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>> In particular I find very compelling the theory that the YDIH hit the laurentide ice sheet over Michigan, sending huge ice boulders out that created the Carolina bays and essentially did great damage, but with water ice, thus leaving very little direct physical evidence -- no craters (apart from the Carolina bays), no rocks out of place, no layer of material from the impactor (because it was a comet rather than an asteroid).

In that case, how do can we tell that's what happened?

Antonio Zamora is a scientist studying this who writes papers and posts videos on YouTube at https://www.youtube.com/@Antonio_Zamora and he does a good job of showing how the Carolina bays point towards the impact location, and what not. I'm not going to summarize it all here, but the point is that there is some, and perhaps enough evidence to go on.

"Science is not an exercise in accepting a scientist's say-so, dammit."

May your words echo in the hallways of this forum!

Don't hold your breath. HN is full of people with credentials, and people with credentials tend to push credentialism, and that means deferring to the experts on other fields so that others will defer to one in one's field of expertise.

Mike Shapiro at Sun was fond of telling us that "we're not specialists -- we're generalists who can specialize as needed". I think that is a good attitude in general. It doesn't mean we get to weigh in on things we know nothing about, but it does mean we get to do critical thinking and that we can self-educate in order to form opinions when necessary.

And sensibility to recognize when having (let alone voicing) an opinion isn't necessary.

OK good to know.

This is caused by comet remains through which Earth goes twice a year, right? If astronomy data supports "Earth totally could get hit by a chunk from it" that's also a step. Are future threats from these comet chunks trackable by NASA?

What do you find disatisfactory about the conventional explanation that the Carolina bays are thermokarsts?

On a smell test level, here's a picture of a thermokarsts:

https://upload.wikimedia.org/wikipedia/commons/7/73/Permafro...

And here's some pictures of the Carolina bays:

https://lh3.googleusercontent.com/-RzXM7ywZkS8/WKW0zLlhU4I/A...

https://en.m.wikipedia.org/wiki/Carolina_bays#/media/File%3A...

Things aren't identical just because they look alike, but again on a smell test level, it doesn't immediately strike me as implausible.

I'm certainly no expert on impact craters but that doesn't really look like a field of impact craters to me. I've never seen a photo of a field of oblate impact craters. In the LIDAR you can see many of them overlap. That would suggest to me that what formed these ovals happened many times, rather than all at once.

If you think about it, the way you get an oblate crater is to hit at an extreme angle, right? But if was an airburst, then the debris would be going down. So it should make circular craters.

Maybe it's an airburst just off the ground, a few hundred feet up or something. That way it's close enough to spray the ground at an extreme angle. But then the Carolina bays would be very close to the epicenter. So we should see some rotation among the "craters". But they're parallel. Which would mean, if they were craters, that the blast was very far away. (In which case, they would have had time to come down in parabolic arcs, and we're back to circular craters.)

If it wasn't an airburst, then it was a direct hit a mere 13k years ago. That's young enough that we should be able to find the crater. I've seen supervolcano caldera much older than that, I wouldn't imagine a crater would erode any faster.

> To say that the YDIH is debunked is not true and not helpful.

I dunno. This isn't a scientific observation, but there's something fishy with this hypothesis. It's being popularized by conspiracy theorists, and the Comet Research Group, some of it's proponents, were busted for faking evidence. The theory posits something really attention grabbing and dramatic, but it's also very speculative and didn't originate in physical evidence.

Meanwhile the alternative explanation that the AMOC was choked out by freshwater melting off the glaciers is very tidy, there's ample physical evidence for it, and it doesn't need to bring in an unlikely and external element like a comet. This explanation amounts to, "what we know was happening at the time kept happening until that forced the environment to change, through a well established mechanism we can continue to make physical observations of today." Contrast that with, "we're going to look at a time the environment changed, and back out an explanation of why that might have happened."

This just feels too convenient for me. This seems to be at least as much a vehicle for people like Hancock to claim their hypothesis - which just so happens to be a very cool and engaging story - isn't getting it's due from the scientific establishment, as it is a serious scientific endeavor to understand what happened in the Younger Dryas.

CRG has a sus vibe indeed. It'd suck if it turns out true but our civilization is wiped out by another comet chunk because every good scientist who had the same idea just didn't want to hang out with that bunch.

A civilization as advanced as ours would have to have bootstrapped via coal mining and burning like we did, and that would leave evidence in the CO2 records in the ice cores. There does not seem to be any evidence of such an advanced civilization in the ice cores, unless it wasn't remotely global in scope. There could have been less advanced (but still advanced) not-global-in-scope civilizations that we don't yet know about, but I don't see the link to the Carolina bays, unless it's to say that the same event wiped them out, but so what, I'm interested in the Carolina bays and their cause, and much less interested in speculation about advanced civilizations.

What are you talking about? Comet research groups in past advanced civilizations? I'm confused. I was taking about our civilization and future.

I thought you were referring to Hancock et. al. Keep in mind I know nothing about "CRG".

I don't know anything about CRG except what I saw in Wikipedia, something about faked evidence and all that.

> What do you find disatisfactory about the conventional explanation that the Carolina bays are thermokarsts?

For one, the bays don't look like thermokarsts, and for another the bays look like they "aim" at the impact sites, and they seem to form perimeters centered on the impact sites. That's highly suggestive.

> This isn't a scientific observation, but there's something fishy with this hypothesis. It's being popularized by conspiracy theorists, and the Comet Research Group, some of it's proponents, were busted for faking evidence.

I've no idea who they are. None. Is Zamora one of them? Can you tell me more about them? Everything I've seen is that he is very careful in what he says, and I've seen nothing from him about advanced civilizations.

> Meanwhile the alternative explanation that the AMOC was choked out by freshwater melting off the glaciers is very tidy

I agree with this. But that doesn't explain the Carolina bays, and the two things can have happened close enough in time, possibly for the same root reasons (impacts).

> For one, the bays don't look like thermokarsts

But they also don't look like craters? They don't look so dissimilar from thermokarsts, but craters really as a rule are circular.

> the bays look like they "aim" at the impact sites

Hey I'm just curious, did you look at the photos I posted? I know I wrote quite a bit, did you see where I raised questions about this specifically?

See this section from the Wiki article on the Carolina bays:

> Modern thermokarst lakes are common today around Barrow (Alaska), and the long axes of these lakes are oblique to the prevailing wind direction.

Are they "aiming at the impact site" or are they "oblique to the direction of the prevailing winds?" They look parallel to me. Wind is parallel in a local area. Shot from a nearby airburst is radial, and very much not parallel. Shot from a faraway airburst might be parallel, but you won't be able to tell because it'll produce circular craters, which isn't what we have.

> Can you tell me more about them?

Only what's in the YDIH Wikipedia article.

> [P]ossibly for the same root reasons (impacts).

I mean, we know about a different phenomenon that was going on that has a tendency to form lakes and pour huge amounts of freshwater into the oceans, right? Do we really have to assert that this comet exists in order to arrive at a plausible explanation? If not, then why are we bringing in the comet?