Archive for October 14th, 2019

Measured one way, the universe appears expanding at a certain rate; measured another way, the universe appears to be expanding at a different rate. And, as a new paper shows, those discrepancies have gotten larger in recent years, even as the measurements have gotten more precise.

“We think that if our understanding of cosmology is correct, then all of these different measurements should be giving us the same answer,” said Katie Mack, a theoretical cosmologist at North Carolina State University (NCSU) and co-author of the new paper.

The two most famous measurements work very differently from one another. The first relies on the Cosmic Microwave Background (CMB): the microwave radiation leftover from the first moments after the Big Bang. Cosmologists have built theoretical models of the entire history of the universe on a CMB foundation — models they’re very confident in, and that would require an all-new physics to break. And taken together, Mack said, they produce a reasonably precise number for the Hubble constant, or H0, which governs how fast the universe is currently expanding.

The second measurement uses supernovas and flashing stars in nearby galaxies, known as Cepheids. By gauging how far those galaxies are from our own, and how fast they’re moving away from us, astronomers have gotten what they believe is a very precise measurement of the Hubble constant. And that method offers a different H0.

“If we’re getting different answers that means that there’s something that we don’t know,” Mack told Live Science. “So this is really about not just understanding the current expansion rate of the universe — which is something we’re interested in — but understanding how the universe has evolved, how the expansion has evolved, and what space-time has been doing all this time.”

Weikang Lin, also a cosmologist at NCSU and lead author of the paper, said that to develop a full picture of the problem, the team decided to round up all the different ways of “constraining” H0 in one place.Here’s what “constraining” means: Measurements in physics rarely turn up exact answers. (Think what this would be if lifted into the field of  forensic science, No murder may be pinned on the guilty.) Instead, they put limits on the range of possible answers. And by looking at these constraints together, you can learn a lot about something you’re studying. (In legal terms it would be a technical loophole). Looking through one telescope, for example, you might learn that a point of light in space is either red, yellow or orange. Another might tell you it’s brighter than most other lights in space but less bright than the sun. Another might tell you it’s moving across the sky as fast a planet. None of those constraints would tell you much on their own, but taken together they suggest  you are looking at Mars.

In an earlier post I had posited that Scientists are looking at universe from the wrong end of the telescope. Closer home things appear reliable and Laws of Newton or Kepler can be proved. Our predicament is that of the Flying Dutchman the more he sails the coast line further eludes him. He sees only what he believes in. Having failed to understand God as the Creator of Universe, sail he must never arriving at the one article that holds everything in order. What reason! What pother!

(Ack: How the Universe Stopped Making Sense/Life Science/Space/Rafi Letzter/Oct. 11,2019)


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This sketch was made of a tree on the premises of Bolghatty Hotel, Fort Kochi, Kerala, 1994

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