The future of the universe is not as hazy as it once was. Solar evolution in our own little system informs us of Earth’s distant future, and observations demonstrate that our own majestic spiral galaxy will one day collide and merge with the Andromeda galaxy, but the evolution and final chapter of the universe has, until the last decade or so, remained a mystery.
Lawrence Krauss, renowned physicist, cosmologist, and public intellectual, tenderly frames the cosmic future as “miserable.” In his talk last Monday titled “Life, the Universe and Nothing: A Cosmic Mystery Story,” Krauss gave the packed lecture hall the best, current answer to where the universe is headed – somewhere “lonely, ignorant, and dominant.”
But to make sense of this prediction, Krauss emphasized a need to look at the historical gains astrophysics has made to arrive at its grim projection.
“The answer to the question means little unless you know why the question matters,” he said.
The early 20th-century view of the cosmos was quite limited compared to our contemporary understanding. The Milky Way galaxy was thought to be the only galaxy, an “island” galaxy that inhabited an unchanging and static universe.
After 1925, however, thanks to considerable discoveries and contributions from the astronomer Edwin Hubble, the universe was found to be not static at all, but expanding, and home to innumerable other galaxies.
In the late ’90s, Hubble turned out to be partially wrong: galaxies were moving away from each other, but rather than doing so at a constant speed, they were accelerating. This phenomenon was soon attributed to the still mysterious dark energy – energy inferred from its effects on the accelerating galaxies.
“Empty space is, as quantum mechanics shows us, not as empty as we once thought,” Krauss said.
Measurements of the universe’s geometry show we live in a flat universe, meaning that expansion is infinite.
“The galaxies and objects that are farthest away are travelling faster than the speed of light,” explained Krauss. Though supposedly impossible, it has some unsettling consequences.
Light will be unable to catch up with expanding space. The longer we observe the universe, the less we are going to see as more and more galaxies disappear from view, and eventually, in about one trillion years, objects in the universe that lie outside our galaxy will no longer be visible. The same will hold true for any observer in any other galaxy and, as Krauss demonstrated, the effect will be universal in the fullest sense of the word.
Astronomers using the scientific method, in any galaxy, hundreds of billions of years from now will construct a cosmic view very similar to that of early 20th-century scientists: an “island” galaxy, in an unchanging, static universe.
Future astronomers will have no idea that the universe is expanding, and therefore no clues to infer the Big Bang. Evidence for the Big Bang, such as cosmic radiation, will be stretched to undetectable wavelengths. Dark matter and dark energy will remain undiscovered, as their effects will be concealed.
“Good science, falsifiable science, will lead to false science,” Krauss explained.
Universal expansion, he also noted, raises important questions about access to knowledge we may have already lost. Since we live 13.7-billion years after the Big Bang, enlightening clues regarding the Universe may have disappeared with time, just as clues concerning the beginnings of our Universe are slowly vanishing.
Before any depression could set in among the audience – if events hundreds of billions of years from now can even be a cause for concern – Krauss made sure to point out that we live in a very special time. Homo sapiens exist at a time when dark energy, dark matter, the Big Bang, and the expansion of the universe can all be detected and studied. We’ve been given a very small, but remarkably crucial window of opportunity to observe some of the most fundamental aspects of our universe.
Dark energy, in particular, helps us understand our evolving universe and where it is heading – an exciting prospect.
“Dark energy means we don’t really understand anything,” Krauss said. “There’s still a lot left to do.”