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 is pushing the galaxies, adding energy to them. A force physicist have named “dark energy”.
“Phantom Forces Have Been Messing with the Cosmos”
Dark, phantom forces have been messing with the cosmos since the time when the universe was about 100,000 years old, writes Dennis Overbye for the New York Times, 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.”
An eon from now, the universe might be 99 percent dark energy, with galaxies expanding away from each other at unimaginable speeds. At this future point, writes writes Gregg Easterbrook for The Atlantic, each galaxy will perceive itself as the whole of creation, a lonely cluster of stars “surrounded by infinite emptiness and all traces of the Big Bang will have vanished from the cosmos.
Each Galaxy Will Perceive Itself as the Whole of Creation
“Each galaxy,” Easterbrook writes, “will perceive itself as the whole of creation, “surrounded by infinite emptiness. At this far-future point, all traces of the Big Bang will have dissipated from the cosmos. Any intelligent beings evolving under those circumstances would not be able to figure out how the universe formed.” The human species is fortunate to have come into existence while the cosmos is “young,” and dark energy has not yet erased the signs and clues about why we are here.
These isolated, far future “dark-energy” galaxies recall the early 20th-century debates of the over the very existence of concept of a galaxy beyond the Milky Way, asking were “spiral nebulae” they could spy with the naked eye simply outlying components of our own Milky Way, or were they instead “island universes” — distant systems of stars comparable to the Milky Way itself? This question was the center piece of the famous Shapley-Curtis debate of 1920, about the scale of the universe, which was later resolved by observations of M31, the Andromeda, as an island universe, a galaxy.
Physicists have calculated that at the Big Bang, dark energy was a tiny fraction of the cosmos; today, it’s an invisible 74 percent of creation and growing. At some far future point dark energy will have accelerated the universe to such speeds that no galaxy will be visible to any other galaxy.
An Unknown Energy Field?
Nobel-Prize laureate Adam Riess, a founder of the dark energy theory, says, “I have absolutely no clue what dark energy is. The most prevalent explanation, according to astrophysicist Paul Martini currently at at the , proposes that Einstein’s theory of general relativity — –an inherent property of spacetime, where with the constant presence of dark energy, the more the universe expands, the more space there is and the more negative pressure–should be modified, suggesting that gravity could change from being an attractive force to a repulsive force on very large scales.
But there may be some unknown energy field or intelligence at work that no one has yet guessed beyond our current knowledge where a mere fraction of the content of the universe is the “ordinary” matter and energy that’s found in our Milky Way galaxy and beyond. Dark energy could be related to an unknown, undiscovered force that scientists have named “Quintessence,” that would join the four fundamental forces — the strong and weak nuclear forces, the electromagnetic force, and gravity — to describe the universe.
And a new, controversial report, writes Overbye, “suggests that this dark energy might be getting stronger and denser, leading to a future in which atoms are ripped apart and time ends.”
Image credit: Hubble Space Telescope/NASA, galaxy, named NGC 3432, is shown directly edge-on to us from our vantage point here on Earth. The galaxy’s spiral arms and bright core are hidden, displaying the thin strip of its very outer reaches.