On 10/3/2022 3:23 PM, Robert Carnegie wrote:
> On Monday, 3 October 2022 at 16:43:07 UTC+1, pete...@gmail.com wrote:
>> On Monday, October 3, 2022 at 11:16:09 AM UTC-4, Paul S Person wrote:
>>> On Sun, 2 Oct 2022 14:38:43 -0700 (PDT), Nils Hammer
>>> <sledgem...@gmail.com> wrote:
>>>
>>>>
>>>>> I thought the idea was to see if we could divert killer asteroids
>>>> Indeed, as compared to the plan where you dock with the asteroid and fire jets for carefully controlled vectors, or blast it with nukes at a carefully planned distance that ought not to break it up.
>>> But docking makes for very exciting movies!
>>>
>>> And, for a killer asteroids, breaking up is not hard to do -- in
>>> movies.
>> It seems that a lot of asteroids are 'dust bunnies', unconsolidated collections of dust, gravel, and rocks with almost no internal strength. There's a lot of void space inside. Hitting one kicks out a *lot* of material, and hitting it too hard may completely disrupt it.
>
> ...Without really solving the "deadly rock from space"
> problem. Just altering it to "a vast rain shower of
> burning gravel".

Pop it far enough out and most of it should miss the planet.

--
I've done good in this world. Now I'm tired and just want to be a cranky
dirty old man.

Dimensional Traveler <dtravel@sonic.net> writes:
>On 10/3/2022 3:23 PM, Robert Carnegie wrote:
>> On Monday, 3 October 2022 at 16:43:07 UTC+1, pete...@gmail.com wrote:
>>> On Monday, October 3, 2022 at 11:16:09 AM UTC-4, Paul S Person wrote:
>>>> On Sun, 2 Oct 2022 14:38:43 -0700 (PDT), Nils Hammer
>>>> <sledgem...@gmail.com> wrote:
>>>>
>>>>>
>>>>>> I thought the idea was to see if we could divert killer asteroids
>>>>> Indeed, as compared to the plan where you dock with the asteroid and fire jets for carefully controlled vectors, or blast it with nukes at a carefully planned distance that ought not to break it up.
>>>> But docking makes for very exciting movies!
>>>>
>>>> And, for a killer asteroids, breaking up is not hard to do -- in
>>>> movies.
>>> It seems that a lot of asteroids are 'dust bunnies', unconsolidated collections of dust, gravel, and rocks with almost no internal strength. There's a lot of void space inside. Hitting one kicks out a *lot* of material, and hitting it too hard may completely disrupt it.
>>
>> ...Without really solving the "deadly rock from space"
>> problem. Just altering it to "a vast rain shower of
>> burning gravel".
>
>Pop it far enough out and most of it should miss the planet.

All you need is to slightly slow it down, or speed it up
and its orbit and earths orbit will no longer intersect.

On Monday, October 3, 2022 at 4:23:37 PM UTC-6, Robert Carnegie wrote:

> ...Without really solving the "deadly rock from space"
> problem. Just altering it to "a vast rain shower of
> burning gravel".

Since it's only very big rocks that don't completely burn up
before hitting the ground, I'd say that blowing up an asteroid
into little pieces is seriously underrated as a solution.

And any asteroid that's a "dust bunny" wasn't a problem to
begin with.

The problem is that a big chunk of rock could be blown up into
a number of harmless small fragments, and a piece or two big
enough to do real damage. So deflecting the whole thing is a
certain solution, and to be preferred.

John Savard

On Monday, October 3, 2022 at 5:08:06 PM UTC-6, Scott Lurndal wrote:

> All you need is to slightly slow it down, or speed it up
> and its orbit and earths orbit will no longer intersect.

Not really.

As an example, let's take an asteroid in an orbit that is at 4 AU at
aphelion, and at 0.85 AU at perihelion.

If you slightly slow down, or speed up, the orbit of that asteroid
at perihelion, its orbit will *continue* to intersect the orbit of the
Earth, only the distance from the Sun at aphelion will change.

If you speed it up *enough* at aphelion so that its perihelion is
greater than 1 AU, _then_ its orbit will no longer intersect the
Earth's. Slowing it down slightly won't achieve that.

The easiest way to ensure such an asteroid will at least miss the Earth
*this* time would be with an off-center impact about halfway between
perihelion and aphelion, so that the tilt of its orbit is changed, and it is
well below, or well above, the plane of the ecliptic for the entire part
of the orbit that is near perihelion.

The thing is, though, that the nodes of orbits usually precess due to
perturbations, so even that won't permanently remove the risk.

But if you can change an impact with the Earth into a close encounter with
the Earth, then the Earth's gravity will drastically change the asteroid's orbit
during that encounter. The bad news is that the new orbit will still intersect
the Earth's orbit.

The _good_ news is that since the change is drastic, a very slight change in the
parameters of the encounter will affect that change in a big way. So now is
the chance, with a small input of energy, to change the asteroid's orbit so that
it will have a close encounter with Mars. (Or some other planet.)

That close encounter *could* change the asteroid's orbit so that it will never
again come anywhere near the Earth (at least until it has _another_ close
encounter with Mars, which could change its orbit to just about anything).
Of course, if it hits Mars, the problem is permanently solved.

John Savard

On Tuesday, October 4, 2022 at 7:30:56 AM UTC-6, Quadibloc wrote:

> The easiest way to ensure such an asteroid will at least miss the Earth
> *this* time would be with an off-center impact about halfway between
> perihelion and aphelion, so that the tilt of its orbit is changed, and it is
> well below, or well above, the plane of the ecliptic for the entire part
> of the orbit that is near perihelion.

Even that, though, might be difficult.

Let's take, say, a sphere 10 kilometres in diameter, with a density of 2.65
grams per cubic centimetre. (That's about right for a stony asteroid;
a nickel-iron one would be heavier, a carbonaceous chondrite would be
lighter.)

This would be a mass of 5.236 * (10^14) kilograms.

Now, if we made a two-stage hydrogen bomb, where an ordinary
hydrogen bomb replaces the atomic bomb as the trigger for a bigger
hydrogen bomb, perhaps a yield of one gigaton or more could be
achieved. Would that be enough to produce any noticeable change
in the motion of such a large object?

Perhaps dinosaur-killers are usually somewhat smaller than that, so
we would have a chance... but I couldn't find a figure on how much
momentum a nuclear explosion might provide. The only thing I did
see was that a 1.2 megaton warhead ought to deflect an asteroid
enough with 5 years advance notice.

John Savard

On Monday, October 3, 2022 at 6:36:38 PM UTC-4, Dimensional Traveler wrote:
> On 10/3/2022 3:23 PM, Robert Carnegie wrote:
> > On Monday, 3 October 2022 at 16:43:07 UTC+1, pete...@gmail.com wrote:
> >> On Monday, October 3, 2022 at 11:16:09 AM UTC-4, Paul S Person wrote:
> >>> On Sun, 2 Oct 2022 14:38:43 -0700 (PDT), Nils Hammer
> >>> <sledgem...@gmail.com> wrote:
> >>>
> >>>>
> >>>>> I thought the idea was to see if we could divert killer asteroids
> >>>> Indeed, as compared to the plan where you dock with the asteroid and fire jets for carefully controlled vectors, or blast it with nukes at a carefully planned distance that ought not to break it up.
> >>> But docking makes for very exciting movies!
> >>>
> >>> And, for a killer asteroids, breaking up is not hard to do -- in
> >>> movies.
> >> It seems that a lot of asteroids are 'dust bunnies', unconsolidated collections of dust, gravel, and rocks with almost no internal strength. There's a lot of void space inside. Hitting one kicks out a *lot* of material, and hitting it too hard may completely disrupt it.
> >
> > ...Without really solving the "deadly rock from space"
> > problem. Just altering it to "a vast rain shower of
> > burning gravel".
> Pop it far enough out and most of it should miss the planet.

Yes, the debris DART kicked out are already forming a 20,000 mile tail.

If you can make it miss entirely, thats clearly the best result. But even
making a lot of it miss would help.

pt

On Tuesday, October 4, 2022 at 9:30:56 AM UTC-4, Quadibloc wrote:
> On Monday, October 3, 2022 at 5:08:06 PM UTC-6, Scott Lurndal wrote:
>
> > All you need is to slightly slow it down, or speed it up
> > and its orbit and earths orbit will no longer intersect.
> Not really.
>
> If you slightly slow down, or speed up, the orbit of that asteroid
> at perihelion, its orbit will *continue* to intersect the orbit of the
> Earth, only the distance from the Sun at aphelion will change.

If a rock has been intersecting our orbit for billions of years, and only *now*
is on an impact vector, making it miss *now* will almost certainly mean it
won't do so again for more billions of years. That's a pretty good solution.

Don't let the best be the enemy of the good.

pt

On Mon, 3 Oct 2022 15:23:35 -0700 (PDT), Robert Carnegie
<rja.carnegie@excite.com> wrote:

>On Monday, 3 October 2022 at 16:43:07 UTC+1, pete...@gmail.com wrote:
>> On Monday, October 3, 2022 at 11:16:09 AM UTC-4, Paul S Person wrote:
>> > On Sun, 2 Oct 2022 14:38:43 -0700 (PDT), Nils Hammer
>> > <sledgem...@gmail.com> wrote:
>> >
>> > >
>> > >> I thought the idea was to see if we could divert killer asteroids
>> > >Indeed, as compared to the plan where you dock with the asteroid and fire jets for carefully controlled vectors, or blast it with nukes at a carefully planned distance that ought not to break it up.
>> > But docking makes for very exciting movies!
>> >
>> > And, for a killer asteroids, breaking up is not hard to do -- in
>> > movies.
>> It seems that a lot of asteroids are 'dust bunnies', unconsolidated collections of dust, gravel, and rocks with almost no internal strength. There's a lot of void space inside. Hitting one kicks out a *lot* of material, and hitting it too hard may completely disrupt it.
>
>...Without really solving the "deadly rock from space"
>problem. Just altering it to "a vast rain shower of
>burning gravel".

While not the best film on this topic, /Greenland/ does have a scene
illustrating that "burning gravel". Since all the actual Big Rock Hits
look the same, this scene provides something refreshingly different to
look at.
--
"In this connexion, unquestionably the most significant
development was the disintegration, under Christian
influence, of classical conceptions of the family and
of family right."

On Tuesday, October 4, 2022 at 8:38:54 AM UTC-6, pete...@gmail.com wrote:

> If a rock has been intersecting our orbit for billions of years, and only *now*
> is on an impact vector, making it miss *now* will almost certainly mean it
> won't do so again for more billions of years. That's a pretty good solution.
>
> Don't let the best be the enemy of the good.

That's a good point. But my point was to note that if one is going to nudge a
body into a different orbit that poses no hazard to the Earth, there are some
ways to do that which are more effective than others.

I'm sure that the people in charge at NASA, should they be faced with deflecting
a body that poses a threat, will have a sound grasp of orbital mechanics, and they
will be willing to settle for anything they can achieve that will avoid a disaster as
well.

John Savard

On Tuesday, 4 October 2022 at 05:33:24 UTC+1, Quadibloc wrote:
> On Monday, October 3, 2022 at 4:23:37 PM UTC-6, Robert Carnegie wrote:
>
> > ...Without really solving the "deadly rock from space"
> > problem. Just altering it to "a vast rain shower of
> > burning gravel".
> Since it's only very big rocks that don't completely burn up
> before hitting the ground, I'd say that blowing up an asteroid
> into little pieces is seriously underrated as a solution.
>
> And any asteroid that's a "dust bunny" wasn't a problem to
> begin with.
>
> The problem is that a big chunk of rock could be blown up into
> a number of harmless small fragments, and a piece or two big
> enough to do real damage. So deflecting the whole thing is a
> certain solution, and to be preferred.

AIUI, in the burning gravel scenario, if the rocks don't
reach the ground, the best does. Ask a dinosaur
oh you can't.

On Wednesday, 5 October 2022 at 00:49:53 UTC+1, Robert Carnegie wrote:
> On Tuesday, 4 October 2022 at 05:33:24 UTC+1, Quadibloc wrote:
> > On Monday, October 3, 2022 at 4:23:37 PM UTC-6, Robert Carnegie wrote:
> >
> > > ...Without really solving the "deadly rock from space"
> > > problem. Just altering it to "a vast rain shower of
> > > burning gravel".
> > Since it's only very big rocks that don't completely burn up
> > before hitting the ground, I'd say that blowing up an asteroid
> > into little pieces is seriously underrated as a solution.
> >
> > And any asteroid that's a "dust bunny" wasn't a problem to
> > begin with.
> >
> > The problem is that a big chunk of rock could be blown up into
> > a number of harmless small fragments, and a piece or two big
> > enough to do real damage. So deflecting the whole thing is a
> > certain solution, and to be preferred.
> AIUI, in the burning gravel scenario, if the rocks don't
> reach the ground, the best

Meaning "the heat". My tablet finger slipped, probably.

>does. Ask a dinosaur
> oh you can't.

On Tue, 4 Oct 2022 16:03:59 -0700 (PDT), Quadibloc <jsavard@ecn.ab.ca>
wrote:

>On Tuesday, October 4, 2022 at 8:38:54 AM UTC-6, pete...@gmail.com wrote:
>
>> If a rock has been intersecting our orbit for billions of years, and only *now*
>> is on an impact vector, making it miss *now* will almost certainly mean it
>> won't do so again for more billions of years. That's a pretty good solution.
>>
>> Don't let the best be the enemy of the good.
>
>That's a good point. But my point was to note that if one is going to nudge a
>body into a different orbit that poses no hazard to the Earth, there are some
>ways to do that which are more effective than others.
>
>I'm sure that the people in charge at NASA, should they be faced with deflecting
>a body that poses a threat, will have a sound grasp of orbital mechanics, and they
>will be willing to settle for anything they can achieve that will avoid a disaster as
>well.

The people in charge at NASA, presumably, devised and implemented the
test under discussion precisely to get a handle on what might or might
not work. Before they have to bet the planet on it.
--
"In this connexion, unquestionably the most significant
development was the disintegration, under Christian
influence, of classical conceptions of the family and
of family right."

On Tuesday, October 4, 2022 at 12:33:24 AM UTC-4, Quadibloc wrote:
> On Monday, October 3, 2022 at 4:23:37 PM UTC-6, Robert Carnegie wrote:
>
> > ...Without really solving the "deadly rock from space"
> > problem. Just altering it to "a vast rain shower of
> > burning gravel".
> Since it's only very big rocks that don't completely burn up
> before hitting the ground, I'd say that blowing up an asteroid
> into little pieces is seriously underrated as a solution.

And you'd be wrong.

William Hyde

In article <2560ba81-c58c-453d-85ae-7b6ad85e2934n@googlegroups.com>,
William Hyde <wthyde1953@gmail.com> wrote:
>On Tuesday, October 4, 2022 at 12:33:24 AM UTC-4, Quadibloc wrote:
>> On Monday, October 3, 2022 at 4:23:37 PM UTC-6, Robert Carnegie wrote:
>>
>> > ...Without really solving the "deadly rock from space"
>> > problem. Just altering it to "a vast rain shower of
>> > burning gravel".
>> Since it's only very big rocks that don't completely burn up
>> before hitting the ground, I'd say that blowing up an asteroid
>> into little pieces is seriously underrated as a solution.
>
>And you'd be wrong.
>
What, there's a downside to a cloud of small debris hitting the
upper atmosphere at 30 km/s and heating the sky to the temperature
of a kiln? Are plants and animals suddenly flammable?
--
My reviews can be found at http://jamesdavisnicoll.com/
My tor pieces at https://www.tor.com/author/james-davis-nicoll/
My Dreamwidth at https://james-davis-nicoll.dreamwidth.org/
My patreon is at https://www.patreon.com/jamesdnicoll

On Wednesday, October 5, 2022 at 2:20:34 PM UTC-4, William Hyde wrote:
> On Tuesday, October 4, 2022 at 12:33:24 AM UTC-4, Quadibloc wrote:
> > On Monday, October 3, 2022 at 4:23:37 PM UTC-6, Robert Carnegie wrote:
> >
> > > ...Without really solving the "deadly rock from space"
> > > problem. Just altering it to "a vast rain shower of
> > > burning gravel".
> > Since it's only very big rocks that don't completely burn up
> > before hitting the ground, I'd say that blowing up an asteroid
> > into little pieces is seriously underrated as a solution.
> And you'd be wrong.

Depends, but Quaddies probably correct.

It greatly depends on how much material you're dealing with.

The problem is that an entering meteor heats up the air around it to plasma
temperatures as it falls. Its BRIGHT, which is why a pea-sized meteor can be
seen 60 miles away on the ground.

When the Chicxulub impactor hit, it was about 4200 km^3. But it may have
ejected another 250,000 km^3 from the crater it made. Some of this was
ejected into space, and minutes or hours later rained down again over the
whole earth.

That volume is enough to cover the planet 50 cm deep. Now, most of that
landed nearby, only a small fraction was blasted into ballistic orbits outside
the atmosphere.

But that small fraction enough to create disaster. Its enough to occupy ever
single bit of sky visible above your horizon with a plasma-hot meteor trail,
simultaneously.

It would be like standing next to an unshielded blast furnace, everywhere on
earth. That's why the world burned, and no animal that wasn't in a burrow or
deep water perished.

Now, in the disrupted asteroid situation, we're dealing with far less material.
Even for Chicxulub, the initial meteor was only 2% the volume of the total
material that could have contributed to the fallout. The vast majority of asteroids
being disrupted would be orders of magnitude smaller, and even if some fragments
reach the ground, would not be able to blast craters capable of
multiplying the problem.

A big enough cloud of white hot gravel would not be something to look at,
and if you know its coming, you might want to head indoors at the appointed
time, but its unlikely to cause serious damage.

Note that despite millions of meteorites falling since Chicxulub, we have no
record of any of them causing widespread fires by thermal radiation.

pt

On Wednesday, October 5, 2022 at 3:30:28 PM UTC-4, James Nicoll wrote:
> In article <2560ba81-c58c-453d...@googlegroups.com>,
> William Hyde <wthyd...@gmail.com> wrote:
> >On Tuesday, October 4, 2022 at 12:33:24 AM UTC-4, Quadibloc wrote:
> >> On Monday, October 3, 2022 at 4:23:37 PM UTC-6, Robert Carnegie wrote:
> >>
> >> > ...Without really solving the "deadly rock from space"
> >> > problem. Just altering it to "a vast rain shower of
> >> > burning gravel".
> >> Since it's only very big rocks that don't completely burn up
> >> before hitting the ground, I'd say that blowing up an asteroid
> >> into little pieces is seriously underrated as a solution.
> >
> >And you'd be wrong.
> >
> What, there's a downside to a cloud of small debris hitting the
> upper atmosphere at 30 km/s and heating the sky to the temperature
> of a kiln? Are plants and animals suddenly flammable?

Not much. The numbers matter, and I run them in a nearby post.

pt

On 10/5/2022 2:50 PM, pete...@gmail.com wrote:
> On Wednesday, October 5, 2022 at 2:20:34 PM UTC-4, William Hyde wrote:
>> On Tuesday, October 4, 2022 at 12:33:24 AM UTC-4, Quadibloc wrote:
>>> On Monday, October 3, 2022 at 4:23:37 PM UTC-6, Robert Carnegie wrote:
>>>
>>>> ...Without really solving the "deadly rock from space"
>>>> problem. Just altering it to "a vast rain shower of
>>>> burning gravel".
>>> Since it's only very big rocks that don't completely burn up
>>> before hitting the ground, I'd say that blowing up an asteroid
>>> into little pieces is seriously underrated as a solution.
>> And you'd be wrong.
>
> Depends, but Quaddies probably correct.
>
> It greatly depends on how much material you're dealing with.
>
> The problem is that an entering meteor heats up the air around it to plasma
> temperatures as it falls. Its BRIGHT, which is why a pea-sized meteor can be
> seen 60 miles away on the ground.
>
> When the Chicxulub impactor hit, it was about 4200 km^3. But it may have
> ejected another 250,000 km^3 from the crater it made. Some of this was
> ejected into space, and minutes or hours later rained down again over the
> whole earth.
>
> That volume is enough to cover the planet 50 cm deep. Now, most of that
> landed nearby, only a small fraction was blasted into ballistic orbits outside
> the atmosphere.
>
> But that small fraction enough to create disaster. Its enough to occupy ever
> single bit of sky visible above your horizon with a plasma-hot meteor trail,
> simultaneously.
>
> It would be like standing next to an unshielded blast furnace, everywhere on
> earth. That's why the world burned, and no animal that wasn't in a burrow or
> deep water perished.
>
> Now, in the disrupted asteroid situation, we're dealing with far less material.
> Even for Chicxulub, the initial meteor was only 2% the volume of the total
> material that could have contributed to the fallout. The vast majority of asteroids
> being disrupted would be orders of magnitude smaller, and even if some fragments
> reach the ground, would not be able to blast craters capable of
> multiplying the problem.
>
> A big enough cloud of white hot gravel would not be something to look at,
> and if you know its coming, you might want to head indoors at the appointed
> time, but its unlikely to cause serious damage.
>
> Note that despite millions of meteorites falling since Chicxulub, we have no
> record of any of them causing widespread fires by thermal radiation.
>
> pt

I thought the big meteor that fell in Russia 50 or 70 years ago started
many fires on the ground.
https://en.wikipedia.org/wiki/Tunguska_event

Lynn

On Wednesday, October 5, 2022 at 5:36:33 PM UTC-4, Lynn McGuire wrote:
> On 10/5/2022 2:50 PM, pete...@gmail.com wrote:
> > On Wednesday, October 5, 2022 at 2:20:34 PM UTC-4, William Hyde wrote:
> >> On Tuesday, October 4, 2022 at 12:33:24 AM UTC-4, Quadibloc wrote:
> >>> On Monday, October 3, 2022 at 4:23:37 PM UTC-6, Robert Carnegie wrote:
> >>>
> >>>> ...Without really solving the "deadly rock from space"
> >>>> problem. Just altering it to "a vast rain shower of
> >>>> burning gravel".
> >>> Since it's only very big rocks that don't completely burn up
> >>> before hitting the ground, I'd say that blowing up an asteroid
> >>> into little pieces is seriously underrated as a solution.
> >> And you'd be wrong.
> >
> > Depends, but Quaddies probably correct.
> >
> > It greatly depends on how much material you're dealing with.
> >
> > The problem is that an entering meteor heats up the air around it to plasma
> > temperatures as it falls. Its BRIGHT, which is why a pea-sized meteor can be
> > seen 60 miles away on the ground.
> >
> > When the Chicxulub impactor hit, it was about 4200 km^3. But it may have
> > ejected another 250,000 km^3 from the crater it made. Some of this was
> > ejected into space, and minutes or hours later rained down again over the
> > whole earth.
> >
> > That volume is enough to cover the planet 50 cm deep. Now, most of that
> > landed nearby, only a small fraction was blasted into ballistic orbits outside
> > the atmosphere.
> >
> > But that small fraction enough to create disaster. Its enough to occupy ever
> > single bit of sky visible above your horizon with a plasma-hot meteor trail,
> > simultaneously.
> >
> > It would be like standing next to an unshielded blast furnace, everywhere on
> > earth. That's why the world burned, and no animal that wasn't in a burrow or
> > deep water perished.
> >
> > Now, in the disrupted asteroid situation, we're dealing with far less material.
> > Even for Chicxulub, the initial meteor was only 2% the volume of the total
> > material that could have contributed to the fallout. The vast majority of asteroids
> > being disrupted would be orders of magnitude smaller, and even if some fragments
> > reach the ground, would not be able to blast craters capable of
> > multiplying the problem.
> >
> > A big enough cloud of white hot gravel would not be something to look at,
> > and if you know its coming, you might want to head indoors at the appointed
> > time, but its unlikely to cause serious damage.
> >
> > Note that despite millions of meteorites falling since Chicxulub, we have no
> > record of any of them causing widespread fires by thermal radiation.
> >
> > pt
> I thought the big meteor that fell in Russia 50 or 70 years ago started
> many fires on the ground.
> https://en.wikipedia.org/wiki/Tunguska_event

You're right. I was mistaken.

Pt

On 10/5/2022 3:35 PM, pete...@gmail.com wrote:
> On Wednesday, October 5, 2022 at 5:36:33 PM UTC-4, Lynn McGuire wrote:
>> On 10/5/2022 2:50 PM, pete...@gmail.com wrote:
>>> On Wednesday, October 5, 2022 at 2:20:34 PM UTC-4, William Hyde wrote:
>>>> On Tuesday, October 4, 2022 at 12:33:24 AM UTC-4, Quadibloc wrote:
>>>>> On Monday, October 3, 2022 at 4:23:37 PM UTC-6, Robert Carnegie wrote:
>>>>>
>>>>>> ...Without really solving the "deadly rock from space"
>>>>>> problem. Just altering it to "a vast rain shower of
>>>>>> burning gravel".
>>>>> Since it's only very big rocks that don't completely burn up
>>>>> before hitting the ground, I'd say that blowing up an asteroid
>>>>> into little pieces is seriously underrated as a solution.
>>>> And you'd be wrong.
>>>
>>> Depends, but Quaddies probably correct.
>>>
>>> It greatly depends on how much material you're dealing with.
>>>
>>> The problem is that an entering meteor heats up the air around it to plasma
>>> temperatures as it falls. Its BRIGHT, which is why a pea-sized meteor can be
>>> seen 60 miles away on the ground.
>>>
>>> When the Chicxulub impactor hit, it was about 4200 km^3. But it may have
>>> ejected another 250,000 km^3 from the crater it made. Some of this was
>>> ejected into space, and minutes or hours later rained down again over the
>>> whole earth.
>>>
>>> That volume is enough to cover the planet 50 cm deep. Now, most of that
>>> landed nearby, only a small fraction was blasted into ballistic orbits outside
>>> the atmosphere.
>>>
>>> But that small fraction enough to create disaster. Its enough to occupy ever
>>> single bit of sky visible above your horizon with a plasma-hot meteor trail,
>>> simultaneously.
>>>
>>> It would be like standing next to an unshielded blast furnace, everywhere on
>>> earth. That's why the world burned, and no animal that wasn't in a burrow or
>>> deep water perished.
>>>
>>> Now, in the disrupted asteroid situation, we're dealing with far less material.
>>> Even for Chicxulub, the initial meteor was only 2% the volume of the total
>>> material that could have contributed to the fallout. The vast majority of asteroids
>>> being disrupted would be orders of magnitude smaller, and even if some fragments
>>> reach the ground, would not be able to blast craters capable of
>>> multiplying the problem.
>>>
>>> A big enough cloud of white hot gravel would not be something to look at,
>>> and if you know its coming, you might want to head indoors at the appointed
>>> time, but its unlikely to cause serious damage.
>>>
>>> Note that despite millions of meteorites falling since Chicxulub, we have no
>>> record of any of them causing widespread fires by thermal radiation.
>>>
>>> pt
>> I thought the big meteor that fell in Russia 50 or 70 years ago started
>> many fires on the ground.
>> https://en.wikipedia.org/wiki/Tunguska_event
>
> You're right. I was mistaken.
>
It was also apparently large enough to get deep into the atmosphere
which I would think had something to do with it.

--
I've done good in this world. Now I'm tired and just want to be a cranky
dirty old man.

On Wednesday, October 5, 2022 at 3:50:20 PM UTC-4, pete...@gmail.com wrote:
> On Wednesday, October 5, 2022 at 2:20:34 PM UTC-4, William Hyde wrote:
> > On Tuesday, October 4, 2022 at 12:33:24 AM UTC-4, Quadibloc wrote:
> > > On Monday, October 3, 2022 at 4:23:37 PM UTC-6, Robert Carnegie wrote:
> > >
> > > > ...Without really solving the "deadly rock from space"
> > > > problem. Just altering it to "a vast rain shower of
> > > > burning gravel".
> > > Since it's only very big rocks that don't completely burn up
> > > before hitting the ground, I'd say that blowing up an asteroid
> > > into little pieces is seriously underrated as a solution.
> > And you'd be wrong.
> Depends, but Quaddies probably correct.
>
> It greatly depends on how much material you're dealing with.
>
> The problem is that an entering meteor heats up the air around it to plasma
> temperatures as it falls. Its BRIGHT, which is why a pea-sized meteor can be
> seen 60 miles away on the ground.
>
> When the Chicxulub impactor hit, it was about 4200 km^3. But it may have
> ejected another 250,000 km^3 from the crater it made. Some of this was
> ejected into space, and minutes or hours later rained down again over the
> whole earth.
>
> That volume is enough to cover the planet 50 cm deep. Now, most of that
> landed nearby, only a small fraction was blasted into ballistic orbits outside
> the atmosphere.
>
> But that small fraction enough to create disaster. Its enough to occupy ever
> single bit of sky visible above your horizon with a plasma-hot meteor trail,
> simultaneously.
>
> It would be like standing next to an unshielded blast furnace, everywhere on
> earth.

I may be behind the times, but I've never seen a reliable calculation that showed
the radiative effect to be this extreme, while we do know that shocked quartz
existed over a thousand miles from the impact, and there is clear evidence
of an "asteroid winter".

Examinations in the teapot dome area by Jack Wolfe, published in Nature,
established the time of the hit as June/July. Evidence, IIRC is for two
debris falls (hypothesized to be one from the main event, more from
a secondary crater), followed rapidly by freezing damage. The site was a
pond so it doesn't really address the burning issue. But we do know
that a fair part of the world did not burn.

That's why the world burned, and no animal that wasn't in a burrow or
> deep water perished.

Not that deep, crocodiles for example. Extinction appears to have been a function of
size, with all large animals that were not sheltered going extinct. Small creatures
survived, including birds.

> Now, in the disrupted asteroid situation, we're dealing with far less material.
> Even for Chicxulub, the initial meteor was only 2% the volume of the total
> material that could have contributed to the fallout. The vast majority of asteroids
> being disrupted would be orders of magnitude smaller, and even if some fragments
> reach the ground, would not be able to blast craters capable of
> multiplying the problem.

It does not matter whether an intact bit of rock reaches the ground. What matters is
the kinetic energy of whatever hits the ground, one rock or a mass of pebbles and
gas.

The smaller the asteroid the smaller the problem, of course.
>
> A big enough cloud of white hot gravel would not be something to look at,
> and if you know its coming, you might want to head indoors at the appointed
> time, but its unlikely to cause serious damage.

As you said, mass is the issue.

I do not think that the integrity of the impactor is terribly relevant at this point. The energy
and momentum do not go away because the components are small. We cannot scale
up the effects of a grain-of-sand sized meteor to an asteroid impact. It's not at all
the same situation: the effects on the planet of the impact of a large mass are going to
be catastrophic, whether it is one rock or one million.

William Hyde

On Thursday, October 6, 2022 at 5:43:08 PM UTC-4, William Hyde wrote:
> On Wednesday, October 5, 2022 at 3:50:20 PM UTC-4, pete...@gmail.com wrote:
> > On Wednesday, October 5, 2022 at 2:20:34 PM UTC-4, William Hyde wrote:
> > > On Tuesday, October 4, 2022 at 12:33:24 AM UTC-4, Quadibloc wrote:
> > > > On Monday, October 3, 2022 at 4:23:37 PM UTC-6, Robert Carnegie wrote:
> > > >
> > > > > ...Without really solving the "deadly rock from space"
> > > > > problem. Just altering it to "a vast rain shower of
> > > > > burning gravel".
> > > > Since it's only very big rocks that don't completely burn up
> > > > before hitting the ground, I'd say that blowing up an asteroid
> > > > into little pieces is seriously underrated as a solution.
> > > And you'd be wrong.
> > Depends, but Quaddies probably correct.
> >
> > It greatly depends on how much material you're dealing with.
> >
> > The problem is that an entering meteor heats up the air around it to plasma
> > temperatures as it falls. Its BRIGHT, which is why a pea-sized meteor can be
> > seen 60 miles away on the ground.
> >
> > When the Chicxulub impactor hit, it was about 4200 km^3. But it may have
> > ejected another 250,000 km^3 from the crater it made. Some of this was
> > ejected into space, and minutes or hours later rained down again over the
> > whole earth.
> >
> > That volume is enough to cover the planet 50 cm deep. Now, most of that
> > landed nearby, only a small fraction was blasted into ballistic orbits outside
> > the atmosphere.
> >
> > But that small fraction enough to create disaster. Its enough to occupy ever
> > single bit of sky visible above your horizon with a plasma-hot meteor trail,
> > simultaneously.
> >
> > It would be like standing next to an unshielded blast furnace, everywhere on
> > earth.
> I may be behind the times, but I've never seen a reliable calculation that showed
> the radiative effect to be this extreme, while we do know that shocked quartz
> existed over a thousand miles from the impact, and there is clear evidence
> of an "asteroid winter".

I've shown that the amount of ejected material could lead to plasma-hot reentry trails
covering the entire sky, over the entire earth. The wikipedia article on Tunguska shows
that that far smaller meteor radiativly scorched trees and started fires for miles.

As for birds, there are many species that nest in burrows.
https://www.birdsandblooms.com/birding/attracting-birds/bird-nesting/ground-nesting-birds/
....and which could thus survive.

> The smaller the asteroid the smaller the problem, of course.
> >
> > A big enough cloud of white hot gravel would not be something to look at,
> > and if you know its coming, you might want to head indoors at the appointed
> > time, but its unlikely to cause serious damage.

I posted that before I read the accounts of the Tunguska event, which did cause
a lot of burning, just by radiation. I was mistaken.

> As you said, mass is the issue.
>
>
> I do not think that the integrity of the impactor is terribly relevant at this point. The energy
> and momentum do not go away because the components are small. We cannot scale
> up the effects of a grain-of-sand sized meteor to an asteroid impact. It's not at all
> the same situation: the effects on the planet of the impact of a large mass are going to
> be catastrophic, whether it is one rock or one million.

The big differences are whether it reaches the ground, and then if it can loft crater material
well out of the atmosphere to reenter as secondary impacts.

Disrupting it may prevent it reaching the ground, but all that kinetic energy instead leads
to a white hot air burst.

Pt

On Friday, October 7, 2022 at 12:03:57 AM UTC-4, pete...@gmail.com wrote:

NASA in the last hour has announced the first results.

The asteroid's orbit around its primary, 11 hours and 55 minutes, has been
shortened by 35 minutes. A 10 minute change would have been regarded as
a success.

pt

On Tue, 11 Oct 2022 12:19:41 -0700 (PDT), "pete...@gmail.com"
<petertrei@gmail.com> wrote:

>On Friday, October 7, 2022 at 12:03:57 AM UTC-4, pete...@gmail.com wrote:
>
>NASA in the last hour has announced the first results.
>
>The asteroid's orbit around its primary, 11 hours and 55 minutes, has been
>shortened by 35 minutes. A 10 minute change would have been regarded as
>a success.

So now we know it /can/ be done.

Of course, the target has to be fairly solid. A bunch of loosely-bound
rubble might not produce the same happy result.
--
"In this connexion, unquestionably the most significant
development was the disintegration, under Christian
influence, of classical conceptions of the family and
of family right."

In article <aordkhd6kbl77elr1ahd8fe2vh2eilvd9s@4ax.com>,
Paul S Person <psperson@old.netcom.invalid> wrote:

> On Tue, 11 Oct 2022 12:19:41 -0700 (PDT), "pete...@gmail.com"
> <petertrei@gmail.com> wrote:
>
> >On Friday, October 7, 2022 at 12:03:57 AM UTC-4, pete...@gmail.com wrote:
> >
> >NASA in the last hour has announced the first results.
> >
> >The asteroid's orbit around its primary, 11 hours and 55 minutes, has been
> >shortened by 35 minutes. A 10 minute change would have been regarded as
> >a success.
>
> So now we know it /can/ be done.
>
> Of course, the target has to be fairly solid. A bunch of loosely-bound
> rubble might not produce the same happy result.

I believe that Dimorphos is a loosely-bound rubble pile. There was,
after all, a plume over 1000 kilometers long. AFAIK, the observed effect
was significantly larger than the pure momentum transfer. I suspect that
the kinetic energy of the impact resulted in ejecta that increased the
amount of deceleration.

--
"We have advanced to new and surprising levels of bafflement."
Imperial Auditor Miles Vorkosigan describes progress in _Komarr_.
-------------------------------------------------------
Robert Woodward robertaw@drizzle.com

On Wed, 12 Oct 2022 21:45:51 -0700, Robert Woodward
<robertaw@drizzle.com> wrote:

>In article <aordkhd6kbl77elr1ahd8fe2vh2eilvd9s@4ax.com>,
> Paul S Person <psperson@old.netcom.invalid> wrote:
>
>> On Tue, 11 Oct 2022 12:19:41 -0700 (PDT), "pete...@gmail.com"
>> <petertrei@gmail.com> wrote:
>>
>> >On Friday, October 7, 2022 at 12:03:57 AM UTC-4, pete...@gmail.com wrote:
>> >
>> >NASA in the last hour has announced the first results.
>> >
>> >The asteroid's orbit around its primary, 11 hours and 55 minutes, has been
>> >shortened by 35 minutes. A 10 minute change would have been regarded as
>> >a success.
>>
>> So now we know it /can/ be done.
>>
>> Of course, the target has to be fairly solid. A bunch of loosely-bound
>> rubble might not produce the same happy result.
>
>I believe that Dimorphos is a loosely-bound rubble pile. There was,
>after all, a plume over 1000 kilometers long. AFAIK, the observed effect
>was significantly larger than the pure momentum transfer. I suspect that
>the kinetic energy of the impact resulted in ejecta that increased the
>amount of deceleration.

The article I read also points to the plume as helping explain the
better-than-expected result.

But it also contained a statement that this might not work if the
whole thing was just rubble: nothing to push on!
--
"In this connexion, unquestionably the most significant
development was the disintegration, under Christian
influence, of classical conceptions of the family and
of family right."