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Posts Tagged ‘symmetry

“Two obsessions are the hallmarks of Nature’s artistic style: Symmetry- a love of harmony, balance, and proportion [and] Economy- satisfaction in producing an abundance of effects from very limited means”*…

Life is built of symmetrical structures. But why? Sachin Rawat explores…

Life comes in a variety of shapes and sizes, but all organisms generally have at least one feature in common: symmetry.

Notice how your left half mirrors the right or the radial arrangement of the petals of a flower or a starfish’s arms. Such symmetry persists even at the microscopic level, too, in the near-spherical shape of many microbes or in the identical sub-units of different proteins.

The abundance of symmetry in biological forms begs the question of whether symmetric designs provide an advantage. Any engineer would tell you that they do. Symmetry is crucial to designing modular, robust parts that can be combined together to create more complex structures. Think of Lego blocks and how they can be assembled easily to create just about anything.

However, unlike an engineer, evolution doesn’t have the gift of foresight. Some biologists suggest that symmetry must provide an immediate selective advantage. But any adaptive advantage that symmetry may provide isn’t by itself sufficient to explain its pervasiveness in biology across scales both great and small.

Now, based on insights from algorithmic information theory, a study published in Proceedings of the Natural Academy of Sciences suggests that there could be a non-adaptive explanation…

Symmetrical objects are less complex than non-symmetrical ones. Perhaps evolution acts as an algorithm with a bias toward simplicity: “Simple is beautiful: Why evolution repeatedly selects symmetrical structures,” from @sachinxr in @bigthink.

Frank Wilczek (@FrankWilczek)


As we celebrate symmetry, we might recall (speaking of symmetry) that it was on this date in 1963 that the Equal Pay Act of 1963 was signed into law by president John F. Kennedy. Aimed at abolishing wage disparity based on sex, it provided that “[n]o employer having employees subject to any provisions of this section [section 206 of title 29 of the United States Code] shall discriminate, within any establishment in which such employees are employed, between employees on the basis of sex by paying wages to employees in such establishment at a rate less than the rate at which he pays wages to employees of the opposite sex in such establishment for equal work on jobs[,] the performance of which requires equal skill, effort, and responsibility, and which are performed under similar working conditions, except where such payment is made pursuant to (i) a seniority system; (ii) a merit system; (iii) a system which measures earnings by quantity or quality of production; or (iv) a differential based on any other factor other than sex […].

Those exceptions (and lax enforcement) have meant that, 60 years later, women in the U.S. are still paid less than men in comparable positions in nearly all occupations, earning on average 83 cents for every dollar earned by a man in a similar role.


“For the moment we might very well can them DUNNOS (for Dark Unknown Nonreflective Nondetectable Objects Somewhere)”*…

When does one give up on a hypothesis?…

In 1969, the American astronomer Vera Rubin puzzled over her observations of the sprawling Andromeda Galaxy, the Milky Way’s biggest neighbour. As she mapped out the rotating spiral arms of stars through spectra carefully measured at the Kitt Peak National Observatory and the Lowell Observatory, both in Arizona, she noticed something strange: the stars in the galaxy’s outskirts seemed to be orbiting far too fast. So fast that she’d expect them to escape Andromeda and fling out into the heavens beyond. Yet the whirling stars stayed in place.

Rubin’s research, which she expanded to dozens of other spiral galaxies, led to a dramatic dilemma: either there was much more matter out there, dark and hidden from sight but holding the galaxies together with its gravitational pull, or gravity somehow works very differently on the vast scale of a galaxy than scientists previously thought.

Her influential discovery never earned Rubin a Nobel Prize, but scientists began looking for signs of dark matter everywhere, around stars and gas clouds and among the largest structures in the galaxies in the Universe…

But… over the past half century, no one has ever directly detected a single particle of dark matter. Over and over again, dark matter has resisted being pinned down, like a fleeting shadow in the woods. Every time physicists have searched for dark matter particles with powerful and sensitive experiments in abandoned mines and in Antarctica, and whenever they’ve tried to produce them in particle accelerators, they’ve come back empty-handed. For a while, physicists hoped to find a theoretical type of matter called weakly interacting massive particles (WIMPs), but searches for them have repeatedly turned up nothing.

With the WIMP candidacy all but dead, dark matter is apparently the most ubiquitous thing physicists have never found. And as long as it’s not found, it’s still possible that there is no dark matter at all. An alternative remains: instead of huge amounts of hidden matter, some mysterious aspect of gravity could be warping the cosmos instead…

Dark matter is the most ubiquitous thing physicists have never found; Ramin Skibba (@raminskibba) wonders if it isn’t time to consider alternative explanations: “Does dark matter exist?” in @aeonmag.

* Bill Bryson on dark matter, in A Short History of Nearly Everything (2003)


As we interrogate the invisible, we might send observant birthday greetings to Val Logsdon Fitch; he was born on this date in 1923. A particle physicist, he shared the 1964 Nobel Prize in Physics with his collaborator James Cronin for their experiments proving that some subatomic reactions do not adhere to fundamental symmetry principles (and are therefore indifferent to the direction of time).

By examining the decay of K-mesons, they proved that a reaction run in reverse does not retrace the path of the original reaction, which showed that the reactions of subatomic particles are not indifferent to time. Thus the phenomenon of CP violation was discovered… and thus was demolished the faith that physicists had previously had that natural laws were universally governed by symmetry.


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