Aug 31 2012 3:00pm

Honey, I Shrunk the Kids and the Science of Scale

Honey, I Shrunk the Kids and the Science of Scale

As a parent, I feel it my duty to introduce my children to the classics of science fiction and fantasy. Arguably, some of the things we watch and read together are more classic than others, but all have their place in the spectrum of classic geekness. Interestingly, my kids immediately identified with the Szalinski family in the film Honey, I Shrunk the Kids (that’s the one with the nerdy dad whose crazy inventions littered the house and often resulted in smoke-filled explosions), while they thought that the sports-loving family next door seemed to be a bit weird—an observation that I must admit filled me with no small amount of irrational pride.

The next day while we were playing with Legos, one of my daughters announced that the movie we had just watched wasn’t very realistic. Interestingly enough, she had no problem with the plausibility of the main premise, that someone had invented a device capable of shrinking matter to an arbitrary size and had accidentally shrunk his children with it. Instead, her problem was that the scale of the film seemed to be inconsistent. This completely ruined her suspension of disbelief via an effect that John Scalzi has called “A Flying Snowman.”

Her reasoning was based on what she perceived as a logical contradiction between two claims made by the film:

  1. Nick, the apparent scientist-in-training of the film, calculates that they have been shrunk to just 3/4 of an inch high (around 19 mm).
  2. As the movie progresses and the children go forth on their tiny-sized adventures, one of the items they happen across is a toy block, which Nick identifies as a “Lego.” However the scale of this lego does not match the scale declared in the first statement.

Wanting to support her in this quest for truth, I took some screen captures of the film to make some calculations. The Lego in question appears to be a standard 2x3 brick (Lego element ID 300223), which the protagonists use as a safe-haven before being attacked by a giant scorpion.

If we assume that the block in the film is in fact a genuine Lego, and not some generic copy, the brick should be 23 mm tall when standing upright. Assuming Nick is in fact 19 mm tall as he claims, the brick he discovers in the film appears to be closer to 60 mm tall. This is about the size of a 2x8 brick, clearly not the one used in the film.

The next discrepancy we looked at was the relative size of “Aunty,” the ant they tame and then subsequently use as a mount. While ant sizes vary, the one in the film appears to be a little over five times as long as Nick is tall. This would place the ant at a little over 100 mm long. Considering the largest ant currently known (the fossilized Titanomyrma giganteum) was only 60 mm long, the ant in the film is unbelievably large.

Aunty the ant

The final discrepancy is the relative distance Nick calculates they need to travel to escape their back yard. He states in the film that since they are now 3/4 of an inch tall, the 64 feet they would normally have to travel is now the equivalent of 3.2 miles. Converting to metric, this is the equivalent of stating that 19.5 meters is now 5149 meters. This is an approximate ratio of 1:264. If we try to use the same ratio to calculate their original height, this would make their original height 19 mm x 264 = 5016 mm tall, an equivalent of 16 and a half feet.

Scaling Things Back

Can we attempt to reconcile these differences by assuming that Nick simply made a mistake in his calculations? If we take the Lego brick as a reference, knowing that it should be 23 mm tall and knowing that Nick’s head comes up about two-thirds of the way to the first post this would put Nick to be at 8 mm tall. This would put the ant’s size at around 40 mm, still a rather large ant for a North American garden, but well within the range of known ant sizes.

We could also assume that Nick’s size estimate is correct and that the block in the film is actually a Duplo block (still technically a Lego). A 2x3 Duplo block is 47 mm tall, which would fit the scale shown in the film. While this solves the child/block height discrepancy, it still leaves us with the problem of the gargantuan ant.

There are, of course, several possible ways to use science fiction to explain the overlarge ant. Perhaps the oversized ant is actually a result of experiments by Mr. Szalinski with the growth ray that is shown in the film’s sequel. Alternatively, it might not be an ant at all. It might just be an uncharacteristically kind-hearted Zanti.

Dr. Lee Falin is a Bioinformatician at the European Bioinformatics Institute, the host of the Everyday Einstein’s Quick and Dirty Tips podcast and the author of the “Science Fictioned” series, in which he takes scientific research articles and turns them into sciece fiction and fantasy short stories for middle grade and young adult readers. You can follow him on twitter at @qdteinstein.

2. olethros
Your daughter is indeed awesome. Reminds me of my niece.
Heidi Breton
3. AnemoneFlynn
I remember having some issues with the scale in that movie, but it was still pretty funny. :-D
Roger Powell
4. forkroot
As a parent, I feel it my duty to introduce my children to the classics of science fiction and fantasy.
Hopefully as a parent you also felt it was your duty to introduce your children to the proper conjugation of the verb "to shrink" :-)

(I'd still like to step on someone's fingers at Disney for that one.)

Sounds like you have a wonderful daughter - more power to you for exploring this topic with her!
Joseph Newton
5. crzydroid
Wow. As a kid, I never realized it should have been called, "Honey I shrank the kids." I always just accepted the title. Now that is going to bother me. What about, "Honey, the kids have been shrunk"? Or, "Honey, the kids are now shrunken." I know--"Honey, where is my super suit?"
Joseph Newton
6. crzydroid
Also, pretend those suggestions are all in title case.
7. Smario
I would also like to point out the size of the children towards the end of the movie, specifically the scene where they are in the bowl of cereal. If memory serves me well, the kids fit inside a Cheerio! That's much smaller than the 3/4 of an inch that you mention.
Chuk Goodin
9. Chuk
That is excellent but I've got to quibble -- a 4 cm ant would be way bigger than any ant I've seen in a North American back yard. Maybe a queen.
11. elli
I loved this article, but I feel the need to point out that Nick claims that they are 1/4 of an inch tall, not 3/4 (his exact words are "a quarter of an inch"). This would fix several discrepancies; for example, instead of 16.5 feet being their original height according to the original ratio calculations, the new calculations would put them at 5.5 feet. They would also be 6.35 mm instead of 19mm, which makes the 23 mm lego brick look far more realistic (relatively speaking), since it appears that four of them stacked up together could be close to that height.

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