The universe came into existence 13.8 billion years ago. What happened then is of great interest to anyone trying to understand why everything is the way it is today.
“I think this question of what happens at the beginning of the universe is profound,” said David Spergel, president of the Simons Foundation, a nonprofit organization that supports research at the frontiers of mathematics and science. “And what’s remarkably exciting to me is the fact that we can make observations that can give us insight into this.”
A new $110 million observatory in the high desert of northern Chile, funded with $90 million by the foundation, could reveal key clues about what happened after the Big Bang by observing particles of light that have traveled throughout the universe since almost the dawn of time.
The data could finally provide convincing corroboration for a fantastical idea known as cosmic inflation. He argues that in the first time frame after the birth of the universe, the structure of space-time accelerated outward to speeds well above the speed of light.
Alternatively, the observatory’s measurements could challenge this hypothesis, a pillar of current understanding of cosmology.
The observatory bears the name of the foundation and its founders: Jim Simons, billionaire and hedge fund philanthropist who died on May 10, and his wife, Marilyn, an economist by training. Two of the four telescopes began taking measurements in April, in time for Dr. Simons’ 86th birthday on April 25.
“That was kind of the goal that Jim had set a long time ago for the completion of the project,” Dr. Spergel said. “And we did it.”
Perched amid a majestically barren landscape at an elevation of 17,000 feet, the observatory has three small telescopes that look a bit like ice cream cones and a larger one that consists of a pointable box, something that resembles a cousin of a “Star Wars”. droid.
Telescopes collect microwaves – wavelengths longer than visible light but shorter than radio waves. Two of the smaller telescopes are already collecting data. The third will join it in a few months and the fourth, much larger, will begin its activities next year.
Around 60,000 detectors installed in the four telescopes will then study the cosmic microwave glow that fills the universe.
“It’s a unique instrument,” said Suzanne Staggs, a physics professor at Princeton University and co-director of the Simons Observatory. “We have so, so many detectors.”
During the first 380,000 years of the universe’s infancy, temperatures were so high that hydrogen atoms could not form, and photons – particles of light – bounced off charged particles, were continually absorbed and issued. But once hydrogen could form, photons could travel unimpeded. The photons cooled to just a few degrees above absolute zero and their wavelengths extended into the microwave part of the spectrum.
The cosmic microwave background was first observed half a century ago, a chance whistle picked up by an antenna in Holmdel, New Jersey.
In the 1990s, a NASA satellite, the Cosmic Background Explorer, revealed tiny temperature ripples in cosmic microwaves – fingerprints of what the early universe was like. The fluctuations reflected variations in the density of the universe, and the densest regions would later coalesce to form galaxies and even larger structures of superclusters of galaxies aligned like a cosmic spider’s web.
The Simons Observatory aims to uncover even more details — swirling patterns of polarized light that cosmologists call B-modes — in microwaves.
Alan Guth, a professor at the Massachusetts Institute of Technology, proposed the idea of cosmic inflation 45 years ago, in part to explain the bland homogeneity of the universe. No matter which direction you look, no matter how far you look, everything in the cosmic microwave background is pretty much the same.
But the observable universe is so large that there isn’t enough time for a photon to travel completely through the universe to equalize temperatures everywhere. But rapid stretching of spacetime – inflation – could have achieved this, although it would have ended when the universe was less than a trillionth of a billionth of a billionth of a second.
Current cosmological observations fit the picture of cosmic inflation, said Brian Keating, a physics professor at the University of California, San Diego and one of the project’s leaders.
But, Dr. Keating added, “to date, there is no compelling evidence.”
The accelerated expansion would have generated titanic gravitational waves that would have jostled matter in a way that would have imprinted B modes among the primordial microwave radiation.
“B-modes, these gravity waves that permeate throughout the cosmos, would be equivalent to gun smoke,” Dr Keating said.
For B modes, scientists will look at a property of light called polarization.
Light is made up of electric and magnetic fields that oscillate perpendicular to each other. Usually, these fields are oriented in random directions, but when light reflects off certain surfaces, the fields can be aligned or polarized.
The polarization of light can be studied with a filter, through which only the portion of light polarized in a particular direction will pass. (This is how polarized sunglasses remove glare. When sunlight reflects off water, it becomes polarized, the same way light in the early universe was polarized.)
The observatory’s detectors are essentially made up of rotating polarizer filters. If microwaves were not polarized, their brightness would remain constant. If they are polarized, the brightness will increase and decrease: brightest when the filter aligns with the polarization, dimest when the filter is at right angles to the polarization.
Repeating this measurement over a portion of the sky will reveal polarization patterns.
There are two types of polarization models. One of these is called mode E, for electric, because it is the analog of electric fields emanating from a charged particle. Previous microwave observations have detected E-modes in primordial microwaves, generated by variations in the density of the universe.
The other polarization pattern has a characteristic found in magnetic fields. Because physics uses the letter B as a symbol for magnetic fields, it is called B mode.
“They look like swirls,” Dr. Spergel said.
Gravitational waves would have shaken electrons in ways that generated tiny B-modes in cosmic microwaves.
“Detection, that’s going to be a Nobel Prize,” said Gregory Gabadadze, professor of physics at New York University and senior vice president for physics at the Simons Foundation. “It doesn’t matter what the Nobel Prize is. A discovery of such magnitude, no matter what price you give it?
Microwave measurements could also reveal other major physical phenomena, including masses of ghostly particles known as neutrinos, or identify dark matter, the mysterious particles that make up 85% of the mass of the universe.
Perhaps the biggest challenge for cosmologists is not to deceive themselves.
That’s what happened ten years ago when scientists working on an experiment known as BICEP2, for Background Imaging of Cosmic Extragalactic Polarization, announced they had discovered compelling evidence of primordial gravitational waves and cosmic inflation.
But after a year, the claim collapsed. The observed microwaves did not come from the Big Bang and inflation, but rather from dust present in our galaxy, the Milky Way.
To avoid repeating this mistake, the Simons Observatory will carry out its observations at several wavelengths. (The BICEP2 findings were based on a single wavelength.)
One of the Simons Observatory telescopes will be dedicated to detecting interstellar dust, which radiates at higher temperatures. This signal will then be subtracted, which the researchers hope will leave only the cosmic microwave background.
“It’s worth it for us to avoid a repeat of the fiasco that hurt us before,” Dr Keating said. “If this happened again, I don’t think anyone would ever trust this domain.”
In the wake of the BICEP2 controversies, Dr. Simons convinced competing research groups to work together at the Simons Observatory. “I joke that he basically forced a merger, leveraging his experience in the hedge fund world,” Dr. Keating said.
The Simons Observatory may still not be able to find what it is looking for or the data may be ambiguous. Perhaps stray dust emissions will turn out to be a bigger problem than expected, obscuring the all-important B-modes.
“It’s like looking at New York through a dirty window,” Dr. Keating said. “Nature does not have a contract with us to produce an observable signal.”
Or maybe there are no B-modes at all. This would delight contrarian cosmologists who don’t like the idea of cosmic inflation. One of the seemingly inevitable consequences of inflation is the multiverse, which causes the universe to continually diverge into an infinite number of alternative possibilities.
“Literally every possible arrangement of matter, space, time and energy occurs somewhere in this cosmic landscape called the multiverse,” Dr. Keating said. “Some people find it very attractive, and others find it unpleasant.”
However, all alternatives predict exactly zero B-modes. Thus, successful detection would rule them out.
“It still wouldn’t prove inflation,” Dr. Keating said, “but it would reduce the number of culprits from four or five to one.”
If the Simons Observatory does not detect any B modes, this would not definitively disprove cosmic inflation. But this would make it more difficult to modify theoretical models in such a way as to produce B modes small enough to be undetectable.
“The inflationary paradigm will be in big trouble,” Dr. Gabadadze said. “The majority will abandon it and we will look for alternatives to inflation.”
Indeed, Dr Keating said Dr Simons, a distinguished mathematician before moving into the world of finance, was among those who would have been happy to see inflation thrown into the dustbin of disproven scientific hypotheses.
“This would then fit with his notion of an eternal cyclical, or rebound, pattern for the universe,” Dr. Keating said. But Dr. Simons was also willing to invest money to find out if he could be wrong.
“His true love was for science,” Dr. Keating said.