In new research, scientists have shared data from a special observatory, leading them to theorize that dark energy could be weakening. All of this data comes from the first year of observation by the Dark Energy Spectroscopic Instrument (DESI), a set of 5,000 robots that have worked together to map the cosmos in more detail than ever before.
Although we still don’t fully understand dark energy, a change in our understanding of the concept – from considering it constant to thinking about it weakening – could affect all of physics and influence the end of our universe.
When discussing the history of the current universe, scientists use a paradigm called the cold lambda dark matter model (ΛCDM), a mathematical equation that works in harmony with our current understanding of the origin of the universe in the Big Bang. And an essential part of it is the cosmological constant, lambda, which dates back to Albert Einstein but has evolved over time in its purpose. The constancy of lambda is essential to our understanding of the ΛCDM model, and is closely related to dark energy, which was also suggested to be constant.
However, after a year of observation at DESI in Arizona, dark energy is not behaving exactly as expected. “We’re seeing some potentially interesting differences that could indicate that dark energy is evolving over time,” director Michael Levi said on the DESI blog.
Discussing this revelation last week, Popular Mechanic’s Darren Orf explained the importance of this discovery to scientists, especially considering that this should be just the beginning of what DESI is going to discover. It is important to note that this data represents only one year of the five planned for the DESI project, and that observations may change or fit a different conclusion as more data is collected.
But it is also, and by far, the most precise set of measurements of the entire cosmos that has ever been collected. With its 5,000 plotting robots, DESI can go back a billion years at a time to create seven slices, each capturing a snapshot of history from 3 billion to 11 billion years ago. Observer robots have sophisticated capabilities to separate the layers of light and darkness in order to obtain information about the oldest reaches of the cosmos. Specifically, the fragment of data capturing the oldest cosmos is by far the most accurate to date.
So, if DESI may not be completely wrong, what does it mean that dark energy is weakening? Well, dark energy pushed the universe apart, while residual energy from the Big Bang holds things closer together. In his article for Space.com, Robert Lea makes the analogy with someone being pushed on a swing: the Big Bang is the push that naturally stops, while dark energy is a mysterious, constant, additional push that keeps the swing going. moving when no one expects it to.
If dark energy is not constant after all, any change in it would affect the rate of expansion or contraction of the universe. Mathematically, convert a ΛCDM equation with x number of variables into one with x+1. If you go back very far into algebra, you know that this means that lambda can no longer be used to link between different versions of the same equation. You will have joined the ranks of things that are always changing and must be resolved. And without a more sophisticated understanding of what dark energy means and is right now, that won’t be easy.
Without a constant for dark energy, Albert Einstein’s original fear could be true: that gravity will pull the universe inward, causing a Big Crunch that reverses or undoes the Big Bang.
While there is certainly no comfortable version of the end of our universe in billions of years, it might be more pleasant to imagine a symmetrical end of events than to imagine the slow, drifting expansion and death of another theory: the Big Chill. In any case, DESI maintains its original plans to deepen and enrich our knowledge of the cosmos. Our current models are, at most, 25 years old, since it was discovered that the universe is expanding rapidly. The DESI team has published a series of preprint papers (not yet peer-reviewed) on the first year of data, as well as a lengthy press release from the Lawrence Berkeley National Laboratory overseeing the project.
What you discover over the next few years of operation will undoubtedly be illuminating.
Caroline Delbert is a writer, avid reader, and contributing editor at Pop Mech. She’s also an enthusiast of just about everything. Her favorite topics include nuclear energy, cosmology, mathematics of everyday things, and the philosophy of it all.
