- 2806 - UNIVERSE AGE - measuring the oldest light. Ancient light from the Big Bang has revealed a new estimate for the universe's age of 13.77 billion years, + or - 40 million years. The new estimate, based on data from an array of telescopes in the Chilean Atacama Desert. The new data also estimates how fast is the universe expanding.
--------------- 2806 - UNIVERSE AGE - measuring the oldest light.
- I finally found something older then the guys in my coffee club. Ancient light from the Big Bang has revealed a new estimate for the universe's age of 13.77 billion years, + or - 40 million years.
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- Physicists need to understand the universe's expansion rate to make any sense of cosmology. They know that a mysterious substance called “dark energy” is causing the universe to expand at an ever-increasing rate in all directions. But, how fast is it expanding? And, is it a constant expansion or an accelerating expansion. And, what is causing it?
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- When astronomers point their telescopes into space to measure the Hubble constant ,the number that describes how fast the universe is expanding at different distances from us or another point, they come up with numbers that disagree with each other, depending on the method they use.
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- The Hubble Constant tells us the universe is expand at an accelerating rate of 49,300 miles per hour for ever million lightyears of distance.
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- One method, based on measurements of how fast nearby galaxies are moving away from the Milky Way, produces one number for H0. Another method, based on studying the oldest light in space, or cosmic microwave background (CMB), produces a different number for H0. Which is right?
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- This disagreement has left scientists wondering whether there's some important blind spot in their measurements or theories.
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- The data from the Planck satellite, released in 2018, were the most important measurements of the CMB before now. With an unprecedented level of precision, they showed how sharply CMB measurements of H0 disagree with measurements based on the movement of nearby galaxies.
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- These new results recalculated the CMB measurement from scratch using an entirely different set of telescope data and calculations, and came up with very similar results. That alone doesn't prove that the CMB measurement of H0 is correct. There could still be some problem with the physics theories used to make the calculation.
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- Relying on data from the Atacama Cosmology Telescope in Chile's Atacama Desert, the researchers tracked faint differences between different parts of the CMB, which appears to have different energy levels in different parts of the sky.
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- The CMB, which formed as the universe cooled after the Big Bang, is detectable in every direction in space as a microwave glow. It's more than 13 billion light-years in the distance, a relic of a time before stars and galaxies formed.
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- By combining theories on how the CMB formed with precise measurements of its fluctuations, physicists can determine how fast the universe was expanding at that moment in time. That data can then be used to calculate H0.
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- The other methodically scanned half the sky looking particularly at microwave light. These researchers spent years cleaning up and analyzing the data with the aid of supercomputers, removing other microwave sources that are not part of the CMB, to stitch together a full map of the CMB.
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- That whole time, they "blinded" themselves to the implications of their work, they wrote in their papers, meaning they didn't look at how their choices affected estimates of H0 until the very end. Only when the full CMB map was complete did the researchers use it to calculate H0.
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- The new CMB map also offered a new measure for the distance between Earth and the CMB. That distance, combined with a new measurement of how fast the universe has expanded over time, allowed a precise calculation of the age of the universe.
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- It's still possible that some error in those theories is messing up the calculation. But it's not clear what the error would be.
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- The other approach to calculating H0 relies on pulsing stars known as “Cepheids“, which reside in distant galaxies and pulse regularly. That timed pulsing allows researchers to perform precise calculations of their motion and distances from Earth.
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- With those direct speed measurements, it's fairly straightforward to come up with a measurement of H0. There are no complicated cosmological theories involved. But it's possible, some scientists have proposed, that our region of the universe is just weirdly empty, and not representative of the whole universe.
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- It is even possible that there are measurement issues with the cepheids, and that these cosmic measuring sticks don't work quite the way physicists expect.
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- Stay tuned there is still more to learn how we got here. I will save that for the next Review.
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- August 31, 2020 2806
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