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Comment by aidenn0 | Hacker News Reader

Thousands of tons of bombs were dropped on Japan in WW2. Many of them didn't explode. This airport was apparently an active airfield at the time the US was bombing Japan and 500lb bombs were the sort of thing used to destroy parked planes.

Yes, someone could have snuck into an airport and buried a bomb underneath the runway, then cleaned up the digging operation so as to not be noticed, but horses, not zebras.

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They're just asking on what basis the article is confident that it's a specific bomb from a specific era. Is it based on a forensic analysis of the shrapnel, something like that? If it's just an assumption based on the context, you'd want to say "an explosion, believed to have been caused by an unexploded WWII-era bomb...".

In how many eras were bombs being dropped on this airport?

An explosion goes off under a runway. The article says "it's a bomb, it was dropped on the runway 80 years ago, buried with dirt, paved over, then it went off".

Cool. Now, how did you figure that out? Did someone analyze the shrapnel and conclusively date it to allied bombing campaigns in WWII, or is that what a source close to the events said, or did the reporter just... look at the picture and shoot from the hip? Any of these is an acceptable answer, so long as readers know which one it is.

If it wasn't from the war, then the more likely scenario is the bomb feel off a plane after the war than somebody snuck into the airfield. Bombs do fall off planes.

My question was more of, how do they determine this sort of thing or is it just an assumption because it is the most likely scenario?

You’re assuming the bombs like this were removed after the war. They weren’t. No one knew they were there.

We are still finding unexploded artillery shells from the first world war in France. Germans are still finding bombs in cities.

The chemicals in the fuses mix and become unstable over time. The explosives don’t degrade as much.

If you wanted further verification, the bomb casing leaves fragments and explosives leave residue.

I'm not doing anything of the sort. I know bombs are still there from WW2. Just because there are still bombs from WW2 does not mean that every bomb that goes off is from WW2. While it is likely that the bomb is from the war, I haven't seen what evidence they have confirming that. That is all I am asking for.

The evidence is likely simple deduction, as in asking "when was the last time this area was bombed" combined with the history of the airport (built for the military in 1943, later converted to civilian use) and also noting other unexploded bombs have been unearthed in the area.

For it NOT to be a WW2 bomb would mean somebody sneaking in another bomb and paving it under the runway without being noticed.

There is a perfectly plausible alternative. A bomb fell off a plane after the war. This happens from time to time and has even happened with a nuclear bomb!

Yes, and it results in a huge amount of paperwork. You can't just randomly show up at your destination missing a bomb - especially during peacetime. They'll be combing over every part of your flight path to find it.

It could've also been intentionally buried there by bored soldiers, or placed there by airport maintenance people as a prank, or ended up there due to a freak teleporter accident. Maybe it was even put there by Godzilla. Maybe the Infinite Improbability Drive spontaneously materialized it, together with a bowl of petunias.

If you find a bomb in an area which is known to have been bombed, without any evidence to the contrary it is pretty safe to assume it's there due to the bombing.

Sorry about that. The article obviously doesn't explain. Here's my thoughts on it.

I don't think they did any exhaustive research. They didn't have to.

You would be able to look at the crater and see sizable pieces of a military air-dropped bomb. Normal bombs don't disintegrate. If they send it to a lab they can tell what explosive was used in it, which will roughly tell you when it was manufactured. (Assuming they don't find a serial number.)

That by itself is hardly conclusive, but that completely changes when you find identical unexploded bombs buried in the same area.

It would be rather odd if somebody came along later and put the same kind of bomb used in WWII in the ground. When the bomb got there isn't that important.

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