Don't Look Up Question (spoilers)

Factual Questions
1

Not sure if there is a factual answer to this but gonna give it a shot.

The recent Netflix movie “Don’t Look Up” involves a killer comet that hits the US and humanity’s failure to pull together to avert the catastrophe. The heroes of the movie are two astronomers from Michigan State University in Lansing, MI who try in vain to get the world to take the threat seriously. At the end, it’s too late; the comet approaches; humanity is doomed. The astronomers and their friends and family spend a last poignant dinner, enjoying food and company and keeping brave faces as death approaches. The comet hits the Pacific off the coast of Chile, triggering worldwide catastrophe. As the little group in Lansing have their last glasses of wine, the table starts shaking as the earth quakes and then - an apparent explosion and silence.
I live near Lansing, which is nowhere near Chile or the Pacific. Is this scenario realistic? Is this how death would sweep across the planet? Would it be that quick? Minutes, hours, days? I was under the impression that the asteroid that killed the dinosaurs kicked up so much material that the planet cooled and sunlight was blocked, but the actual dying took days to years. Would MSU Spartans be obliterated that quickly, or would there be some (presumably terrible) time before the end?

2

There was a whole thread on what sort of damage the dinosaur killer did; but the one thing I do remember is splatter, possibly molten, falling down for a day or more all around the world, after being thrown up by the collision. I even saved a link:

https://agupubs.onlinelibrary.wiley.com/doi/full/10.1029/2001JE001532

This bit is a hint of what happens:

because most of these effects are the direct or indirect result of the ejected debris as it rains through the atmosphere [e.g., Toon et al. , 1997; Kring , 2000]. These effects include shock-heating of the atmosphere as material reaccretes to Earth, affecting nitrogen chemistry, producing nitric acid rain [ Lewis et al. , 1982; Prinn and Fegley , 1987; Zahnle , 1990], and leading to the spontaneous combustion of vegetation [ Melosh et al. , 1990]; an enhancement of atmospheric opacity, causing surface temperatures to fall and preventing sunlight from reaching the surface where it is needed for photosynthesis [ Alvarez et al. , 1980; Toon et al. , 1982; Pollack et al. , 1983; Covey et al. , 1990, 1994]; enhancement of stratospheric sulfuric acid aerosols which also depresses surface temperatures and eventually leads to sulfuric acid rain

Michigan may be a bit inland to worry about tidal waves, but I wonder if sloshing Great Lakes could be an issue? The additional question being the level of seismic activity that will result, as the earth rings like a bell (Or a more apt analogy would be it jiggles like a water balloon?)

So (I assume) first you get the seismic action, then any local flooding, then chunks of molten rock falling randomly and setting the surrounding forests on fire, then the air itself overheating from all the hot debris…

The meteor captured by numerous dashcams and security cameras in Russia a while ago was believed to be about 5 stories tall in diameter, and apparently broke a lot of windows for a hundred miles or more around simply due to the shock wave - despite, as apparently an ice ball - not having a ground impact.

3

If the impact is big enough, yeah. You’d get earthquake like effects first as the shockwave would probably move faster in solids than in the atmosphere, but the air shockwave will arrive as well at some point. Such things generally move at the speed of sound in whatever medium carries the wave, and that tends to be higher in solids.

How far away the shockwave is deadly depends on the size of the comet that hits. Smaller ones probably wouldn’t cause world-wide immediate destruction, but over a certain size threshold, we’re all screwed.

4

There’s an Earth Impact Effects calculator on the web.

I tried one set on inputs, that seemed reasonable:

Distance from Impact: 8500.00 km ( = 5280.00 miles ) 
Projectile diameter: 7.50 km ( = 4.66 miles ) 
Projectile Density: 1500 kg/m3 
Impact Velocity: 51.00 km per second ( = 31.70 miles per second ) 
Impact Angle: 45 degrees 
Target Density: 1000 kg/m3 
Target Type: Liquid water of depth 2.5 km ( = 1.6 miles ), over crystalline rock.

The comet of Don’t Look Up is said to be 6-9 km in diameter, so I took the mean.

The effects seen in the movie are a bit exaggerated:

The major seismic shaking will arrive approximately 28.3 minutes after impact.
Richter Scale Magnitude: 9.7 (This is greater than any earthquake in recorded history)
Mercalli Scale Intensity at a distance of 8500 km:

    I. Not felt except by a very few under especially favorable conditions.

    II. Felt only by a few persons at rest, especially on upper floors of buildings.

Some of the debris kicked up by the comet then makes an appearance (probably at the upper atmosphere, as near as I can tell):

The ejecta will arrive approximately 47.8 minutes after the impact.
At your position there is a fine dusting of ejecta with occasional larger fragments
Average Ejecta Thickness: 117 microns ( = 4.6 thousandths of an inch ) 
Mean Fragment Diameter: 4.67 microns ( = 0.184 thousandths of an inch )

Then, they must have had a very long dinner, and were living in a very brittle house:

The air blast will arrive approximately 7.15 hours after impact.
Peak Overpressure: 3820 Pa = 0.0382 bars = 0.543 psi
Max wind velocity: 8.87 m/s = 19.8 mph
Sound Intensity: 72 dB (Loud as heavy traffic)
Damage Description:

    Glass windows may shatter.

It’s possible they were hoping for a larger effect from a larger impactor, but cut the size down in the script somewhat. Maybe I’ll play around with the calculator and see what size impactor would create a hurricane-force air shockwave in Lansing.

5

When I double the diameter of the impactor, I get:

The major seismic shaking will arrive approximately 28.3 minutes after impact.
Richter Scale Magnitude: 10.4 (This is greater than any earthquake in recorded history)
Mercalli Scale Intensity at a distance of 8500 km:

    III. Felt quite noticeably by persons indoors, especially on upper floors of buildings. Many people do not recognize it as an earthquake. Standing motor cars may rock slightly. Vibrations similar to the passing of a truck.

    IV. Felt indoors by many, outdoors by few during the day. At night, some awakened. Dishes, windows, doors disturbed; walls make cracking sound. Sensation like heavy truck striking building. Standing motor cars rocked noticeably.

Still significant, but probably a little less than what was in the movie.

But, the atmospheric shockwave is still less than deadly:

The air blast will arrive approximately 7.15 hours after impact.
Peak Overpressure: 10100 Pa = 0.101 bars = 1.43 psi
Max wind velocity: 22.8 m/s = 51 mph
Sound Intensity: 80 dB (Loud as heavy traffic)
Damage Description:

    Glass windows will shatter.

Redouble the diameter of the impactor (note that this is 64x the mass of the original impactor in Don’t Look Up):

The major seismic shaking will arrive approximately 28.3 minutes after impact.
Richter Scale Magnitude: 11.1 (This is greater than any earthquake in recorded history)
Mercalli Scale Intensity at a distance of 8500 km:

    IV. Felt indoors by many, outdoors by few during the day. At night, some awakened. Dishes, windows, doors disturbed; walls make cracking sound. Sensation like heavy truck striking building. Standing motor cars rocked noticeably.

    V. Felt by nearly everyone; many awakened. Some dishes, windows broken. Unstable objects overturned. Pendulum clocks may stop.

And when the wind hits:

The air blast will arrive approximately 7.15 hours after impact.
Peak Overpressure: 32100 Pa = 0.321 bars = 4.56 psi
Max wind velocity: 67 m/s = 150 mph
Sound Intensity: 90 dB (May cause ear pain)
Damage Description:

    Wood frame buildings will almost completely collapse.

    Glass windows will shatter.

    Up to 90 percent of trees blown down; remainder stripped of branches and leaves.

So that looks a little more like what the movie showed. But, from the calculator:

The average interval between impacts of this size somewhere on Earth during the last 4 billion years is 4.0 x 10^9years

(Edited to add the caret for clarity.)

This would be an impact of literally unique size over the history of the earth.

6

In Tanis, North Dakota is a fossil site that is believed to have preserved effects of the Chixalub impact in the Yucatan, Mexico. You might wish to read up on it in the link for some idea of what this would be like in real life.

From the link:

At Tanis, unlike any other known Lagerstätte site, it appears freak circumstances allowed for the preservation of exquisite, moment-by-moment details caused by the impact event. These include many rare and unique finds, which allow unprecedented examination of the direct effects of the impact on plants and animals alive at the time of then large bolide impact some 3,000 kilometers (1,900 mi) distant. The events at Tanis occurred far too soon after impact to be caused by the megatsunamis expected from any large impact near large bodies of water. Instead, much faster seismic waves from the massive magnitude 10 – 11.5 earthquakes….[snip]… probably reached the Hell Creek area as soon as ten minutes after the impact, creating seiche waves between 10–100 metres (33–328 ft) high in the Western Interior Seaway… [snip]…and perhaps in other waters nearer Tanis, which was near an ancient river. These waves carried sea, land, freshwater animals and plants, and other debris several miles inland. The seiche waves exposed and covered the site twice, as millions of tiny droplets and debris from the impact were arriving on ballistic trajectories from their source in what is now the Yucatán Peninsula

In other words, it would be a Very Bad Day Indeed.

Yes, that is a possibility.

Basically… yep.

Actually, there were rocky debris which have been acquired by various scientists. No doubt some also were sold on eBay.

Of course, exact effects depend on many factors, including overall size. As demonstrated by @SunUp

You mean, like the Theia impact hypothesis? If so, maybe we’ve gotten our one in and done during the Hadean Eon.

7

Not my area of expertise, but here is my understanding of it.

The dinosaur killer smacked down in Chixalub with enough force that debris from the impact itself (not stuff that was kicked up into the air and fell down later, but actual impact debris) has been found at least as far north as Kentucky. A huge shock wave spread out in all directions, eventually all converging on the point exactly opposite on the Earth from Chixalub, ripping the crust apart and causing huge volcanic eruptions. Hot debris starts raining down all over the Earth, catching the entire world on fire. “Hell on Earth” seems to be a pretty accurate description if you ask me.

A lot of dinosaurs manage to survive this part, but it’s a lot worse than just blocked sunlight.

The plants are all burned, and the plant-eating dinosaurs have nothing to eat. A lot of plants aren’t completely killed and start sprouting new growth, but the blocked sunlight you mention is definitely a big issue. Dust and debris kicked up from the impact plus ash from all of the new volcanic eruptions on the other side of the Earth pretty well choke up the atmosphere and don’t allow much sunlight to reach the surface. All of the crap in the atmosphere makes the rain acidic. The plants that survive regrow slowly. Plant-eating dinosaurs die from starvation. Meat-eating dinosaurs and scavengers initially have a feast. But then they run out of dead plant-eating dinosaurs and start dying off (and eating each other).

The largest species to survive are crocodilians up to about 3 feet in length, who manage to get through his mess partly because they can stay submerged for extended periods of time and were able to dive down and keep out of the raining fires of Hell, and partly because they can go for very long periods of time without eating.

I think conditions were a bit worse than what you were imagining. Much of the Earth died in the first hours of the impact. A lot died in the fires that came for days after. Sure, some things managed to survive for months and even years (and some to this day), but a lot of the Earth was dead just days after the impact.

The oceans didn’t burn (obviously) so death there took a bit longer. The lack of sunlight killed off the plant life, which then killed off the animals the fed on the plants through starvation, and so on up the food chain.

I haven’t seen the movie, but it’s my understanding that the movie contradicts itself. The scientists say that the asteroid is bigger than the one that killed the dinosaurs, but then they give a size that is about half that of the dinosaur killer.

8

Amongst other places. At $20 a gram it sold cheap, too. Some famous falls of ordinary chondrites go for hundreds a gram.

Here’s a nice adventure story:

9

The largest recovered piece was 540 kilograms, total recovered around 1,000 kilograms. (Note the photos of several dozen specimens at the bottom of the entry.)

https://www.lpi.usra.edu/meteor/metbull.php?code=57165

10

Yeah, the science of the movie is not good. (Also, the rest of the movie is not good.)

11

Coastal cities such as Detroit would be seriously sloshed, but Lansing’s in the center of the state, about 100 miles from the big lakes. Whether there would be enough overspill from east or west is an interesting question.

A very, very bad day indeed.

That’s what the movie seemed to be going for, despite the misstatements in size.

:open_mouth:

So, earthquake, yes, possibly worse than depicted; explosion - maybe, if the atmospheric shock wave was hot and deadly enough (or some local structure, maybe a gas station, exploded); possible flooding (not shown); overwhelming heat and fire (not shown). A very bad ending to the dinner party either way.

Thanks everyone for the replies!

12

(I didn’t see this movie.) What did these two astronomers suggest the people of the world should do, if everybody had taken the threat seriously?

13

The astronomers themselves weren’t advising a course of action. They wanted someone who could do something about it to try. The NASA Planetary Defense Dept ( the movie notes this is a Real Agency) does take it seriously and argues for action. The consensus was to send a fleet of nukes to hit the comet to either break it to pieces or veer it off course. This was an urgent and expensive mission and there was much arguing about who should do it and who should pay for it; but there was also much cynical argument about who could make what kind of political hay out of it. All of this delayed anybody doing anything until nearly the last minute. In the end, the US aborted their attempt to nuke the comet, claiming that it wasn’t that bad and there could be jobs generated from letting it land (seriously). A consortium of the EU, India, Japan and Russia also tried but the launch failed. A private company led by an Elon Musk-type character also tried and failed.
The movie is supposed to be satire but it was not nearly exaggerated enough when it came to portraying individual and government responses to a crisis. Perhaps it couldn’t be.