Sunday, 2021 November 7, 18:29 — blogdom

coming in the side door

Spam comments on this blog have always been concentrated on a few old posts, so I tried disabling comments on some that look unlikely to ever attract legitimate comments.

Didn’t work. I guess all that happens when I unclick “Allow comments” is that the comment form goes away, without closing whatever channel the bots use.

Saturday, 2021 October 23, 15:32 — general

how to enact a balanced budget

(Moving here from a separate file for greater visibility.)


Suppose each member of Congress were to name a budget amount, and the median number is made law. Why the median? Because this is a number such that half the members have approved at least that number.

Of course, this number is likely to include a deficit. What to cut?

There are 435 numbers for each budget item. Let B(i,m) be mth-lowest amount chosen for budget item i; let T(m) be the sum over i of B(i,m). Let k be the highest number such that T(k) < revenue. If each budget item is enacted as B(i,k), then the budget is balanced. (Of course, if B(i,k) is higher than the median in one house or the other, it must be lowered.) This rule has the effect of temporarily requiring a supermajority for spending. Congressmen won't gain by inflating their numbers; that would just lower k. Pork-barrels would be highly vulnerable to clipping, while programs backed by a consensus would be immune.

Thursday, 2021 October 21, 18:55 — mathematics


I just thought of a new kind of packing problem, a mutant extension of the Thomson problem. In this version, each particle has coordinates in two independent spaces; in each it is confined to a sphere (of some dimension). In each space, pairs of particles repel each other with a force inversely proportional to the square of their distance in the other space.

(I was imagining a head with striped hairs, as one does, and considered making each hair’s phase anti-correlated with those of its neighbors, and what that would mean.)

Friday, 2021 October 8, 11:07 — mathematics

O fairest of randomizers

On most numbered dice, opposite sides are complementary; on a cube, for example, they add to 7. As a result, if you have the skill to throw a die so that the {1,2,3} corner lands on the table, the upward face must be at least 4.

I would prefer to design dice so that, if numbers are considered as masses, the center of mass coincides with the geometric center. I think this is equivalent to saying: the sum of the numbers in any hemisphere must be equal.

You can’t do that with a tetrahedron, cube, D10 or regular dodecahedron; but I found three solutions for the octahedron, and 876 for the rhombic dodecahedron. (At least I see no obvious way to reduce that number further with symmetries.)

For a cube the best you can do is put pairs of adjacent numbers on opposite faces.
The twelve best arrangements on the regular dodecahedron all have 0 and 11 opposite each other, 1–5 around 11, and 6–10 around 0.
The two best arrangements for D10 are 0285364179 and 0582367149 (reading around the fivefold axis, alternating upper and lower faces).
(Add 1 to each number if you don’t like zero-based indexing; it doesn’t affect the math.)

I’ll update here if I come up with an approach to the icosahedron problem that won’t take thousands of years.

Thursday, 2021 September 16, 19:58 — sciences

shining eyes

Could an animal have eyes like a reflecting telescope, rather than with a lens? The back of the eyeball is a paraboloid mirror, and the retina is a small body on its focal plane.

Because the retina must be small, such an eye would have poorer resolution than a vertebrate eye of similar size.

Are there any organic mirrors in the real world? How smooth is the reflective layer behind a cat’s retina?

Perhaps I’ll inflict this idea on – in the form of a question, though I dislike Jeopardy for that gimmick.

Thursday, 2021 August 26, 19:02 — astronomy, mathematics

witness on Whidbey

I watched Behind the Curve (2018), a documentary about the Flat Earth movement. In the beginning, Mark Sargent says (I paraphrase), “I know the Earth is not round because I can see Seattle from here [Whidbey Island].”

If I knew the distance from the Space Needle to Sargent’s house, the altitude of that house and the altitude of the lowest part of the Space Needle visible from there, I could put an upper bound on the curvature.

Saturday, 2021 August 14, 12:41 — prose

escapism within escapism

I recently read the Long Earth saga by Terry Pratchett and Stephen Baxter. The story begins in the near future when an eccentric engineer anonymously publishes plans for a “stepper box” which takes the user to a parallel world, adjacent in a chain of millions.

It soon emerges that a few humans have the talent of Stepping without a box. In one episode, two of these (including an ancestor of a main character) help the Underground Railroad, provoking in me a question they did not ask: Rather than sneaking the escapees to Canada, what if we leave them in a side-world? They’d have to learn to live Paleolithic-style (metallic iron cannot be transported), but that life evidently was not so bad.

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