Posts by Bill Gray

Researchers claim spoof-proof random number generator breakthrough

And, of course, the obligatory counterpart to the famed XKCD documentation :

https://dilbert-viewer.herokuapp.com/2001-10-25

User demanded a ‘wireless’ computer and was outraged when its battery died

Re: No need for the nuclear option

As noted by Stevie, they did need shielding against radiation, probably both from the sun and cosmic rays. But the RTGs emit alphas, which have a hard time making it through a piece of paper. In fact, most of the alphas will be generated inside the lumps of plutonium and won't make their way out.

Re: No need for the nuclear option

I'd have thought it would "of course" be impossible. But...

https://en.wikipedia.org/wiki/MHW-RTG

(Voyager's radioisotope thermoelectric generator, closest thing to a real-life nuclear battery) says :

"Each RTG has a total weight of 37.7 kg... Collectively, the [three] RTGs supply each Voyager spacecraft with 470 watts at launch."

Or about 155 watts for a 37.7 kg RTG. Scale back a bit, make your laptop a power-sipping one, hand-wave the fact that the thermal output is about fifteen times the electrical output so it's gonna run hot, and you _almost_ have something feasible.

Behold! Humanity has captured our first look at the Sun's South Pole

Re: Other bright stars

I'm still hoping to find out for myself eventually.

At 18, I made my first trip to Southern California (latitude +33). I'd lived in Maine (latitude +44) before then, and was quite familiar with the night sky as seen from there.

The first night I stepped outside in my new southerly location, it took me a minute or two to get used to the idea that my vestibular system was telling me one thing, but the sky was very clearly tilted relative to that. Not sure how I'd react to looking up and seeing Orion or Scorpius "upside down".

Re: Other bright stars

That's "Gamma Crucis", third-brightest star in the Southern Cross, slightly fainter than Alpha Crucis = Acrux (which made the list) and Beta Crucis = Becrux (which made the list under the alternative name 'Mimosa').

The fourth star is (surprise!) Delta Crucis. The Greek-letter designations don't always line up neatly in the order of Alpha=brightest, Beta=second brightest, etc. But in this case, they do.

Must admit that, not having been south of latitude 29 N, I've never seen the Southern Cross (nor the Magellanic Clouds, nor... well, quite a bit of the universe visible from Earth.) Something I should probably correct before my eyes age much further...

Probability of Asteroid 2024 YR4 hitting the Moon increases

A fair question. There's no safety aspect here. It should be of some scientific interest, in that it'll give us a look a few metres below the moon's surface at freshly-exposed lunar material, and we may learn a bit about crater formation. We've gotten some knowledge of such things from looking at the craters of the upper stages of Apollos 14 to 17 (they were deliberately aimed at the moon), but this is much larger and heavier.

I would expect at least a few smallish rocks to be ejected into geocentric and heliocentric orbits, mostly the former. (Not lunar orbit.) Such rocks would eventually hit the moon again, or the earth, or be ejected into heliocentric orbits. If they hit the earth, and survive re-entry, and have the good grace to hit land rather than ocean, we get lunar samples without having to send astronauts (Apollo) or a sample retrieval probe (Chang'-es 5 and 6) to do the job.

In 2028, this object will be visible again, and we'll be able to compute a very precise orbit and will know with basically metaphysical certitude if it'll hit the moon. If it does, I'd hope somebody lands a seismometer on the moon between now and 2032 Dec 22. The Apollo missions left such (and measured moonquakes caused by the aforementioned upper stages). It'd be a rare opportunity to really learn something about the moon's internal structure.

(But I'm not getting my hopes up all that much yet. As noted, odds are still against a lunar impact.)

Hmmm... 2024 YR4 is about 60m across. The moon, at 1737km radius, is about 60000 times larger in diameter, so it'd have a volume about 2.2e+14 times greater.

The object is probably silicate, with a density comparable to that of the moon. So the moon's mass is probably (again) about 2.2e+14 times that of 2024 YR4.

Impact speed would be about 13.9 km/s. So the change in the moon's speed would be 13.9 / 2.2e+14 km/s = 6.3e-11 m/s. The component of the speed change that is perpendicular to the moon's velocity won't change anything much, but if the rock hits "head on", it will slow the moon by that amount, and if it hits the moon from behind, the moon will speed up by that amount. Either way, the change in speed will be permanent, and there will be a change in the orbital period (admittedly of the order of microseconds).

(Note that I'm simplifying things the orbital mechanics here. But the change in speed will be roughly as indicated above.)

Now we come to the difficult part of the problem (at least for me; I'm an astronomer, not an entomologist.) I don't even know if gnats have external genitalia.

The first hit when searching for "gnat penis size" was

https://en.wikipedia.org/wiki/Muggeseggele

"...a humorous Alemannic German idiom used... to designate a nonspecific very small length... it refers to a housefly's scrotum."

The problem is that the Interwebs have a great deal of information about human penis sizes, and not much about insects. I don't think they'll help. Let's try this another way.

Another search came up with various gnat sizes from 1/16 to 1/8 "inch". Not sure if that's US or International inches, but call it 2mm. Let's be generous to the gnat and assume it's well-endowed, with genitals 1/10 as long as that, or 0.2mm, or 2e-4 metres. I can weasel out here by pointing out that you didn't specify a particular type of gnat anyway; perhaps some of the larger ones would fit my guesstimate. (Or perhaps there's an entomologist lurking in these fora who can comment.)

So, after 2e-4 / 6.3e-11 = 3.2 million seconds, or about five weeks, the moon's orbit would have been diverged from what it otherwise would have been by roughly the suggested amount.

However, that's short-term thinking. After, say, a million years, the divergence will be about two kilometers.

China's asteroid-and-comet hunter probe unfurls a 'solar wing'

Re: ! ES

(Yank here) To be fair... it's a rare country that does accept inconvenient facts of its history. Germany is a rare counterexample; it faced its actions in World War II, but only a couple of decades afterward, and under considerable pressure from its youth and from other countries. [0] Japan has never really done anything similar; the atrocities committed in China and Korea are a non-subject. Russia and China would both claim they never did anything wrong to their own citizens or anyone else. That sort of denial, I would argue, is "normal". Admitting error is so rare as to be almost weird.

The US started to do some introspection a few decades back (again largely due to pressure from youngsters [1]), realized there were a lot of skeletons in our closets, and we now flinch from looking at them. Similarly, Germany is now re-thinking this whole idea that they may have been imperfect.

Openly admitting that you screwed up takes some courage, either for an individual or a country. Back in the 1960s and 1970s, the US had more confidence in itself; we felt we had what it took to face our demons. Nowadays, we're at what I'd argue is (unfortunately) the normal state of affairs : a lot of people who feel that simply acknowledging the bare facts of our history (slavery was a bad thing, killing most of the native population wasn't nice, etc.) is a sign of weakness.

[0] I suppose that looking around at Germany in 1945 might also have caused people to admit, at least to themselves, that maybe this whole fascism thing wasn't a great idea. I hope my country doesn't figure things out in the same way, but am not optimistic.

[1] I speculate that it's easier to recognize your country's flaws when you see them as being your parent's flaws.

If it can’t double our money, we’re not building it, Intel Products chief says

Re: 50% is probably a bit low

"...it's Gross Margin... not Profit Margin."

True, and it causes me to wonder why one would care much about gross margins? If I were picking things to build and sell, I'd want to know how much money I'd have at the end of it. Looking at a 50% gross margin and saying "whoopie, we've doubled our money!... okay, we actually lost money if you include all the stuff I can't be bothered to type" seems remarkably pointless.

I suppose saying "we plan to double your money" sounds good, and those with short attention spans won't think about the difference between gross and net margins?

Techies thought outside the box. Then the boss decided to take the box away

Re: I know it's an old joke but on the topic of office signs...

Dunno if this is just a USAian thing, but one frequently encounters signs in the restroom saying "Employees must wash hands". To which I'm always tempted to add a note saying "if no employee is available, wash your own hands".

For which we should perhaps be thankful...

And when they do think outside the box, I am reminded of a cartoon in which a cat is scolded by a man saying, "Never, ever think outside the box".

Re: Shredder

Old joke :

A secretary (told you it was old) sees the CEO standing next to the shredder, holding a document. CEO turns and says, "How do I make this thing work?" Secretary smiles, inserts document, and hits the start button.

"Thank you," the CEO says as the document vanishes inside the shredder. "I just need one copy."

User unboxed a PC so badly it 'broke' and only a nail file could fix it

Re: Re:high pitch noises

Whilst in college, I had neighbors in the dorm with a TV that, for some reason, had a rather loud and annoying (to me) flyback-frequency (15.75 KHz on the US side of the pond) whine. They, and most of our fellow students, heard nothing. Fortunately, I wasn't usually close enough to the TV (five or ten meters) to really be bothered by it.

Forty years later, I don't hear it. And it's not just because CRTs have become obsolete.

Re: fixed a keyboard related 'fail to boot' remotely

Such beeps aren't all identical. Some are higher-pitched than others.

At 60, I've started to lose the high frequencies. I can hear most adult male voices with no trouble at all. I visit my wife at the elementary school where she works, and can barely decipher what the kids are saying. I hear the microwave and other higher-pitched electronic beeps, but if I'm a few rooms away, not very well.

I'm not too badly off yet, but can see where the trend is going.

If I were around at the design phase for such gadgetry, I'd recommend a lower-frequency beep for such gadgets. (Not to mention that even when younger, I found high-pitched shrieks more annoying than lower-pitched noises.)

Microsoft revives DOS-era Edit in a modern shell

TUI development

Dunno about it being 'cool', but TUI never really died, and curses programs are still being written. PDCursesMod provides a curses library for X11, Windows (both within the console or within a separate window), Linux framebuffer or DRM [0] (i.e., without X running), DOS, OS/2, etc. (Disclaimer : I'm the current maintainer. I use it for a variety of my programs, particularly software for determining asteroid orbits from observations.)

[0] DRM = Direct Rendering Manager, not Digital Restrictions Manager. They really should have chosen another acronym...

Torvalds' typing taste test touches tactile tragedy

Re: Strange keyboards are the bane of IT support

Clearly, we need a keyboard split in the middle and at the numeric keypad. Three separate bits of hardware that you can shuffle around on your desk, and with adjustable feet so you can get each bit to tilt the way you want it. And the split keyboard such that another user can just push the two parts together to get a "regular", unsplit keyboard.

(A bit of online searching turns up a _lot_ of separated numeric keypads, so I appear -- unsurprisingly -- not to be the first to think along these lines.)

Re: Can't see the difference?

black on black on black

Your name is Hotblack Desiato and I claim my £5.

Such idiocy didn't bother me as a PFY (and doesn't bother me now on a keyboard, because I touch-type). But at age 60, endless electronic devices that I don't use often enough to use by touch require me to take off glasses, take device over to a bright light, and squint to see where the buttons are and what they say on them. In some cases, a bit of Wite-Out® (Tipp-Ex™ on the east side of the Atlantic) can help make a button stand out. But the plastic for a button/switch should never be exactly the same color as a device's case.

Must admit that were I a forty-year-old building such things, I probably wouldn't have even thought about such matters.

Experiences vary. Mine was the opposite of yours (had quite bad carpal tunnel, switched to ergonomic, carpal tunnel went away... though I did various other things, such as switching to a Dvorak layout and moving my mouse to the other hand; it was by no means a controlled experiment.) I see other anecdotal evidence (see Edwin's reply below). And as I write this, you have three upvotes and zero down, suggesting some agreement with your experience.

But the plural of anecdote isn't data, even if the anecdotes agreed with each other. A bit of Web searching for evidence for/against ergo keyboards helping with RSI got me lots of people trying to sell me keyboards, and almost nothing in the way of actual data. The Interwebs are getting seriously enshittified... but I digress.

I could imagine that a good Model M keyboard might hurt your wrists less than a bad ergonomic one. Hunt/peck typists may have a different result from touch-typists. Ergo proponents will say that "it stands to reason" that having a keyboard that doesn't force your wrists into an unnatural attitude will improve matters. Well, yes, it stands to reason, but that doesn't mean it actually helps.

If someone were foolish enough to ask for my advice, I'd probably say : if you have carpal tunnel, try a different keyboard. It does seem apparent that people switch and sometimes feel better.

NASA keeps ancient Voyager 1 spacecraft alive with Hail Mary thruster fix

2026 Nov 19, 02:00 Universal Time

I thought that question sounded familiar... I'll recycle my answer from a year back.

(For Voyager 2, the equivalent date would be 2035 Nov 1, and it again happens only once. Pioneer 10 and 11 and New Horizons have some years to go. That's all we have for tracked objects launched into interstellar trajectories.)

Re: If only...

Some time back, there was a discussion in these fora of toaster reliability, and I mentioned this article :

https://www.nytimes.com/wirecutter/blog/your-toaster-will-eventually-fail/

Apparently, the heating elements used 'way back when used more corrosion-resistant metals (Nichrome, etc.). The article comments that "...It seems that modern toasters are the kitchen equivalent of printers—everything in the category is pretty crappy."

I guess we shouldn't buy toasters from HP. (Unless they're about three decades old.)

Re: If only...

Nah, you'd be fine. Those units emit alphas, easily shielded against. [0]

Initially, the RTGs were to provide (according to Wikipædia) 157W of electrical power, halving every 87.7 years. However, they generated about 2.4 KW of heat. After ~fifty years, they'd be down to 2.4 * (0.5)^(50/87.7) = 1.6 KW. Still enough to toast bread. And there are three per spacecraft, so you could have a three-slice toaster.

[0] Though now that I think of it... I suppose there may be impurities?

Of course, only 0.5^(50/87.7) = 67% of the plutonium-238 is still intact. The other ~33% has decayed to U-234, which is also an alpha emitter, but with a half-life of about a quarter million years. So that shouldn't be a problem.

On further thought, your greatest risk might be that the RTG is physically coming apart a bit, such that some bits of the Pu-238/U-234 mix come out onto your toast. If that happens, you may be toast.

Linus Torvalds goes back to a mechanical keyboard after making too many typos

Re: Touch typing in 10 hours*

If you're learning to touch-type from scratch anyway, you might consider the "programmer's Dvorak" layout. This extends the idea of the Dvorak layout (put commonly-used letters where they're easier to reach) to include puting commonly-used characters in source code where they're easier to reach. I've seen it as an option when installing most OSes.

I learned to type circa 1980, it was on QWERTY via the Biblical method (seek and ye shall find). When I developed carpal tunnel in 1995, I switched to standard Dvorak, touch typing, and a split keyboard. (I've not had carpal problems since, but have no way to tell which of these changes helped.) Were I doing it today, I'd probably go with programmer's Dvorak.

So your [expletive] test failed. So [obscene participle] what?

Re: Good to keep a sense of humour

Also, (in most cases) really should be

fprintf( stderr, "Fuck me, no memory left!\n")

Techie solved supposed software problem by waving his arms in the air

When my daughter was about four or five years old, she was very fond of a Richard Scarry book (large picture book with cute anthropomorphic animals) with a few pages describing the adventures of a mouse named Able Baker Charlie.

Oddly, he did not have a dog named Easy, nor was he pursued by a fox named George.

Windows profanity filter finally gets a ******* off switch

Re: Could Latinise the Anglo-Saxon profanities instead of asterisks

The other four letter Anglo-Saxon obscenity (no not "work")

Hmmm... I've heard that both 'golf' and 'boat' are so named because all the other four-letter words were taken.

I could see some buttons provided so you can choose between the many styles of profanity obscuration :

"this ******* phone is a ******* piece of ****"

"This fornicating phone is a gosh-darn piece of fæces"

"This fu***ng phone is a g_dd**n piece of s**t"

"This $%&*!^ phone is a #@!^& piece of %^&*<>"

"This (censored) phone is a (censored) piece of (censored)"

With, I'd hope, some ability to modify the list of profanities. Some of us don't consider "goddamn" to be a swear word, but do consider "Microsoft" to be one.

When Microsoft made the Windows as a Service pivot

Re: Lessons skipped and still not enough paranoia

I thought it was Henry Kissinger, but it appears we're both wrong. The origin of the phrase is uncertain, but predates 1973.

Tesla fudged odometer to screw me out of warranty, Model Y owner claims

Re: Cockup?

I think the reference is to an April Fool's Day prank saying that Alabama had officially reset π to the "Biblical value" of 3.

"The Bible very clearly says in I Kings 7:23 that the alter [sic] font of Solomon's Temple was ten cubits across and thirty cubits in diameter, and that it was round in compass."

Heat can make Li-Ion batteries explode. Or restore their capacity, say Chinese boffins

Re: OK I have some swollen LiPo packs

"LiPo" (with a lowercase 'o') refers to Lithium Ion batteries with a polymer electrolyte (Lithium Polymer)

You saved me a Google. I was looking at "LiPo" in full confidence it couldn't possibly refer to lithium-polonium batteries (presumably popular with certain Russian intelligence agencies and definitely not to be tried at home), but my mind was blocking on what it actually meant.

Dev loudly complained about older colleague, who retired not long after

Re: What management need to know

Sounds about right. My self-evaluation was that I was a metaphysical genius at about age 18. That was when I was at the peak of Mount Stupid. Everything went downhill after that.

Zorin OS 17.3 takes the Brave step of changing its default browser from Firefox

Such was my thought. Any idea why they didn't stick with Firefox but with uBlock Origin pre-installed? Seems as if that would have been easier, addressed the privacy issue, and given them an added selling point : "keep your existing machine despite Microsoft®'s best efforts, and say goodbye to annoying ads."

(Generally, when I come up with a seeming obvious idea slightly outside my actual area of knowledge, it turns out I'm just overlooking the obvious flaw in said idea. I suspect such is the case here, but still don't see said flaw.)

European Gaia mapping satellite is retired but proves very tough to kill

Ah, I made two mistakes here. First, not mentioning the number Gaia got from observation. From the article :

"...[Gaia]... calculated that we're moving closer and closer to the Milky Way's heart, accelerating inwards at around 0.23 nanometers/s^2."

And second... when I did the computation, using wcalc, I got 0.00000000031. I saw eight zeroes where there were nine. So the acceleration I computed is a mere 0.31 nm/s^2, about 40% high.

Well, I did just pull r and t from memory. Let's see if we can do better...

Wikipædia says Sgr A*, the black hole at the center of the galaxy, is only 26996 +/- 33 light-years away (had no idea the distance was that precisely known!) A 'galactic year' is about 225 million 'normal' years. So my memory was pretty far off on both. Both my overstatement of the radius and understatement of how long it takes us to go around the galaxy resulted in a lower acceleration. Using these revised values of r and t, I'm getting 0.20 nm/s^2, somewhat closer to the actual measured acceleration.

Re: If It's Not Broken, Don't ... Break it?

(Note : my knowledge of this comes from being involved with asteroid survey efforts, and in trying to make sure we don't ID spacecraft and junk as "asteroids.")

To its credit, ESA is pretty careful about disposing of old/dying hardware responsibly, and has been for a few years now. When launching spacecraft to heliocentric orbits, or to Earth/Sun L1 or L2, they make sure the upper stages will enter heliocentric orbits with minimal likelihood of coming back to our neighborhood close enough to cause trouble.

Not everyone has been that responsible. There are maybe a dozen bits of assorted junk left in high Earth/Moon orbit that will eventually hit the earth or moon or (more likely) get ejected into heliocentric orbits. (They get picked up by the asteroid surveys, which is why I know about them.) I think SpaceX has started to be more careful, and similarly with CNSA and NASA. Except for that last, they aren't all that communicative on such matters. Or maybe I haven't pestered the right people.

At these distances from the sun, collision with other objects is very, very unlikely. Then again, there's the (probably apocryphal) story that in 1895, there were only two cars in the entire state of Ohio, and they collided.

This nerd-sniped me a bit.

My recollection is that we're about 33000 light-years from the center of the galaxy, and go around it once every 200 million years or so.

r = 33000 light-years = 3.12e+20 metres [0] roughly. t = 200 million years = 6.31e+15 seconds.

Our velocity around the galaxy would be 2*π*r / t = 310700 m/s = v. Call it about 31.07 km/s. Seems about right.

The acceleration required to keep us in that circle would be v^2/r = 3.1e-9 m/s^2, or about 3.1 nm/s^2. Pretty decent agreement between theory and observation, I'd say.

I wouldn't say it rises to the icon ("may contain highly technical content requiring degree-level education or above"), but might make a nice problem for a high-school physics course.

[0] I'm a Yank. But I approve of the idea of not spelling the unit of measurement the same way you spell a measuring device. And I still sort of think of this as a UK site anyway. And with the current dismantling of my country's scientific apparatus, it may soon not matter how we spell such things.

Microsoft is redesigning the Windows BSoD to get you back to work ‘as fast as possible’

Re: " maybe the “B” in “BSoD” could change from Blue to Black"

banana, beige, biscuit, blond, blueberry, bronze, brown, burgundy, butterscotch, byzantine

Or, from the list of colors resulting from the XKCD color survey :

barf green #94ac02

baby shit green #889717, not to be confused with...

baby puke green #b6c406

barney purple #a00498

booger #9bb53c, not to be confused with...

booger green #96b403

(I actually found the list to be useful; I converted it to C #defines so that I could write code such as

set_color( RGB_PALE_LIGHT_GREEN);

Infosec pro Troy Hunt HasBeenPwned in Mailchimp phish

(Late reply) Thank you; the linked "update 6" and the Stack Exchange answer are both helpful.

Troy is, of course, correct that if you know or guess an e-mail address, you can still hash it and see if it's in the 'removed' list. (Obviously so; that's exactly what the legitimate owner would do -- _has_ to be able to do -- to see if the address in question is in the list.) I'd still argue (and Troy appears to sort of agree) that the hashing does mean you can't just grab the full list of e-mail addresses. You have to hash everything in a much larger list and look for matches.

The "gold standard" Troy mentions is yet another level : give people the option to say "remove my address _completely_ and don't even store a hashed version of it; I'll accept the fact that this means you have no way of checking my address should it crop up again." That does seem like a good idea, though it's a separate issue from whether hashing occurs.

Mailchimp holds a list of unsubscribed email addresses for each account. This is not visible to the account holder, but is used to prevent the account holder re-adding someone to an audience.

An interesting point, and obvious once you mention it.

Hmmm.... off the top of my head : maybe store a list of salted hashes of unsubscribed addresses? If that list is extracted, it's a heck of a lot less useful than the plain-text addresses. Though somebody else who has given it >15 seconds of thought has probably come up with a better solution.

BOFH: Have you tried forcing an unexpected reboot?

Re: The spinning wheel lies.

Every spinner/progress indicator I've ever programmed was in the thread doing the actual work. It hadn't even occurred to me to put it in a separate thread, since (a) as you note, it would cease to be a valid indicator of things locking up and (b) you spin up a new thread where there's a for-real performance issue and need to spread the effort out, and a progress indicator (properly written, anyway) is not a performance hog.

(I don't deny that you've seen situations where somebody put the progress indicator in a separate thread. I'm just saying that they did something pointless and stupid.)

AI bubble? What AI bubble? Datacenter investors all in despite whispers of a pop

Re: The thing about bubbles

I'm reminded of the old saw that "the market can remain irrational longer than you can remain solvent."

Occasionally, over the years, I've thought it might be a good idea to invest against some irrationality or other. Say, selling SCO short at the time it was making transparently inaccurate statements about Linux and intellectual property. In hindsight, given just how long SCO was able to remain afloat (in part due to Microsoft helping to keep it afloat), it's probably just as well that I refrained.

Earth's atmosphere is shrinking and thinning, which is bad news for Starlink and other LEO Sats

Re: Just wondering...

if Russia wanted to disable Starlink in Ukraine, it would only need to mine the orbits passing over Ukraine...

It doesn't work that way. The Starlinks go around the earth every hundred minutes or so, with the earth rotating underneath them. So the same Starlink that goes over Ukraine now will, a hundred-odd minutes later, be going over someplace about 20 degrees longitude to the west, say Poland or Germany. And a hundred minutes after that, France or the UK. And in between, going around the earth and covering various places in Russia, Australia, and (depending on whether it's northbound over Ukraine or southbound) the Americas. You can't ruin service for just one part of world; you can only degrade it for some part of the world some of the time, to be replaced by other Starlinks a little later.

Re: Just wondering...

You're thinking of Project Westford. The 'needles' acted as a sort of artificial ionosphere. As noted on Wikipædia, most of the needles were blown around by solar radiation pressure and re-entered after a few years. Unfortunately, some deployed incorrectly and formed lumps. A few dozen clumps over 10 cm (i.e., large enough to be tracked) are still up there, along with (presumably) some clumps too small to track.

In re a retrograde orbit : that would be a little difficult for the Starlinks, since there are a lot of orbital planes. Probably conceivable, though. Quite a while back, I read an article pointing out that sending a spacecraft past the moon, then using lunar gravity to assist insertion into retrograde orbit, could put an object into a retrograde geostationary orbit.

The advantage of this is that there's only one orbit plane, and all those valuable geosats are in one consistent orbit. Gently release your debris cloud, and twelve hours later, you've wiped out most of the geosats. (Admittedly, yours along with everyone else's.)

iRobot may be iDead in iYear

That pun sucked.

Satnav systems built for Earth used by Blue Ghost lander as it approached the Moon

Re: GNSS uses signal time-in-transit to calculate distance

I suspect refraction (really, ionospheric issues) won't be an issue, because only satellites that are straight-line visible without passing through the atmosphere would be used. The number of navsats that are that close to the earth's limb, but not so far behind the earth that their signals are blocked anyway, will usually be zero or one.

The larger issue is that the entire navsat constellation, as seen from the moon, will span about eight degrees. You'd have something resembling the "urban canyon" problem, where a navsat receiver surrounded by skyscrapers can only see the navsats near the zenith, resulting in "geometric dilution of precision". (Or, for the urban canyon problem, sometimes not seeing the minimum four navsats required for a position fix. I don't think the lunar navsat units will have that problem. They'll be able to see plenty of navsats; they just won't be all that well spread around the sky.)

Einstein Probe finds two stars that have spent 40 million years taking turns eating each other

Re: Unfamiliar unit

The full sky is about 40000 square degrees, or deg² (and, of course, 4π sr). Square degrees, square arcseconds and, more rarely, square arcminutes get frequent use in astronomy.

The solid angle of Wales is dependent on one's location, of course. But if you were at the center of a hollow earth, looking up at Wales from the underside, it would cover about 1.66 square degrees.

Microsoft vet laments a world where even toothbrushes need reboots

Re: Mental

What possible consumer benefit is there from using [an electric toothbrush]?

That was my thought for about fifty years of my life. Couldn't imagine why one would use such a thing. My dentist nudged me strongly in that direction; I eventually gave it a try.

The improvement in dental health is quite noticeable. I think it's a combination of reasons. The motor does a somewhat better job of cleaning. With less wrist involvement, I can usually hold a book in the other hand or do some other activity with it, which makes me much more likely to brush for the recommended two minutes. With a manual, the motion of the brush-holding hand makes the "off" hand less steady. Would recommend to a friend, or to a fellow commentard.

(Though this is a simple electric toothbrush. Why it would be connected to anything except an electrical outlet for recharging, I can't imagine.)

Asteroid as wide as 886 cans of spam may hit Earth in 2032

Re: "moving away from Earth at 17.32 km/s "

(I assume asteroid is actually clocking 30+17.3 km/s.)

The relative speed between us keeps changing. It was moving away from us at 17.32 km/s on 2025 Jan 27 at 13:00 UTC. Right now (call it 18:00 UTC on Jan 31), we're looking at 18.20 km/s.

On impact in December 2032, its speed (as described below) is quite well-determined, even if we don't know where (or even if) it'll impact. If it does, it will (through sheer coincidence) do so at about 17.2 km/s. It'll initially be a bit slower than that, but will pick up speed over the last hour or so as the earth pulls it in.

Collision will never be at less than about 11 km/s (earth escape speed). That'd be for an object basically in our orbit around the sun, only gaining energy because it's falling into the earth's gravity well.

Head-on collisions could be at up to about 70 km/s. That would be a retrograde object on a parabolic orbit (us going ~30 km/s one way and it going ~40 km/s the other way). There are some comets that come close to doing that, but for most objects, we're looking at something much closer to that 17.2 km/s level of havoc.

Interstellar object could, of course, be much faster. But the odds of that are a million to one (and yes, I know how often those happen).

17.2 km/s

Speed at impact would be 17.2 km/s. While much remains uncertain (whether it will hit at all, if so where along a long "impact corridor" running from Colombia to the India/China border), conservation of energy makes it fairly easy to determine what the speed would be.

Energy is less easy to determine. We don't know how big it is; it's more like maybe 400 to 800 cans of spam, and the density is something of a guess. At the low end, we're talking Tunguska. At the high end, maybe ten times that?

I don't know the speed of an African swallow (AUUUGGHH!), but if you do, divide it into 17.2 km/s and you'll have your answer. (Rough estimate : barn swallows in my part of the world -- not Africa -- are pretty fast birds and can keep up with a slowish car going about 40 km/hr. 2024 YR4 would be about 1550 times faster. A laden swallow is presumably slower.)

(Incidentally, the close match to the speed at which the asteroid is receding in the article is coincidence. The speed varies with time, and it's actually accelerating away from us at the moment. It'll go through further changes, but would eventually be 17.2 km/s were it to impact us.)

Got a telescope? Bid farewell to ESA's retiring Milky Way mapper

'Passivated' has a very specific meaning in this situation of "got rid of all the fuel". I don't know if it involves opening a valve or just running the thrusters/engines until they stop doing anything.

It started as a common thing for earth-orbiting spacecraft, when it was found that leftover upper stages would sometimes sit around for years before going boom. You then had a lot of small bits to track/evade.

Gaia (like JWST) is in a halo orbit around the earth-sun L2 point. It requires periodic adjustments to keep it in that orbit, sort of like keeping a yardstick balanced on your palm. If they just abandoned it, it would eventually slide off that orbit, probably into one that would drop toward the earth. Herschel, Planck, and WMAP were in similar orbits; each was given a bit of thrust to put it into a "graveyard orbit" around the sun, one that would be reasonably unlikely to hit the earth.

You could point out that these objects are all small; if they _did_ hit the earth, I can't say it'd matter much. But it wouldn't be a good look.

Re: Great work!

Are you observing visually? ESA seems to expect ~mag 15 at brightest. That's at the faint end of what you might get with an 8-inch = 20cm telescope. Worth a try, since the magnitude appears to be a rough prediction and actual visual limiting magnitude depends on a lot of variables.

Observe with a CCD, and you should have absolutely no trouble at all.

Re : amateur observations

The original plan was that Gaia would be tracked optically by small telescopes. (Its exact position doesn't matter much for observing stars. But for analysis of the asteroid observations, you really want to know where Gaia is to within better than a kilometer or so.)

Problem was, it turned out to be about three magnitudes fainter than expected. ESA compensated by switching to larger telescopes, which was annoying but doable, plus a bit of trickery involving the difference in reception times at two different radio telescopes.)

ESA has posted information about observing Gaia over the next few months. (Scroll down to "perform Gaia observations yourself".) Among other things, they hope to find out why it was so $%&! faint over the last ten years. (I'm hoping it turns out to be something that can be used intentionally to keep Starlinks and similar megaconstellations dark, but that's probably a bit much for which to hope.)

For us asteroid observing guys, Gaia has really transformed the field in two ways. The star catalog removes a lot of systematic biases that occurred in older catalogs. So when you've observed an asteroid and are measuring its position relative to other stars, a big source of error goes away. We can (for example) tell you if a near-earth asteroid is really dangerous with much greater accuracy.

The other big advantage is that Gaia's observations of the asteroids themselves have helped a lot in predicting occultations of stars by asteroids. It used to be that we'd have a rough idea of the path of the occultation, would set up telescopes, and if we were really lucky, we'd actually be in the path. You often had to enlist observers over a big area and hope somebody got lucky.

Nowadays, we're observing occultations almost routinely. With each one, we get a good idea of the diameter and shape of the asteroid, and sometimes even see the star blink out twice, indicating that the asteroid has a satellite. (Or, in some cases, is irregularly shaped.)

The solar system crowd was a mere afterthought for this mission, and we still got a lot out of it. The impact on stellar astronomy has been mind-bogglingly transformative.

NATO's newest member comes out swinging following latest Baltic Sea cable attack

Huh! Hadn't heard about that. (For other curious commentards, Wikipædia article on Swedish subs powered by Stirling engines.)