Yep. If Hawking is right, black holes don't live forever.

I think the large majority of astrophysicists accept this. Not because it's Hawking's idea, but because his arguments are solid.

The second point - that the impact of the CMB (and "local" conditions) on a BH's event horizon will mean that BHs with a mass above a certain limit (and so, effective temperature of their event horizon below a certain value) are not shrinking at the moment, while smaller BHs are shrinking (by radiating into the CMB and their local conditions) is also, I think, generally accepted, but the position of that limit may be less sure. In particular, a BH with, say, a galaxy centre in it's sky is going to have a complex absorbtion/ emission integral over it's surface. Which leaves a lot of room for argument.

We're both old enough to remember when the decay of Primordial Black Holes (PBHs) was proposed as a solution to the problem of gamma-ray bursts. And the long arguments that entailed - is the distribution isotropic because they're very local, and the thousand LY range to the edge of the galactic disc takes us beyond their detectability range, or are they isotropic because they're far outside the galaxy and very rare per cubic gigaparsec per year. We're seeing the same arguments regurgitated, but with PBHs playing the role of "dark matter candidates" this time, instead of GRB progenitors.

I agree that PBHs are interesting ideas ("provocative" is the word I used when considering the recent analysis of the idea that the Sun contains a PBH. See https://wellsite-geologist.blo..., discussing https://arxiv.org/pdf/2312.076... "Is there a black hole in the center of the Sun?".), but being an interesting, or provocative, idea doesn't mean that the idea represents a real object. Stephen Jay Gould introduced me to the word "reification" when he was undermining the reification of the "intelligence quotient" in his "Mismeasure of Man" book, back in the early 1980s - and it's an important concept to remember. It's also a self-reifying idea - which should be up there with self-defeating prophecies.

My memory was playing tricks on me. I had been writing about the Sun containing a (compact body, including Primordial Black holes, Neutron Stars, etc) more recently than the last may page I cites, but I couldn't find it. I've added a few key words and these "label" things, and now this link is easier to find. Yes, I had been looking at the Kippenhahn diagrams used by these authors, though they used them in linear time, not logarithmic time. Yeah, I think "BH" needs to be a label.

From the Headline:

Earth-Sized Planet

From TFS:

a planet that's twice as big as Earth

It gets worse. FTFA (Article/ Abstract) :

The 1.95-R_Earth and 8.8-M_Earth planet 55 Cnc e

Just to put that into a Solar system context - that's a size and mass of planet we don't have, though it is approximately what Brown & Batygin predict for "Planet 9". (The now discarded "Planet 9" of "Pluto/Charon" masses about 1/600 of Earth, has 1/6 the diameter (so 1/216th the volume and 1/3 the density) and is completely controlled in it's orbit by Neptune.

FWIW, the lnk given is to Nature, and you need to do some hunting, or have UnPaywall running to get the paper itself without shelling out cash. The Open Access paper is at https://arxiv.org/pdf/2405.047....

Anything else from TF(Article/ Abstract) ?

an equilibrium temperature of ~2000 K

So I'm not sure where the 2300 K mentioned above came from.

These observations disfavor a primordial H2/He-dominated atmosphere, but cannot conclusively determine whether the planet has a secondary atmosphere

Typical "maybe".

The measurements rule out the scenario where the planet is a lava world shrouded by a tenuous atmosphere made of vaporized rock29â"32, and indicate a bona fide volatile atmosphere likely rich in CO2 or CO.

The CO - carbon monoxide - is important. It may be literal poison to us - it is "isoelectronic" with di-oxygen, O2 and the cyanide ion, and all three species bind to the "haem-" structure in haemoglobin. But only oxygen is easily removed as well - which is why the other two are poisons to pretty much all eukaryotes (and a lot of prokaryotes). But as a species for building organic molecules when getting life going - CO is even more popular with the chemists than CO2. Important species, probably.

Two spectral observations, two times ; two instruments, two different analytical "pipelines" ... all the usual suspects of doing science properly, trying to prove yourself wrong.

What if we find a different planet before then, with no signs of an oxygenated atmosphere but a thriving technological civilisation?

It is a hypothesis that free oxygen in the atmosphere is necessary for the development of "complex" (whatever the fuck that means) life. As a geologist with a close eye on the fossil record of metazoans on Earth, I'm far less convinced. Back in the early parts of the "great oxidation event" at about 2.1 Gyr BP, there were macroscopic organisms (now preserved in the Francevillian of Gabon - discovered in uranium exploration) when the Earth atmosphere was under 1% v/v oxygen (possibly under 0.1% ; quite likely varying between those limits on a frequent if irregular basis).

We have precisely one example of a living planetary ecology. That tells us very little about the limits of environment life can develop in (one problem) and persist into (not necessarily the same problem). If (unlikely, but possible) life developed on Mars, then transferred to Earth - it is now functionally extinct (if not absolutely extinct) on Mars. But that's a pretty dubious proposition, IMHO (early Mars and early Earth would both have had the same problems from the "Faint Young Sun" problem, with Mars 30 to 50 degC colder).

I wouldn't hang any great credence on oxygenation being necessary - it's what we do, but that, itself, doesn't make, say, a sulphur-centred redox biochemistry impossible. We already have 4 oxidation states of sulphur active in terrestrial biochemistry, compared to 3 (very rarely, 4) oxidation states of oxygen in use.

We really need to look very closely at the water escaping from Enceladus' "tiger stripes". That's going to come from a different geochemistry ("Encelado-chemistry", even?), if not biochemistry, and might be really illuminating. Or it might be contaminated with Earth-bacteria already.

You cannot get there from here.

Oh I'm pretty sure you can. The next couple of billion years will probably boil the oceans (it is a bit unpredictable on the timing, because there are lots of feedback loops in the Earth's atmosphere, and as stars move along the Main Sequence towards red-giant state, they tend to get more variable too) and leave the planet as habitable as Venus for several billion years before the Sun goes full-on red giant. Whether the Earth gets "swallowed by the Sun" is also a bit uncertain - the same questions about inflating the Sun's atmosphere, and how much drag there is on the planet - It's not the certainty often presented, but it's a good likelihood ; most people think Venus is definitely going to go down.

It's not going to happen in your lifetime, but it's got a pretty good chance of happening in the foreseeable future.

No, more specifically, there is a size below which tiny black holes decay. Above this size (about 10^8 tons) black hole decay takes longer than the lifetime of the universe. That's a diameter of about 3E-13 meters, or 0.003Angstroms, still tiny by any reasonable meaning of "tiny".

Assuming you're the Geoffrey.Landis your screen name purports, I'm similarly going to assume that your quite specific limit refers to the size at which the temperature (well, spectrum) of the radiation emitted has a similar flux to the CMB, so that at larger sized, the CMB delivers mass-energy to the BH, and at smaller sizes the BH delivers mass-energy to the rest of the universe.

In which case, that's a moving target. Slowly moving, but moving nonetheless.

Above this size (about 10^8 tons) [...] still tiny by any reasonable meaning of "tiny".

10^8 tonnes, at density of 2.5 tonne/m^3 (icy rock ; rocky ice ; a "dirty snowball) would be a cube 342m on edge, and such an icy body would have a surface escape speed of 0.4m/s. Any self-respecting flea - with a flea-ish space suit - should be able to achieve interplanetary flight fomr it. Really quite "Bennu"-ish. Which, yes, is "tiny", and yes, is big enough to see from hundreds of millions of km away, and land sample-return probes on. "Tiny" is such an imprecise word.

What is the proper adjective for a "flea-ish" space suit? The beast is "Pulex irritans" (a family friend did her PhD on Pulex ; she's been dead for 40-odd years, but you remember these things), so ... "puliform", if it comes from Latin? "Puce" in Fr, so ... "puce"? (already a yucky shade of yellow - related to "pus"?) - that sounds good. A puce space suit.

Neutrinos weren't detected until the 1930s because they interact very weakly.

Neutrinos were hypothesised in the 1930s to provide a "classical" fudge factor in a reaction that was expected to be fully quantised. Further observations showed that a "neutrino" (IT: "little uncharged one") would also balance the angular momentum in a number of reactions involving charged (viz: easily detected) particles, which would have made them that much more useful.

But neutrinos weren't detected (and filled a substantial and insubstantial hole in the theories) until the mid-1950s - late 50s even - by mucking around in nickel mines. Sorry - nuclear reactor, not nickel mine ; and 1956.

primordial black holes

That one has been pretty dead since the late 1980s. People have been looking for the flashes produced by such objects in the galaxy (against a background of more distant parts of the Galaxy since the early 1980s. They have been seeing occasional such flashes - but not enough to provide the mass necessary to account for the Galaxy's anomalously fast rotation. Whatever the "missing mass" is, MAssive Compact Halo Objects (MACHOs, to name one of the searches ; I forget what "OGLE" - another search - means, but "meh" ; I'm sure you can wiki them) are not a large component of it, and as the search statistics get better, the proportion of the "missing mass" that can be in MACHOs is going down.

Interestingly (to me, maybe not to you), I came across a paper recently on the consequences of a Primordial Black Hole - asteroid or "Everest" size - becoming lodged in the Sun. It would be surprisingly hard to notice, from Earth. The authors introduced (to me) an interesting diagram for summarising such behaviour, where you plot the behaviour of the star (or even, Thorne-Åytkow object, https://en.wikipedia.org/wiki/...) with the diameter of a behaviour zone (compact object ; accretion disc ; nuclear fusion ; convective zone ; photosphere) against log(enclosed mass) on one axis, and log(time) on the other axis. You'd be surprised how long a sun-like star can survive against being eaten from the inside. I scratched down a few ideas about it when I saw the paper (so I don't have to remember all the details) at - good grief, was it a year ago? https://wellsite-geologist.blo... Odd, I thought I'd included a couple of those weird "wotsit" (EDIT ; "Kippenhahn")diagrams in my discussion, but they're in the original paper at https://arxiv.org/pdf/2305.073... - check page ... Damn. Wrong paper. This is why I write things down - it's easier than remembering them, or than having to do the research again. So, now I'm going to have to do the research again, and then re-write my "notes" page tomorrow.

The diagrams I'm thinking of are called "Kippenhahn" diagrams - thank you, sole remaining functional brain cell, and presumably Mr Kippenhahn. An example is at https://www.nature.com/article... (figure 1 ; get the PDF, it's Open Access), which describes models for the internal structure of stars which may (or may not) undergo oscillation in their structure. There is other work on the Sun as a TÅO, but I've got to search deep to find it, and write the details down. But it's way past bed-time now.

They're really fun objects, Thorne-Åytkow Objects. Fun, but I'm not sure I'd want one in the next stellar system over. With an estimated 20-odd in the Galaxy, that's hardly likely.

The problems I see with WIMPs is we would have discovered these objects by now.

How do you make that out?

We've explored a range of particle masses, from the 511keV mass-energy of an electron-positron pair down to the (small) handful of eV for neutrinos (all flavours, though their exact masses are still buried in the fog of measurement noise), and up to the 13.6TeV working energy of the LHC, recognising the Higgs boson at an energy of 125-odd TeV. We've explored in a less-controlled way, the "landscape" up to small numbers of ZeV (10^21eV). Beyond that ... we know (in technical terms) diddly squat. I haven't heard any serious arguments about a maximum mass-energy for a particle (though I've occasionally played in those waters, and found them decidedly unsettling), and we've already got the words for describing them - up to 10^30eV, before one needs to get involved with the administrivia of the BIPM.

If a WIMP has a rest-mass of 10^31 eV, we wouldn't have either words for it, or a technology for detecting it - or even differentiating it as "brighter than current airburst measurements can differentiate". But that doesn't mean we know such things don't exist - just that we haven't a technology to detect them (or a motivation to develop such a technology).

But dark matter curves space-time inwards (toward the center of mass).

So - exactly like "bright" matter. Which - from a gravitational point of view, is exactly correct. Dark matter has the same effect on gravity as normal matter - it's oddity is twofold : that it doesn't produce as much light as a similar amount of "bright matter" (baryonic matter), and it seems to interact less with electromagnetic radiation than"bright matter" in other ways then generating EM radiation. Which also - automatically - means it's going to be harder to detect in the lab. (Show me a measurement technique that doesn't involve EM interaction, and I'll buy you a pint while I find the holes in your argument.)

Yeah, bleeding edge indeed, about a century old at that point.

Give or take a couple of millennia. Simply describing it as "non-Euclidean" means someone has looking at Euclid's axioms, and wondering "what if?"

By the time that calculus and projective geometry were around, and in particular the routine use of complex numbers (for example, in infinite series for calculating trigonometric ratios and constants like pi and e) - which really challenge the algebraic interpretation of geometry - people were starting to see that it might be worth actually following these loose threads in the fabric of knowledge.

"Head Canon" has a very suggestive misspelling. "Just stick your head in this small round metal-edged window", your Pontificate."

"Next Pontiff, please!"

Eileann Sgiathanach - the island of the wings, which is a reference to the five "wing-shaped peninsulae which make up the island.

Some sort of twisted, ironic humor?

Nope, just a different language.

I thought, with so many Americans being "proud" of their Scottish ancestry, there would be no shortage of Gaelic speakers over there to have explained this in infants school. I mean - I just live in the country and have never professed to Scottish ancestry, but I've got a working language of "mountaineer's Gaelic", describing the shapes, colours and textures of the hills. Obvious relations to Erse Gaelic too - not that I know much more of that. It's on my "to-do" list, but at lower priority than my Swahili (because I liked working in Tanzania). And higher priority than Korean, because I hated working there. Unless the much interfered-with DPRK project gets off the surface and into the ground, when it would shoot up the priority list. I wonder if Southern and Northern Korean have diverged much in the couple of generations of separation.

He is angry. At people not accepting the arrival of Messiah Trump.

Specifically, who is going to pay for this device - and it's solar charging([b]*[/b]) - to be fitted to my 25 year-old bike, which is otherwise perfectly functional? It certainly isn't going to be me. I'll stick with the reliable tech - which is 10 years older than the bike - of cycling with a wrench in my driver-side hand, and smashing the wing of any car driver stupid enough to come within reach.

The law here is to give at least 1.5m of road space when overtaking any cyclist. My arms are not over 1.5m long, so your, dear driver, dented wing is your admission that you were driving illegally. And I hope your insurance company denies your claim - because you were driving illegally - and kills your no-claims bonus because of your actions. Even better if the court cancels your driving license until you're passed the current driving test.

I've had drivers pull over and start making threatening gestures. Oddly, a large wrench in the hand is worth a lot of loud arguments.

[b]*[/b] - well, I'm not going to pay for batteries for it. It's to protect car drivers from their own stupidity.