Huh, I knew that polycarbonate was tougher (hence my surprise that it wasn’t what was used-- Maybe it was too expensive?), but I didn’t know that Lexan was polycarbonate.
And yeah, glass can end up with some really weird internal stresses and hence failure modes, but I don’t think that either of the plastics under discussion is subject to the same sort of thing.
I read the story on CNN or NPR. Some of the fish survived in puddles of water and were moved to other tanks.
Glass has a very small elongation before breaking, and it’s subject to cracking in a very bad way. It’s very rigid and its cracks concentrate a great deal of stress at their advancing edges. It’s not very tough, meaning it doesn’t take a lot of energy to break. Glass artifacts have come down to us from thousands of years ago in fairly good condition, but they can be destroyed in a millisecond from this sudden failure mode.
Acrylic is somewhat the same way, though it’s much less rigid and has a bit more elongation before break I think. Still, if you hit it with a hammer, it can shatter.
Polycarbonate is much tougher. As a first approximation, I think it’s fair to say you can work with it like you’d work with aluminum, bending and drilling and hammering on it. It’s really a very versatile mechanical engineering material, tough enough that they make boat propellers out of it. Like steel, it has the desirable quality that it doesn’t usually fail suddenly, it fails a bit gradually so you can often mess it up without causing an accident in the process (I mean your bicycle will bend but it won’t drop you on the pavement without warning). Though, it does have a sort of Achilles heel, in that there are many solvents that will attack it and cause its structural failure, so you have to be careful about that. Acrylic is somewhat the same way but not quite as bad. Just like you have to worry about glass and acrylic shattering, you have to worry about polycarbonate getting attacked.
And they use both acrylic and polycarbonate for making glasses. They have different advantages.
Possibly there have been energy-saving measures in place, what with the energy price crisis? If it’s an atrium open to the public with doors opening and shutting repeatedly…
Sure, but that’s all normal material properties. Extreme values for some of the numbers, maybe, but everything you said can be summarized by a short list of numbers. What’s really unusual about glass is its inhomogeneities: You can have a glass object that has really high toughness on most of the object, but one small spot where it’s vulnerable to even the slightest trauma. Prince Rupert’s Drops are the most extreme example of this, but all glass objects have a tendency towards this effect to some degree. That’s what leads to things like a table that’s survived being a table for decades, suddenly shattering when you open a door, or a plate that’s survived unharmed from being dropped multiple times, but then breaking when you were just lifting it into the cupboard.
All of this is probably irrelevant, though, since the aquarium wasn’t glass.
Wow, you’ve met? Cool. Nobody talks about Prince Rupert’s Bottles (you can use them to hammer nails, but drop a grain of abrasive into the bottle and it atomizes itself), or the drops.
There are some wonderful high=spreed videos of Prince Rupert’s Drops disintegrating on YouTube
From what I’ve seen, it’s an atrium where the definition is an outdoor space between buildings.
It wasn’t in an indoor heated space.
I have actually been there. And no, you are incorrect. It’s an indoor lobby type atrium.
As you had seen it, a question: from the before photographs it looks like that lobby was used for breakfast seating and the breakfast buffet of the hotel. Was that the case? The aquarium burst at 5:43 in the morning; it does not bear thinking if it had happened two hours later with the breakfast crowd present.
When we walked in the main doors, the approach to the base of the aquarium cylinder (where you board the elevator) was controlled with maybe ten to twelve meters of velvet queueing rope. On the right, there was a restaurant, with most of the seating inside, and a few tables outside the restaurant wall, inside a cordoned area. I can’t say whether the restaurant was associated with the hotel, but it looked like a pretty conventional lunch-and-dinner joint, not a breakfast buffet.
I really liked that acuarium, I used to go there every now and then when I happened to be close to the Alexanderplatz. Truly spectacular. So sad for the fish, but at least there were no tourists in the lobby, no divers in the tank itself and nobody in the elevator.
I can guarantee that there was no freezing involved, it was a big atrium in front of the hotel, but closed to the weather. And 1000 m³ of salty water do not just freeze when the temperature drops to minus 5°C outdoors during a night or two. The temperature of the water was of course controleld for the sake of the fish. Tropical fish.
As I said: very sad.