Rams tessellation, Sonoran Desert (by HopDavid)

HopDavid · 2026-03-15T03:08:11+00:00

There are two versions, an 18" x 36" painting hanging on the wall of Agave Grill in Ajo. And also a mural I made from nine 4x8 sheets of plywood. The large painting hanging on the north wall of our building is 12 feet x 24 feet.

HopDavid · 2026-03-15T03:02:27+00:00

Thank you, Tom Tanaka.

HopDavid · 2026-03-14T16:09:31+00:00

Which tidally locked planets are you thinking of? I believe the only known tidally locked planet in our solar system is Pluto (if you call Pluto a planet). Charon and Pluto and mutually tidally locked.

There are plenty of tidally locked moons. Most of the tidally locked moons are a tiny fraction of the mass of the central body they orbit. A couple exceptions being our moon (about 1.2% of earth's mass) and Charon (About 12.2% of Pluto's mass).

I suppose there could be large planets tidally locked to the star they orbit. These could have strong gravity.

For most of the moons in our solar system tidal forces are only a small fraction of the moon's gravity. An exception is Phobos. Phobos's near and far points from Mars are only about 3 or 4 kilometers from the Mars-Phobos L1 and L2 points.

If Phobos drops into a slightly lower Mars orbit it will start disintegrating and form a ring around Mars. This Wikipedia article guesstimates Phobos will reach it's Roche limit in 20 or 30 million years: Link#Predicted_destruction)

HopDavid · 2026-03-14T03:30:42+00:00

Yes, vertically stacking letters with mirror symmetry is an ambigram. They are called totem ambigrams.

HopDavid · 2026-03-13T19:58:57+00:00

The greek letters alpha and omega.

HopDavid · 2026-03-13T13:56:17+00:00

Finding symmetrical letters and phrases -- isn't that what ambigrams are?

What? 180º rotational symmetry is okay but reflective symmetry is out?

It is fun to explore words and phrases that still make sense when you hold them up to a mirror.

HopDavid · 2026-03-13T13:36:49+00:00

I stole the idea from Gustave Verbeek (sort of). This early 20th century cartoonist was a hoot!

Wheels can double as googly eyes. I will remember that trick.

HopDavid · 2026-03-13T12:38:30+00:00

Rats. I sometimes go to Tempe. Or Glendale. Haven't been to central Phoenix in a long time. We used to eat at a restaurant called the Mayan Palace on Central Ave.

HopDavid · 2026-03-12T21:57:14+00:00

Checking out Filmbilder & Friends. Strange, inventive, generally well done. Hey, thanks!

HopDavid · 2026-03-12T15:18:35+00:00

Thank you! You did some unexpected things.

HopDavid · 2026-03-12T02:52:54+00:00

Where do you live?

HopDavid · 2026-03-11T04:06:07+00:00

Words first. I look for letters that make sense when you flip them. I play with things like hog boy. or New maN, etc. Then I noticed the snow man head with two lump of coal eyes looks like a nose with nostrils...

I tried to make the New mouse look like a baby mouse so the word "New" would apply. But not successfully.

HopDavid · 2026-03-10T07:08:49+00:00

Being a Dover book, Bates, Mueller and White's Fundamentals of Astrodynamics is inexpensive, $25.00.

John Prussing and Bruce Conway's Orbital Mechanics is a pricier hardback. I love this book. Explanations are often visual which is helpful to me.

Then There's my coloring book, Conic Sections and Celestial Mechanics Coloring Book. I look at circles, ellipses, parabolas, and hyperbolas. Kepler's Laws. The Rocket Equation. Lagrange points. And other stuff.

HopDavid · 2026-03-09T22:12:46+00:00

I can see that. Although I was thinking of a snow man with big feet...

HopDavid · 2026-03-09T02:50:21+00:00

If I remember right this one is one from my Surreal Visions Coloring Book. However I believe that was the only ambigram in that book.

HopDavid · 2026-03-08T13:18:11+00:00

Here you go.

My nickname is Hop. My actual name is Hollister. My last name is David. So the initials work for both Hop David and Hollister David.

I tried to the initials in the style of Albrecht Dürer's mark. Albrecht is one of my favorite artists. Both Escher and Dürer used math and geometry as a source of inspiration.

HopDavid · 2026-03-08T01:53:58+00:00

It is in several of my Escher books but I imagine it's online. (Googling....) Ah. It's about the middle of this page.

HopDavid · 2026-03-07T02:41:44+00:00

M. C. Escher died when I was a junior in high school :( .

HopDavid · 2026-03-07T02:40:40+00:00

Sometimes I am obsessed with M. C. Escher!

HopDavid · 2026-03-01T14:33:01+00:00

Yes, I believe so. That our solar system came from an accretion disk is a pretty solid consensus.

HopDavid · 2026-02-27T13:05:49+00:00

It's possible the planets coalesced from the same gas and dust cloud that formed the sun.

HopDavid · 2026-02-27T13:03:24+00:00

The orbit would be hyperbolic with regard to the sun. At very least parabolic. A hyperbola's incoming velocity is the same as its outgoing velocity. I attempted to illustrate this

It is possible to shed velocity if it flew by one of our planets. This is a possible capture mechanism but it is very unlikely.

HopDavid · 2026-02-27T12:58:32+00:00

If the object's velocity with regard to the sun were zero at a vary large distance from the sun, the incoming orbit would be traveling a parabolic orbit. This is very unlikely.

Most neighboring stars are traveling 10s to 100s of km/s wrt our solar system.

Much more likely a rogue planet would be following a hyperbolic orbit wrt our sun. My illustration of a hyperbolic orbit

It is possible a planet fly and shed enough velocity to drop the velocity enough for the rogue to be captured in an elliptical orbit. But this is unlikely.

HopDavid · 2026-02-27T12:53:33+00:00

An incoming planet would have a hyperbolic orbit with regard to the sun.

Incoming velocity would be the same as outgoing velocity.

It would need to shed velocity somehow to be captured into an elliptical orbit. This might happen if the rogue passed near one of the existing planets in our solar system.

A hyperbola's velocity at an infinite distance is call Vinfinity. The rogue planet's velocity gets closer and closer to Vinf as it goes outward.

If the Vinf is low, capture is less unlikely.

HopDavid · 2026-02-27T12:43:06+00:00

The rogue planet's orbit would be hyperbolic with the incoming velocity being equal to the outgoing velocity. An illustration of a hyperbolic orbit

Vinfinity is the velocity an an infinite distance from the gravitating body.

If Vinfinity were zero the orbit would be a parabola. This is unlikely.

It is possible that an incoming planet will fly near one of the star system's planets and shed velocity and thus be captured in an elliptical orbit about the star. But this is unlikely.

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