- 3763 - DARK MATTER - by comparing distant stars? - Like alpha, the fine structure constant, we know precious little about dark matter, and some theoretical physicists suggest the inner parts of our galaxy might be just the dark corner we should search for connections between these two "damn mysteries of physics." If we can observe these much more distant suns with the largest optical telescopes, maybe we'll find the keys to the universe.
--------------------- 3763 - DARK MATTER - by comparing distant stars?
- How to explain electromagnetism, the law of how atoms and light interact, which explains everything from why you don't fall through the floor to why the sky is blue.
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- Our theory of electromagnetism is arguably the best physical theory humans have ever made, but, it has no answer for why electromagnetism is as strong as it is. Only experiments can tell you electromagnetism's strength, which is measured by a number called α ( alpha is the fine-structure constant).
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- The American physicist Richard Feynman, who helped come up with the theory, called this "one of the greatest damn mysteries of physics" and urged physicists to "put this number up on their wall and worry about it."
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- Astronomers tried to test whether alpha is the same in different places within our galaxy by studying stars that are almost identical twins of our sun. If alpha is different in different places, it might help us find the ultimate theory, not just of electromagnetism, but of all nature's laws together, the "theory of everything."
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- Physicists really want one thing: a situation where our current understanding of physics breaks down. New physics. A signal that cannot be explained by current theories. A sign-post for the theory of everything.
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- To find the Theory of Everything they might wait deep underground in a gold mine for particles of dark matter to collide with a special crystal. Or, they might carefully tend the world's best atomic clocks for years to see if they tell slightly different time. Or, smash protons together at nearly the speed of light in the 27-kilometer ring of the Large Hadron Collider.
- Astronomers were looking beyond Earth, beyond our solar system, to see if stars which are nearly identical twins of our sun produce the same rainbow of colors. Atoms in the atmospheres of stars absorb some of the light struggling outwards from the nuclear furnaces in their cores.
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- Only certain colors are absorbed, leaving dark lines in the rainbow. Those absorbed colors are determined by alpha.
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- The problem is, the atmospheres of stars are moving, boiling, spinning, looping, burping, and this shifts the lines. The shifts spoil any comparison with the same lines in laboratories on Earth, and hence any chance of measuring alpha. Stars, it seems, are terrible places to test electromagnetism.
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- If you find stars that are very similar maybe their dark, absorbed colors are similar as well. So instead of comparing stars to laboratories on Earth, we compared twins of our sun to each other.
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- A new test with solar twins astronomers measured the spacing between pairs of absorption lines in our sun and 16 "solar twins" stars almost indistinguishable from our sun. The rainbows from these stars were observed on the 3.6-meter European Southern Observatory (ESO) telescope in Chile.
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- While not the largest telescope in the world, the light it collects is fed into probably the best-controlled, best-understood spectrograph: HARPS. This separates the light into its colors, revealing the detailed pattern of dark lines.
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- The ESO 3.6-meter telescope in Chile spends much of its time observing Sun-like stars to search for planets using its extremely precise spectrograph, HARPS. From these exquisite spectra, we have shown that α was the same in the 17 solar twins to an astonishing precision: just 50 parts per billion. That's like comparing your height to the circumference of Earth. It's the most precise astronomical test of α ever performed.
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- Astronomers identified new solar twins much further away, about half way to the center of our Milky Way galaxy. In this region, there should be a much higher concentration of dark matter, an elusive substance astronomers believe lurks throughout the galaxy and beyond.
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November 28, 2022 DARK MATTER - by comparing distant stars? 3763
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--------------------- --- Tuesday, November 29, 2022 ---------------------------
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