The universe was created 13.8 billion years ago. What happened at that earliest moment is of great importance to anyone trying to understand why everything is the way it is today.
“I think this question about what happens at the beginning of the universe is profound,” says David Spergel, chairman of the Simons Foundation, a nonprofit that supports research at the boundaries of mathematics and science. “And what is 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 $90 million by the foundation, could uncover important clues about what happened after the Big Bang by looking at particles of light that have passed through the universe since almost the beginning of time. have traveled the universe.
The data could finally provide compelling confirmation for a fantastic idea known as cosmic inflation. It implies that in the first time frame after the birth of the universe, the fabric of space-time accelerated outward to speeds much faster than the speed of light.
Alternatively, the observatory’s measurements could undermine this hypothesis, a pillar in the current understanding of cosmology.
The observatory is named after the foundation and its founders: Jim Simons, the hedge fund billionaire and philanthropist who died on May 10, and his wife Marilyn, a trained economist. Two of the four telescopes began taking measurements in April, in time for Dr.’s 86th birthday. Simons on April 25.
“That was pretty much the goal Jim set long ago for completing the project,” said Dr. Spergel. “And we got there.”
Located amid a majestic barren landscape at an altitude of 17,000 feet, the observatory has three small telescopes that bear a passing resemblance to ice cream cones and a larger one that consists of an aimable box, something akin to a “Star Wars” cousin. droid.
The 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 in a few months, and the fourth, much larger, will become operational next year.
About 60,000 detectors in the four telescopes will then study a cosmic glow of microwaves filling the universe.
“It’s a unique instrument,” says Suzanne Staggs, professor of physics at Princeton University and co-director of the Simons Observatory. “We just have 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 – light particles – bounced off charged particles, which were continually absorbed and emitted. But once hydrogen was able to form, the photons could travel unhindered. The photons have cooled to just a few degrees above absolute zero, and their wavelengths have extended into the microwave portion of the spectrum.
The cosmic microwave background was first observed half a century ago, an accidental hiss picked up by an antenna in Holmdel, NJ
In the 1990s, a NASA satellite, the Cosmic Background Explorer, revealed tiny temperature ripples in the cosmic microwaves—fingerprints that hinted at what the early universe was like. The fluctuations reflected variations in the density of the universe, and the denser regions would later merge into galaxies and even larger-scale structures of superclusters of galaxies that would line up like a cosmic spider web.
The Simons Observatory wants to discover even more details – swirling patterns of polarized light that cosmologists call B-modes – in the 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 boring homogeneity of the universe. No matter which direction you look, no matter how far you look, everything in the cosmic microwave background looks pretty much the same.
But the observable universe is so big that there isn’t enough time for a photon to travel all the way through the universe to equalize the temperature everywhere. But a rapid expansion of space-time – inflation – could have achieved that, even if it would have ended when the universe was less than a trillionth of a billionth of a billionth of a second old.
Current cosmological observations fit the cosmic inflation picture, says Brian Keating, a professor of physics at the University of California, San Diego, and one of the project’s leaders.
But, added Dr. Keating added, “so far there is no smoking gun.”
The increasingly rapid expansion would have generated gigantic gravitational waves that would have displaced matter in a way that would have imprinted B-modes into the original microwave radiation.
“The B-modes, these waves of gravity percolating through the cosmos, would amount to the smoke of the gun,” said Dr. Keating.
For the B modes, the scientists will investigate a property of light known as polarization.
Light consists of electric and magnetic fields that are perpendicular to each other. Normally these fields are oriented in random directions, but when light reflects off certain surfaces, the fields can become aligned or polarized.
The polarization of light can be studied with a filter, through which only the part of the light that is polarized in a certain direction passes. (For example, polarized sunglasses suppress glare. When sunlight reflects off water, it becomes polarized, similar to how light was polarized in the early universe.)
The detectors in the observatory essentially consist of rotating polarizer filters. If the microwaves were not polarized, the brightness of the microwaves would remain constant. When polarized, the brightness will rise and fall – brightest when the filter is aligned with the polarization, dimmest when the filter is at a right angle to the polarization.
Repeating that measurement across a portion of the sky will reveal the patterns of polarizations.
There are two types of polarization patterns. One is called an E-mode, for electric, because it is analogous to electric fields emanating from a charged particle. Previous microwave observations have detected E-modes in the primordial microwaves, which are generated by the variations in the density of the universe.
The other polarization pattern has a characteristic that occurs in magnetic fields. Because physics uses the letter B as a symbol to indicate magnetic fields, this is known as B mode.
“They look like swirls,” said Dr. Spergel.
The gravitational waves would have shuffled electrons in a way to generate small B-modes in the cosmic microwaves.
“Detection, that will be a Nobel Prize,” says Gregory Gabadadze, professor of physics at New York University and senior vice president of physics at the Simons Foundation. ‘Never mind the Nobel Prize. The discovery of such magnitude, who cares what price you give it?”
The microwave measurements could also reveal other important physical phenomena, including the masses of ghostly particles known as neutrinos, or identify dark matter, the mysterious particles that make up 85 percent of the universe’s mass.
Perhaps the biggest challenge is that cosmologists do not fool themselves.
That’s what happened a decade ago when scientists working on an experiment known as BICEP2, for Background Imaging of Cosmic Extragalactic Polarization, announced they had found the smoking gun of primordial gravitational waves and cosmic inflation.
But within a year the claim fell apart. The observed microwaves did not come from the Big Bang and inflation, but rather from dust in our Milky Way Galaxy.
To avoid repeating that mistake, the Simons Observatory will make its observations at different wavelengths. (BICEP2’s findings were based on just one wavelength.)
One of the telescopes at the Simons Observatory will be dedicated to detecting interstellar dust, which radiates at higher temperatures. That signal will then be subtracted, leaving researchers hoping that only the cosmic microwave background remains.
“It is worthwhile for us to guard against a repeat of the fiasco that hurt us before,” said Dr. Keating. “If that were to happen again, I don’t think anyone would ever trust this field.”
In the wake of the BICEP2 controversies, Dr. Simons competing research groups to collaborate in the Simons Observatory. “I joke that he basically forced a merger using his experience in the hedge fund world,” said Dr. Keating.
It could be that the Simons Observatory is still failing to find what it is looking for, or the data may be ambiguous. Perhaps spurious emissions from dust will prove to be a bigger problem than expected, obscuring the original B-modes from view.
“It’s like looking at New York City through a dirty window,” said Dr. Keating. “Nature has no contract with us to produce an observable signal.”
Or maybe there are no B modes at all. That would delight contrarian cosmologists who hate the idea of cosmic inflation. One of the seemingly inevitable consequences of inflation is the multiverse, which is the universe continually diverging into an infinity of alternative possibilities.
“Literally every possible arrangement of matter, space, time and energy takes place somewhere in this cosmic landscape called the multiverse,” said Dr. Keating. “Some people find that very attractive, other people find it distasteful.”
However, all alternatives predict exactly zero B-modes. A successful detection would therefore rule them out.
“It still wouldn’t prove inflation,” said Dr. Keating, “but it would reduce the number of guilty parties from four or five to one.”
If the Simons Observatory does not detect any B-modes, that would not definitively refute cosmic inflation. But it would make it harder to twist theoretical models to create B-modes small enough to be undetectable.
“The inflation paradigm will be in big trouble,” said Dr. Gabadadze. “The majority will give up and we will look for alternatives to inflation.”
Dr. Keating said that Dr. Simons, a leading mathematician before moving to finance, was among those who would have liked to see inflation thrown into the bin of disproven scientific hypotheses.
“That would be consistent with his idea of an eternal cyclical or bouncing model for the universe,” said Dr. Keating. But Dr. Simons was also willing to invest the money to find out if he could be proven wrong.
“His real love was science,” said Dr. Keating.