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Comment by zh3 | Hacker News Reader

>The burst even appears to have caused Earth’s ionosphere, the upper layer of Earth’s atmosphere, to swell in size for several hours.

For a gamma ray burst from an object that's 2.4 billion light years away, that seems pretty worrying. If it had been in our galaxy (50k light years across, so about 50,000 times closer) I'd assume the consequences would be serious indeed.

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There's a hypothesis that Ordovician-Silurian extinction cca 450 milion years ago, one of the big five mass extinctions, was caused by a GRB.

Would the Earth shield one side of itself? If yes by how much?

Seems like that would only help if the duration of the blast was less than 24 hours

Or perhaps more like 12 hours, as half of the Earth would be exposed instantly.

But even then it depends on whether it's the direct radiation that's the issue or something more indirect (atmospheric changes, etc.)

doesn't this depend on the blast's origin relative to the Earth's axis?

The longest gamma ray bursts only last a few minutes.

Just how many nines reduction from peak intensity after a few minutes are we talking? Because I'd imagine 0.01% of a nearby gamma ray burst would still be bad news.

Rotation around the axis doesn't expose the northern hemisphere to the southern sky, nor vice versa.

That depends on the orientation with regard to the poles. If the source were directly over a pole, only fifty percent of the planet would be directly exposed. If it were over the equator, however, the whole planet would be, if it were a magic GRB that lasted way longer than usual.

So the upside is that anything that can get through 10k km of rock is very unlikely to interact with anything on the other side (eg neutrinos)

It will affect atmospheric chemistry. It will produce a ton of NO2 and make atmosphere unbreathable without equipment.

I imagine that killing half the planet is enough to send the "lucky" half into chaos and collapse.

Is there any data to back this up? (not attacking, just genuinely curious, i love learning about mass extinctions)

Only extremely circumstantial evidence. Some guesses about which species died off vs being protected, some climate change signatures that are consistent with a high UV burst.

About the best you can say for it is "you can't prove it didn't happen". Which, given that it was half a billion years ago, may be the best you can get. There isn't a real smoking gun.

The leading hypothesis is more that a long-term climate change caused secondary effects in a vicious cycle. We know the climate change was happening; there's very strong evidence. But it's not clear exactly what caused it or exactly how it led to mass extinction.

No, and the idea is widely derided by paleontologists because it's pretty much untestable.

If I'm not mistaken, gamma ray bursts properly directed from a close enough entity are a realistic "wipe out all life on Earth" event, though extremely improbable.

Indeed, I think a supervolcano like Yellowstone erupting is much more likely.

That would not even kill all humans. It would possibly destroy all of civilization though. But even then, the coming generations would have artefacts to study and be inspired by.

Call me selfish but I don’t make much of a distinction since there’s a good chance me and everyone I know are dead.

Wait 80 years and you'll get the same effect.

Another question is, how selfish are your genes? Half-kidding. :)

I suppose people in North America have very slim chances either way, though.

Sure, but since we’ve used up all easily accessible oil and gas they’d have a hard time to find the energy required to level up a society.

That's an interesting thought. ACOUP did a blog post a while back [1] outlining the very specific circumstances that led to the Industrial Revolution and arguing that it's hard to imagine another way it could have happened. I suppose a rebuild would have to find a completely new route. Perhaps fields of Don Quixote esque wind mills connected to giant led-acid batteries rather than coal! With a couple hundred years gap between Armageddon and a substantial human population making progress, at least there would hopefully be decent timber reserves to work through the early phases.

[1] https://acoup.blog/2022/08/26/collections-why-no-roman-indus...

Using recycled copper from scavenged wiring, because there’s no high grade copper ore anymore.

All that copper went somewhere, though. A rising post-apocalypse civilization would probably mine our dumps and ruins, Rimworld-style.

In a rebuilding event, we'd have the advantage of knowing it was possible and desirable. This book, for instance, would be worth kingdoms in such a situation - https://www.amazon.com/Knowledge-Rebuild-Civilization-Afterm...

Just make sure to purchase the paper copy and not kindle

Or this one: https://www.amazon.com/Machinerys-Handbook-Toolbox-Erik-Ober...

> For more than 100 years, Machinery's Handbook has been the most popular reference work in metalworking, design, engineering and manufacturing facilities, and technical schools and colleges throughout the world. It is universally acknowledged as an extraordinarily authoritative, comprehensive, and practical tool, providing its users with the most fundamental and essential aspects of sophisticated manufacturing practice.

I think the level of scientific knowledge we have accumulated would be a tremendous short cut.

Even without books, the myths and obvious ruins of previous technological success would be a huge cultural guidepost for recovery.

Perhaps we would go through a 1000 year energy poor "dark age", and recovered populations wouldn't peak as high as ours, but I would expect that to be the worst case if an awareness of our history was not lost.

And maybe 10,000 years, after a complete cultural breakdown to hunter gathering with little functional memory of the past.

Given rewrites of first versions are often much improved for having seen previous failure modes, it would be interesting to pop into the future of a recreated civilization and see how they might do things better!

Even having this written knowledge available to us it might still be impossible to recreate the technologies; so much knowledge exists in an active state only.

Like the F1 engines on Saturn V. We couldn't just "recreate them" because all of the know-how was lost.

Written info is useless without the right sort of culture where the necessary experimentation and problem solving can occur to work out those undocumented details. That is all that matters.

However, that is also true today and the effects are visible through the variations in technological progress of different populations currently on earth.

If you can jump right to electric power, then hydro power can give you all the power you need to get civilization going again. I don't think that tech knowledge would be likely lost if people survive at all.

My guess is that all the required knowledge, including sufficient people, are squirreled away in the bottom of Cheyenne Mountain and probably a few similar locations around the world.

I guess it depends on how long before the collapse happens, but I think there's enough accessible fossil fuels left to sustain a less than 10-figure human population for under a century while it figures out what else to do. They'd probably have to live with far more local supply and distribution networks, but global communication should still be fine.

Probably shouldn’t worry much about that:

https://m.youtube.com/watch?v=fXb02MQ78yQ

They are. Luckily the only GRB candidate close enough to do that is eta carinae and it's probably pointing in the wrong direction.

Sounds like it's a perfect case where "probably" is not enough.

Enough for what? Useless worry? I don't think there's much we could do about it.

I mean, not much you can do about it, can you?

Either way, it's not likely to produce a GRB in the first place, it's too far away to really affect the earth in dramatic sci-fi story ways, and it's pointed in the wrong way.

It's a "GRB candidate" in the same way you're a "lottery winner candidate" if you buy a ticket.

What does “pointed in the wrong direction” mean? Isn’t it a sphere? Genuine question; I am ignorant of such things.

Stars have a magnetic field and rotate along their axis, similar to planets. The burst is emitted along the axis of rotation (the geographic north and south pole).

Many stellar objects rotate and/or have a magnetic field, and thus an "up", "down", and "side" in spite of being a sphere. Pulsars (extinguished stars that emit radio waves from their poles) are another famous example.

> What does “pointed in the wrong direction” mean?

Gamma-ray bursts [1] are a class of observations, not single event. (Like how we first saw pulsars, and then learned they're neutron stars.) Some GRBs may originate from relativistic jets [2] emitted by massive, spinning, charged objects colliding (e.g. black holes) or collapsing (supernovae). Those jets' intensity is not uniform, they emit from the poles. (See: spinning, charged.)

There are other proposed mechanisms that columnate emissions [3][4]. These involve a star's rotation creating a radiating column along the star's axis. (I'm not sure if the atoms in that column radiate with a bias.)

[1] https://en.wikipedia.org/wiki/Gamma-ray_burst

[2] https://en.wikipedia.org/wiki/Astrophysical_jet

[3] https://arxiv.org/abs/astro-ph/9808355

[4] https://www.plasma-universe.com/gamma-ray-bursts/

Stars, like planets, rotate around an axis. GRBs that are emitted by collapsing stars are believed to be directionally aligned with the axis of rotation.

> I mean, not much you can do about it, can you?

Work to shed our biology faster.

We'll get to that sometime in the next hundred years or so.

Mate I've got some bad news for you

>I mean, not much you can do about it, can you?

AKA: How I stopped worrying and learned to love the GRB

It's probably enough.

Your comment helped my worrying about this a lot, thank you.

Probably not? Half of the life on earth would probably survive the initial radiation burst, due to geography, and while there will be massive atmospheric chemistry changes that would be highly traumatic it seems like life would find a way, as they say.

Anton Petrov discussed this [1] a bit, but the essence was that there still would not be any obviously noticeable immediate effects, but that it would kick off a chain of changes like changes in atmospheric composition that would unfold over a longer time span.

[1] https://www.youtube.com/watch?v=4AWaqeUmQik

The object is likely an active galactic core, so couldn't have been in our galaxy.

2.4 x 10^9 light years away, so not in our galaxy by a very large measure.

I think the meaning was more, that our galaxy can't produce such events, so that's one thing we don't have to worry about in our galaxy.

Edit: a (to me) random site [0] says the Milky Way does not have an active galactic nucleus.

0: https://socratic.org/questions/does-the-milky-way-have-an-ac...

Okay, missed that. https://en.wikipedia.org/wiki/Active_galactic_nucleus says

"An active galactic nucleus (AGN) is a compact region at the center of a galaxy that has a much-higher-than-normal luminosity over at least some portion of the electromagnetic spectrum with characteristics indicating that the luminosity is not produced by stars. Such excess non-stellar emission has been observed in the radio, microwave, infrared, optical, ultra-violet, X-ray and gamma ray wavebands. A galaxy hosting an AGN is called an "active galaxy". The non-stellar radiation from an AGN is theorized to result from the accretion of matter by a supermassive black hole at the center of its host galaxy."

Do we? https://en.wikipedia.org/wiki/Sagittarius_A\* says

"Sagittarius A*, abbreviated Sgr A* is the supermassive black hole[4][5][6] at the Galactic Center of the Milky Way"

Front row seat! Get in!

Sgr A* isn't a very active black hole (meaning that it's accreting only very little matter), compared to black holes at the center of AGNs.

Is that so? There is the theory that our galaxy could be a Seyfert Galaxy, we just haven't witnessed it so far.

https://link.springer.com/article/10.1007/BF00717870

https://earthsky.org/space/explosion-milky-way-center-seyfer...

https://www.bbc.com/news/science-environment-49955468

Edit: I meant to say that our galaxy could, and has had such fits of rage, not that this event could have come from it.

These types of GRBs are caused by the death of massive stars with low metallicity, not active galactic nuclei. There absolutely could be a GRB inside of the milky way galaxy pointed at us, but it is very unlikely.

From the article

"It’s also likely that the BOAT’s powerful jet was pointed toward us"

The energy given out is(?) very non-isotropic. A random shot got 'lucky' and hit us.

And this answers the Fermi Paradox. The universe is an extremely hostile environment for life to evolve.

This does not really answer anything. As far as we can tell (modulo the precision of our instruments), it's likely there are many, many stars like our sun and planets like Earth, even if they are not in the majority. It also seems like life sprang up almost immediately after the Earth cooled enough for it to be feasible.

If the universe is filled with violent incidents then it doesn't really matter how probable life is. It will take an extreme amount of luck to manage to survive through all those events. The Fermi Paradox doesn't exclude life, just the frequency of it. You could still have plenty of alien civilizations out there, but at a frequency of one every a thousand galaxies or so because everything else gets wiped out every so often.

Even with 'one every thousand or so' (which feels like a fantastically speculative number) the law of big numbers suggests this does not, in fact, 'answer the Fermi paradox'.

FWIW my (comparably uninformed by more than one data point) money is on mitochondria.

If you take the Drake equation and start speculating on a conservative way, the one in a thousand galaxies estimation is very probable. It could be mitochondria, or it could be that the universe is still too young to be safe for life on a mass scale. We're just lucky to be one of the first.

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