Happy Atheist Forum

General => Science => Topic started by: Tank on September 27, 2022, 06:37:46 PM

Title: One hundred and eighty!!!
Post by: Tank on September 27, 2022, 06:37:46 PM
DART scores a direct hit.

Title: Re: One hundred and eighty!!!
Post by: Asmodean on September 28, 2022, 07:35:18 AM
Heh! It looks like it was transmitting a picture just as it smashed into the rock, so the last one ended up like some of my surveillance footage just as the camera goes down.
Title: Re: One hundred and eighty!!!
Post by: Tank on September 28, 2022, 09:20:00 AM
It does. The bit I find interesting is the rubble like appearance of the target.
Title: Re: One hundred and eighty!!!
Post by: Tank on September 30, 2022, 11:12:11 AM
DART impact images (https://www.sciencealert.com/hubble-and-webb-pics-reveal-dart-impact-was-even-bigger-than-expected?)

Quote"I was really worried there was nothing left of Dimorphos" at first, Carnelli told AFP.

The Hera mission, which is scheduled to launch in October 2024 and arrive at the asteroid in 2026, had expected to survey a crater around 10 meters (33 feet) in diameter.

It now looks like it will be far bigger, Carnelli said, "if there is a crater at all, maybe a piece of Dimorphos was just chunked off."
Title: Re: One hundred and eighty!!!
Post by: Tank on October 04, 2022, 08:31:18 PM
Smacked asteroid's debris trail more than 6,000 miles long (https://phys.org/news/2022-10-smacked-asteroid-debris-trail-miles.html)

Very interesting result.
Title: Re: One hundred and eighty!!!
Post by: Dark Lightning on October 04, 2022, 09:10:12 PM
Now we'll have a train of meteors that may actually on a collision course with us.  :???:
Title: Re: One hundred and eighty!!!
Post by: Recusant on October 04, 2022, 09:41:59 PM
Quote from: Dark Lightning on October 04, 2022, 09:10:12 PMNow we'll have a train of meteors that may actually on a collision course with us.  :???:

 :lol:   I admire that determined pessimism.
Title: Re: One hundred and eighty!!!
Post by: Dark Lightning on October 04, 2022, 10:46:55 PM
I went and read the article about it over at phys.org. It would appear that my pessimism was (thankfully) misplaced. I also read where a lot more ejecta was noted than was expected. I was always told to be careful where I was throwing rocks, when I was a kid. :D
Title: Re: One hundred and eighty!!!
Post by: Tank on October 05, 2022, 01:26:05 PM
Quote from: Dark Lightning on October 04, 2022, 10:46:55 PMI went and read the article about it over at phys.org. It would appear that my pessimism was (thankfully) misplaced. I also read where a lot more ejecta was noted than was expected. I was always told to be careful where I was throwing rocks, when I was a kid. :D

The really interesting thing has been the composition of what was hit. It's appears to be a small agglomeration of dust and rubble brought together by micro-gravity. There is no inherent strength in what is essentially a pile of rubble. What I'd love to know is if this is the norm for asteroids. 
Title: Re: One hundred and eighty!!!
Post by: billy rubin on October 05, 2022, 06:52:51 PM
yes.

is an asteroid just a clod of debris weakly held together by gravitation or is it a chunk of solidly consolidated material maybe broken off something bigger?

an impact of either on earth woyld be the same, i think
Title: Re: One hundred and eighty!!!
Post by: Tank on October 05, 2022, 07:04:07 PM
Would you rather be hit by a rock or the equivalent weight of sand? Or put it another way one 1,000kg rock or that rock cut into 100,000 pieces. I would think that one rock would make it to ground but the 100,000 pebble would burn up through the atmosphere.
Title: Re: One hundred and eighty!!!
Post by: Dark Lightning on October 05, 2022, 09:59:00 PM
I'd take 100k pebbles, gladly.
Title: Re: One hundred and eighty!!!
Post by: billy rubin on October 06, 2022, 12:15:06 AM
could be, but getting hit by a charge of buckshot does as much damage as a bullet

th eburning up part makes sense though

i once watcghed a meterorite break up into chunks over my head. spectacular. i wonder how much ablation a soccer ball-sized piece of stone would undergo
Title: Re: One hundred and eighty!!!
Post by: Dark Lightning on October 06, 2022, 01:28:41 AM
A charge of buckshot hitting the ground with an entry speed of many thousands of miles an hour (they won't) is quite different from standing even 100 yards from a shotgun blast. I've seen meteorites much less than the size of a bowling ball that have reached the ground. Those aren't loose aggregates of carbonaceous chondrites, they are chunks of nickel and iron...and left quite a bit of their pre-entry volume in a nice ionization trail across the sky.
Title: Re: One hundred and eighty!!!
Post by: Bluenose on October 06, 2022, 01:38:30 AM
Quote from: Tank on October 05, 2022, 07:04:07 PMWould you rather be hit by a rock or the equivalent weight of sand? Or put it another way one 1,000kg rock or that rock cut into 100,000 pieces. I would think that one rock would make it to ground but the 100,000 pebble would burn up through the atmosphere.

Well, the amount of kinetic energy to be transferred to the Earth system would be the same. If the solid rock is big enough to be a cause for concern, the same mass of sand would still have major consequences of the same order of magnitude.
Title: Re: One hundred and eighty!!!
Post by: Dark Lightning on October 06, 2022, 02:05:23 AM
An infall of sand wouldn't reach the surface, generally speaking. A solid object of the same mass striking the earth would be a catastrophic event, like a dinosaur-killing one.
Title: Re: One hundred and eighty!!!
Post by: Tank on October 06, 2022, 08:21:27 AM
Quote from: Bluenose on October 06, 2022, 01:38:30 AM
Quote from: Tank on October 05, 2022, 07:04:07 PMWould you rather be hit by a rock or the equivalent weight of sand? Or put it another way one 1,000kg rock or that rock cut into 100,000 pieces. I would think that one rock would make it to ground but the 100,000 pebble would burn up through the atmosphere.

Well, the amount of kinetic energy to be transferred to the Earth system would be the same. If the solid rock is big enough to be a cause for concern, the same mass of sand would still have major consequences of the same order of magnitude.

The kinetic energy would be the same. But the surface area of the sand and thus drag would be considerably higher. The sand would spread out and burn up high in the atmosphere. Hardly anything would reach the surface if anything at all.

Thousands of tons of dust and small space debris fall on the Earth yearly and we don't even notice most of it.

https://en.wikipedia.org/wiki/Cosmic_dust
Title: Re: One hundred and eighty!!!
Post by: Bluenose on October 07, 2022, 06:11:04 AM
Quote from: Tank on October 06, 2022, 08:21:27 AMThe kinetic energy would be the same. But the surface area of the sand and thus drag would be considerably higher. The sand would spread out and burn up high in the atmosphere. Hardly anything would reach the surface if anything at all.

Thousands of tons of dust and small space debris fall on the Earth yearly and we don't even notice most of it.

https://en.wikipedia.org/wiki/Cosmic_dust

However, the in-fall of dust is spread over the whole atmosphere plus the whole year, so each particle is essentially its own thing.  However, if we are talking about a large lump of sand, IOW an object like the NASA Dart object loosely held together by mutual gravity, then the effect of each grain of sand would not be independent, and the effects would be cumulative since they would not be spread over the whole atmosphere but concentrated in a relatively small area and at the same time.

This has always been my problem with the Hollywood trope of blasting an incoming asteroid with atomic weapons shortly before it hits the Earth.  The best that could actually hope to achieve if to increase the area of devastation.  The real solution to an Earth bound object is the one just tested by NASA, which is to nudge the object during part of its orbit well before it is a danger to the planet.  The amount of delta-V required in that scenario is orders of magnitude less than trying to divert it just before it hits.
Title: Re: One hundred and eighty!!!
Post by: Tank on October 07, 2022, 09:48:56 AM
The rubble would spread out. Not across the entire planet but a significant area. A solid rock would not.
Title: Re: One hundred and eighty!!!
Post by: billy rubin on October 07, 2022, 11:04:32 AM
it has to be a distant enough nudge to ensure a clean miss. if it just means the asteroid is deflected enough to hit calcutta instead of paris, things will get ugly
Title: Re: One hundred and eighty!!!
Post by: Tank on October 07, 2022, 11:57:20 AM
I think we are discussing different issues here. One is the nature of asteroids, are they mostly solid or piles of rubble? Another is what happens when a solid or rubble asteroid hits the atmosphere? Another is how to disperse or deflect an asteroid well away from the Earth so it doesn't even impact.



Title: Re: One hundred and eighty!!!
Post by: Bluenose on October 07, 2022, 11:59:29 PM
Quote from: Tank on October 07, 2022, 09:48:56 AMThe rubble would spread out. Not across the entire planet but a significant area. A solid rock would not.

Why would it be spread out?
Title: Re: One hundred and eighty!!!
Post by: Tank on October 08, 2022, 10:00:24 AM
Quote from: Bluenose on October 07, 2022, 11:59:29 PM
Quote from: Tank on October 07, 2022, 09:48:56 AMThe rubble would spread out. Not across the entire planet but a significant area. A solid rock would not.

Why would it be spread out?

Differential aerodynamic drag.
Title: Re: One hundred and eighty!!!
Post by: billy rubin on October 08, 2022, 12:49:33 PM
when a super nova blows up and heavier stuff like iron is transmuted, what is the next step?

i have some iron meterorites i picked up in the desert in arizona. they are solid chunks of metal.

were iron atomsnjust floating around that magically coalesced into what i habe, or were they smashed into solid chunks during the supernova events?

obviously the asteroids were never part of a preexisting planet, so whether they are solid, or accreted solid, or loose sandballs depends on prior history
Title: Re: One hundred and eighty!!!
Post by: Asmodean on October 10, 2022, 07:46:53 AM
My limited understanding is this;

After a supernova, what you are left with is a planetary nebula. Basically, it's a cloud of gas and dust. Gravity acts on it and tiny clumps of stuff clump together to form larger and larger clumps until eventually, they become what passes for meteorites.

As I see it, and this is probably somewhat simplistic, it makes sense for the thing to be iron for two reasons. One is that before impacting the Earth, the thing has to travel through the atmosphere. If it has a coating of "weaker" stuff, that coating burns up as a result of atmospheric friction. The other component is that iron is the last fusion product a star makes, so it is made in a layer of sorts, such that after the supernova event, while iron is dispersed, it's still more likely to find other iron to clump together with than, say, carbon or nickel.

That said, I seem to remember having read that the supernovae are where the heavier elements are produced. It takes more energy to fuse iron than that fusion releases, so iron cannot be used as a star fuel in the conventional sense. However, given such energy, it can be smashed together with stuff in order to make even heavier stuff. The amounts, however, would be rather on the tiny side, and this seems to hold when we look at what the Universe is made of (speaking of matter only, for the purposes of this thread) so it's possible that your meteorites contain trace amounts of this and that, heavier than iron - as well as some lighter elements, should they have survived the trip through the atmosphere still attached to their lump of iron.

Still, it would be interesting to hear a take from someone less pedestrian than me on the subject.
Title: Re: One hundred and eighty!!!
Post by: Tank on October 11, 2022, 09:48:15 PM
It worked  ;D

Nasa's Dart spacecraft 'changed path of asteroid' (https://www.bbc.co.uk/news/science-environment-63221577)
Title: Re: One hundred and eighty!!!
Post by: Bluenose on October 12, 2022, 01:58:21 AM
Quote from: Tank on October 11, 2022, 09:48:15 PMIt worked  ;D

Nasa's Dart spacecraft 'changed path of asteroid' (https://www.bbc.co.uk/news/science-environment-63221577)

Yes, indeed!  Regrettably, I wonder just how many of the general public understand that this approach will only work on a threatening object if it is detected early enough to be able to impact it in a part of its orbit where the delta-V required is very small.  An approaching object on a hyperbolic trajectory is an altogether different kettle of fish.
Title: Re: One hundred and eighty!!!
Post by: Tank on October 12, 2022, 08:32:43 AM
I wonder just how many of the general public understand... anything.  :'(  :'(  :'(
Title: Re: One hundred and eighty!!!
Post by: billy rubin on October 12, 2022, 07:26:07 PM
lol
Title: Re: One hundred and eighty!!!
Post by: Asmodean on October 13, 2022, 10:41:23 AM
Quote from: Tank on October 12, 2022, 08:32:43 AMI wonder just how many of the general public understand... anything.  :'(  :'(  :'(
Yes. Humans bad. General humans worse. >:(

Speaking of detection time, are we not likely to be forewarned about a cataclysmic asteroid impact type of event years and years in advance? But then again, for all I know, those years and years may be years and years too late to sufficiently alter its course with a kinetic impactor... Yeah. There is that.

On a unrelated topic, watched me some PBS Spacetime yesterday, and they were talkuing about ways of mapping extrasolar planets using gravitational lensing around the Sun with fleets of small solar sail ships... Now that would be really cool. I do hope I get to see a actual picture of the surface of a planet orbiting another star - even if it's more barren than the Moon - before I kick the proverbial bucket.
Title: Re: One hundred and eighty!!!
Post by: Tank on October 13, 2022, 10:51:27 AM
Center for New Earth Object Studies  (https://cneos.jpl.nasa.gov/)

The thing is that in general the bigger the object is the easier it is to detect. So we could well have detected the vast majority of planet killers. And the techniques and technology to find these big bastards is improving every day.
Title: Re: One hundred and eighty!!!
Post by: billy rubin on October 14, 2022, 04:12:42 AM
if the orbit of a collision prone asteroid is highly elliptical

most arent

then it might appear for the first time on its way and not far and therefore not be on the maps
Title: Re: One hundred and eighty!!!
Post by: Tank on October 14, 2022, 11:03:53 AM
Quote from: billy rubin on October 14, 2022, 04:12:42 AMif the orbit of a collision prone asteroid is highly elliptical

most arent

then it might appear for the first time on its way and not far and therefore not be on the maps

These would be the 1% wild cards that are the worry and why we need defence rockets designed, built and ready to launch at the next available 'window' of opportunity.
Title: Re: One hundred and eighty!!!
Post by: Asmodean on October 14, 2022, 11:43:05 AM
If The Asmo wills it, a asteroid will land. If The Asmo wills it not... It may still land because what, is The Asmo supposed to divert every little cataclysm coming this way? When will He have time for evil plots then?!
Title: Re: One hundred and eighty!!!
Post by: Tank on October 14, 2022, 11:54:16 AM
Luxembourg?
Title: Re: One hundred and eighty!!!
Post by: Asmodean on October 14, 2022, 12:08:31 PM
The Asmo can neither confirm nor deny that the impact site mauy or may not be a mountain dutchy. And if he were to confirm or deny that, which He can neither confirm nor deny, then He would neither confirm nor deny which mountain dutchy - or even if it's one of them grand dutchies, or one of more regular variety. The Asmo calls any observation of a Smart car-shaped object hurtling towards any unconfirmed-nor-denied piece of real estate vicious slander spread most recklessly by His opponents.

In unrelated news, The Asmo can neither confirm nor deny possibly having an inclanation to learn to speak like an politician.