
The Tunguska Event - bootload
http://www.slate.com/blogs/atlas_obscura/2016/02/22/more_than_a_century_later_there_are_still_questions_about_what_happened.html
======
amelius
> Given a long enough time period, there is a nearly 100-percent chance an
> asteroid large enough to destroy most life on Earth will impact our planet.

No worries. Since quantum mechanics dictates that, given enough time, anything
can happen, we can also say that given a long enough time period, life will
spontaneously reappear.

~~~
grondilu
A more interesting question is : what kind of delay is worth worrying about?

I mean, for instance it is known that life will remain possible on Earth for
about 500 million years, after which the Sun will be too bright. We don't
seriously worry about it, since so many things can happen in half a billion
years that it does not make much sense to try to plan or predict anything in
such a timeframe.

Similarly, I personally don't worry about an impactor of 10 km diameter or so.
Such an event is so rare that it's not likely to happen in several million
years. To me that's still the kind of timeframe it does not make sense to
worry about. I'm sure some people will disagree though.

What is the limit? 10,000 years? 1,000? 100?

~~~
mikeash
Reminds me of one of my favorite jokes.

The professor is lecturing, and says, "The Sun will grow to be a red giant,
destroying all life on Earth in about a billion years...."

A distracted student suddenly sits up and cries out, "Oh my god!"

The professor says, "What's wrong? A billion years is a long time, you know.
Nothing to worry about."

The student is visibly relief. "Oh, great! I thought you said a million
years!"

Personally, I'd say a few hundred years is probably the reasonable max, maybe
a thousand years. Beyond that, technology will be so incomprehensibly
different that the risks and challenges will be completely different as well.
What would be a civilization-killing asteroid today might just be "ooh, tasty
resources already on a convenient trajectory" tomorrow. Or "aw shucks, it's
going to make a big splash in the gray goo."

~~~
NoMoreNicksLeft
I strongly suspect that our species is already on its way to inevitable
extinction, and much more quickly than a few hundred years.

Barring some science fiction scenarios, fertility has dropped below
replacement and is of a nature where it never truly rises. Children who grow
up in a low-fertility environment learn behaviors and personality traits that
encourage and enhance the already-low fertility, and any who are atypical and
have above-replacement fertility themselves are never enough to get the global
average back to (or above) replacement. Not only have we trained the kids to
have few kids themselves, we've trained them to train those few kids of their
own the same (but with extra!).

You can disagree, almost everyone does. But the implications of disagreement
are bizarre, you must imagine some future where all 5th generation-only
children wake up and say "I want 2.1 children" or 10 percent of those 5th
generation children wake up and say "I want 20 children".

~~~
grondilu
Long ago I read "essai de prospective demographique"[1] written by French
demographers. They were raising the concerns you mention and were trying to
warn the public of a coming "demographic winter". So your point of view is not
rare.

That being said, even if a demographic winter would probably have very adverse
consequences, as it is not clear how well the industrialized society would
fare if the population was drastically reduced, I have hard time picturing how
that could lead to the complete extinction of mankind.

There will always be pockets of population with high fertility, at the very
least among highly religious communities. Even if as you suggest reproductive
behavior is transmitted, that works both ways, and simple natural selection
will always, in the end, favor the reproductive behavior that leads to
increasing numbers.

Demographic winter is a serious concern, but I can't imagine it leading to a
complete extinction.

1\.
[https://books.google.fr/books/about/Essai_de_prospective_d%C...](https://books.google.fr/books/about/Essai_de_prospective_d%C3%A9mographique.html?id=lz9mPQAACAAJ&hl=fr)

~~~
NoMoreNicksLeft
> There will always be pockets of population with high fertility,

What makes you say that? Is there some underlying principle I've failed to
consider?

> I have hard time picturing how that could lead to the complete extinction of
> mankind.

It's simple math. Below-replacement fertility leads to extinction. More people
die than are born, and since the original number is finite, the end number
must be zero.

If you think that will not happen, what you're imagining is that the fertility
rate will either rise at some point in the future, or at least plateau at
whatever number leads to a stable population.

Why would they rise? If you grow up in a world where everyone around you has
few children, then you grow up thinking/feeling that few children is the way
things should be. You have few yourself. You might even have fewer than your
parents' generation... but you'll rarely if ever have more. On average, you'll
never have more.

Even in the fertility hot spots, this is true. They're above replacement
fertility still, but each generation has a lower number. It's not exactly some
sort of hidden trend, it's pretty basic.

> at the very least among highly religious communities.

It looks like the children of these communities break away from their
religious upbringing at a higher rate than their pious siblings can replace
with nephews and nieces. Especially in those religious communities that are
unable to achieve a healthy economy... the FLDS communes that dispose of their
sons, the ultraorthodox jews in their own self-imposed ghettos where there is
little employment to be had.

> Even if as you suggest reproductive behavior is transmitted,

That's a little silly of me, actually. It must be the one behavior pattern
that isn't transmissible.

> and simple natural selection will always, in the end, favor the reproductive
> behavior

The natural universe has no favorites. It does not preclude this sort of
extinction. Those few who buck this trend will be starved for adequate mates
at some point, and will raise their own children in a culture that ostracizes
fertility...

~~~
grondilu
> What makes you say that? Is there some underlying principle I've failed to
> consider?

Low fertility rates is a statistical rule. It's not absolute. There will
always be people with high fertility, at the very least because they will be
at the edge of the bell curve. Also again, look at religious communities, like
the Amish. Those people do exist. Among seven billion human beings, you
certainly can find a few millions that are very much willing to make babies.
It only takes a small minority to ensure that the numbers will not go to zero.

> The natural universe has no favorites. It does not preclude this sort of
> extinction.

The lineage of people who don't have children will simply disappear, leaving
room for the lineage of people who do. It's as simple as that.

> Why would they rise?

The fertility rate will rise because people with low fertility rate will die
with no children. What will remain will be the children of people with high
fertility rate, and presumably those children will have a similar reproductive
behavior than their parents. Low fertility reproductive behavior will be
"naturally" filtered out.

> Those few who buck this trend will be starved for adequate mates at some
> point, and will raise their own children in a culture that ostracizes
> fertility...

Fertility declines, but it's quite a stretch to talk about ostracization of
fertility. And ostracization is not prohibition.

------
sun_of_deep
> With this in mind, we can view our future with some certainty. Something big
> is going to smash into us, sooner or later, and probably sooner.

I started reading Cosmos by Carl Sagan a week ago and he discusses the
Tunguska event for several pages. It's an amazing book that I wish I had
studied long ago. Had I not read that book, this statement would have
instilled an impending sense of doom into me, which does nothing but
demoralize me. Now that I've read that book, I can now tell with certainty
that this prophecy is utter crap. As this article mentions, the asteroids are
being tracked, so, we most likely will know it before hand.

OTOH, here's an article from science alert

[http://www.sciencealert.com/next-month-an-asteroid-will-
pass...](http://www.sciencealert.com/next-month-an-asteroid-will-pass-so-
close-to-earth-that-we-could-see-it-in-the-sky)

> Before you freak out, there's no chance that the asteroid is going to smash
> into us. The space agency is still determining its exact trajectory, but at
> the closest estimate, it'll be 18,000 km (11,000 miles) away as it passes us
> by - which would make it easily viewable with the help of a telescope. To
> put that into perspective, that's roughly one-twentieth the distance from
> Earth to the Moon. Alternatively, the asteroid could travel further afield,
> and pass us at a distance of around 14 million km (9 million miles).

> The reason for the big difference in these two estimates is that NASA only
> discovered this asteroid three years ago - hence the very-catchy name,
> asteroid 2013 TX68 - and haven't had much time to observe it just yet.

------
gmisra
There is a great twitter feed, @AsteroidMisses, that tweets out based off a
NASA monitoring dataset. Browsing it provides some perspective on just how
many asteroids are whizzing around the Earth all the time.

[https://twitter.com/asteroidmisses](https://twitter.com/asteroidmisses)

------
bsenftner
A fun science fiction read is "Singularity" by Bill DeSmedt; the premise is
the Tunguska event being a mini-black hole - and it's caught inside the earth,
eating it from the inside out.

~~~
NoMoreNicksLeft
David Brin did that too. Then an earth goddess showed up, some white guilt
about overpopulation and coke can pull tabs.

Is the DeSmedt book better?

~~~
norea-armozel
I would argue it's much better. I don't want to give away too much of the
story but it has lots of questions about physics, politics, and alternate
history. It's quite a good read.

------
JoeAltmaier
My favorite conspiracy theory on Tunguska:

[http://www.reformation.org/tesla-and-
tunguska.html](http://www.reformation.org/tesla-and-tunguska.html)

~~~
alexandre_m
The Tunguska+Tesla event is quite fascinating (the whole life of Tesla is
actually).

People love to make up a lot of theories and conspiracies, it's nothing new.

What is particularly worrisome is that Tesla was a very brillant man and that
he believed himself to have caused this. From the information that we have, it
wasn't a marketing stunt by his entourage. The guy himself was working on this
particle-beam for some time and claimed to have triggered it that night. He
tried to sell the technology for more almost 3 decades.

Was this made up, was this a coincidence, or did it actually happen?

It's been over 100 years and no one is certain.

~~~
greglindahl
Extraordinary claims require extraordinary proof. "No one is certain" is not
the right way to approach the possibility that Tesla actually caused Tunguska.

edit: clarified what "this" means

~~~
alexandre_m
I don't think it's plausible that Tesla is responsable for it, but we can
raise some questions surrounding the event.

Apparently there's still no scientific consensus (is that even possible?) on
the Tunguska explosion and NASA seems to acknowledges that.

Taken from: [http://science.nasa.gov/science-news/science-at-
nasa/2008/30...](http://science.nasa.gov/science-news/science-at-
nasa/2008/30jun_tunguska/)

"A century later some still debate the cause and come up with different
scenarios that could have caused the explosion," said Yeomans"

No remains of the asteroid, no impact crater and the claims from Tesla
together is what is fascinating to me.

------
mrfusion
I'm curious if we could mine in areas where large asteroids impacted and gets
lots of minerals. Why do asteroid mining if we already have a few in the
ground?

~~~
krylon
I saw a documentary a couple of years back which looked into a correlation of
former (likely/suspected) meteor impact sites and natural resources. It looked
like lots of areas rich in interesting metals/minerals turned out to probably
have been hit by meteors in the past.

So in a way, we are doing that already (at least if that documentary was not
totally bogus).

~~~
stevedonovan
New evidence for that: [http://www.bbc.com/news/science-
environment-14827624](http://www.bbc.com/news/science-environment-14827624)

------
smoyer
I read an entire book about the Tunguska explosion when I was in junior high,
but it's interesting that astronomers now think an event like this could
happen every 300 years.

~~~
krylon
One interesting detail I found, I think, on Wikipedia, is that if the meteor
had hit about four hours later, due to Earth's rotation, it would have roughly
hit Saint Petersburg.

If such events happen so frequently, we're pretty lucky so far. Given that
much of Earth is covered in water, I could imagine a lot of these simply hit
the ocean, but I don't know what would happen if it hit close to the coast.

~~~
saiya-jin
a simple hit of ocean might be more devastating than hitting uninhabited parts
of taiga. think about massive tsunami (at least that's what I would expect,
depending on the impact force of course)

~~~
goldenkey
water is very dampening. tsunamis are from sustained force

~~~
cr1895
It's literally wet! You'll get dampened indeed.

Tsunamis are generated by water displacement from e.g. underwater seismic
activity or a massive landslide. Wind-driven waves or tides would be driven by
sustained forces.

Whether or not an asteroid can/has cause(d) a tsunami I don't know.

~~~
raattgift
A sufficiently energetic meteor strike will cause a high enough amplitude wave
to qualify as tsunamis (and which therefore would produce destructive effects
onshore).

Exact modelling is tricky, but that sort of thing appeals to some
geophysicists.

Funny headlines, serious research:

[http://news.ucsc.edu/2003/05/355.html](http://news.ucsc.edu/2003/05/355.html)
[http://www.livescience.com/49298-asteroids-causing-
tsunamis....](http://www.livescience.com/49298-asteroids-causing-
tsunamis.html)

------
gaur
The scaling with meteor size is impressive.

A 100 m object will flatten some trees in Siberia.

A 10 000 m object will kill 75% percent of all species on the planet (the KT
event).

~~~
elorant
The problem with the latter is that it will cause a nuclear winter. So that
75% will not die instantly but in 2-3 years after the impact. Add an order of
magnitude or even half of that and then you have an extinction level event. It
could kill organisms even at microbe level.

~~~
EGreg
Ok simple... figure out what will disperse all the ash to prevent the nuclear
winter!

Lets start testing this stuff now... may also solve the greenhouse gas
problem.

------
pmoriarty
Here's a fantastic simulation of a much bigger impact:

    
    
      https://www.youtube.com/watch?v=zc4HL_-VT2Y

~~~
dr_zoidberg
A few questions/comments:

* What is the "4 billion years ago impact" that is refered in the video? At first I thought it was the Theia impact, but the sizes and speeds don't quite match, and the simulation doesn't result in a second moon.

* It also mentions that it has happened 6 times. The only impact large enough I can remember of the top of my head that sort of matches that scale would be the canadian impact basin. A quick search on wikipedia tossed me to this list [0] but everything there seems to be on a different scale than what's described in the video. Are those impacts mentioned in the full program?

* It was recently reported that an expedition drilling in a part of the ocean where the crust is thin had found microbes near the magma, but I can't find any link. Given that it has been theorized even Venus may hold life in it's upper atmosphere [1], my guess would bethat, life is far more resilient than we imagine it to be.

[0]
[https://en.wikipedia.org/wiki/List_of_impact_craters_on_Eart...](https://en.wikipedia.org/wiki/List_of_impact_craters_on_Earth)

[1]
[http://web.archive.org/web/20110807004311/http://gltrs.grc.n...](http://web.archive.org/web/20110807004311/http://gltrs.grc.nasa.gov/reports/2003/TM-2003-212310.pdf)

