“Staggering” –The Implications of Infinite Space

Hubble Ultra Deep Field

 

“If space is truly infinite,” observes Dan Hooper, head of the Theoretical Astrophysics Group at the Fermi National Accelerator Laboratory, in At the Edge of Time, “the implications are staggering. Within an infinite expanse of space, it would be hard to see any reason why there would not be an infinite number of galaxies, stars, and planets, and even an infinite number of intelligent or conscious beings, scattered throughout this limitless volume. That is the thing about infinity: it takes things that are otherwise very unlikely and makes them all inevitable.”

(Each day, between Christmas and New Year’s Day, we’ll post one of The Daily Galaxy’s 2019 most viewed posts as ranked by Google Analytics. With our best wishes for The Holidays.)

The nature of 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.

“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.”

Physicists have found that for the last 7 billion years or so galactic expansion has been accelerating. This would be possible only if something is pushing the galaxies, adding energy to them. Scientists are calling this something “dark energy,” a force that is real but eludes detection.

A Strange New Energy Field

“Long, long ago, when the universe was only about 100,000 years old — a buzzing, expanding mass of particles and radiation — a strange new energy field switched on,” writes Dennis Overbye for New York Times Science. “That energy suffused space with a kind of cosmic antigravity, delivering a not-so-gentle boost to the expansion of the universe.”

The 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.

“In order for our universe to be expanding faster today than it was yesterday, the vacuum of space throughout our universe must contain a small density of energy—the equivalent of only a few protons per cubic meter. The density of this so-called dark energy is so small that we can’t detect its effects on Earth or even within our Solar System. But averaged across much larger volumes of space, dark energy dominates our universe—making up about 69 percent of the total energy, with the remaining portions consisting of dark matter (26 percent) and atoms (5 percent), along with trace amounts of neutrinos and light.

The fact is, we don’t really understand what this dark energy is. And that means that we don’t understand why our universe’s expansion rate is accelerating.

Dark Energy –“New Exotic Matter or ET Force Field?”

Although, in our current era of accelerating expansion space is continuously being divided into a larger number of disconnected universes there was a point in cosmic history at the Big Bang during which the accelerating expansion of space was far more dramatic.

Hubble’s Tension –Darkness Will Descend Upon the Cosmos

 

Hubble Constant

 

The illustration above shows the three basic steps astronomers use to calculate how fast the universe expands over time, a value called the Hubble constant. All the steps involve building a strong “cosmic distance ladder,” by starting with measuring accurate distances to nearby galaxies and then moving to galaxies farther and farther away. This “ladder” is a series of measurements of different kinds of astronomical objects with an intrinsic brightness that researchers can use to calculate distances. NASA, ESA, and A. Feild (STScI)

Incredibly Weird Dark Energy –“Its Source Unknown, Location Unknown, Physics Unknown”

“The Hubble tension between the early and late universe may be the most exciting development in cosmology in decades,” says Nobel laureate Adam Riess of the Space Telescope Science Institute (STScI) and Johns Hopkins University, about new Hubble Space Telescope data that suggest a faster expansion rate in the modern universe than expected, based on how the universe appeared more than 13 billion years ago strengthening the case that new theories may be needed to explain the dark energy forces that have shaped the cosmos.

“This mismatch has been growing and has now reached a point that is really impossible to dismiss as a fluke. This disparity could not plausibly occur just by chance,” stresses Riess.

The end result for our cosmic island of infinite space is that in some distant future thanks to its continued expansion, long after the sun grows to engulf Earth clusters of once-neighboring galaxies will begin zooming away from each other so fast that even light won’t be able to bridge the gap and darkness will pervade the cosmos.

A “Quintessent” Universe?

An alternative to the accelerating expansion is the theory of “quintessence,” an emerging relative of the Higgs field that permeates the cosmos that evolves. “Regardless of whether one can realize a stable dark energy in string theory or not, it turns out that the idea of having dark energy changing over time is actually more natural in string theory,” says Harvard string theorist Cumrun Vafa. “If this is the case, then one can measure this sliding of dark energy by astrophysical observations currently taking place.”

“Nothing Like Ours” –Billions of Years from Now a Strange New Universe Emerges

A discovery of quintessence would revolutionize fundamental physics and cosmology, including rewriting the cosmos’s history and future. Instead of tearing apart in a Big Rip, a “quintessent” universe would gradually decelerate, eventually stop expanding and contract in either a Big Crunch or Big Bounce.

So far all astrophysical evidence supports the cosmological constant idea, but there is some wiggle room in the measurements. Upcoming experiments such as Europe’s Euclid space telescope, NASA’s Wide-Field Infrared Survey Telescope (WFIRST) and Chile’s Simmons Observatory being built in the desert will look for signs that dark energy was stronger or gradually diminish over tens of billions of years –the cosmic acceleration is gradually changing, as in quintessence models.

Vafra suggests a dark energy density that instead of being constant, is slowly decreasing with time. If so, that would have profound consequences, says string theorist Timm Wrase at the Vienna University of Technology in Austria: “It certainly has huge implications for the fate of the universe.” Over the coming tens of billions of years, dark energy may go to zero, or even become negative. “And then maybe the universe would end in a big crunch, instead of expanding forever.”

The Cosmic Iceberg

But what about the fate of universes beyond ours that Dan Hooper writes about in The Edge of Time? The expansion of space, he observes  “divides it into a number of causally disconnected regions. For all intents and purposes, these regions are not part of a single universe; rather, each is a universe of its own. Each point in space is surrounded by an impenetrable cosmic horizon, the size of which is determined by how fast space is expanding. The faster that space is expanding, the closer this cosmic horizon will be to the point that it surrounds. During eras of accelerating expansion—such as our current era—space is continuously being divided into a larger number of disconnected universes.”

During the epoch of inflation that lasted from 10−36 seconds after the Big Bang space expanded at an absolutely staggering rate, observes Hooper, “tearing space and everything in it apart. No two objects—even elementary particles—remained close enough to one another for long enough to interact. Two objects separated by the width of an atom at the beginning of inflation were trillions of miles apart from one another by the time it was over—only a minuscule fraction of a second later.

“Inflation took regions of space that had once been neighbors and forever disconnected them from each other. So utterly complete was this act of sequestration, that these regions became more than merely distant. Inflation left them in entirely different universes. A small piece of the space that emerged from inflation went on to form our universe.”

There is good reason to think that everything we can see from our most powerful telescopes, concludes Hooper, represents only the smallest tip of the cosmic iceberg.

The image at the top of the page is the new version of Hubble’s deep field image. In dark grey you can see the new light that has been found around the galaxies in this field. That light corresponds to the brightness of more than one hundred billion suns. It took researchers at the Instituto de Astrofísica de Canarias almost three years to produce this deepest image of the universe ever taken from space, by recovering a large quantity of ‘lost’ light around the largest galaxies in the iconic Hubble Ultra-Deep Field.

The Daily Galaxy, Max Goldberg, via NASA Goddard Space Flight Center, New York Times, Johns Hopkins University, and Dan Hooper, At the Edge of Time (p. 187-188). Princeton University Press. Kindle Edition.

Originally posted on Nov 17, 2019