a complete success, its results including data about the anistropy — directional dependence — of the background radiation. More dramatic, however, was the graph comparing the predicted spectrum of the black-body radiation to values actually observed. In effect, the data proved that the Big Bang theory was correct. When this graph was presented to the National Academy of Scientists, it produced a spontaneous standing ovation from the scientists present. Stephen Hawking called the data it showed “the most important discovery of the century, if not of all time.” (Mather said he “didn’t agree,” citing Einstein’s discoveries as perhaps more important, “but thank you, Stephen.”) It was for this that Mather won his “diploma” from the King of Sweden, along with a little medal that “doesn’t have a string on it, so you can’t wear it around your neck.” Perhaps most impressively, however, the graph led to a novelty T-shirt by way of a popular web comic.
Mather then moved onto his current work: the James Webb Space Telescope, an infrared telescope intended to replace the aging and much less powerful Hubble telescope. Mather is lead scientist for the project, which is led by NASA but highly international: it “takes a village,” says Mather. Using infrared means that the telescope will be able not only to search for light left over from the first stars formed after the Big Bang, but also to see through dust clouds in order to look at both the formation of new stars and to search for extrasolar planets. Mather says that the most exciting possibility with this telescope is that it could potentially find a planet and determine the composition of its atmosphere.
The telescope uses novel cooling systems to avoid disturbing imaging with its own heat, as well as other significant inventions related to its mirrors (learning from the Hubble mirror mishap). It will be located at Earth’s L2 point, which means that the telescope will orbit with Earth while not having to worry about it getting in the way…but it also means that, being significantly farther from the Earth than the Moon, “it’s too far to go fix if something goes wrong, so we’ll get it all right.”
Mather ended on a slightly more personal note. When asked, “What made your Swarthmore experience special?” his reply was, “I survived.”