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June 24, 2021

How the Slinky buckles — A series of experiments shed light on 'overcurvature'

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As opposed to haute couture.

But I digress.

Below, excerpts from Evelyn Lamb's March 2013 Scientific American article.

Camping enthusiasts and aspiring modern sculptors take heed: researchers have achieved a breakthrough in understanding and controlling overcurvature, which is found in such disparate settings as pop-up tents, DNA plasmids and curved origami.

Overcurvature occurs when a ring is too curved to lie flat in a plane the way a normal circle does.

For example, if you detached a segment of a Slinky and connected its ends to make a closed loop, you would have a hard time getting the whole thing to lie flat on the floor.

The intrinsic curvature of the Slinky would cause the ring to buckle and assume a three-dimensional saddle shape.

In fact, the Slinky played a major role in this research project, the results of which were published in the journal Nature Communications last December.

After observing overcurved rings of various sizes and materials, the researchers found a family of curves with fairly simple mathematical descriptions that they believed would model the shapes these overcurved rings take in space.

They used loops made from portions of plastic Slinkys as the setting for precise measurements and found that their predicted curves were indeed what they observed in the Slinkys.

"It was really surprising to us," says Alain Jonas, a materials scientist at the Catholic University of Leuven in Belgium, who led the research. "It was this experience where you find something and it actually fits!"

The paper includes an efficient pathway for folding pop-up tents and other overcurved rings, as shown in the illustration at the top.

1) To fold a ring into three loops, place your hands on opposite sides of the ring.

2) As you lift up, bring your hands together and grab the opposite sides in one hand.

3) Use your free hand to coax the two opposite sides down and toward each other to form a saddle shape.

4) At both the top and the bottom, push one side over the other and collapse the loops together.

This method differs from the approach that people usually take: it requires more energy initially but uses less overall.

"It's not very intuitive when you do it," Jonas says, "but that's what the physics of the problem wants."

After performing the research, he borrowed a friend's tent to practice the technique and his colleagues had developed.

It was a success.

June 24, 2021 at 04:01 PM | Permalink | Comments (1)

'For All Mankind'

This alternate history sci-fi series imagines what would have happened if the Soviet Union had been first to land a man on the moon in 1969.

It's tightly written and quite plausible and very entertaining, especially the episodes at the end of Season 1 focused on the establishment of rival bases on the moon in the early 1970s.

Season 2 ends in 1995; a third season is upcoming.

June 24, 2021 at 02:01 PM | Permalink | Comments (0)

What is it?

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Answer here this time tomorrow.

Hint: smaller than a bread box.

Another: no moving parts.

A third: plastic.

June 24, 2021 at 12:01 PM | Permalink | Comments (4)

Picture of the day

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June 24, 2021 at 10:01 AM | Permalink | Comments (0)

Bizarro World Clock Runs Backwards

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From their world to ours.

$14.99.

June 24, 2021 at 08:01 AM | Permalink | Comments (1)

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