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Sylph_uscm t1_j6imxlh wrote

Reply to comment by ttystikk in ‘Extraordinary’ footage shows one of the closest known approaches of a near-Earth object — On 26 Jan. 2023, asteroid 2023 BU was about 2,200 miles above the surface of the Earth by marketrent

(This one was too small to warrant trajectory calculation, since it would be harmless if it hit, but...)

Isn't it still the case that, if there is a potentially disastrous impact detected, knowing doesn't do much good? Its not like you can evacuate a city within a short time frame.

I guess what I mean to ask is - how does knowing about an impact help save us when we can't stop them?

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Rhaedas t1_j6jzbo5 wrote

Knowing what's out there is the first step. Perhaps if we knew there were a lot more and the odds were good one would hit soon, there'd be more push to fund doing whatever we could to intercept. Plus getting better ways to detect and project paths leads to a longer time knowing a better final target, so even if we couldn't do anything, having days instead of hours to move people from a city would be worth it.

It's how hurricane and other storms used to be vs. what we know now. We can't do much of anything about the smaller threats of tornadoes, but we still try to improve accuracy of time and location.

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Sylph_uscm t1_j6llc2b wrote

Funding the search effort is no different than funding technology to stop them, if that's the motivation behind the search (I don't believe that it is, I'm counterpointing people that believe that 'it's the life-or-death nature of impacts that make people search' here.)

Ergo, if we really want to survive impacts, we need to work on ways to stop them - our detection is already 10000x further than our ability to stop anything. It's more than good enough for our current abilities to stop anything.

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ttystikk t1_j6klkda wrote

The bigger they are, the easier it is to see them at greater distances, which makes it easier to do something to alter their trajectory because the farther away we intercept them, the less energy is needed to move them off course.

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Sylph_uscm t1_j6lkry9 wrote

Agreed, but last I checked, any detection is happening way to late to do anything with current technology.

My thoughts are that, if we were truly motivated by the 'life or death' nature of a potential impact as some here implied (I disagree with this reasoning) ; efforts would be going into means of stopping them (we have pretty much none), rather than detection.

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ttystikk t1_j6m3hxh wrote

Taking these in order:

>Agreed, but last I checked, any detection is happening way to late to do anything with current technology.

Simply not true; big ones are spotted and plotted years in advance, plenty of time to mount missions to deal with them.

>My thoughts are that, if we were truly motivated by the 'life or death' nature of a potential impact as some here implied (I disagree with this reasoning)

You disagree that a large asteroid would be an extinction level event? The one that wiped out the dinosaurs was a bit more than 6 miles in diameter- and it would do the same to humanity.

Apophis, the one that blew by here a few years ago, was discovered in 2004. Its diameter is only 600' but we know it comes close to Earth occasionally. If the probability of impact were high, we definitely would put together a mission to meet it...

>efforts would be going into means of stopping them (we have pretty much none), rather than detection.

..which leads to my last points; first, we have to detect them to know they're coming. Hell, we want to know about every chunk of rock flying around the solar system just because!

Second, between large boosters to get heavy payloads into orbit, high yield nuclear weapons, and precision guidance of the kind demonstrated by NASA's recent impactor mission, we definitely have the capability to do the job. It's a question of will, that's all.

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Sylph_uscm t1_j6m6hxb wrote

OK, thanks. It appears that my information must be out of date then. (I was taught about nuclear explosions being ineffective due to objects either re-coalescing (long range, rubble piles etc), or being too close to divert from earth (close range).

I was taught that the 'buckshot' effect of a bolide being destroyed via nuclear explosion would only be slightly, if at all (depending on size) preferable to the original impact, given that tracking so many fragments makes evacuation of specific cities/countries etc impossible. There's arguments involved about total kinetic energy transfer from impactor to earth, too.

(I was also taught that other options, propelling the object in a more controlled manner, are terrible in comparison to nuclear explosions, due to the age old limitations of the rocket equation. I'm sure you're familiar. )

However:
Now that we're discussing it, it might well be the case that I was being taught about interstellar objects, since the lecture grew out of a lesson about objects with an orbital eccentricity > 1.

Thanks for your post, I'll find some more recent opinions and info about solar system objects and educate myself further!
(If we have anything like the technology to propel even solar system objects I'll be super-impressed!)

Oh, the 'other thing' -

I certainly didn't mean that I disagreed that an impact could be disastrous. What I disagree with is: The idea that we have become as adept as we are at detecting asteroids and comets, out of a desire to survive.

If you read the other comments in this topic you'll see a few examples of this claim, and it's that I am challenging. (I'm really hoping this is clear now, because I'm trying really hard to state it clearly but it still seems hard to have it land. I really never said what you took me to mean, sorry.)

To clarify again: I believe that we have become as adept as we currently are because of an interest in astronomy, the general desire to understand physics, even geology and the origins of the universe etc! Not out of a desire to survive impacts.

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ttystikk t1_j6mdlqf wrote

The desire to detect near earth and potentially threatening objects has been a recurring theme in proposals for detection equipment, budgets and observation time for at least several decades. It might not be the headline reason, but it often makes the list. NASA has also built up an extensive library of such discussions over the years. I hope that makes you feel better.

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