Another telescope has entered the debate about the age and expansion rate of the Universe.
This topic has recently become the subject of an energetic to and fro among scientists using different astronomical facilities and techniques.
The new entrant is the Atacama Cosmology Telescope in Chile.
It’s been studying the “oldest light” on the sky and has concluded the Big Bang occurred 13.77 billion years ago, give or take 40 million years. That’s almost exactly the same number we got from Europe’s flagship Planck space observatory mission, which mapped the ancient light in the early 2010s.
But therein lies the problem because other telescopes using different methods have come out with ages that are a few hundred million years younger.
What they’ve all been trying to do is measure what’s known as the Hubble Constant – the value used by astronomers to describe cosmic expansion.
The further away you look, the faster galaxies are receding from us. Ever since the American astronomer Edwin Hubble first detailed this relationship in 1929, researchers have meticulously tried to put a number on it.
There are two leading approaches. One is to map the distance to local variable (cepheids) and exploding (supernovas) stars and try to gauge the recession rate from their movement. The other is to look at the state of the cosmos shortly after the Big Bang and to use what we know about the physics at work at this early time to predict what the constant should be.
Planck, and now the ACT, pursued this latter concept. To do it, they’ve both surveyed the Cosmic Microwave Background.
The CMB was the first light to sweep out across space once the Universe had cooled sufficiently to permit the formation of neutral hydrogen atoms – about 380,000 years into the life of the cosmos.
Both groups have now hammered down the uncertainties in their respective measurements to such a degree that the gap between them is unbridgeable. One or both is wrong somewhere, or perhaps there is some new physics out there that neither side has grasped.
“It’s possible that there are still some small biases in either the CMB or supernova datasets (or both) that are not being accounted for completely. But as the observations improve, it’s becoming more difficult to see what that could be,” commented Prof Isobel Hook from Lancaster University, UK.
“The alternative is that there’s something fundamental about the Universe that we’re not understanding.
Source: BBC
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