NARRATOR：

Listen to part of a conversation between a student and the professor of his history of technology class.

MALE STUDENT：

Would it be OK to focus on something related to agriculture?

FEMALE PROFESSOR：

Sure, farming technology is fine, as long as it's premodern.

But this isn't a long paper, so you're gonna need to pick a specific area of premodern agriculture, like, um, irrigation... or food crops of ancient Greece...

MALE STUDENT：

I'm actually interested in hydroponics.

FEMALE PROFESSOR：

[Unsure, without enthusiasm]Hydroponics... growing plants in water instead of soil...

MALE STUDENT：

Well, not in pure water-in water that has the proper mix of nutrients.

FEMALE PROFESSOR：

O-OK, but... is it a premodern technology?

I mean, hydroponics isn't really my specialty, but from the research I've read, we're talking the nineteenth century... maybe the seventeenth century, if you really stretch it.

MALE STUDENT：

[Not trying to say “gotcha”]Oh? But the Aztec civilization back in the thirteenth century in... basically where Mexico City is today...

An article I read said the Aztecs were using hydroponics in something they called... I've got the word right here... um...[A bit hesitantly] Chinampas.

FEMALE PROFESSOR：

Chinampas-the so-called floating gardens...

MALE STUDENT：

Exactly! So, yeah, the chinampas... The article said, very clearly, these floating gardens are proof that the Aztecs invented hydroponic farming.

FEMALE PROFESSOR：

Well, chinampas are artificial islands, built up in shallow lakes-islands made from packed earth and weeds, and, uh, material from the bottom of the lake.

They may have appeared to be floating in the water, but in fact they reach all the way to the bottom of the lake.

So the primary growing medium-what the plants draw nutrients from-is actually soil, not water.

MALE STUDENT：

So the article was wrong about that. Too bad. It seemed like a great topic, but I guess...

FEMALE PROFESSOR：

Wait a minute. Uh, just because chinampas were not technically hydroponic... doesn't mean this couldn't be an appropriate topic for your paper.

Chinampas were still a great premodern technological achievement.

I mean, they enabled the Aztecs to grow plenty of food... in an area without much available farmland.

MALE STUDENT：

But I wonder why the author wrote that chinampas were hydroponic?

FEMALE PROFESSOR：

Well, it's pretty common for writers to generalize-say, use a term like "hydroponics" to describe other types of agriculture.

Personally, I'd never say "hydroponic" except for plants growing in liquid.

The crops on chinampas definitely benefitted from the water surrounding them, [doubt, questioning] but hydroponic?

MALE STUDENT：

OK, so I'll go with chinampas, but leave out the "hydroponics" part...

FEMALE PROFESSOR：

Actually, there's an important lesson here: we should pay attention to what happened in history, but also how historical events are presented.

Why, for example, would writers use a word like "hydroponics" so casually?

MALE STUDENT：

I guess 'cuz it's a popular topic people wanna read about?

FEMALE PROFESSOR：

Or... to help modern-day readers understand something historical, maybe these writers think a familiar frame of reference is needed.

MALE STUDENT：

Well, that article was in a popular magazine, not a scholarly journal for historians.

FEMALE PROFESSOR：

OK, but historians sometimes do the same thing.

MALE STUDENT：

So I guess then that all historians might not describe chinampas in quite the same way either.

FEMALE PROFESSOR：

Good point. Why not look into that too? ... and include it along with your description and analysis.