“There is probably no way to tell whether the mysteries faced by cosmologists today are the signs of a coming scientific revolution or merely the last few loose ends of an incredibly successful scientific endeavor. There is no question that we have made incredible progress in understanding our universe, its history, and its origin,” says Dan Hooper, a senior scientist at the Fermi National Accelerator Laboratory about 40 miles west of Chicago and a professor of astronomy and astrophysics at the University of Chicago.
“But it is also undeniable that we are profoundly puzzled, especially when it comes to the first fraction of a second that followed the Big Bang,” Hooper adds. “I have no doubt that these earliest moments hold incredible secrets, but our universe holds its secrets closely. It is up to us to coax those secrets from its grip, transforming them from mystery into discovery.”
Big Bang Theory–”Our Universe Appears to be Remarkably Comprehensible”
“When we compare the results of different kinds of measurements—the expansion rate of our universe, the temperature patterns in the cosmic microwave background, the abundances of the various chemical elements, and the distribution of galaxies and other large‐scale structures—we find stunning agreement,” observes Hooper. “Each of these lines of evidence supports the conclusion that our universe expanded and evolved in just the way that the Big Bang Theory predicted. From this perspective, our universe appears to be remarkably comprehensible.”
“If the general picture of an expanding universe and a Big Bang is correct,” said Carl Sagan about the most famous scientific theory since Einstein’s relativity, decades before Hooper penned his thoughts, “we must then confront still more difficult questions. What were conditions like at the time of the Big Bang? What happened before that? Was there a tiny universe, devoid of all matter, and then the matter suddenly created from nothing? How does that happen?”
The Four Fundamental Puzzles
Hooper argues in his new book “At the Edge of Time: Exploring the Mysteries of our Universe’s First Seconds” that there are four big fundamental puzzles stumping cosmologists right now. The biggest of these are the twin mysteries of dark matter and dark energy, which have never been directly observed but are thought to make up 95% of all matter and energy in the universe.
Dark Energy and Dark Matter–”Akin to our Knowledge of Air in the 1850s”
According to Hooper, our knowledge of dark matter is akin to our knowledge of air in the 1850s – “we knew it was there but we didn’t know what it was made of. Similarly, astronomers can infer the existence of dark matter based upon its gravitational influence on objects we can see. But dark matter does not interact with light – hence the “dark” – and we do not yet know what it is.
“Dark energy,” says Hooper, “ is even more mysterious but it could help explain one of the biggest mysteries of modern cosmology: the accelerating expansion of the universe.”
Physicists have found that for the last 7 billion years or so — the anticipated halfway point of the lifetime of the cosmos – galactic expansion has been accelerating. Some unknown force has been messing with the cosmos since the time when the universe was about 100,000 years old, reported Dennis Overbye for the New York Times mirroring Hooper’s observation, “when a buzzing, expanding mass of particles and radiation — a strange new energy field switched on. That energy suffused space with a kind of cosmic antigravity, delivering a not-so-gentle boost to the expansion of the universe, a theoretical force referred to as early dark energy.”
”Even More Mysterious”
“What we really do know for sure is that our universe is expanding faster today than it was in the past. And that’s something we can’t explain using Einstein’s Theory of Relativity if the universe was full of only things like ordinary matter, or light,” said Hooper about the phenomenon that will result an eon from now in a universe might be 99 percent dark energy, with galaxies expanding away from each other at unimaginable speeds. “To make a universe or a piece of space to grow faster as time progresses you really need something else, a form of energy that occupies space and doesn’t get diluted as space expands.”
“Finding out that the universe is going faster over time is just as surprising as you throwing up a baseball and you watching it rocket off and speeding up away from the Earth,” said Hooper. “That requires some extra thing to be pushing that baseball upward. And in the case of our universe it requires some extra thing, namely dark energy, whatever that is, to make our universe grow faster.”
Hooper is in good company. ”“Dark energy is incredibly strange, but actually it makes sense to me that it went unnoticed,” said Noble Prize winning physicist Adam Riess, in an interview with The Atlantic. “I have absolutely no clue what dark energy is. Dark energy appears strong enough to push the entire universe – yet its source is unknown, its location is unknown and its physics are highly speculative.”
Answers Lie in the Very First Fractions of a Second after the Big Bang
“What really intrigues me is that each of them seems to point us toward the first moments that followed the Big Bang,” says Hooper who believes that the answer to these and other mysteries – including the lack of anti-matter in the universe – lies in the very first fractions of a second after the Big Bang. “In this sense, our inability to detect particles of dark matter, as well as the simple fact that atoms exist in our world today, suggests that the earliest moments of our universe’s history may have included events, interactions, or forms of matter and energy that we still know nothing about. Cosmic inflation also took place during these earliest of times, raising far more questions than we currently have answers. These are our universe’s greatest mysteries, and all indications are that their solutions lie in the first fraction of a second that followed the Big Bang.”
“The Big Bang Didn’t Happen Just Once”
“There are things that we see about our universe that we can only explain – at least for the moment – if we postulate that there was an era very, very early in our universe’s history where space expanded extremely dramatically in a giant, sudden burst,” said Hooper about the era of so-called cosmic inflation when the universe expanded much faster than the speed of light – that lasted for a little over one millionth of a billionth of a billionth of a billionth of a second. “These are bigger numbers than you can ever wrap your head around but you can just think of the universe growing almost instantly to a vast, vast volume from a tiny little space. If that’s true, and a lot of cosmologists think it is very likely to be true, then the Big Bang didn’t just happen once, but this inflating space in a sense pops off these kind of bubble universes one after the other.”
Infinite Number of Universes–Each Surrounded by an Impenetrable Cosmic Horizon
This expansion of space, driven by the unsolved mystery of dark energy, observes Hooper in The Edge of Time, “divides it into a number of causally disconnected region, each is a universe of its own surrounded by an impenetrable cosmic horizon, the size of which is determined by how fast space is expanding.
Infinity is such that with an infinite amount of space, there are an infinite number of universes — collections of atoms and other particles located at specific places at specific times oriented in almost exactly the same way that they are in our Earth world. Within an infinite space, suggests Hooper, there are inevitably an infinite number of universes that are indistinguishable from our own. Yet some of the regions within the multiverse are likely to be alien worlds with unknown forces and new forms of matter along with more or fewer than three dimensions of space –worlds utterly unlike anything we can imagine./
“These worlds contain a star that is nearly identical to the Sun, which is orbited by a planet that is nearly identical to the Earth, which contains upon it people who are nearly identical to you and me,” he writes. “If space as we know it extends forever, this conclusion is inevitable. All things and all events that are possible, no matter how unlikely, will exist and will occur within this greater collection of space.”
Think of the multiverse says Neil deGrasse Tyson, “as multiple ships at sea far enough away from one another so that their circular horizons do not intersect yet they all share the same body of water.”
“A Very Different Picture of the Universe?”
“I find myself asking whether these cosmic mysteries might be the symptoms of something more important or expansive than a few loose ends,” says Hooper. “Perhaps these puzzles are not as unrelated as they might seem, but are instead each pointing us to a very different picture of our universe’s earliest moments. When it comes to our understanding of our universe’s origin, I sometimes find myself wondering: Is a revolution coming?”
The Daily Galaxy, Max Goldberg, via “At the Edge of Time: Exploring the Mysteries of Our Universe’s First Seconds” (Kindle Edition) and Dan Hooper WTTV Interview
Image credit: With thanks to the NSF