The Persistence of Memory

The goal of this blog is make everyone a star at the Friday night dinner table....

Every 133 years, a 26-km (16-mi) diameter rock called Comet Swift-Tuttle flies right though Earth's orbital plane.

(Fortunately, the Earth has always been far away from that part of our orbit when it passes by.)

It leaves a trail of debris, tiny particles of dust. When the Earth wanders around to that part of our orbit, that dust hits our atmosphere "windshield", each little bit burning up in a brief brilliant flash.

Perhaps you were lucky enough to be outside last night and happened to turn your gaze to Heaven at just the right time to enjoy one of these so-called "Perseid" shooting-stars.

(If you missed it this global fireworks show, tonight should be pretty good viewing too. Just make sure you're looking in the right direction. And if you miss it tonight, mark your calendar for next August 10 or 11).

(And if you see one, you can say a bracha.)

So yesterday when I asked someone, "Are you going to go out and look for shooting stars," he dismissed the idea, saying, "I've seen them before."

Hmm... Let's think about that a bit.

"Want to go watch the sunset?"
"Naw, I've seen sunsets before."
"Want to go snorkeling?"
"Naw, I've seen fish before. Ate my share of 'em too."
"Want to go to a ball game?"
"Naw, I've been to ball games before."
"Want to play frisbee?"
"Naw, done that before..."

(BTW, just looking out the window last night, I saw a huge one that must have covered 20° of sky.)

In a separate conversation this week, I mentioned to someone that Rosh Hashana is six weeks away.

Response: "Six weeks? How could it be so soon? It feels like we just finished Pesach!"

(At least she didn't say, "I'm skipping Rosh Hashana this year. I've done it before.")

Question #1 for your table: What do Jewish holidays and the Perseid Meteor Shower have in common?

Well, they each come once a year.

Question #2: Why do we need holidays once a year, and why a person who saw the Perseids - even as recently as last year - should get off the couch and go see them again?

A: We forget.

We think we remember, but we forget.

What we think we recall is actually a fuzzy approximation. It's a persistent memory, but is like the clocks in Dali's painting, warping with time.

That's why we need, for example, the 9th of Av again (this Saturday night - Sunday). Lest we forget.

That's why we need to put away the phone and seize those amazing encounters with nature.

Yet I imagine most of us have our experiences that we did enjoy but would not choose to have again.

Question #3 for your table: What's yours?


Shabbat Shalom

PS - In addition to our teachamazingnature.com.program for teachers and schools, we have this free resource for parents (try searching under category: school supplies)

PPS - The New Yorker has become a notable source of interesting, succinct science writing.

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When Life is Hanging by a Thread

There are two things I’ll bet you don’t know about the lowly caterpillar:

1 – Why is it called caterpillar?

2 – Why do you often see one hanging from what looks like a spider thread?

A1 – The name caterpillar supposedly derives (as usual) from a French word, meaning “hairy cat”. The hairy part I get, but cat? Let’s send that one back to the etymological drawing board.

A2 – caterpillars have a real problem. They have really really poor senses of sight, hearing and smell.

Imagine a caterpillar sitting on a leaf.

The wind blows and rustles the leaf, no problem.

A twig falls and strikes the leaf, not at all scary.

A fly lands on the leaf, our little furry fella yawns.

But when a wasp lands on the leaf and starts to approach his blind and deaf prey, the little guy shoots out a silk thread which sticks to the leaf, and leaps over the edge, dangling out of sight and out of danger. After the bloodthirsty wasp departs, little caterpillar hoists himself up the lifeline and resumes his busy eating schedule.

Prof. Ignacio Castellanos (Hidalgo, Mexico) has proven that the caterpillar can distinguish between all of these various motions of the leaf by mere sense of touch.

How did it learn to do that?

(Sometimes I wonder why biology departments are not full of religious people.)

Here’s a summer challenge for you….When you are outside, enjoying the warm weather and natural beauty of this world, find the “picture perfect” moment (butterfly, sunset, etc.) and DON’T take a picture. Take it in with a deep breath, knowing that it is THIS moment that counts, not the digital memory of it.

Shabbat Shalom

PS – hat-tip to Highlights for Children for alerting me to Dr. Castellanos’s research!

PPS – Remember The Very Hungry Caterpillar? Creator Eric Carle has a whole zoo’s worth of sequels...click here.

Sometimes hanging by the thread brings it’s own danger:



“One ought never to turn one’s back on a threatened danger and try to run away from it. If you do that, you will double the danger. But if you meet it promptly and without flinching, you will reduce the danger by half. Never run away from anything. Never!” - Churchill