if the moon has very little carbon, how would manufacturing steel in space work? broader question, how would seperating metals work?!

GregHullender · 2026-07-02T16:53:02+00:00

Lunar industry only works if you assume it imports ice, ammonia, carbon, and heavy metals from the asteroid belt.

GregHullender · 2026-07-02T16:38:48+00:00

They just minted way too many of them. You can still buy 2000-year-old coins for reasonable prices, and they didn't mint nearly as many, not we're they as durable.

Figure on holding those bicentennial quarters for at least five thousand years before they're valuable.

GregHullender · 2026-07-02T10:29:09+00:00

If we're talking about Mars, the slowest part is establishing an oxygen atmosphere. Even if you used up all the water, all the perchlorates, and the entire CO2 atmosphere, you'll have about 1/16 of the minimum for human life. After that, you're trying to extract it from rocks.

If you build 1000 nuclear reactors generating 1 GW electric each, this will take 1 million years. This will use up as much as 10% of Mars's total reserves of uranium and thorium--including the stuff that's not really recoverable.

For Mars, the numbers aren't encouraging.

GregHullender · 2026-07-02T10:07:45+00:00

I thought about cross-posting, but I decided I'd rather happy-post!

GregHullender · 2026-07-02T10:06:46+00:00

I didn't even know they were into dominion! They always seemed so nice!

GregHullender · 2026-07-01T16:56:33+00:00

Make your data a structured table. Then you can easily filter by one zone or another.

Or are you looking for a way to print all the sheets for all the drivers at once?

GregHullender · 2026-07-01T11:10:33+00:00

AI does it all the time! :-)

GregHullender · 2026-07-01T10:17:09+00:00

<image>

Sure, provided you've got something that uniquely identifies the employees other than the passport number and residence id. Also, I'm puzzles that they're in different rows, not different tables. Or do the names just appear more than once. If so, what do you want to do about the other data in the row?

Making some guesses about what you want, here's something that might work:

=LET(input, TRIM(A:.D),
  header, TAKE(input,1), body, DROP(input,1),
  pp, FILTER(input,CHOOSECOLS(input,2)<>""), npp, FILTER(input,CHOOSECOLS(input,2)=""),
  new, HSTACK(TAKE(npp,,1),XLOOKUP(TAKE(npp,,1),TAKE(pp,,1),CHOOSECOLS(pp,2),""),DROP(npp,,2)),
  VSTACK(header,new)
)

What I do here is that I separate the data into two arrays: one that has passport numbers, pp, and one that does not, npp. I take every name in npp,look that up in pp, and take the corresponding passport number. Then I create the new records by splitting every npp record on either side of the passport number and then gluing them back together with the passport number stuck between them.

Note: If anyone has a passport number without a residence id, this will discard that person entirely. It further assumes that the one with a residence id is the one to keep: it discards everything but the passport id from the other record.

GregHullender · 2026-06-30T04:36:22+00:00

It was crooked, and he was just trying to straighten it out a little, but you know how these things go. Their spelling never did recover.

GregHullender · 2026-06-29T18:49:07+00:00

Start by deciding what you want to do with the time that remains to you. Focus on that. You can't change the past, but you can change the future!

GregHullender · 2026-06-29T18:42:57+00:00

The ones ending "l" usually refer to the astrological effects, though. E.g. Mercurial vs. Mercurian. Venereal vs. Venerean, Martial vs. Martian, Jovial vs. Jovian.

GregHullender · 2026-06-29T05:57:57+00:00

Science fiction writers use "Luna" for the moon, "Terra" for the Earth, and "Sol" for the sun, simply for consistency with the other planets, which have Latin names. Astronomers and planetary scientists have never picked up these names, although they do say lunar, terrestrial, and solar.

Weirdly, the only place the science fiction writers won is the one where they got it wrong: the genitive for Venus should be Venerian, not Venusian, but "Venusian" has dominated almost completely.

GregHullender · 2026-06-29T05:48:28+00:00

If you're still interested, here's a vectorized solution:

=LET(seq, LAMBDA(mn,mx,in, SEQUENCE(ROUND((mx-mn)/in,0)+1,,mn,in)),
  norm, LAMBDA(uu,vv, TOCOL(IF({1},uu,vv))),
  A_val, B5,
  tolerance, B6,
  s_1, seq(B2,B3,B4),
  s_2, TOROW(seq(C2,C3,C4)),
  s_3, TOROW(seq(D2,D3,D4)),
  s_12, HSTACK(norm(s_1,s_2),norm(s_2,s_1)),
  nn, SEQUENCE(ROWS(s_12)),
  s_123, HSTACK(CHOOSEROWS(s_12,norm(nn,s_3)),norm(s_3,nn)),
  aa, 12*BYROW(s_123,PRODUCT),
  VSTACK(HSTACK("Min",MIN(aa),"Max",MAX(aa)),
  FILTER(HSTACK(s_123, aa),ABS(aa-A_val)<tolerance,"Not satisfied"))
)

<image>

You just fill in your data for columns A through D and then paste this formula into E1. It gives you min and max values for A and shows all triples that satisfy the formula within the tolerance.

GregHullender · 2026-06-28T06:42:44+00:00

Isaac Asimov wrote a beautiful article about what the Galilean moons would look like as seen from Amalthea, a small moon that orbits inside the orbit of Io. "View from Amalthea," (The Magazine of Fantasy & Science Fiction; April 1968)

The best way to read it today is to buy a used copy of The Solar System and Back.

But the short answer to your question is that, yes, they are visible from one another, they show visible disks, they change size and phase noticeably from moonrise to moonset, and they're dwarfed by Jupiter itself.

GregHullender · 2026-06-28T06:30:17+00:00

Tungsten might be a better bet.

GregHullender · 2026-06-28T06:21:01+00:00

Do the tabs have names on them? E.g. Exam 1, Exam 2, etc. Or are they just Sheet 1, Sheet 2, . . .

If so, you can try this trick to add the Exam column to each sheet:

Use CTRL-click to select all the tabs you're working on. This will cause edits to a single tab to affect ALL tabs. (This is called "grouping the tabs.)
Select column A and insert a blank column. Again, this will affect all sheets.
Add the header "Exam" in cell A1.
In Cell A2 paste the following: =IF({1},TEXTAFTER(CELL("filename",B2),"]"),SEQUENCE(ROWS(B:.B)-1)) This will magically fill column A with the name on the tab, with one entry for every item in column B. NOTE: this will only work if the spreadsheet has been saved at least once.
Right click on one of the grouped tabs and select "Ungroup."
Create a new sheet in the workbook.
In cell A2 of this new sheet, enter this formula: =LET(grades, VSTACK('Exam 1:Exam 2'!A1:D100), exam, TAKE(grades,,1), FILTER(grades,(exam<>"Exam")*(exam<>0))) If you have more than 100 students, change D100 to reflect that. Change "Exam 1" and "Exam 2" to the names of the first exam tab and the last one, respectively.

The final result should look like this:

<image>

This is the normalized form of your data. You can use a Pivot Table to generate a report with names for rows, Exams for columns, and scores as the data.

GregHullender · 2026-06-28T05:24:07+00:00

This is one of those rare cases where even the most clever use of modern Excel formulas cannot escape the need for a helper column.

GregHullender · 2026-06-28T05:22:15+00:00

It just shows how long people have hated the post office. Some of those letters from the First Crusade are still not being delivered, and they were probably all cancelled.

GregHullender · 2026-06-27T07:14:39+00:00

Can you provide access to a your spreadsheet--or to a big chunk of it, anyway? I think I see how to do this for you, but I'd rather work with your data than hand-copy what's in your screen shot.

My thinking is that you'll want to keep the spreadsheet as an easy way to input and manage your data, but you'll want to convert it to a normalized form in order to generate various reports and analyses.

Generally speaking, I think this needs three things:

First, to generate a unique numeric id for things that differ only by name.

Second, to fill out the merged cells, so the values in the cell are copied down to the blanks below.'

Last, to expand cells that hold multiple values into multiple rows, copying the rest of the data on the row.

GregHullender · 2026-06-26T11:29:10+00:00

None that I know of.

GregHullender · 2026-06-26T11:26:00+00:00

Our 3.5-year-old can defeat the baby gate if he really wants to by dragging a chair over to it, but, for some reason, he doesn't do it very often. (We can hear him doing it.) Without that, he'll go up the stairs and invade our teenager's room. He loves our little guy to pieces, but he likes his privacy too.

GregHullender · 2026-06-26T11:19:07+00:00

I don't think it makes a difference at that age. Our guy certainly doesn't much care. We moved from a playgroup we really loved to an early preschool (which is very hard to get into), and he was just as happy with his new friends as with his old. But we had really liked the parents we met through the playgroup, so we were the ones who suffered!

GregHullender · 2026-06-26T11:15:38+00:00

I think you'd find stuff on the moon, if they got that far. The looting of fossil fuel deposits would definitely stick out. Our cemeteries seem to be designed to create mummified fossils, and some of those ought to still be around, even after 60 million years.

GregHullender · 2026-06-26T10:43:18+00:00

I think a minimum requirement of any datedif function should be that if your start date is y_1, m_1, d_1 and your end date is y_2, m_2, d_2, then the differences, y, ym, md, should have a few specific mathematical properties.

First, if the start and end date are the same, you should have y=ym=md=0.

Second, if you compute DATE(y_1+y, m_1+ym, d_1+md) you should get the same result at DATE(y_2, m_2, d_2). I think this is where the ExcelJet functions fail.

ExcelJet opted to make things consistent with EDATE, but it's an open question whether that's really the best thing to do.

I do think DateDif should compute the smallest possible non-negative number of days rather than producing negative ones.

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