@Cervaise was way ahead of ya on the escalating cascade theory 
One potential extinction level event was just brought to my attention. If something happens to the magnetosphere solar radiation is going to do a number on everything. I was reading an article about how we’re statistically overdue for a pole flip and how much the magnetosphere fluctuates in field strength.
If for some reason Earth’s molten iron core stopped spinning and the magnetosphere shut down, yeah, that would be bad news. Though not so bad as the bad sci-fi action movie The Core, where the sun’s rays are blasting radiation at people and giving them immediate third- degree burns. It would be a much more gradual march toward the end of humanity. More of a slow burn, hehe.
A pole flip, on the other hand from what I’ve heard, has not only happened fairly recently in the past in geologic terms, is also not that serious. It might mess with our electronics or something, but it (probably?) wouldn’t be a species-killer.
/minor hijack
The convo has slowed enough that I’m comfortable with a small excursion. Apologies if you believe otherwise.
The average is 300 thousand years and the last one was 780 thousand, so, statistically overdue.
In the past 200 years, Earth’s magnetic field has weakened about nine percent on a global average. Some people cite this as “evidence” a pole reversal is imminent, but scientists have no reason to believe so. In fact, paleomagnetic studies show the field is about as strong as it’s been in the past 100,000 years, and is twice as intense as its million-year average. While some scientists estimate the field’s strength might completely decay in about 1,300 years, the current weakening could stop at any time.
1300 years seems exceedingly pessimistic and implausible. That would require a straight-line decline over that time period.
No, I welcome interesting tangents to my OP topics. Though your scenario doesn’t really seem like a tangent at all, it’s pretty on point, actually.
But I still don’t understand after reading your linked article, how that might lead to humanity’s extinction, however indirectly.
The pole flip would only be an inconvenience for a while. The threat would be the collapse of the magnetosphere mentioned as an aside in the article.
That would leave everyone and everything exposed to unfiltered solar radiation. Which would be a slow death for the planet.
I admit, I skimmed the article and didn’t notice that it mentioned that. But as I said, yeah, the collapse of the magnetosphere would be a major bummer, and at first I thought, maybe deserves its own category. But then I thought it might also fall under the “cosmic crapshoot” category. Not sure.
If, in 300 years, we notice that this is happening (IE that the straight line decline in the strength of the field continues), we’d have 1,000 years to artificially strengthen the magnetic field, maybe with satellites? Is that something feasible for us on that time scale?
For a non-scholarly but very fun take on your question @Babale - I give you THE SCIENCE!
Seriously, I love Austin’s The Science! videos, and link them. It’s like what one of us would do if we had a Youtube Channel. Anyway, one of the points in the video is building an artificial magnetosphere for Mars, and it boiled down (minus the additional huge issues of getting all of the materials to Mars) of scale. Using current tech, I’d say no way no how in terms of materials and power. Using the tech of 300 years from now onto the critical weakening period? I’d have to guess yes, but only if we don’t cripple ourselves in some other way first to the point of no improvements or even regressing which seems more likely ATM.
It’s a fun video, and I recommend it and the others he’s done. He starts talking about blocking solar wind and the magnetosphere right around 2:45, so if you want to skip the last half of the video, which is all about the rest of issues of colonizing Mars. So if you only watch from 2:45 on, the rant about the hundreds of billions of tons of copper and power requirements (on Mars minds you, which is further away and a smaller volume!) ends around 10:45, a much more manageable chunk.
I haven’t watched that video yet, but I’m familiar with the general issue. There was a series a few years back, I think made by National Geographic (I believe just called ‘Mars’) that depicted the possible trials and errors of the first manned mission to Mars with the intent to establish a Mars base. If I recall correctly, their solution to the lack of a magnetosphere is they searched for and found a canyon or old lava tube on Mars to set up their living quarters, so they would be shielded from solar radiation.
Issues like that make me think…the general consensus is that there are so many stars in our galaxy alone that there must be alien life out there just statistically. But knowing how many wide and varied conditions on Earth had to be just right in order for our fragile asses to have evolved and survive, I wonder sometimes if perfect Goldilocks Earth-like conditions that can support life are more rare than we suspect.
- The planet should be not too large or small
- Probably rocky and not mostly gaseous
- Orbiting a star that’s similar to our sun
- Not too close or too far from the star
- With a rotating molten metal core that generates a megnetoshere
- Has to have enough of a variety of elements to support complex life forms
- Has to have water
- Should probably have a moon like ours, since tide pools are thought to have been a birthplace of life
I realize that it may be possible for forms of life that are different from us to have evolved in different conditions, but carbon-based is the most viable way to have complex life forms, and would likely need at least somewhat similar conditions as Earth to support life (silicon-based life has been proposed as a possibility. But my understanding is that the chemistry involved would have problems. For example, the silicon-based version of carbon dioxide, silicon dioxide, is a solid in a wide range of temperatures, not a gas. But maybe silicon-based creatures would poop out their silicon dioxide waste, not exhale it.)
Heh, it’s your thread so I won’t suggest we take it to the half a dozen other threads I’ve seen on the goldilocks problems in the 3 years I’ve been here (and who knows how many before that!). My short take is probably the mainstream version to such a speculative consideration: life is probably “common” out there, intelligent life far less so, and technological intelligent life vanishingly rare. And if it exists, or will exist, maybe so separated from us (past or future) by the lifetime of a society or species the the point that interaction absent some form of FTL (and likely even with!) is pointless.
But (watch me bring it back to your OP!) is that I suspect any species that makes it past all those hurdles then has to worry about all the possible sources of destruction laid out in the OP. You can beat all those odds given a sufficiently infinite universe, but the odds of a random cataclysmic event are likely far higher at some point. So, yeah, getting to point we’re at currently is like winning the lottery big, twice! But it DOES happen. It’ll probably happen again. But a lot more people never win, and are instead killed by some unspeakably rare quirk of fate.
Makes you wish we had something to blame for it rather than the uncaring randomness of it all. Blech.
Ha, yeah, I do tend to hijack my own threads, and you’re right, the whole Fermi’s Paradox thing has been done to death. I tend to agree with your assessment of the possibility and possible types of alien life. I’m just saying that when I think about all the many things that had to be just right to support life here on Earth, I wonder sometimes if maybe life itself is vanishingly rare.
I told a story in another thread here awhile back; how when I was a kid walking around outside, I saw a mud puddle along the side of a road from recent spring rains that had a lot of tadpoles swimming around in it. And I thought, those poor tadpoles, happily living their little tadpoles lives for the time being, with no idea that that little mud puddle was probably going to dry up long before the tadpoles grew legs and were able to hop away to better living conditions. Then later in life I had the thought “we are all just tadpoles in a mud puddle, too!l”
Then a poster came along and said that I was wrong about the mud puddle, that it probably lasted longer than I assumed, that the frog or toad that laid the eggs likely knew instinctively that the puddle could support the lifecycle of its offspring, etc etc. 
I’m surrounded by Old-Order Mennonites, and a few other old-fashioned farmers, who do. Even I have some idea.
And there are still areas of the world where there a lot of people who still are, or only recently were, subsistence farmers or even hunter-gatherers.
A lot of people would starve. Some of the ones who otherwise wouldn’t starve will be killed by other humans, and/or by disease. But anything that leaves something resembling a functioning ecology in at least some areas isn’t going to kill all humans by starvation.
This is what i think, too. But i think those wars end up with nuclear or biological warfare, and that’s what does us in.
For me, it’s always been about Global Thermonuclear Warfare. And then I saw the end credits to “Dr. Strangelove” and learned to stop worrying and love Vera Lynn’s “We’ll meet again”
I do like the “cosmic event” choice too. That will either be a solar flare where we have a day or three to contemplate the end of all things electrical or it’ll be gamma rays. “Hey, this looks like a supernova in Pegasus…” EOT
That was both entertaining and educational. Thanks!