This Week’s Cosmic Inflation Discovery: Five Big Questions Answered
Chances are you read a headline about the Big Bang earlier this week. Perhaps you clicked to an article about it and started reading up. But you may still have some burning what-is-this-Big-Bang-news-anyway questions.
Enter a recent episode of KQED Forum that featured some bright minds in physics and astronomy. Here are some highlights from the show that answer not only what this Big Bang discovery is, but why it matters and what’s next for science.
1. What Did Astronomers Discover?
There’s been a theory floating around astronomy and theoretical circles for decades called “inflation theory.” It suggests the universe expanded at an extremely rapid rate in roughly the first trillionth of a trillionth of a trillionth of a second after the Big Bang. The discovery announced this week proves the theory true, that this “period of inflation” actually happened.
“It not only confirms inflation, it says that the inflation was stronger than we previously expected,” said Leonard Susskind, a professor of physics at Stanford University.
Radio astronomers stationed at the South Pole, using a high-power telescope called BICEP2, announced Monday that they detected the evidence of this explosive, faster-than-the-speed-of-light expansion in the form of radio waves. As Andrew Fraknoi, chair of the Astronomy Program at Foothill College put it, they detected “the afterglow” of gravitational waves created by this rapid expansion.
The afterglow “started out as a very intense and energetic radiation,” Fraknoi explained. “But as all the galaxies expanded and the universe got bigger and colder, this afterglow is now radio waves, microwaves. And these microwaves from the beginning of time are there as a kind of signal from the Big Bang.”
2. Why Is It Such a Big Deal?
“I’m not a person of superlatives,” Susskind said. “I don’t like hype, but boy, this is a big one.”
Fraknoi pointed out that astronomers and physicists didn’t think they had the equipment to detect the first moments of the universe.
“What’s really exciting here is that we’re looking at an era of precise cosmology,” Fraknoi said. “Cosmology is the study of the entire universe. It’s a mind-blowing part of astronomy where we study the properties of everything that exists. And for a long time we could make general statements about the universe—theoretical statements—but now we’re able to measure with amazing precision the characteristics of the universe.”
Think about it. Here’s an event that happened 13.8 billion years ago. No one was there to document it. Earth itself wouldn’t come along for 9 billion years. Humans, with brains that ask questions like, “where did we come from,” wouldn’t come along for 13,798,000,000 years. And yet, we can actually know what happened? With a credible amount of certainty?
Brian Greene, professor of physics and mathematics at Columbia University, said the discovery provides a “mathematical framework” that will allow scientists to “wind the cosmic film back.”
Greene said it’s important to recognize that without inflation, the Big Bang theory contained an unsolved puzzle: “It wasn’t at all clear what drove the outward swelling in the first place. One of the big contributions of the inflationary theory is that it provides an answer to that.”
3. How Is it Possible for the Universe to Expand Faster than the Speed of Light?
Do not panic. This discovery confirming the theory of cosmic inflation does not conflict with Einstein’s theory of special relativity.
Greene said when people hear of things moving faster than the speed of light they tend to reject the notion that it’s possible. “They often say ‘But, wait! Einstein taught us that nothing goes faster than the speed of light.’”
What Einstein actually theorized, Greene said, was “that no object can move through space faster than the speed of light. But nothing in his ideas prevents objects from riding the swell of space itself, and in that way, moving apart faster than the speed of light.”
As Susskind elaborated, if the entirety of space is being swept away from you like the tide going out, then “then ripples on space very, very far away from you can appear to be going faster than the speed of light” because all of space is being swept along with the tide.
“And, no,” Susskind said, “there is no conflict about things very, very far away from you moving away from you faster than the speed of light. There would be a conflict if we saw a light ray going right by our nose faster than the speed of light.”
4. What Does this Discovery Say about the Multiverse? Does it Prove String Theory?
Slow down a little bit here.
“To take the leap and to try to use this as something that confirms string theory, that is jumping off the deep end,” Greene said. “That would be jumping the gun. By a huge amount.”
But when asked whether proof of rapid expansion occurring after the Big Bang offers clues about whether ours is the only universe, or whether there are multiple universes, an idea known as the multiverse, Leonard Susskind was more optimistic.
“There’s something going on in that data that’s not so easy to see. And what it’s suggesting is—it’s a vague suggestion—what it’s suggesting is that there’s an event that took place even before inflation. Even before this trillionth of a trillionth of a trillionth of a second,” said Susskind.
According to Susskind what’s going on in that data looks consistent with what is called “‘bubble nucleation’ – the creation of the universe out of a multiverse.”
But given the decades of research likely needed to prove that, Susskind cautioned against the leap: “We don’t know, we can’t tell. That may be stretching a point a little bit too far.”
5. Where Does Science Go from Here?
For Greene, the proof of inflation is powerful in part because it allows theorists and experimentalists to refocus their work. He pointed out that inflation is an umbrella concept similar to democracy that can be constructed in many different ways.
“Inflation is a paradigm that suggests that the universe underwent incredibly rapid stretching in its earliest moments,” he said, “but there are many detailed theories that differ in the way they implement the paradigm.”
“What we can begin to do with this data is to winnow down the versions of the inflationary paradigm that are worth still considering, Greene continued. “That allows us to really home in on our equations and our ideas.”
Susskind said one area he’d like to see explored is the curvature of space.
The data gathered by Chao-Lin Kuo and his collaborators “adds a little bit of weight to the idea that we can detect the curvature of space,” said Susskind. “That would be huge. This experiment doesn’t do it, but I think it adds to the fuel that we should go out and try to measure the curvature of space.”
Fraknoi said it’s too early to predict the practical implications of the data but he’s optimistic.
“Every time we have looked at these fundamental rules of how the universe works,” Fraknoi said, “all kinds of amazing applications have come.” He cited Global Positioning Systems, or GPS, as one such application. “As we uncover these rules, and these behaviors about the universe, amazing things may flow from them.”
You can listen to Forum’s complete discussion of the topic below: