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Deleted the Artistic License – Physics discussion of Gus being blown off the comet is actually not correctly represented.
The actual dialog is "he's at 1000 feet altitude and has reached escape velocity".
Escape velocity on something as small as the comet in question is less than 10m/s. Traveling 1000 feet (300 meters) in a couple of seconds (the time shown in the movie) requires an acceleration of only equivalent to a couple of "g". The section also severely over-estimates the amount of force applied to the astronaut's suit by the gas pulse.
The depiction is close enough to how it would actually happen to be reasonable. The primary error is the "1000 feet" one, which would more properly be 100m or so. But it's no so off of reality that this trope applies (since only a very, very technical reading would possibly consider this somewhat incorrect).
Also deleted the Imperial Stormtrooper Marksmanship Academy entry. The missiles didn't miss. They were simply stated to not succeed, which in this context, means that while at least some of them hit, the effects of surface-detonations of nukes on the comet wasn't enough to make any difference.
If anything, this would be No Sell.
Deleted some Natter that violated Example Indentation from these trope listings.
Outrun the Fireball
Deleted the following from trope entries because they have nothing to with the trope.
Made of Explodium
This entry has some valid points, but it is long, rambling, and filled with Natter. Can someone more attuned with the science behind it clean this one up?
1. The gas on the comet isn't igniting. It's changing from a solid to a gas state, and obviously expanding rapidly. Technically, it's sublimating - moving from a solid to a gaseous state without first becoming liquid. The depiction is *entirely* scientifically correct as to what would happen
2. The nuclear bombs were quoted as 5,000 kilotons, or 5 Megatons. However, the ship is several DOZEN miles away (if not closer to 100 miles) when the detonation occurs, so, realistically, there should have been virtually no physical damage to the spacecraft except from very small debris of which very little should have hit the ship. The transmission interruption due to EMP is very correctly handled, though.
When it comes to the physics behind the separation of the comet into 2 chunks, it's a bit hard to evaluate. We're not told exactly how deep the "moles" went, and while 5MT sounds like a lot, a 7-mile-diameter comet has a *LOT* of mass. Presuming they got the fracture points right, the cleaving is entirely reasonable. When it comes to the ICB Ms, they're mostly useless, because merely detonating something on the surface (which is what the ICBM would do) absolutely wouldn't have much effect on a large solid mass. To use the analogy from another movie: put a firecracker in your open hand. When it goes off, it's likely to hurt but not severely damage your hand. Now, hold that firecracker in a closed fist. When it goes off, you're gonna need a whole new hand.
3. Phil's (mostly) incorrect about the effects of a pulverized comet. The main issue, of course, is how far away from the Earth the comet was when detonated - it's extremely hard to tell from the movie, but let's assume it was several minutes from impact (otherwise, flying the spacecraft into it is pretty much impossible). That puts the comet inside the lunar orbit, but still several tens of thousands of miles up. At that distance, a significant portion of the mass of the comet is going pushed AROUND the earthy due to the internal explosion. Even better, the total mass that does hit the earth is going to be: (1) made up of small fragments, and (2) spread out over a larger period of time (dozens of seconds) than the single comet.
While you're likely to have a "shotgun" effect on the earth - meaning that the footprint of actual strikes would be significantly greater - only a tiny portion of the mass would make it through the atmosphere to actually impact. So, rather than a huge billion-ton comet striking the surface, there'd be dozens of single-digit ton and below chunks hitting the surface. That's still bad - you'd end up with what looks like dozens of 1MT nuclear blasts covering a million square miles or so. But that's far, far, far better than the 20,000,000 MT explosion that intact comet would cause.
As to "dumping kinetic energy into the atmosphere" thing: the large portion of the fragmented comet does convert kinetic energy into heat while entering the atmosphere. But a significant portion is converted into light energy. It also matters a great deal that that energy is transmitted much more slowly and over a vastly larger volume than a solid impactor: so much so, that we're talking a dozen orders of magnitude difference. It's still a very significant effect, and yes, it would have major climate implications. But it's ludicrously better than a massive impactor.
4. Impact-produced waves are not any different than typical tsunamis. Here's a decent projection for a strike in the Eastern Atlantic: http://news.ucsc.edu/2003/05/355.html Note this was for a meteor about 1% of the volume of the comet in the movie. 1km+ height tsunamis across the Eastern Seaboard are entirely realistic.
And, no, waves aren't noticeably restricted by gravity or friction. The restriction is pretty prosaic: the total volume of water in the tsunami, and the height of the land being inundated. Due to the relatively flat nature of most of the Eastern Seaboard, particularly from Maryland southward, it's entirely likely that a 1km tall tsunami (which is likely a wave 25km or more deep) would travel up to the foothills of the Appalachian Mountains, or 200km+ inland.
Also, a major impact-caused tsunamis in the Atlantic Ocean would likely devastate pretty much all civilization within 100km of ANY place that had a coast with the Atlantic Ocean. That's the entire Eastern shores of North, Central and South America, the entire Caribbean island chain, Iceland, the British Isles, Western Europe, and the West Coast of Africa. In other words, roughly 10% of the world's population, and close to half of it's total wealth.
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