mdturnerphys

"Seeing this minaret, medieval Europeans mistook it for the biblical Tower of Babel (Gen. 11:1-9), and, as such, it lent its form to medieval and Renaissance representations of the tower, as in the famous “Tower of Babel” by Bruegel (1563)."

There was a talk on this back in 2007: https://www.youtube.com/watch?v=yL_-1d9OSdk

Actually, the first automated in-car navigation systems used mechanical couplings to a wheel to determine progress along a set route: https://arstechnica.com/cars/2020/01/turn-by-turntables-how-...

Flight tracking: https://flightaware.com/live/flight/GKA264/history/20220420/...

The bill doesn't appear to have an effective date: https://www.congress.gov/bill/117th-congress/senate-bill/623...

More info here: https://www.reuters.com/world/us/us-senate-approves-bill-tha...

Important note: "Senator Marco Rubio said after input from airlines and broadcasters that supporters agreed that the change would not take place until November 2023."

Watching the events in Ukraine unfold recently reminded me of his cynical "War is Kind":

Do not weep, maiden, for war is kind.

Because your lover threw wild hands toward the sky

And the affrighted steed ran on alone,

Do not weep.

War is kind.

--

Hoarse, booming drums of the regiment,

Little souls who thirst for fight,

These men were born to drill and die.

The unexplained glory flies above them,

Great is the battle-god, great, and his kingdom—

A field where a thousand corpses lie.

--

Do not weep, babe, for war is kind.

Because your father tumbled in the yellow trenches,

Raged at his breast, gulped and died,

Do not weep.

War is kind.

--

Swift, blazing flag of the regiment,

Eagle with crest of red and gold,

These men were born to drill and die.

Point for them the virtue of slaughter,

Make plain to them the excellence of killing

And a field where a thousand corpses lie.

--

Mother whose heart hung humble as a button

On the bright splendid shroud of your son,

Do not weep.

War is kind.

Submarines have been using gravity gradiometers for navigation for decades. Tom Clancy revealed what was then classified information about these in The Hunt for Red October. They can serve as passive collision avoidance systems or let the navigators use geological features to correct drift in inertial navigation. The later application requires gravity gradient maps. They are useful for submarines because they are completely passive, unlike active sonar that produces a signal others can detect.

Sweden planted 300,000 oak trees on a particular island in the 1830s, after the Napoleonic wars, to provide lumber for future naval ships. It takes the trees about 150 years to reach a suitable size, so they were well obsolete for their intended purpose before they were ready.

https://www.atlasobscura.com/places/visingso-oak-forest

Ring laser gyros are fairly well known, but there's another way you can make a gyro with no mechanically spinning parts using the right combination of magnets. This paper describes an experimental apparatus that incidentally serves as a solid-state gyrocompass: https://arxiv.org/abs/hep-ph/0606218

(Disclaimer: I did my PhD in this group but started there after this paper was published.)

Oh, wow, that brings back some nostalgia. There's a picture of this in one of Richard Scarry's non-Busytown books that I had as a child.

Thanks! I wonder how I haven't heard of this before.

Edit: Just saw that the Brawley is off-road only. It doesn't meet DOT standards. That would probably explain why I haven't heard of it.

I got to see NASA's Super Guppy land and unload a T-38 (I think) at Ellington Field 15 years ago while prepping for a flight on the Vomit Comet. It's pretty absurd to see a plane come out of a plane.

With The Martian, a later "classroom edition" was published with the profanity removed. Maybe he just wanted to avoid making a second edition this time.

There's a nice Nature episode on beavers and their interaction with people and the environment. It's titled "Leave it to Beavers" and you can find it in various places online.

Two of my kids had a 2nd-3rd grade teacher who spent a lot of time teaching about beavers, so they know all sorts of random beaver information. Their class mascot was a stuffed beaver named "Justin Beaver" :)

For those interested in the development of the English language, I highly recommend this podcast: https://historyofenglishpodcast.com/

I recently got back into the Euclidia geometric puzzle app [0]. You start with compass and straightedge tools and build up the techniques to exactly construct the solution to various challenges with the minimal set of operations.

[0] https://www.euclidea.xyz/

The For Whom the Bell Tolls quote is a striking way to start the introduction. It makes the point of their inquiry much more obvious than the formal scientific language that follows. I'd love to see more of this ("real-world" connections, not movie quotes) in scientific writing.

> in Thai, Thai basil leaves aren't even called basil

In Thai there are completely separate words for different types of basil. There's no word that just means basil, so holy basil and other varieties aren't called basil either.

Ha, I posted this two days ago [0]. I knew it was front-page material :)

[0] https://news.ycombinator.com/item?id=28848009

There are a few experimental physicists on here. I work for Microsoft now, but I found out about HN from a grad school officemate, who found out about it from a YC grad who did a postdoc in our research facility. I credit HN with helping me have enough understanding of the tech industry to land a job as a data scientist at Microsoft, which set me up for joining the quantum computing team a few years later.

I have one memory of Napster. My senior year of HS, 2000-2001, one of my teachers told me I could skip an assignment in exchange for helping her install it on her (school-owned) computer. It would make a better story if the class was Ethics, but it was pretty close--World Religions.

I wonder if the right weather conditions could result in enough atmospheric refraction to make the mountain visible.

Related: https://en.wikipedia.org/wiki/Free_will_theorem

That is evidence for dark matter, not dark energy.

Previous discussion on similar article: https://news.ycombinator.com/item?id=16936769

Good question. They say that they need 10^-11 pascals. The pressure in low earth orbit is 10^-8 pascals [0], but the suggestion is to put it at a Langrange point (L1 or L2), where the pressure should be much below that.

[0] https://en.wikipedia.org/wiki/Orders_of_magnitude_(pressure)

I think finding someone reputable to publicly attest to the legality (which appears questionable in the US) will be difficult. The best bet may be law school faculty who could write a paper on the subject.

You create matrices that represent the operator. For instance, suppose you had a 1D function and were interested in the evenly spaced points (x1, x2, x3, x4, x5), with the function values at these points being

  y1
  y2
  y3
  y4
  y5

If the differential equation had a first derivative in it, you'd construct something like this, multiplied by some constant (e.g. 1/(2*dx) for an unscaled derivative):

  ? ? ? ? ?
  -1 0 1 0 0
  0 -1 0 1 0
  0 0 -1 0 1
  ? ? ? ? ?

So the derivative at each element is defined by the difference of the next and previous elements. Multiplying the column of function values by this gives you the derivatives. This doesn't work for the first and last element, and in fact you'll usually modify these rows depending on what boundary condition is needed, so I've just left them filled in with "?".

For a solver, you don't know what the y values actually are, so you construct a column that corresponds to the right side of the differential equation. For instance, if the equation was something like the trivial dy/dx = c and you were using the operator above the column would be

  ?
  c
  c
  c
  ?

with the first and last values to be filled in based on the boundary conditions. You then left matrix divide that by the operator matrix (i.e. multiply it by the inverse of the operator matrix). That gives the solution to the equation.

This is just a simple example and in practice the matrices will be larger and more complex.

I like the Shark brand. I get it at a local Asian market, but you can also find it online [0].

[0] https://importfood.com/products/thai-sauces-condiments/item/...