How stiff is spacetime?

This is one of my titles ending in a question-mark, which I reserve for special occasions. Like "not having anything good to type about this evening".

Anhydrous glass, beryllium, and graphene all share a property: the Young Modulus. This stress:strain is called "stiffness". It turns out that gravity bends space. Kip Thorne in 2018 delivered the Hamilton Lecture “Exploring the Universe with Gravitational Waves” on the topic, after a lot of this bending had been measured. Someone in the audience pondered spacetime's Young Modulus; Rainer Weiss gave an answer.

Thus far, 25 minutes into Physics Explained's youtube.

Looking around, other physicists have questions, like David Izabel and A. C. Melissinos. They all agree with Weiss that spacetime has a Young.

Weiss was caught backfooted. He thought the Young depended on frequency of gravitational waves, and based on 100 Hz threw out a number: 1e+20 more than steel. Melissinos gave it a little more thought, and from "first principles" calculated 1e−9 Pascals, which is 1e-14 that of... jello. Maximum. An uncharitable soul might compare these results to Bottke and Loeb tussling over Chicxulub.

The Youtuber pulls further, I think, from Tello-Strong asking at what point the space-time... breaks. I think that question is a secondary at this point.

Making Chicxulub

Everyone agrees Chicxulub wasn't from here. Since February 2021 a consensus has formed is that it was a carbonaceous chondrite. These are rare down here but they do get here; 142 Polana, for instance, is in the B class of these and has spawned many a pile of dangerous rubble. But I don't think many believe that Polana dropped the bomb on me (baby).

Instead, Makhatadze's team say: the Ornans class, CO or maybe CT. They did this by measuring the nickel isotopes. A CO / CT might be, or have been, carboniferous but the harder stuff is in there, even prevalent now (see below).

As hinted, carbonaceous chondrites are diverse. Which one was it? Hence the check for nickel. This comes in five isotopes as might have halflives beyond the 4.567Gy after coalescing into CCs. Each type of CC formed in different environments with their own recipes for nickel. They say CI is special here, and that CY (which is new) groups with them. Which led them to exonerate this whole subgroup from our crater.

Previous estimates had clustered around CM. The nickel rules closer to CO. They formed around the same place, 3.7 AU; they are differentiated, as it were, in time, CO forming earlier. CT is also possible but they aren't as well-constrained as yet, and as North Americans say when they hear hoofbeats, horses be more likely than zebras.

CO Chondrites are also, they say, dry - until this one splashed into shallow water that is. Previous estimates on the sulfur sent into the atmosphere had been estimated from the assumption of a sulfur-rich CM so those estimates are going to have to change. Unless the monster struck an oil field admittedly, and this is the future Gulf of America we are discussing here.

They point to Bottke 2007 as one line of evidence, on this rock coming from a 160Mya breakup. That would be the 298 Baptistina hypothesis. I know Bottke's been around awhile but I personally would not do this, except as a nod to those discredited pre-CC theories. Because it's the wrong rock (it's S) at the wrong time (80 Mya). CO rocks instead formed past the present (and CM era?) snowline although perhaps not the 2.7My-after-solar-system snowline. We are here not discussing the Grand Tack.

I have to wonder about 495 Eulalia ...

The Precambrian Asteroid Punch

800 million years ago, the Boring Billion ended as our Moon broke its nineteen-hour tidal resonance and started its gradual march outward. There was nothing naturally geological going on down here; supercontinent Rodinia had formed 100My before (supercontinents are even more dead and boring) and would last another 50My. Perhaps we might have been pushed from outside.

Bottke et al. say our moon got a surge of craters (including Copernicus); Earth too should have had still more. Keep in mind that Bottke like Loeb has a history of meddling in Chicxulub and getting it wrong, although Bottke hasn't since gone as totally stupid as far as I know.

A lot of this relies on simulation. The craters match if a swarm of loose asteroids had reached the 3:1 Jupiter resonance all of a sudden. A big impact would push fragments into 3:1J (they call it "J3:1"). So, a bunch of impacts immediately; then the Yarkovsky Effect kicks in for more of the surviving rubble, heating and outgassing the volatiles to 3:1J over the next 150My.

That resonant region, noted on this blog, includes 495 Eulalia and 142 Polana. Eulalia is currently 1:2 resonant with Mars; Polana more like that 3:1J. Polana, we know, is tossing stuff like Bennu at us. But the Bottke Boys be pointing at Eulalia because they note it broke up ... 800 Mya. Polana has probably not been where it is for long.

They also blame these inner-crossing rocks for a surge of volcanism over then-dead-already Mars. And with "shifts in the biosphere" here. At that time nonplant life here was still stolonic. Wiki points to a "Choanozoa" postfungal but not yet animal.

Back to LHS 1140

Three summers ago I got moderately excited about Gliese 3053 = LHS 1140 b - the M star's outer planet, 24.7 days. I didn't really look at later-discovered c, which I thought would be irradiated and airless. The Alfvén surface habitability criterion looked good for b however so it got attention at the time.

I started pondering underground water as might deflate the rocky part's density and raise its radius, so held off on saying much more about this unconstrained planet. I had questions needing answers about its atmospheric composition.

So: more data's come in (h/t Zim, but poorly worded). Still looking at a mass of 5.60 ±0.19 Earth masses (M_⊕) and a radius of 1.730 ±0.025 Earth radii (R_⊕). Star is just under 15 parsecs away and hasn't been flaring, and spins 131 days, so is deemed 3+Gy old. Planet b only gets 42% incoming flux but that's enough for HZ status on its sun-facing side.

The star probably used to flare which is how come c, just over Earth mass, is blasted out. The paper is going to float implications for the Cosmic Shoreline (to the extent I hadn't already). I don't believe any further planets are detected here; there might not be room below the 25 day range.

What is found here (and not down on c) is "metastable helium". That is the 2 ³𝑆₁ excited state, bumping an electron to a higher ring; as on WASP-107b. Once excited it takes around 7870 seconds to cool back down again. As Collin Cherubim et al. say in their title, Helium escaping from the atmosphere (pdf). And the helium isn't always found: it was found 2024 (when this blog was looking) but not 2025.

Also there's not much hydrogen. Although the planet is ill-lit, it should still be warm enough for low-melt methane to rise past the "cold trap" of the convective troposphere (so the paper), where it would be broken up. So no new methane is being created downbelow. Water on the other hand can form into clouds below all that helium. Venerians will pipe in that so can sulfuric acid. Good case for the Sudarsky II.

Don't watch Emily Wilson

The Odyssey was a fanfic of Homer (and, possibly, also of The Sack of Troy), and we cannot rule out that a woman composed it. Emily Wilson has made the text relevant for a modern audience.

And dvorstone explains why I ain't watching Nolan's rendition of Wilson's vision:

The Odyssey is not a universal story. It is not a detachable “hero’s journey” that can be stripped of its cultural origins and modernized for contemporary audiences. Its power lies in its particularity. The audience must do the work of closing the gap; the text does not come to us.
The values that animate it, xenia (reciprocal guest-friendship), oikos (the household and its obligations), mētis (cunning intelligence), kleos (glory), and timē (honor), are not interchangeable with modern liberal abstractions. They are embedded in a specific ancient Greek moral and social world.

All this, besides Claire Lehmann promoting it whom I don't trust one bit. Besides Razib Khan linking whatever this is I guess because that particular midwit had read the word "xenia" back in philosophy class once.

If we're going back to the Palatial Period, LHIII before LHIIIC, I suspect mētis won't show up much. The Linear B tablets float plenty of -klewēs names suggesting every other one of dvorstone's themes; the wanax presided over an honor-culture. Mētis however seems unhelpful to the Palace, more helpful to the peasantry (and to the slaves).

But mētis we do want to see in Odyssey. This might be a tale of a man of mētis redeemed back into the oikos. The postArchaic story. Pity Wilson can't tell it and Nolan won't.

ERRATUM 7/21: it's Wilson not Watson. Gaahhh. I'll leave the URL up.

The Grand Tack, or not

Kyplanet is pulling up Franklin et al. ... from 2004. Franklin's team suggested that Jupiter captured the Hilda asteroids (those 3:2's) on a tack of 0.45 AU inward. This is a problem for the Grand Tack which predicts a much longer inward migration, pulled back by Saturn. Zheng et al. also dispute the grandness of any tack. D'Angelo and Marzari in 2012 questioned if Saturn had that force if Jupiter ever wandered within 4 AU of the nascent Sun.

At least Franklin as a 2004 paper is vulnerable to later data, especially since we've now been visiting the Jovian-region 'stroids. Vokrouhlický et al. want to know how the slow-short-tack theory of Franklin's team can account for the dispersed ...distribution of Hilda inclinations. Overall that 2004 paper is treated as a minority-report (although not yet refuted).

More trouble for Grand Tack might be that it doesn't actually explain what it was supposed to explain, namely Mars' tiny mass. Other constraints we don't got include whatever other large bodies were in this system and might have been yeeted.

The great freeze

This March I noted the great swamping of Europe from an Iberian refug(ium). At the time I'd figured it as violent... and then I found that the original Neanders didn't totally die out. Today is served a second helping of crow.

I had collapsed the earlier Neanders' fall with the demic diffusion of 63kBC - ah hell, this long ago, "65 thousand years ago" might be better. But populations of (presumably) similar tech are rarely simply stomped on; more likely, something had slashed the general Neander population before the Iberian diffusion. Tübingen brings the archaeology. The population outside Iberia had been (too) low for ten thousand years.

We may compare the Neanders from 45k-42kya (43-40kBC) who got replaced by, well, us.

So what was going on in Europe 75-65kya? This is about when most would place Toba but I don't think Toba could have dumped on 'em for ten millennia. What GoogleAI does find is MIS 4, 71-57kya. That is also incidentally about when humans (with quite a bit of Denny DNA) crossed the great Sunda into the island continent Sahul, and the hobbits died out also.