Wilkinson Microwave Anistotropy Probe (WMAP)
By Mac Gardiner
On the face of it, the WMAP project seems not only impossible, but silly. After all, who would build a two-telescope observatory, ship it to the Earth/Sun Lagrangian #2 point, out 1.5 million kilometers, in space, and then leave it there for years. As shown, it keeps the Sun, Earth and Moon “behind” its shadowing solar power “umbrella,” as it scans the sky with its back-to-back telescopes comparing the Cosmic temperatures read from one telescope to the other. However, all that it does is to look at nothing in particular, in great detail. What gives?
To quote the investigators:
We use our new detailed picture to ask: “What happened earlier to make these pictures happen?” We now begin to probe the earliest moments of the universe: Inflation (the rapid expansion of the universe a fraction of a second after its birth). We have ruled out one textbook example of a particular Inflation model. But other examples will be supported with this new evidence.
Starting from the time of our picture we can ask: “What must have happened later?” The answer is that we have compared and combined the new WMAP data with other diverse cosmic measurements (galaxy clustering, Lyman-alpha cloud clustering, supernovae, etc.), and we have found a new unified understanding of the universe:
a. The Universe is 13.7 billion years old with only a 1% margin error. b. The first stars ignited 200 million years after the Big Bang. c. There was light in WMAP picture from 380,000 years after the Big Bang. d. The content of the Universe includes: 4% Atoms, 23% Cold Dark Matter, 73% Dark Energy. * The data places new constraints on the dark energy. It seems more like a “cosmological constant” than a negative-pressure energy field called “quintessence.” But quintessence is not ruled out. * Fast moving neutrinos do not play any major role in the evolution of structure in the universe. They would have prevented the early clumping of gas in the universe, delaying the emergence of the first stars, in conflict with the new WMAP data. e. Its Expansion rate (Hubble constant) value: Ho= 71 km/sec/Mpc is now known to a margin of error of about 5%. f. There is new evidence for Inflation in the polarized signal. Apparently, the trip was worthwhile and worthy of further investigation! It seems incredible that:
1. The measurement of very small temperature differences would assure us that the universe is older than any of its elements--comforting, as it seems logical, and also, if the objects were older than the universe, they would have no place to be in since space did not exist before the universe started. 2. We are seeing light very close to the start of things, which seems to be the most active and interesting period of our existence. 3. Dark stuff makes up 96% of the universe; we don¹t know what it is and how it operates. (What laws does it respond to?) Cosmologists also don't know what dark energy is. One leading candidate is a repulsive force called the cosmological constant, which Einstein created as a fudge factor to keep the universe from collapsing in his equations, and later disavowed. But some theories of modern physics postulate mysterious force fields called quintessence as the dark energy. While the new analysis has not solved the problem, its data seem to favor Einstein's fudge factor—as though Einstein can never really miss. 4. In addition to measuring the brightness of the temperature of the microwaves, the satellite's instruments, like a pair of Polaroid sunglasses, can also measure the polarization of the microwaves. Most astronomers suspected that this had happened at about the time of the most distant and early quasars, around 800 million years of age. It was a surprise, astronomers said, to find the stars had formed so early. The first stars were probably monsters 100 times as massive as the Sun and burned out rapidly and violently, transmuting primordial hydrogen and helium into heavy elements like carbon and oxygen, spewing them out into space to form the basis for future (Cont. on p. 7) generations of stars and eventually life elements like carbon and oxygen. The satellite's instruments, like a pair of Polaroid sunglasses, can also measure the polarization of the microwaves. That ability was crucial to the discovery of the era of the first stars. Like light skipping off a lake, the electric and magnetic fields that constitute light bouncing off an electrified gas are not jumbled but show a preference to vibrate in a particular plane. Last year astronomers showed that a polarization had been imparted to the cosmic microwaves at the moment that the first atoms formed and the cosmic fireball thus lost its free electrons.
5. That theory, known as Inflation, hypothesizes that the universe underwent an enormous growth spurt during the first trillionth of a second of time under the influence of a brief but powerful anti-gravitational field that permeated space. Such behavior is allowed by the laws of physics, and it has formed the core of Big Bang BPAA Newsletter page 7 March – April 2003
theorizing, but the details depend on the unknown physics that prevails at the energies of the early universe far beyond the capacity of modern particle accelerators. And so Inflation is often called a paradigm instead of a theory.
By analyzing the bumps in the cosmic microwaves, which according to Inflation are the result of microscopic fluctuations in the mysterious force-field that drove Inflation, along with other data, the scientists have ruled out one simple version of Inflation that is often seen in textbooks. Dr. Andrei Linde, the inventor of the model that was ruled out, said that it was "great" that theories were getting culled. He said it was "painful" for him that one of his theories got killed, but that it was good news that several of his other versions were doing well.
And so the satellite carries on, spinning for the next three years, calmly generating data that will continue to confound the public and thrill the scientists for generations.
This leads me on to wonder what and how much something as equally silly as a telescope for amateurs might produce if it were in a similar Lagrangian position beyond the Earth. Such a dream, Project ALPHA, underway since last year, includes a telescope located at the Winer Observatory in Sononita, AZ which Richard Berry presented to us on February 25th (see following article). A prototype of the one intended for space, it is a computer-controlled instrument with CCD cameras and a satellite Internet link and is operated from Vanderbilt University in Brettwood, TN. Its purpose is for people to test the kind of ‘scope that will work in space and to learn to solve the problems of operating it remotely: Once the instrument is in space, no one will be able to get near it. Project ALPHA has provided much-needed experience for solving such technical problems as how to restart a computer when that computer will drive the ‘scope into the ground in half an hour and the nearest nerd is a mere 2,000 miles away.
For more information on: the ISSAT and Project ALPHA go to www.issat.org; the WMAP Project go to http://www.nasa.gov/nasagov/search/search.jsp?nasaInclu de=wmap