Ye Olde Universe
[image credit: Hubble / Wikipedia]
Or did it just confirm the unhappy status of the ‘dark energy’ seekers, long after Nobel prizes were handed out for its ‘discovery’? Quote: ‘despite much searching, astronomers have no clue what dark matter or dark energy are.’ A Nobel for having no clue – where’s the physics?
– – –
For decades, measurements of the universe’s expansion have suggested a disparity known as the Hubble tension, which threatens to break cosmology as we know it. Can it be fixed? asks Live Science.
Now, on the eve of its second anniversary, a new finding by the James Webb Space Telescope has only entrenched the mystery.
Something is awry in our expanding cosmos.
Nearly a century ago, the astronomer Edwin Hubble discovered the balloon-like inflation of the universe and the accelerating rush of all galaxies away from each other. Following that expansion backward in time led to our current best understanding of how everything began — the Big Bang.
But over the past decade, an alarming hole has been growing in this picture: Depending on where astronomers look, the rate of the universe’s expansion (a value called the Hubble constant) varies significantly.
Now, on the second anniversary of its launch, the James Webb Space Telescope (JWST) has cemented the discrepancy with stunningly precise new observations that threaten to upend the standard model of cosmology.
The new physics needed to modify or even replace the 40-year-old theory is now a topic of fierce debate.
“It’s a disagreement that has to make us wonder if we really do understand the composition of the universe and the physics of the universe,” Adam Riess, a professor of astronomy at Johns Hopkins University who led the team that made the new JWST measurements, told Live Science.
Reiss, Saul Perlmutter and Brian P. Schmidt won the 2011 Nobel Prize in physics for their 1998 discovery of dark energy, the mysterious force behind the universe’s accelerating expansion.
. . .
[Later in the article…]
The simplest and most popular explanation for dark energy is that it is a cosmological constant — an inflationary energy that is the same everywhere and at every moment; woven into the stretching fabric of space-time. Einstein named it lambda in his theory of general relativity.
As our cosmos grew, its overall matter density dropped while the dark energy density remained the same, gradually making the latter the biggest contributor to its overall expansion.
Added together the energy densities of ordinary matter, dark matter, dark energy and energy from light set the upper speed limit of the universe’s expansion. They are also key ingredients in the Lambda cold dark matter (Lambda-CDM) model of cosmology, which maps the growth of the cosmos and predicts its end — with matter eventually spread so thin it experiences a heat death called the Big Freeze.
Many of the model’s predictions have been proven to be highly accurate, but here’s where the problems begin: despite much searching, astronomers have no clue what dark matter or dark energy are.
“Most people agree that the universe’s present composition is 5% ordinary, atomic matter; 25% cold, dark matter; and 70% dark energy,” Ofer Lahav, a professor of astronomy at University College London who is involved in galaxy surveys of dark energy, told Live Science. “The embarrassing fact is, we don’t understand the last two of them.”
But an even greater threat to Lambda-CDM has materialized: Depending on what method astrophysicists use, the universe appears to be growing at different rates — a disparity known as the Hubble tension. And methods that peer into the early universe show it expanding significantly faster than Lambda-CDM predicts. Those methods have been vetted and verified by countless observations.
“So the only reason that I can understand, at this point, for them to disagree is that the model that we have between them is perhaps missing something,” Riess said.
Full article here.
via Tallbloke’s Talkshop
January 2, 2024 at 01:36AM
Iowa Climate Science Education 