- 3744 ELECTROMAGNETISM - is hard to explain? There is an awkward problem with our understanding of nature's laws which physicists have been trying to explain for decades. It's about “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.
--------------------- 3744 - ELECTROMAGNETISM - is hard to explain?
- 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 alpha, or 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 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 it this new theory scientists went deep underground in a gold mine to measure particles of dark matter colliding with a special crystal. They also carefully tended to the world's best atomic clocks for years to see if they tell slightly different time. They also smash protons together at (nearly) the speed of light in the 27-km ring of the Large Hadron Collider.
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- Astronomers decided to look 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 so measuring the dark lines very carefully also lets us measure 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 are terrible places to test electromagnetism.
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- If you find stars that are very similar, twins of each other, 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 measured the spacing between pairs of absorption lines in our sun and 16 "solar twins", stars almost indistinguishable from our sun.
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- The rainbows from these stars were observed on the 3.6-meter European Southern Observatory (ESO) telescope in Chile. The light it collects is fed into 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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- HARPS spends much of its time observing sun-like stars to search for planets. Handily, this provided a treasure trove of exactly the data. From these exquisite spectra, astronomers have shown that alpha 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 alpha ever performed.
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- Astronomers have recently 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.
- Like alpha, 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 mysteries of physics.
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- If we can observe these much more distant suns with the largest optical telescopes, maybe we'll find the keys to the universe.
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- In their research astronomers have found the original nucleus of the Milky Way galaxy.
Astronomers have long theorized that a nucleus of stars almost certainly exists at the center of the Milky Way galaxy, but until now, they have been unable to find proof.
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- They began sifting through data from the “Gaia space telescope“. If there is a nucleus of stars at the center of the galaxy, they very likely contain much less metal than other stars because they would have been formed before such metals were scattered across the area where the Milky Way formed, approximately 12.5 billion years ago.
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- Thus, they would likely be made up mostly of helium and hydrogen. Looking only for stars that fit into this category narrowed things down somewhat, and, so did theories that have long suggested that if there is a nucleus of stars at the center of the galaxy, it would most likely be located in the constellation Sagittarius, as it is situated at what appears to be the center of the disk that makes up the galaxy.
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- Astronomers began sifting through 2 million stars, a daunting task. But through computer assistance and perseverance, they found what they were looking for, a cluster of approximately 18,000 stars at the center of the Milky Way galaxy. The stars in the cluster have less than 3% of the metal concentration of stars farther away.
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- To further test the star cluster, the researchers noted its movement compared to other stars around it and also pinpointed the location of what should be the center of the galactic disk.
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- They also accounted for stars blocked by dust or other objects. Convinced that they had found the heart of the Milky Way, they took measurements and found the cluster makes up just 0.2% of the mass of the galaxy.
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- The great thing about astronomy is we still have a lot more to learn.
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November 13, 2022 ELECTROMAGNETISM - is hard to explain? 3741
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