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[McTraveller]

Yeah my educated layman's impression is that the article at least is playing fast and loose with definitions. There's no rigor there.

[Telgin]

That was my initial impression too, but found an explanation on Reddit that at least gives an attempt at explaining it based on the paper: Reddit Link.  The thread there has a few other good comments too.

The comment there says that blackholes growing with the expansion of the universe cause spacetime to dilute to conserve energy.  That kind of makes sense, but I'm not going to pretend to know the math or physics well enough to say more than that.  I haven't read the paper directly and suspect I'd get very little out of any attempt for the same reasons.  I'm a computer scientist, not an astrophysicist.

I'm also not really sure what the implications are if the paper turns out to be accepted by the scientific community.  It seems most people agree that we won't get any new physics out of this, but it sounded to me like this is a pretty big improvement on our understanding of blackhole evolution and should be pretty profound.

[Il Palazzo]

That is super interesting.

Odd final phrasing. Given the headline, I would have expected "the universe expanding as they increase in mass". Which rather calls into question the true causation/correlation they're trying to put forward.

It's not odd. The causative chain goes like this: universe expansion - leads to - black holes gaining mass - leads to - acceleration of the expansion setting in.
I.e. it's not that dark energy causes expansion. In the FLRW model of the universe expansion would occur even without dark energy. The latter is not causative of the former. DE is almost negligible in the initial stages of the expansion.

(Also, they will stop/slow forming stars because of less remaining material available to, it won't be that the lowered star formation means a reduced amount of "new mass" to feed the holes, in any meaningful way.)

But it does mean just that, at least in part. The accretion disc is mostly gas. Compact objects, like stars, are more difficult to accrete, as the can only drag through which they can feasibly lose orbital energy is gravitational. So depletion of interstellar gas quenches both star formation and black hole accretion. Additionally, there is tentative evidence of a feedback mechanism, where active galactic nucleus (i.e. accreting black hole) blows the free gas away through a number of processes, stopping both star formation and further accretion.

I shall read the full article later ("larger" is in size/extent, not mass, I assume, and they ruled out other reasons why later populations could be seen to be shifted up the scale a bit), when I have the time, but you'd have thought even the summaryised language on a science site wouldn't be so... confusing.

Larger in mass. Which happens to necessitate increase the size, but it's the mass that's being measured and important for the proposed mechanism.

[McTraveller]

If energy is conserved, how much is there in the universe? Is it a finite amount?

Entropy is always increasing, but what was the initial entropy?

Would ChatGPT know the answer? 

[Telgin]

I've read that energy isn't conserved on a universal scale, which always felt odd to me but I don't know enough physics or math to truly understand why.  Naively, I'd expect redshifting of photons due to expansion of the universe to imply that they lose energy and that energy really isn't conserved, but I'd be surprised if it really was that simple.

[Starver]

Having read and cogitated, I'm not really convinced...

The new result shows that black holes gain mass in a way consistent with them containing vacuum energy, providing a source of dark energy and removing the need for singularities to form at their center.[/url]
...maybe I'm odd in actually prefering that there be a singularity, and finding it the neatest obvious solution. However beyond the usual maths/physics understandings.

Odd final phrasing. Given the headline, I would have expected "the universe expanding as they increase in mass". Which rather calls into question the true causation/correlation they're trying to put forward.

It's not odd. The causative chain goes like this: universe expansion - leads to - black holes gaining mass - leads to - acceleration of the expansion setting in.
I.e. it's not that dark energy causes expansion. In the FLRW model of the universe expansion would occur even without dark energy. The latter is not causative of the former. DE is almost negligible in the initial stages of the expansion.

I clearly don't get this, properly. This sounds dangerously close to the "infill" version of the Steady State theory ("yes, things are clearly moving away from each other, but new stuff is spontaneously happening to fill the gaps..."). Maybe my head is in the wrong place, though.


I shall have to revisit it.

[martinuzz]

Due to a micrometeorid (debris?) impact with the Sojoez-MS22 re-entry vessel in december last year, the craft has now been deemed too dangerous for human beings to re-enter the atmosphere.
The impact struck a radiator, allowing radiator fluid to leak.
Due to this, the inside of the vessel will reach temperatures over 40C on re-entry. Combined with high humidity inside making it too dangerous for human beings, Roscosmos decided to send a replacement, the Sojoez-MS23, which will depart without crew.
The damaged MS22 will return to earth carrying only equipment that can stand the temperature and humidity.

The MS23 was scheduled to launch last weekend. However, when a Russian cargo vessel also developed a coolant leak at the ISS, the launch was delayed for an extra inspection. It is scheduled to launch this friday.

For the astronauts aboard the ISS, missing their flight means a half year delay.

Either Russia makes bad radiator parts, or we are starting to see the effects of space debris.

[martinuzz]

oops double post instead of edit

[Starver]

Given that we think (though the Russians want to say otherwise) the 2018 Soyuz leak may have been a manufacturing error[1], I'm inclined to go with the same view of this other. After already having pondered a little since the original coolant leak, etc. Not sure any clearer evidence will make its way out into the armchair space-community (maybe even not enough find its way to NASA, other concerned space partners or the kind of intelligence analyst who specialises in this area of operations).


[1] Or ground-based sabotage? Probably not. Or, at least, if Moscow has evidence of that kind then they've clearly gone on to deal with what they found out whilst maintaining their blame on external factors in currently typical self-serving manners, playing politics.

edited for tyops

[jipehog]

Any news on the new space race ?

[Starver]

Any news on the new space race ?

New? Well, Voyager 1 is still ahead, and not going to be passed any time soon. Pioneer 10 is about 26AU behind, in second place (and losing ground on first) but Voyager 2 is only in 3rd by about žAU and going almost a third as fast again as its nearest rival, so may well gain 2nd quite soon. Pioneer 11 trails these to hold a solid 4th, on paper, but New Horizons has so far reached half as far in nearly 17 years as the former has gotten in a full half century. Not actually much faster (currently about midway between the Pioneer velocities and those of the Voyagers) but sent on on a trajectory without so much deliberate loitering around the planets in the initial years of the mission

Then there's various final boost stages and released counterweights, in partly associated trajectories as uncounted placings slotted and interleved into the above list, but I'd class all of them the same as riderless horses or unhorsed riders!


(If, instead, you're looking for something like the Starship/Superheavy launch, they're promising a possible full launch test in the next month or maybe not, last I checked, but that might depend upon the FAA, et al, regardless of SpaceX's feelings on the matter. There's both optimism and pessimism aplenty, in the 'expert' places that chatter about this sort of thing. Hard to narrow down the realistic answer to this question, especially given the timing by Musk always seems to keep sliding... )

[Great Order]

I think they may be referring to the Artemis program.

[Starver]

Yeah, which is why I, eventually, mentioned Starship (a planned element of it). But I'm not sure there's really a race yet. The famous chinese, russian and/or sino-russian plans are not obviously even on the starting-blocks, so only NASA (and SpaceX) seem to be doing anything solid insofar as the manned flight around/to the Moon, and it's more a cooperative than competitive thing.

There is a chance of a "before the decade is out..." possible shift into gear, like the US overcame its own lagging behind to be the one to burst through the finishing tape. And it wouldn't actually surprise me too much if a Tiangong (3+?) also seemed suddenly capable of upwardsly leaving orbit, by demonstrably doing so one day without even a heralding press-concerence beforehand...

This is one reported summary of the known future, that might help, or keep an eye on public updates and confirmations to https://en.wikipedia.org/wiki/List_of_missions_to_the_Moon#Crewed perhaps...


(But I'd also recently read up on the status of 'departing' probes, so I really couldn't resist a narrative summary of that interesting info for fun and profit.  )

[jipehog]

I was talking about China starting to nibble at your feet, it is a long march..

[Starver]

Well, yes, but it's into the 2030s when anything (manned) is likely to happen, unless they do something surprising with their Celestial Palaces. Just the Rabbits, until then.

But a decade could be a long time in space science. And it might not take until 2063 (and a 'spare' nuclear missile in Montana, left over from an intervening worldwide conflict) for more advanced space transportation systems to be developed by some genius or other...


(BTW, I meant to give these three links earlier. For those interested in what I'd been looking at. Had to go elsewhere for estimates on the two-decades-dead, or thereabouts, Pioneers.)

ETA: Meant to also say that unless my country has a hidden capability, my own personal feet aren't even anywhere where they might be at risk of being nibbled..!