True, you can always have leaks, but hydrogen leaks seem to be way, way more common than leaks of other fuels as a percentage of launch attempts. The shuttle was scrubbed on average almost once per launch, and a large percentage of the scrubs were caused by hydrogen leaks (source).
You're right; that link, and the Ars Technica one it references, is a pretty damning condemnation of hydrogen.
The link to Nature is behind a paywall.
Annoyingly, the paper isn't on Ariv - yet.
Researchgate just feeds you back to Nature.
I'll try to remember to look for it again next week.
your (366 * great) grandchild could see this,
And they would be as far from you, as you are from the first humans who got most of their calories from farmed rather then hunt/gather foodstuffs.
Generally you're correct, but,
condensed directly out of the still very hot >1300 K supernova gas,
No. The melting of the CAIs (which in the early 2000s averaged to the memorable date of 4567 million years ; more have been measured since, but the average is still pretty close to that. And it is a memorable number. Which is why I remember it.) is thought to have been caused by the "turning on" of the early Sun. Maybe by flares as the proto-Sun was having magnetic conniptions as it approached "turn on". But certainly not remnant heat from the nearby supernova which, as you say, peppered the debris with Al-26.
That Al-26 half-life puts an upper limit on the travel time from the supernova system to the proto-Sun, but it's comfortably within the duration of star-forming in the molecular clouds we can see. So, not a troublesome constraint.
a rocky planet can be filled with Oxygen and Carbon
The carbon content of the Earth is pretty negligible. By volume it is about 50% oxygen, 10% iron, and I'd have to go looking to get a number for silicon and magnesium, but they're fairly comparable to the iron. The rest of the periodic table fits into the remaining 20% or less of volume.
Carbon is not very common on Earth because while the planetesimals which formed it were accreting and turning little mud-balls into bigger mud balls, it was too hot (locally ; it was cooler further out) for either carbon monoxide or carbon dioxide to be stable as solids. They were literally "volatile" and flew away to cooler parts of the solar nebula.
For the same reason, there's not a lot of water on Earth (less on Venus and Mars). Water in a vacuum is unstable above temperatures of about 100~150 K (if you need American units, there is likely a conversion application somewhere).
I am trying to get a sense of how many Billions of years it may take such that a rocky planet can be filled with Oxygen and Carbon
We've found a moderate number of planets around stars which are (from their rotation rates) considerably older than the Sun, but I don't have the "oldest planet-bearing star" number in my mental RAM. Possibly they formed as old as 8 billion BP (so a look-back age of about 5 billion years after the big bang) ; certainly there was enough "metals" (Saganesque "star-stuff") by 4.5 billion years BP (look back age of about 8.7 years after the big bang). Otherwise
It is conceivable that different galaxies have different levels of metal contamination, and it is also possible that different regions of a single galaxy have different levels of metal contamination. People are probably still getting PhDs for arguing on that point in both directions. (One direction per PhD thesis, mostly.)
Quibble, non-trivial
The first stars after the big bang were composed mainly of hydrogen and are called population III [wikipedia.org] stars.
Approximately 75% hydrogen, 25% (by nucleus count) helium. Tiny (parts per million ; 1ppm = 0.0001%) proportion of primordial lithium, if it survived the early period of rising temperature and pressure in the forming Pop1 star.
But then, yes, the amount of contamination with "metals" (anything heavier than helium) increased. Whether it increased linearly, and how well mixed the interstellar medium was at those epochs is a very argued question. Ask Ariv for the last couple of years of articles that report "review" and "initial mass function" - that should cure your insomnia.
We can't see the Big Bang.
We can see the "surface of last scattering", where the radiation component of the universe last interacted with the charged particles of the cooling universe - because they dropped through the temperatures where the free protons and free electrons recombine to make neutral hydrogen, which interacts negligibly with photons with a blackbody temperature less than about 3000K.This event took place about 300,000 years after the Big Bang, and fomr out point of view, at a redshift of about 1000 to 1200.
We can infer, with high confidence, the existence of earlier events. A few millennia before the "surface of last scattering" there were several similar events when electrons combined with (first) He++ nuclei, then [He++ & e-] ions. But our chance of actually seeing radiation evidence of that is slight, because the light form that spent several millennia interacting with the free electrons and protons, which would have "thermalised" the radiation. Unless some subtle physicist thinks of something.
Looking back beyond the (inferred) recombination of helium ions, I think the next thing we'd see would be the thermonuclear reactions which turned primordial protons and electrons into a mixture of protons, deuterons ("heavy hydrogen" nuclei) and helium nuclei. That ended about the 3 minute mark after the Big Bang.
then we should be able to see the outer edge of the time/space bubble that we exist in
We can't ; the "surface of last scattering" gets in the way. If you look in the opposite direction, you see exactly the same thing, at (very close to) the same distance and red shift.
If the universe is positively curved and relatively small, it is possible that by looking in the opposite direction you actually look back to the same point behind you as ahead of you. That's topology, man. That will really screw with your head.
But that fell out of favor when it was discovered that the expansion of the universe is actually accelerating.
Not really. It had been falling out of favour for years (decades, even) before then.
The question of the long-term future of the universe essentially comes down to the question of what the average density of mass-energy in the universe is. Too high, and the universe Bangs, expands for a bit, then starts to contract and Crunches (Big Bang, Big Crunch) ; too low, and the universe Bangs, then expands infinitely ; and there is a borderline case where the universe is constantly on the borderline between eternal expansion and eventual Crunch.
Since the second estimates of the Cosmic Microwave Background temperature, in the early 1970s - which is probably still our best tool for estimating the average density of the universe - the majority opinion (not the only opinion) has been has been that we are, indeed on that borderline. And theoretical cosmology from the late 1970s onwards has produced a number of arguments why the universe would naturally be on that borderline case. Or, at least they did until that pesky "Dark Energy" thing in the late 1990s, at which point there was a prompt realignment of theoretical cosmologists (3 free theoretical cosmologists and 2 dollars will get you a coffee) to agree (or disagree) with the Emperor's New Clothes.
Personally, I think that it is premature to even seriously attempt theoretical cosmology until we have either a (working) quantum theory of gravitation or a (working) classical theory of the strong and electro-weak forces. Which won't stop people playing with such theories, and probably won't even slow them down. But since the difference between classical gravity and quantum electro-weak interactions is somewhere beyond the 15th significant digit (base 10)
The OP/ OQ neglects the fact that in real galaxies (or, for massive stars, real star-forming regions) there is considerable turbulence. In an empty universe with one star (total), you might possibly get such a symmetrical explosion and collapse. But in a real universe, you wouldn't.
Actually, in real supernovæ a common outcome is an asymmetrical explosion. See "natal kicks" and "runaway stars". A significant proportion of young pulsars (the easiest neutron stars to spot) are seen flying away from their natal supernova remnants at considerable velocities. If we can identify the supernova remnants - which is by no means a universal case.
How does that venerable saying continue? Oh yes :
Monetise, Exterminate
Astonishingly, I have not fallen out of my chair with astonishment on receiving this news.
To be fair, "tagging images", i.e. supervised learning, is pretty widely supplemented by unsupervised techniques today because it usually works a lot better. He also says things like just scaling up won't work forever, which seems to be true; the current LLM models are not just scaled up versions of previous ones, and the current LLM craze itself is the result of architectural innovation.
He also says things like "I argued that 'deep learning is hitting a wall'" which suggests he doesn't really understand the difference between deep learning, which involves the very fundamental observation that deeper computational graphs can be much more efficient than shallower ones, and specific examples like a particular LLM architecture.
As the Mountain Rescue at Chamonix say, "tous les meilleurs alpinistes sont tuées en rapelles". (For the linguistically challenged, "all the best alpinists are killed abseiling".)
It's so common - someone who regularly pushes their sport to the bleeding edge
Vale.
Paragliders: the only aircraft that you assemble while you're taking off.
This guy was an adrenaline junkie. The very kind of guy who is attracted to aviation and the last kind of guy who should be practicing it.
Lots of assumptions. He completed a lot of flights, many of them more carefully planned than anything most of us have ever done, flying or otherwise. He died on what sounds like a pleasure flight and "fell ill while flying" might be Italian police speculation for "had a heart attack."
TFS didn't say (or I didn't notice) if he'd had children or not. Without knowing that datum, you can't say whether or not he has been removed from the gene pool.
You don't jump off a balloon at 100,000 feet without a lot of calculation. Baumgartner was the spam in the can but there are whole teams behind these things, from figuring out whether it's possible to designing the spacesuit that kept him alive.
How did the stock market get into this discussion?
Introducing, the 1010, a one-bit processor. 0 NOP No Operation 1 JMP Jump (address specified by next 2 bits)
