Asteroid Impact on Earth 2032 with Probability 1% and 8Mt Energy

It's a bit of both, observing has uncertainty in a lot of places, if you are on the ground you get atmospheric effects, imprecision of timing, imprecision of optics, etc etc. You are also observing an object where you dont know how far away it is. That distance has to be solved by basically doing a sort of triangulation, which requires either the observer or the object to move enough. So if you observe over a short time (hours for example), you can see it is moving, but it is hard to tell distance.

Once you have an estimated orbit, if it has any interactions with planets (IE: flyby of Earth), small differences in positions during the close encounter make LARGE differences decades later. Add to this the effects of photons from the sun pushing on the smaller asteroids or dust, or out-gassing /dust from comets cause these objects to slightly drift from just the basic gravitational forces. Generally inner solar system asteroids (inside mars) are very chaotic over hundreds of years, though typically predictable less than a century.

Note that I am not an expert on impact calculations, I just know a bit about and and can do back of the envelope ones. There are a number of ways to get to the ~1%, the orbit fits have uncertainties on them and those can be propagated forward in time. However there are all sorts of complexities with doing that, and often the easiest method is to sample the uncertainty region a few hundred thousand times (Monte-carlo), and propagate those and see what hits.

Parent mentioned Monte Carlo simulations, which allow you to simulate across a range possible scenario parameters and see what % result in some outcome (like a collision with Earth or the moon).

My guess is that small objects like this suffer greatly from the 3-body problem, and multiple trajectories are generated from various starting points inside our measured error bars for the current states of these objects. Small inaccuracies compound over the years.

There's going to be some degree of measurement error, which will likely be greater for objects which have not been observed many times. Multiple observations should allow both better estimation of the object attributes (average out the noise), and allow some judgement of the quality of predictions given what you think you know about it.

Mesurement uncertainty when propagated over long periods of time leads to very large uncertainties, imperfect gravity models, space weather

https://www.usgs.gov/observatories/yvo

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

How concerned? https://www.agiweb.org/geotimes/june05/feature_supervolcano.... not very.

We would see it years before, and we would know with certainty years before.

If the object really looked like it might impact I'm sure someone would get time on a powerful telescope to lock in the orbit.

> how much time before that impact would be able to ascertain over 50% probability of impact? hypothetically.

I understand it's hypothetical, but even a 10% chance of hitting a city, for example, would be a crisis.

FAST [0] in China maybe?

[0] https://fast.bao.ac.cn/

That warms my heart on a winter night.

I think that was supposed to be some kind of small black hole passing through the solar system or something more exotic. Maybe I'm misremembering. Great book though and still haunts me sometimes when staring up at the night sky:)

SE leaves the question of exactly what impacted the Moon unspecified, referring to it as the "agent". Both narratively and in-story, the question of what the ramifications of the event are is far more significant than its origin. It's not possible to change the past, nor does an understanding (narratively or in-story) have any appreciable impact on what transpires as a consequence.

As others have noted, an 8 MT impactor on the Moon would be a quite minor event. It would likely be visible to terrestrial observers (if on the near-side) and leave a visible crater. Might generate ejecta which itself could enter the Earth's atmosphere over time, though likely with little effect on the ground.

An 8 MT impact on the Moon is what the Moon calls "Tuesday." It has dealt with far, far worse.

The impact probably wouldn't even be visible with the naked eye unless it hits a part of the Moon not then illuminated by the Sun -- in which case one might see a brief flash of light.

See also: https://en.wikipedia.org/wiki/Australasian_strewnfield (debris over 10% to 30% of the Earth's surface from an impact ~788,000 years ago). Smaller, for sure, but very recent and large enough for "nuclear winter" type scenarios.

If the media does not contextualize risks correctly, as it never does, it's absolutely a crisis—a crisis of a poorly-informed, panicked society lashing out and doing irrational things.

It's not a costless error if a warped illusion of risk drives countries to, i.e., deploy nuclear-tipped space weapons for asteroid defense, which then precipitate a genuine crisis. It's not obvious that having more defenses is obviously safer than having less; some thoughtful people have argued the opposite:

>"In our view, development of this asteroid-deflection technology would be premature. Given twentieth-century history and present global politics, it is hard to imagine guarantees against eventual misuse of an asteroid deflection system commensurate with the dangers such a system poses. Those who argue that it would be prudent to prevent catastrophic impacts with annual probabilities of 10^-5 would surely recognize the prudence of preventing more probable catastrophes of comparable magnitude from misuse of potentially apocalyptic technology."

https://sci-hub.se/https://doi.org/10.1038/368501a0 ("Dangers of Asteroid Deflection" (1994), Carl Sagan & Steven Ostro)

This. It’s a crucial step for our civilisation to be able to protect earth from any incoming dangers be it asteroids or Umuamua type objects. There must be a global effort with all countries to build such a system.

What is it with people like you's selective memory? People were dying in droves in places like India or China, scroll down about halfway to see the funeral pyres: https://www.buzzfeednews.com/article/piapeterson/covid-pande...

They were even just dumping bodies in their holy river because they couldn't afford proper funerals.

Congrats for living (I assume) in a modern world with good health and clean air where you were just "inconvenienced" by shut restaurants and having to wear a mask, but hey, MAGA is fixing that too, let them "doge" your life into poorer air quality and less health protections! Winning!

Let's not observe false vacuum.

On the other hand, if people are told constantly to look up, eventually they stop looking.

> Why crisis? People should simply not look up.

I don't understand why this apt pun on that movie is being downvoted.

Would anyone of the downvoters of parent care to explain?

What I just learned from ChatGPT…

Asteroids mostly contain the same naturally radioactive elements we find in Earth's rocks - mainly potassium, uranium, and thorium in very small amounts. When they hit Earth, they don't typically create radiation hazards. Scientists have checked out famous impact sites like Meteor Crater in Arizona and found normal radiation levels. While impacts can briefly create some radioactive isotopes through the collision process, it's really the impact's explosive force that does the real damage, not radiation.

So a 14 km blast radius it seems.

So you wouldn't want to be under it, but a good-sized hill would be enough cover?

I don't want to come off too harsh here -- not a personal attack -- but I genuinely don't understand why folks are sharing the output from LLMs. It's usually too long, it's not written by a human (which is why I came to HN), and I could have trivially asked an LLM myself!

Yeah it is bad and a lot of damage if it hits somewhere populous but my understanding is we've tested nukes that powerful

It depends, on where exactly will hit. Similar to nuclear explosions, if one happen over sea or ocean near coast, it will cause extremely large wave, which will be similar to tsunami. If it will hit land, will be small earthquake.

This is why nearly all nuclear explosions was over land or far from coast. Few experiments near some coast or island, created tsunami-like wave on those coast (island), which considerable widen polluted territory (ocean is usually considered as self-cleaning).

You are slightly mistaken. There have been hit-and-run asteroids that entered the upper atmosphere and skipped through. https://en.wikipedia.org/wiki/1972_Great_Daylight_Fireball The Grand Teton Meteor / The Great Daylight Fireball of 1972 came within 35 miles of the surface. A huge iron meteor might survive a low pass but this would be a very rare event.

https://en.wikipedia.org/wiki/Category:Earth-grazing_firebal...

If you come in at exactly the right angle (because you'll skip off the upper atmosphere if you come in too flat) and if you're fast enough, it's entirely possible to enter the atmosphere but fail to complete the aerobreaking maneuver, resulting in an exit from the atmosphere at above escape velocity.

The stress of this maneuver is considerable, especially if you get as low as 20m above ground, so the object would need considerable shear strength and yield strength. Also high density and high thermal capacity. But not unrealistic, I think a tungsten ball (or better yet, a solid tungsten lifting body with aerodynamic steering authority) should make it through.

You can even exit the atmosphere but not have escape velocity, effectively using the aerobreaking maneuver to assist in the gravity capture of your object. But you'd better circularize the orbit shortly after, otherwise your next pass through the atmosphere is going to be terminal.

Relativistic baseball effects aren't very relevant yet, I'm talking about objects hitting the upper atmosphere with around 20-50 km/s. Enough to leave again, not enough to start a fusion reaction.

The mass of such an object is likely be miniscule compared to the mass of the earth. So even a very close approach isn't likely to make much difference to the earth's orbit.

E.g. an asteroid 100m across with the same density as the earth is going to have ~0.0000000000001 the mass of the earth.

...and dense enough and with enough shear strength and yield strength. Air blast disintegration is making a lot of scenarios impossible.

The errors should be a function of time until impact. I'd like to know what that error variance vs time plot looks like.