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Our current cosmological model—known as lambda cold dark matter, or ΛCDM—relies on hypothesized dark energy to explain the accelerating expansion of the universe.
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However, one competing theory known as “timescape cosmology” suggests that many observations can be explained by differences in how time flows between dense regions of the universe (such as galaxies) and immensely large voids.
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A new study of 1,535 Type 1a supernovae—a celestial object commonly used for analyzing the expansion of the universe—reports that this “lumpy” universe theory better explains new observations than the standard ΛCDM model.
A looming mystery lies at the heart of modern cosmology, and it has everything to do with the ever-accelerating expansion of the universe. First discovered in 1998 by analyzing distant Type 1a supernovae using the Hubble Space Telescope (a discovery that eventually won the Nobel Prize in Physics in 2011), this perceivable expansion isn’t easily explained with any known matter or energy. So, the current front-running cosmological model—known as lambda cold dark matter, or ΛCDM—relies on dark energy to explain this accelerated expansion.
However, a new study put forth by one of the proponents of an alternative cosmological model—known as “timescape cosmology”—asserts that emerging evidence, such as the ever-thorny problem known as the Hubble Tension and new data from the Dark Energy Spectroscopic Instrument (DESI)—shows that dark energy may actually be an illusion caused by the way we calculate values for time and space. The results of the study were published in the journal Monthly Notices of the Royal Astronomical Society.
Calling a Nobel Prize-winning discovery essentially a measurement error is a big assertion, but David Wiltshire—who first proposed the timescape theory in 2007—and a team of scientists from the University of Canterbury (located in Christchurch, New Zealand) argue that improved analysis of Type 1a supernovae light shows that time dilation between dense matter regions of the universe (such as the Milky Way) and large void regions (such as Boötes Void) could account for the perception of an ever-accelerating expansion of the universe.
Instead of relying on the unproven idea of dark energy, the authors argue that differences in kinetic energy expansion spread across a “lumpy” universe could explain these observations.
“Our findings show that we do not need dark energy to explain why the universe appears to expand at an accelerating rate,” Wiltshire said in a press statement. “Dark energy is a misidentification of variations in the kinetic energy of expansion, which is not uniform in a universe as lumpy as the one we actually live in… With new data, the universe’s biggest mystery could be settled by the end of the decade.”
Unlike ΛCDM, which sees the universe as uniform if you take a macro-enough view, the core idea behind Wiltshire’s “timescape cosmology” is that time moves differently throughout the universe—specifically, it varies significantly between dense regions and voids. In this view, time could flow as much as 35 percent slower in dense regions like a galaxy, than it does in void regions. This means time would pass much faster in these void regions than it does here on Earthwhich could explain the appearance of an accelerating, expanding universe.
In this new study, authors analyzed 1,535 distinct Type 1a supernovae and conducted a Bayesian analysis of the data—a technique that essentially defines parameters and quantifies probabilities based on incomplete information. The results showed a strong correlation with the timescape theory, especially in the low-redshift regime (relatively nearby).
This doesn’t mean dark energy is dead—far from it. The authors explain that much more data would be needed to fully vindicate the timescape model. But, luckily, that data could be provided by the European Space Agency’s Euclid spacecraft (a machine purpose-built to explore the evolution of the dark universe) or NASA’s Nancy Grace Roman Space Telescope.
This latter spacecraft won’t nestle into one of Earth’s Lagrange points until 2027. But when it does, it’ll begin searching for answers to all the lingering questions surrounding dark energy—chief among them being whether it even exists at all.
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