Is the universe halfway to its end? New theory predicts a Big Crunch in 33 billion years
That might sound far off, but in cosmic terms, it's uncomfortably soon.
Over the past year, astronomers working with the Dark Energy Survey (DES) and the Dark Energy Spectroscopic Instrument (DESI) have spotted something intriguing: dark energy, the mysterious force causing the universe to expand faster and faster – might not be a constant after all. Instead, it could be changing over time. And if that's true, it's a big deal. It would challenge one of the core assumptions of modern physics: that dark energy is a stable, unchanging force.
Right now, the leading model of dark energy is the cosmological constant, a number Einstein introduced in his equations over a century ago. But the new observations suggest that this constant might not be enough to explain what's really going on.
A fresh, not-yet-peer-reviewed paper (The Lifespan of our Universe) from June proposes a more complex idea- that dark energy is made up of two components. The first is an axion- a strange, hypothetical particle so light and elusive that it hardly ever interacts with anything. Imagine these axions as a gentle energy mist, quietly stretching across the universe, fueling its current accelerated expansion.
The second is the cosmological constant, but in this model, it's negative. Unlike a positive constant that pushes space outward, a negative one would pull it back. Right now, the axions are doing most of the expanding work. But as time passes, the axions are expected to fade. And when they do, the negative cosmological constant will start to dominate- slowing down the expansion, then reversing it.
This would kickstart a dramatic new phase- the Big Crunch. Galaxies would crash into each other. Space would shrink. The universe would heat up and grow denser, spiraling into a final singularity, the opposite of the Big Bang.
According to the theorists, the 'beginning of the end' will start in about 10 billion years, which is less than the current age of the universe. After that, it'll take another 10 billion years for everything to collapse. The universe, then, would have a total lifetime of around 33 billion years- meaning it's already past the halfway mark.
Of course, this theory is still highly speculative.The DES and DESI findings are early results. They'll need to be confirmed by future observations. And even if the cosmological constant turns out to be inaccurate, it doesn't automatically prove this two-part axion model is right. Still, it opens the door to new questions about the ultimate fate of everything we know.
Until then, the universe keeps expanding—and we keep watching the skies.s
(This article has been curated by Kaashvi Khubyani, who is an intern with The Indian Express.)
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