<p>There are problems with this:</p>

<h1>What happens when an asteroid hits the atmosphere</h1>

<p>The asteroid will be travelling fast, more than 10 <em>km per second</em>. In front of it the atmosphere will be compressed and heat up, this causes the "meteor" (a streak of light in the sky). It also causes puts a lot of stress on the asteroid. </p>

<p>If the asteroid is very small (sand grain to pebble sized), it gets destroyed completely.  If it is larger it can explosively break up. But several chunks can continue at terminal velocity (ie no faster than a stone dropped from a high building) and don't form craters. These chunks can later be picked up as meteorites.</p>

<p>If the body is very large it can survive the atmosphere, hit the Earth at hypervelocity (several km/s) and form a larger crater.</p>

<p>If you want the body to survive, but only form a small crater you need either a very strong body (a solid iron asteroid) or an odd set of events, such as at the <a href="https://journals.uair.arizona.edu/index.php/maps/article/view/15749/15737" rel="noreferrer">Carancas impact</a>. In these cases a small crater or crater field can form. The size of the impactor is about 50cm.</p>

<h1>Detecting and forecasting impact</h1>

<p>A 50cm asteroid is not currently detectable until very close to the Earth.  We have seen asteroids that are a couple of metres across, but they need to be close to the Earth (and we need to be lucky). </p>

<p>In 2008 we did get lucky and saw a <a href="https://en.wikipedia.org/wiki/2008_" rel="noreferrer">small</a> object before it hit Earth. In that case we had a few hours of observations and by about an hour before impact we were able to narrow the impact zone down to "Northern Sudan".  Now (North) Sudan is huge, an area about 3 times the size of Texas. And in 2008 we already had an active Near Earth Object search program, something that we did not have in 1987.  Even if the asteroid was noticed by lucky amateur, before the internet it would have been very hard to coordinate the observations needed even to predict "Northern Sudan". This meteorite exploded at altitude and did not form a crater.</p>

<p>To conclude, most meteorites will not take out a single house and leave neighbours standing.  Such meteorites that could are not currently detectable before impact.  Even with current technology and lots of luck we could not predict the impact location better than "somewhere between New Mexico and Florida" but not a single address.</p>

<p>There are other things that can destroy a house, perhaps a sinkhole? Perhaps these are more predictable (with luck) than an asteroid impact.</p>

CC BY-SA 4.0
2018-08-30T20:45:12.727Z
Rob and James, †hank you so much for the replies. I thought of asking on here on a whim, but never expected I'd get such deep and helpful answers. Thank you both so much. I see my choices are to think of something else or go completely into fiction (at the risk of straining credibility)! In fiction, there is a bit of leeway allowed, but I'd had to completely fabricate things.

James: I had originally thought of a sinkhole! But my problem was that I wanted the family to have advanced warning.
outflare
CC BY-SA 4.0
2018-08-30T20:30:48.723Z
2018-08-30T20:51:44.567Z
2018-08-30T20:51:44.567Z
James K
<p><a href="https://www.nature.com/news/2009/090325/full/458401a.html" rel="nofollow noreferrer">Truth is stranger than fiction: an asteroid was observed less than 24 hours before striking Earth in 2008</a>. JPL predicted the time of the collision to within 15 seconds, but the meteor exploded in the upper atmosphere, and the fragments were scattered over many kilometers of Sudanese desert.</p>

CC BY-SA 4.0
2018-08-31T09:34:49.200Z
2018-08-31T09:34:49.200Z
rob
<p>Good People,</p>

<p>I am writing a short story, and I wanted to include a section wherein a family is told that an asteroid is going to strike their home. The thing is, I would like to set the story in 1987, but I'm not sure if there was the capability of that kind of prediction back then. To be honest, I'm not even sure that kind of accuracy is possible now! But I will allow myself some creative freedom in that area, but I don't want to stretch it so much that someone would keep thinking to themselves, "Really, in 1987 they could predict <em>that</em>?" Would such a thing have been possible then? If not then, what about sometime in the 90s?</p>

<p>While I have your eyes, is there a specific size that an asteroid would have to be in order to just destroy one home (or a couple on the side of the home).</p>

<p>Thank you for any insight and info! I appreciate the resources here. I did some digging around before asking this question: nothing seemed to be particular to my frame of reference. If it exists, please let me know.</p>

CC BY-SA 4.0
2018-08-30T19:20:28.963Z
"a family is told that an asteroid is going to strike their home. " Unclear what you mean. Just their home? Their city? Their country? The whole world? And how far in advance?
ProfRob
CC BY-SA 4.0
2018-08-30T19:25:44.793Z
Hmmm... I'm a little confused on what you're asking. Are you just wondering about the size of an asteroid that would destroy a single home? What are the dimensions of this home, and where would it be located in terms of sea level?
MystaryPi
CC BY-SA 4.0
2018-08-30T19:50:51.350Z
Thanks so much for your replies! Let me try and clear things up:

Rob: Yes, just their home. Or at least their home and maybe some areas around it. Roughly speaking, imagine a two-story suburban home. What size asteroid would be needed to destroy that? In terms of how far in advance, I'd like to say 2-3 months in advance. But that might be stretching credibility too far.

MystaryPi: Yes, just how large the asteroid would need to be to just destroy a single home. Two-story suburban, in terms of sea level, about 800' (I'm basing this on a town in Indiana). 

Again, thanks to you both!
outflare
CC BY-SA 4.0
2018-08-31T00:03:11.880Z
Bear in mind that the Earth is a moving target. On average, it moves along its orbit a distance equal to its own diameter in around 7 minutes.
PM 2Ring
CC BY-SA 4.0
2018-08-31T02:28:51.183Z
You're asking 3 different questions, which makes it too broad/unclear. One is on historical technical capacity to identify an asteroid on a collision path [definitely a valid question]. One is whether *any* technology could predict the impact site with an accuracy of ~100m [I greatly doubt it]. And a third is how small an asteroid has to be for impact to only affect an area of ~100m radius - best to ask this separately, perhaps on [Physics.SE], with more detail such as angle of impact and kind of asteroid (research on Wikipedia recommended!). :-)
Chappo Hasn't Forgotten
CC BY-SA 4.0
2018-08-31T15:40:09.217Z
take a look at https://smile.amazon.com/Lucifers-Hammer-Novel-Larry-Niven/dp/0449208133/  .   Then look at https://smile.amazon.com/Last-Policeman-Novel-Trilogy/dp/1594746745/
Carl Witthoft
<asteroids><impact-probability>
Accuracy of predicting an asteroid strike in 1987
outflare
# Accuracy of predicting an asteroid strike in 1987

(Asked by: username_0 on 2018-08-30)

Good People,

I am writing a short story, and I wanted to include a section wherein a family is told that an asteroid is going to strike their home. The thing is, I would like to set the story in 1987, but I'm not sure if there was the capability of that kind of prediction back then. To be honest, I'm not even sure that kind of accuracy is possible now! But I will allow myself some creative freedom in that area, but I don't want to stretch it so much that someone would keep thinking to themselves, "Really, in 1987 they could predict *that*?" Would such a thing have been possible then? If not then, what about sometime in the 90s?

While I have your eyes, is there a specific size that an asteroid would have to be in order to just destroy one home (or a couple on the side of the home).

Thank you for any insight and info! I appreciate the resources here. I did some digging around before asking this question: nothing seemed to be particular to my frame of reference. If it exists, please let me know.

**Tags:** asteroids, impact-probability

> **Comments:**
> **username_1**: "a family is told that an asteroid is going to strike their home. " Unclear what you mean. Just their home? Their city? Their country? The whole world? And how far in advance?  
> **username_2**: Hmmm... I'm a little confused on what you're asking. Are you just wondering about the size of an asteroid that would destroy a single home? What are the dimensions of this home, and where would it be located in terms of sea level?  
> **username_0**: Thanks so much for your replies! Let me try and clear things up:  Rob: Yes, just their home. Or at least their home and maybe some areas around it. Roughly speaking, imagine a two-story suburban home. What size asteroid would be needed to destroy that? In terms of how far in advance, I'd like to say 2-3 months in advance. But that might be stretching credibility too far.  username_2: Yes, just how large the asteroid would need to be to just destroy a single home. Two-story suburban, in terms of sea level, about 800' (I'm basing this on a town in Indiana).   Again, thanks to you both!  
> **username_3**: Bear in mind that the Earth is a moving target. On average, it moves along its orbit a distance equal to its own diameter in around 7 minutes.  
> **username_4**: You're asking 3 different questions, which makes it too broad/unclear. One is on historical technical capacity to identify an asteroid on a collision path [definitely a valid question]. One is whether *any* technology could predict the impact site with an accuracy of ~100m [I greatly doubt it]. And a third is how small an asteroid has to be for impact to only affect an area of ~100m radius - best to ask this separately, perhaps on [Physics.SE], with more detail such as angle of impact and kind of asteroid (research on Wikipedia recommended!). :-)  
> **username_5**: take a look at https://smile.amazon.com/Lucifers-Hammer-Novel-Larry-Niven/dp/0449208133/  .   Then look at https://smile.amazon.com/Last-Policeman-Novel-Trilogy/dp/1594746745/  

---

## 2 answers

### Answer by username_6 on 2018-08-30. Score: 5

There are pusername_7lems with this:

# What happens when an asteroid hits the atmosphere

The asteroid will be travelling fast, more than 10 *km per second*. In front of it the atmosphere will be compressed and heat up, this causes the "meteor" (a streak of light in the sky). It also causes puts a lot of stress on the asteroid.

If the asteroid is very small (sand grain to pebble sized), it gets destroyed completely. If it is larger it can explosively break up. But several chunks can continue at terminal velocity (ie no faster than a stone dropped from a high building) and don't form craters. These chunks can later be picked up as meteorites.

If the body is very large it can survive the atmosphere, hit the Earth at hypervelocity (several km/s) and form a larger crater.

If you want the body to survive, but only form a small crater you need either a very strong body (a solid iron asteroid) or an odd set of events, such as at the [Carancas impact](https://journals.uair.arizona.edu/index.php/maps/article/view/15749/15737). In these cases a small crater or crater field can form. The size of the impactor is about 50cm.

# Detecting and forecasting impact

A 50cm asteroid is not currently detectable until very close to the Earth. We have seen asteroids that are a couple of metres across, but they need to be close to the Earth (and we need to be lucky).

In 2008 we did get lucky and saw a [small](https://en.wikipedia.org/wiki/2008_) object before it hit Earth. In that case we had a few hours of observations and by about an hour before impact we were able to narrow the impact zone down to "Northern Sudan". Now (North) Sudan is huge, an area about 3 times the size of Texas. And in 2008 we already had an active Near Earth Object search program, something that we did not have in 1987. Even if the asteroid was noticed by lucky amateur, before the internet it would have been very hard to coordinate the observations needed even to predict "Northern Sudan". This meteorite exploded at altitude and did not form a crater.

To conclude, most meteorites will not take out a single house and leave neighbours standing. Such meteorites that could are not currently detectable before impact. Even with current technology and lots of luck we could not predict the impact location better than "somewhere between New Mexico and Florida" but not a single address.

There are other things that can destroy a house, perhaps a sinkhole? Perhaps these are more predictable (with luck) than an asteroid impact.

> **Comments:**
> **username_0**: Rob and James, †hank you so much for the replies. I thought of asking on here on a whim, but never expected I'd get such deep and helpful answers. Thank you both so much. I see my choices are to think of something else or go completely into fiction (at the risk of straining credibility)! In fiction, there is a bit of leeway allowed, but I'd had to completely fabricate things.  James: I had originally thought of a sinkhole! But my pusername_7lem was that I wanted the family to have advanced warning.  

---

### Answer by username_7 on 2018-08-31. Score: 0

[Truth is stranger than fiction: an asteroid was observed less than 24 hours before striking Earth in 2008](https://www.nature.com/news/2009/090325/full/458401a.html). JPL predicted the time of the collision to within 15 seconds, but the meteor exploded in the upper atmosphere, and the fragments were scattered over many kilometers of Sudanese desert.


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