[ad_1]
Over ten years in the past, the Darkish Vitality Survey (DES) started mapping the universe to seek out proof that would assist us perceive the character of the mysterious phenomenon referred to as darkish power. I’m considered one of greater than 100 contributing scientists which have helped produce the ultimate DES measurement, which has simply been launched on the 243rd American Astronomical Society assembly in New Orleans.
Darkish power is estimated to make up practically 70% of the observable universe, but we nonetheless don’t perceive what it’s. Whereas its nature stays mysterious, the impression of darkish power is felt on grand scales. Its main impact is to drive the accelerating enlargement of the universe.
The announcement in New Orleans might take us nearer to a greater understanding of this type of power. Amongst different issues, it provides us the chance to check our observations in opposition to an thought known as the cosmological fixed that was launched by Albert Einstein in 1917 as a means of counteracting the consequences of gravity in his equations to attain a universe that was neither increasing nor contracting. Einstein later eliminated it from his calculations.
Nevertheless, cosmologists later found that not solely was the universe increasing, however the enlargement was accelerating. This remark was attributed to the mysterious amount known as darkish power. Einstein’s idea of the cosmological fixed may truly clarify darkish power if it had a constructive worth (permitting it to adapt to the accelerating enlargement of the cosmos).
The DES outcomes are the end result of many years of labor by researchers across the globe and supply probably the greatest measurements but of an elusive parameter known as “w”, which stands for the “equation of state” of darkish power. Because the discovery of darkish power in 1998, the worth of its equation of state has been a elementary query.
This state describes the ratio of strain over power density for a substance. Every part within the universe has an equation of state.
Its worth tells you whether or not a substance is gas-like, relativistic (described by Einstein’s idea of relativity) or not, or if it behaves like a fluid. Understanding this determine is step one to actually understanding the true nature of darkish power.
Our greatest idea for w predicts that it needs to be precisely minus one (w=-1). This prediction additionally assumes that darkish power is the cosmological fixed proposed by Einstein.
À lire aussi :
The Euclid spacecraft will rework how we view the ‘darkish universe’
Subverting expectations
An equation of state of minus one tells us that because the power density of darkish power will increase, so the unfavorable strain additionally will increase. The extra power density within the universe, the extra repulsion there’s – in different phrases, matter pushes in opposition to different matter. This results in an ever-expanding accelerating universe. It would sound a bit weird, as it’s counterintuitive to every part we expertise on Earth.
The work makes use of essentially the most direct probe we now have on the enlargement historical past of the universe: Sort Ia supernovae. These are a kind of star explosion they usually act as a sort of cosmic yardstick, permitting us to measure staggeringly giant distances far into the universe. These distances can then be in comparison with our expectations. This is similar approach that was used to detect the existence of darkish power 25 years in the past.
The distinction now’s within the dimension and high quality of our pattern of supernovae. Utilizing new strategies, the DES crew has 20 instances extra knowledge, over a variety of distances. This enables for one of the vital exact ever measurements of w, giving a worth of -0.8
At first sight, this isn’t the exact minus one worth that we predicted. This would possibly point out that it’s not the cosmological fixed. Nevertheless, the uncertainty on this measurement is giant sufficient to permit minus one at a 5% probability, or betting odds of solely 20 to 1. This stage of uncertainty is just not adequate but to say both means, nevertheless it’s a superb begin.
The detection of the Higgs Boson subatomic particle in 2012 on the Giant Hadron Collider required odds of 1,000,000 to 1 probability of being incorrect. Nevertheless, this measurement might sign the tip of “Large Rip” fashions which have equations of state which might be extra unfavorable than one. In such fashions the universe would increase indefinitely at a sooner and sooner charge – finally pulling aside galaxies, planetary methods and even space-time itself. That’s a reduction.
As normal, scientists need extra knowledge and people plans are already properly underway. The DES outcomes counsel that our new strategies will work for future supernova experiments with ESA’s Euclid mission (launched July 2023) and the brand new Vera Rubin Observatory in Chile. This observatory ought to quickly use its telescope to take a primary picture of the sky following building, giving a glimpse into its capabilities.
These next-generation telescopes may discover hundreds extra supernovae, serving to us make new measurements of the equation of state and shedding much more gentle on the character of darkish power.
[ad_2]
Source link
