Explanation: On the first planetary defense test mission from planet Earth, the DART spacecraft captured this close-up on 26 September 2022, three seconds before slamming into the surface of asteroid moonlet Dimorphos. The spacecraft's outline with two long solar panels is traced at its projected point of impact between two boulders. The larger boulder is about 6.5 meters across. While the DART (Double Asteroid Redirection Test) spacecraft had a mass of some 570 kilograms, the estimated mass of Dimorphos, the smaller member of a near-Earth binary asteroid system, was about 5 billion kilograms. The direct kinetic impact of the spacecraft measurably altered the speed of Dimorphos by a fraction of a percent, reducing its 12 hour orbital period around its larger companion asteroid 65803 Didymos by about 33 minutes. Beyond successfully demonstrating a technique to change an asteroid's orbit that can prevent future asteroid strikes on planet Earth, the planetary-scale impact experiment has given the 150-meter-sized Dimorphos a comet-like tail of material.
So the question I have is given this test and assuming the same impact conditions, how, far away or months of lead time, would be required for Dimorphos to miss Earth if it were on a direct collision course with us? This is a very specific case but one that this question should be answerable.
First of all, I want to extend my congratulations, once again, to NASA, on your highly successful DART mission.
Second, I hope someone will answer alter-ego's important question:
So the question I have is given this test and assuming the same impact conditions, how, far away or months of lead time, would be required for Dimorphos to miss Earth if it were on a direct collision course with us? This is a very specific case but one that this question should be answerable.
That's an extremely interesting question, but the person answering it is not going to be me.
Instead, I'm going to teach you some Swedish poetry by a man named Gustaf Fröding (1860-1911). The poem, written near the end of his life, is called Gråbergssång (Gray Mountain Song). I'm going to translate the Swedish word "stå" (= stand) as "stay", to make the poem rhyme.
Stå
grå,
stå
grå,
stå
grå,
stå
grå,
stå
grå-å-å-å.
Så är gråbergs gråa sång
lå-å-å-å-å-å-å-å-å-ng.
Stay
gray,
stay
gray,
stay
gray,
stay
gray,
stay
gra-a-a-y.
So is gray mountain's gray song
lo-o-o-o-o-o-o-o-o-ng.
The Swedish group Mando Diao have set Fröding's poem to music.They have made a video of the song, too, where, fascinatingly, a huge meteorite or asteroid is seen impacting the Earth.
Click to play embedded YouTube video.
It seems obvious to me that most rocky bodies in the Universe are probably more or like Dimorphos. They are gray, hard and stiff. Okay, they may be orangish like Mars, or covered in thick ice, like so many moons of the outer solar system. They may even be like Io, writhing under the tidal forces of being trapped between Jupiter and the other three Galilean moons, so that is almost turning itself inside out and spewing molten sulfur all over the place. But still.
How unbelievably lucky we are to have a green world with blue skies and seas like the Earth. (Well, we must inevitably have been just so lucky, because otherwise we would not have been here. Duh. Yes, but still.)
We are doing so many stupid things to the little cosmic jewel that is our world. Thank you, NASA, for doing your bit to help protecting Earth from one kind of danger that isn't humanity's fault.
Ann
Re: APOD: DART vs Dimorphos (2023 Mar 09)
Posted: Thu Mar 09, 2023 2:08 pm
by Chris Peterson
alter-ego wrote: ↑Thu Mar 09, 2023 5:17 am
So the question I have is given this test and assuming the same impact conditions, how, far away or months of lead time, would be required for Dimorphos to miss Earth if it were on a direct collision course with us? This is a very specific case but one that this question should be answerable.
It's not really a question that can be answered except on a case by case basis. A "direct collision course" means that our orbits intersect, and to calculate the required deviation means knowing the orbital parameters of the body. And Dimorphos couldn't be on a collision course with Earth, because it's orbiting its own, more massive asteroid parent.
Re: APOD: DART vs Dimorphos (2023 Mar 09)
Posted: Thu Mar 09, 2023 2:31 pm
by HellCat
Great job NASA...
Let's DO IT AGAIN!
Re: APOD: DART vs Dimorphos (2023 Mar 09)
Posted: Thu Mar 09, 2023 2:39 pm
by Chris Peterson
HellCat wrote: ↑Thu Mar 09, 2023 2:31 pm
Great job NASA...
Let's DO IT AGAIN!
:lol2:
Of course, the dark side of this is that the ability to divert an asteroid away from a collision with the Earth also means the ability to divert an asteroid into a collision!
It seems obvious to me that most rocky bodies in the Universe are probably more or like Dimorphos. They are gray, hard and stiff. Okay, they may be orangish like Mars, or covered in thick ice, like so many moons of the outer solar system. They may even be like Io, writhing under the tidal forces of being trapped between Jupiter and the other three Galilean moons, so that is almost turning itself inside out and spewing molten sulfur all over the place. But still.
HellCat wrote: ↑Thu Mar 09, 2023 2:31 pm
Great job NASA...
Let's DO IT AGAIN!
Of course, the dark side of this is that the ability to divert an asteroid away from a collision with the Earth also means the ability to divert an asteroid into a collision!
After their initial assault, the Fithp land ground forces in the center of North America, primarily in and around Kansas. They initially repel attacks with orbital lasers and kinetic energy weapons, but a combined Soviet and US nuclear attack wipes out their beachhead. The Fithp, who are familiar with nuclear weapons, but prefer to use cleaner ones, are shocked by what they consider the barbarity of humans' willingness to "sow radioactive fire on their own croplands". The Fithp respond to the defeat of their invasion by dropping a large asteroid into the Indian Ocean, whose impact results in environmental damage on a global scale, particularly the almost total destruction of India.
Many if not most larger boulders have sharp edges and acute corners. How do we explain their formation on an asteroid body?
Re: APOD: DART vs Dimorphos (2023 Mar 09)
Posted: Thu Mar 09, 2023 4:52 pm
by Chris Peterson
Tekija wrote: ↑Thu Mar 09, 2023 4:47 pm
Many if not most larger boulders have sharp edges and acute corners. How do we explain their formation on an asteroid body?
They don't form on the asteroid body. They are fragments from collisions which collapsed into a big rubble pile, which is what most asteroids appear to be.
HellCat wrote: ↑Thu Mar 09, 2023 2:31 pm
Great job NASA...
Let's DO IT AGAIN!
:lol2:
Of course, the dark side of this is that the ability to divert an asteroid away from a collision with the Earth also means the ability to divert an asteroid into a collision!
Of course, the dark side of this is that the ability to divert an asteroid away from a collision with the Earth also means the ability to divert an asteroid into a collision!
Or The Expanse book 5 Nemesis Games (which is much better science fiction than Footfall).
I liked Footfall when I read it 40 years ago. Still have to try to get into The Expanse again after only making it through the first 5 episodes. I just wasn't liking the characters that much, no matter how rationally plausible the science may have been.
Or The Expanse book 5 Nemesis Games (which is much better science fiction than Footfall).
I liked Footfall when I read it 40 years ago. Still have to try to get into The Expanse again after only making it through the first 5 episodes. I just wasn't liking the characters that much, no matter how rationally plausible the science may have been.
I really like both the books and the series. Probably the best scifi example I know of where the science is just spot on. And the politics. I liked Footfall, but it sure reveals some of Niven's screwed up ideas, even more than other stories (which also demonstrate that).
Or The Expanse book 5 Nemesis Games (which is much better science fiction than Footfall).
I liked Footfall when I read it 40 years ago. Still have to try to get into The Expanse again after only making it through the first 5 episodes. I just wasn't liking the characters that much, no matter how rationally plausible the science may have been.
I never read Footfall, but I read Ringworld, also by Larry Niven. I really disliked the hero, and the story, for that matter. The short, short summary of the plot of the books reads like this: The 200-year-old hero and his 20-year-old girlfriend crash on the Ringworld, a ring-shaped "planet" "orbiting" its sun. (I guess it might have been our Sun.)
Anyway, the hero gets separated from his girlfriend. He wanders the Ringworld and comes across a people who greet strangers by having sex with them, or rather, their women have sex with them. After sharing his bed with all the women of this Ringworld people, the hero wanders on.
He meets his girlfriend, who has now been transformed into a horrible monster, and the hero has to kill her by slowly dismembering her, body part by body part.
Again the hero wanders on. He now finds out that the Ringworld has become unstable, and he has to save it by directing an enormous laser at the precise part of the Ringworld whose entire female population the hero has had sex with. Dutifully he uses his laser on them and kills them all.
The hero then wanders on, and now he meets a 3,000-year-old prostitute who looks like a 20-year-old, and who has spent her three millennia perfecting her erotic craft.
Well. I didn't read on after that. And I decided never to read a book by Larry Niven again.
Of course, the dark side of this is that the ability to divert an asteroid away from a collision with the Earth also means the ability to divert an asteroid into a collision!
Or The Expanse book 5 Nemesis Games (which is much better science fiction than Footfall).
Since Footfall was written 30 years before Nemesis Games, I think we have to give the nod to Niven and Pournelle, regardless of the subjective quality of the material.
Or The Expanse book 5 Nemesis Games (which is much better science fiction than Footfall).
Since Footfall was written 30 years before Nemesis Games, I think we have to give the nod to Niven and Pournelle, regardless of the subjective quality of the material.
I decided to see if Footfall is available for free, and low and behold, there are both PDF and epub versions available here: https://oceanofpdf.com/authors/larry-ni ... -download/. Somehow, I suspect this isn't quite legal though...
[ EDIT: Oh, and Ann, in case you were wondering, Ringworld is also available for free there! ]
Re: APOD: DART vs Dimorphos (2023 Mar 09)
Posted: Thu Mar 09, 2023 10:28 pm
by johnsemailis@yahoo.com
Maybe it is just me but in the top right corner of the Dart vs Dimorphos picture there appears to be am object that does not look like the rest of the rocks. It looks smooth , not angular and appears to have a dark handle sticking out of it . Sort of like a blow drier ?
How far off the surface was the Dart 3 seconds before impact ?
Re: APOD: DART vs Dimorphos (2023 Mar 09)
Posted: Fri Mar 10, 2023 4:28 am
by MarkE
Has the look of a pile of Type 1 building material; good luck moving that with a firecracker!
Could perhaps look at vaporising the smaller looser material, or melting it with acid or something, and then throw everything you have at the bigger pieces remaining, while they're loose/separate, by way of explosive projectiles?
Or The Expanse book 5 Nemesis Games (which is much better science fiction than Footfall).
Since Footfall was written 30 years before Nemesis Games, I think we have to give the nod to Niven and Pournelle, regardless of the subjective quality of the material.
I decided to see if Footfall is available for free, and low and behold, there are both PDF and epub versions available here: https://oceanofpdf.com/authors/larry-ni ... -download/. Somehow, I suspect this isn't quite legal though...
[ EDIT: Oh, and Ann, in case you were wondering, Ringworld is also available for free there! ]
Ha ha! I've already got it. No, actually, I haven't got it any more, because I threw it away!
Ann
Re: APOD: DART vs Dimorphos (2023 Mar 09)
Posted: Sat Mar 11, 2023 4:26 pm
by HellCat
Well. I didn't read on after that. And I decided never to read a book by Larry Niven again.
Ann
Thank you for this summary Ann!
Now I have no regrets for ever reading this, or Niven.
I once thought Heinlein brilliant, but his mysogyny creates quite the bitter aftertaste.
Steve
Well. I didn't read on after that. And I decided never to read a book by Larry Niven again.
Ann
Thank you for this summary Ann!
Now I have no regrets for ever reading this, or Niven.
I once thought Heinlein brilliant, but his mysogyny creates quite the bitter aftertaste.
Steve
A shame. Both Heinlein and Niven are great writers with some great ideas and inventive technology. I hope the planned series based on Ringworld actually happens and ends up being well done: I'm looking forward to seeing it! You both might even be tempted if the prediction in this statement turns out to be true:
https://www.wired.com/2022/03/geeks-guide-ringworld-tv/ wrote:Ringworld is currently being adapted for television by Akiva Goldsman, with Game of Thrones director Alan Taylor slated to direct the pilot. Science fiction author Mercurio D. Rivera thinks that Ringworld could make a great show, provided certain changes are made to the source material. “I could see this being turned into something really fantastic,” he says. “Because there’s no way they’re going to include some of the things that bothered us in the TV series—about the way that the female characters are treated. That’ll be fixed. And the setting will be phenomenal. They just need to come up with a better plot.”
DART vs Dimorphos
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