# Kaiju growth and development (need answer fast) **URL:** \ **Category:** Cafe Society\ **Created:** [May 23, 2022, 8:17pm UTC](https://boards.straightdope.com/t/kaiju-growth-and-development-need-answer-fast/964954 "2022-05-23T20:17:10Z")\ **Posts on this page:** 16\ **Page:** 1
**Author:** ![Chronos](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/chronos/32/134_2.png) [@Chronos](https://boards.straightdope.com/u/Chronos)\ **Post date:** [May 23, 2022, 8:17pm UTC](https://boards.straightdope.com/t/kaiju-growth-and-development-need-answer-fast/964954/1 "2022-05-23T20:17:10Z")
I’m writing a quiz for my Algebra II class, and I promised one of my students that there’d be a kaiju-related question on it. But I just realized that I don’t have the relevant information to write the question. What I ideally need to know: 1: How much does a newly-hatched Mothra larva weigh? 2: How much does the adult Mothra weigh? 3: How long is it between the larva hatching and it spinning its cocoon? Alternately, I could go with equivalent information for any other kaiju, but Mothra would be ideal. And because I procrastinated, I need to figure this out by tomorrow. Any help? ---
**Author:** ![GreysonCarlisle](https://avatars.discourse-cdn.com/v4/letter/g/a87d85/32.png) [@GreysonCarlisle](https://boards.straightdope.com/u/GreysonCarlisle)\ **Post date:** [May 23, 2022, 8:24pm UTC](https://boards.straightdope.com/t/kaiju-growth-and-development-need-answer-fast/964954/2 "2022-05-23T20:24:17Z")
I think that’s going to all depend a lot on which Mothra. [This site](https://wikizilla.org/wiki/Mothra) has a bunch of stats through the eras. ---
**Author:** ![Chronos](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/chronos/32/134_2.png) [@Chronos](https://boards.straightdope.com/u/Chronos)\ **Post date:** [May 23, 2022, 9:23pm UTC](https://boards.straightdope.com/t/kaiju-growth-and-development-need-answer-fast/964954/3 "2022-05-23T21:23:36Z")
Hm, that has figures for the larval form, but each source seems to have only one size for the larva, and it’s the growth that’s essential to the problem. Still, it’s a start, at least. And I’m also not seeing any timescales, there, though maybe I just didn’t look close enough. ---
**Author:** ![Qadgop\_the\_Mercotan](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/qadgop_the_mercotan/32/83_2.png) [@Qadgop\_the\_Mercotan](https://boards.straightdope.com/u/Qadgop_the_Mercotan)\ **Post date:** [May 23, 2022, 9:40pm UTC](https://boards.straightdope.com/t/kaiju-growth-and-development-need-answer-fast/964954/4 "2022-05-23T21:40:07Z")
I suggest you contact the [Kaiju Preservation Society](https://whatever.scalzi.com/2022/03/15/the-kaiju-preservation-society-out-now/) for more info. ---
**Author:** ![GreysonCarlisle](https://avatars.discourse-cdn.com/v4/letter/g/a87d85/32.png) [@GreysonCarlisle](https://boards.straightdope.com/u/GreysonCarlisle)\ **Post date:** [May 23, 2022, 9:41pm UTC](https://boards.straightdope.com/t/kaiju-growth-and-development-need-answer-fast/964954/5 "2022-05-23T21:41:06Z")
Imago is the fully grown Mothra. The eras are just when the film/book/videogame was made. The longest was the Showa era, which is basically the reign of Hirohito. Showa era: Length: Larva: 180 meters (original Mothra film) & 40 meters (Mothra vs. Godzilla and Destroy All Monsters) Imago: 80 meters (Mothra and Mothra vs. Godzilla) & 65 meters (Ebirah, Horror of the Deep) Weight: Larva: 15,000 metric tons (Mothra) & 10,000 metric tons (Mothra vs. Godzilla and Destroy All Monsters) Imago: 20,000 metric tons (Mothra and Mothra vs. Godzilla) & 15,000 metric tons (Ebirah, Horror of the Deep) And so on through the later eras. ---
**Author:** ![Chronos](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/chronos/32/134_2.png) [@Chronos](https://boards.straightdope.com/u/Chronos)\ **Post date:** [May 23, 2022, 9:46pm UTC](https://boards.straightdope.com/t/kaiju-growth-and-development-need-answer-fast/964954/6 "2022-05-23T21:46:30Z")
Right, that’s a single number for the mass of the larva. But the larva grows. It’s (presumably) smaller right after it hatches, and larger right before it forms its chrysalis. ---
**Author:** ![epbrown](https://avatars.discourse-cdn.com/v4/letter/e/e47774/32.png) [@epbrown](https://boards.straightdope.com/u/epbrown)\ **Post date:** [May 23, 2022, 10:27pm UTC](https://boards.straightdope.com/t/kaiju-growth-and-development-need-answer-fast/964954/7 "2022-05-23T22:27:18Z")
Fun book, but I’m a Scalzi fan. ---
**Author:** ![GreysonCarlisle](https://avatars.discourse-cdn.com/v4/letter/g/a87d85/32.png) [@GreysonCarlisle](https://boards.straightdope.com/u/GreysonCarlisle)\ **Post date:** [May 23, 2022, 10:49pm UTC](https://boards.straightdope.com/t/kaiju-growth-and-development-need-answer-fast/964954/8 "2022-05-23T22:49:08Z")
Ah, okay, I see. The twin larvae from Mothra vs. Godzilla were newborns, and the one from Mothra was fully developed and ready to cocoon. So I’m thinking newborns are around 40 meters and 10,000 tons, and the fully developed one was 180 meters and 15,000 tons. What might happen inside the cocoon, I have no idea. ---
**Author:** ![Chronos](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/chronos/32/134_2.png) [@Chronos](https://boards.straightdope.com/u/Chronos)\ **Post date:** [May 24, 2022, 1:25am UTC](https://boards.straightdope.com/t/kaiju-growth-and-development-need-answer-fast/964954/9 "2022-05-24T01:25:04Z")
Over quadrupling in length, while increasing in mass by only 50%, sounds implausible to me… maybe the square-cube law works in reverse for kaiju, and that’s how they can get so big? Still, I’ve found enough evidence to conclude that a factor of 3ish in linear dimension is a reasonable range for Mothra larvae, which (assuming constant shape and density) would mean a factor of 30ish in mass, and 20,000 tons seems to be a consensus value for the mass of an adult Mothra. And I’m not sure on the timeline for egg-to-chrysalis, but based on Godzilla: King of the Monsters (I think the only movie to show the entire lifecycle), a span of a week or two seems reasonable. That’s enough for me to come up with an at least vaguely justified problem. ---
**Author:** ![Atamasama](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/atamasama/32/12961_2.png) [@Atamasama](https://boards.straightdope.com/u/Atamasama)\ **Post date:** [May 24, 2022, 1:38am UTC](https://boards.straightdope.com/t/kaiju-growth-and-development-need-answer-fast/964954/10 "2022-05-24T01:38:00Z")
> [@Chronos](#): > > Over quadrupling in length, while increasing in mass by only 50%, sounds implausible to me… maybe the square-cube law works in reverse for kaiju, and that’s how they can get so big? They’re inflated with gas lighter than air, so the bigger they are, the less they weigh (proportionally). Hey, it would explain how Mothra can fly! (Basically a blimp with flapping wings.) That’s my WAG. ---
**Author:** ![GreysonCarlisle](https://avatars.discourse-cdn.com/v4/letter/g/a87d85/32.png) [@GreysonCarlisle](https://boards.straightdope.com/u/GreysonCarlisle)\ **Post date:** [May 24, 2022, 1:52am UTC](https://boards.straightdope.com/t/kaiju-growth-and-development-need-answer-fast/964954/11 "2022-05-24T01:52:13Z")
You can probably chalk the size problems up to Mothra having existed as an independent monster. When they paired her up with Godzilla, they had to drastically reduce her size so that the two of them would be roughly the same. Otherwise, she would have stomped on Godzilla and spent the rest of the film wondering what was stuck to her shoe. ---
**Author:** ![Chronos](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/chronos/32/134_2.png) [@Chronos](https://boards.straightdope.com/u/Chronos)\ **Post date:** [May 24, 2022, 9:55pm UTC](https://boards.straightdope.com/t/kaiju-growth-and-development-need-answer-fast/964954/12 "2022-05-24T21:55:32Z")
Well, the quiz was today, and the kaiju-fan student was in fact enthused and engaged by the question, so win there. For the record: > [@](#): > > At hatching, a Mothra larva has a mass of 1000 tons. It then grows exponentially, at a rate of 35% per day, until it reaches its full adult size. This can be described by the equation m(t) = 1000(1.35)^t, where m(t) is its mass in tons as a function of time, and t is its age in days. How long does it take it to reach its full size of 30,000 tons? I’ve also got one about Godzilla rampaging through Tokyo lined up for the final exam next week. ---
**Author:** ![Biggirl](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/biggirl/32/3294_2.png) [@Biggirl](https://boards.straightdope.com/u/Biggirl)\ **Post date:** [May 24, 2022, 10:12pm UTC](https://boards.straightdope.com/t/kaiju-growth-and-development-need-answer-fast/964954/13 "2022-05-24T22:12:24Z")
You are the best kind of teacher. _respect knuckles_ ---
**Author:** ![N9IWP](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/n9iwp/32/3154_2.png) [@N9IWP](https://boards.straightdope.com/u/N9IWP)\ **Post date:** [May 24, 2022, 10:21pm UTC](https://boards.straightdope.com/t/kaiju-growth-and-development-need-answer-fast/964954/14 "2022-05-24T22:21:35Z")
My answer: 1000(1.35)^t = 30,000 1.35^t = 30 t(log 1.35) = log(30) t = log(30)/log(1.35) ~ 11.333 Checking: 1000(1.35)^11.333 = 29,996 That was fun – thanks Brian ---
**Author:** ![abcdefghij](https://avatars.discourse-cdn.com/v4/letter/a/43a26b/32.png) [@abcdefghij](https://boards.straightdope.com/u/abcdefghij)\ **Post date:** [May 24, 2022, 11:44pm UTC](https://boards.straightdope.com/t/kaiju-growth-and-development-need-answer-fast/964954/15 "2022-05-24T23:44:55Z")
Nice effort, but you didn’t put any units on your answer. I don’t know about @Chronos, but I’d slam you. 😉 ---
**Author:** ![N9IWP](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/n9iwp/32/3154_2.png) [@N9IWP](https://boards.straightdope.com/u/N9IWP)\ **Post date:** [May 25, 2022, 12:14am UTC](https://boards.straightdope.com/t/kaiju-growth-and-development-need-answer-fast/964954/16 "2022-05-25T00:14:32Z")
You are correct, I should get dinged. Brian ( hangs head in shame)