Is there any niobium-92 left?

What primordial radioactive nuclides (isotopes) still exist in the Earth's crust? To figure that out, we might need to know the original abundances of various nuclides in the matter that now makes up the Earth's crust. I haven't found good data on that. But it's pretty easy to calculate what the abundances would have to …

GIF plain text extensions

Plain text extensions is an obsolete feature of the GIF (version 89a) image format. Essentially, it allows an animated GIF to have ASCII text frames, as well as the usual graphical frames. As far as I know, it was pretty much never used at all. The only GIF file with plain text extensions that I'm …

The northernmost and southernmost trees

Where are the northernmost and southernmost naturally-growing trees in the world? I thought it would be easy to find the answer, but it turn out, not so much. Northernmost The northernmost trees are most certainly Dahurian larch (Larix gmelinii) trees growing in north central Russia. They are apparently somewhere in the marked region below, or …

X-Face format

X-Face is an odd little graphics format, designed around 1990 as a standard way to include your picture/icon/avatar in the email messages you send. It's not exactly a file format; it's a special string of text that can be included in email headers. A number of email applications supported it, and maybe some still do. …

Simple classification of radioactive decay

In how many different ways can an isolated neutral non-exotic atom decay? When an atom decays, it spontaneously changes into something else. That "something else" is inevitably two or more particles, none of which is the same kind of atom as the original. I also need to also explain what a "kind of atom" is. …

How to walk around the Earth

Suppose we start at Cape Horn, at the southern tip of South America. We are challenged to travel from there to Tasmania (the big island south of Australia). We can travel freely over land, but only for X consecutive kilometers over water. How small can X be, and still allow us to reach Tasmania? Ground …

Survey of MacPaint brush patterns

MacPaint is a paint program for early Macintosh computers. You can see it, and try it out, at the Internet Archive: <https://archive.org/details/mac_Paint_2&gt;. Its native image file format is very limited, and very obsolete. But a large number of MacPaint files were created, back in the day, and some of them can still be found. For …

True AI would definitely destroy us

I've never seen a single credible reason why an artificially intelligent computer program (AI), one comparable to a human brain, wouldn't spell doom for humanity. (Please note that I'm talking about true, strong AI, which by all accounts does not yet exist. I'm not talking about a neural network that beats you at chess, or …

Corrupting ZIP files

The ZIP (PKZIP) compressed file format is organized in a backwards fashion. To unzip a ZIP file, you start by looking for a special byte sequence near the end of it. This is a marker for a data structure (the end of central directory) that points to other data structures that appear earlier in the …

Superstalemate solution

This is a solution to the chess challenge I posed in a previous post. It is not the only solution. From this position: 8/7p/6p1/2K3pk/6pb/6p1/6P1/8 b - - 0 1 Black plays ...h6. Any move by white then stalemates black. Occasionally in a chess discussion group, someone will suggest that stalemate being a draw is a …