Venerable entertainer and mechanical engineer Bill Nye — famous for his schtick as “the science guy” — returns to Netflix on Friday, Dec. 29, for season two of his Emmy-nominated series “Bill Nye Saves the World.”

Nye leads the empirical resistance to our anti-science cultural moment with 12 episodes structured around a specific topic and special guests. The season examines computer hacking, sleep science, superbugs, extinction and time travel, with guests like comics Drew Carey and Tim Meadows; the rock band OK Go; astronaut Scott Kelly; “Jackass” star Steve-O; and actor/filmmaker Zach Braff. But first, the scientist focuses on marijuana.

Guaranteed to make Twitter go nuts, Nye visits a medical cannabis retailer, takes a trip through hemp history and talks cannabis policy with film director and proud pothead Kevin Smith, as well as a medical researcher and a Washington state marijuana regulator.

The Chronicle talked to Nye before season two’s debut.

Q: What did you learn taping the cannabis episode?

A: I didn’t really know what “Schedule 1’” meant ... I also didn’t really know the history of marijuana becoming Schedule 1, and I didn’t really know how the medical profession feels about marijuana.

Q: What does Schedule 1 mean? What is its history and how do doctors feel?

A: Schedule 1 means it’s addicting and presumed to have no medical value. But people use marijuana for everything medically and there’s questions about how it affects you when you’re young, like drinking alcohol. So we investigated this, and the upshot is if anybody tells you he knows all about marijuana and how it works, he really doesn’t.

Q: Dr. Sanjay Gupta and former U.S. Surgeon General Joycelyn Elders have said that cannabis science has been systematically politicized and institutionally misrepresented. Given what you’ve learned, what do you think?

A: Oh yeah, marijuana was made Schedule 1 to oppress or suppress poor people. That’s pretty well-documented. That was certainly, in the last 40 years, the intent. But in George Washington’s time, it was used as legal tender. You would buy and sell the marijuana species as the reefer of the realm. So things changed for economic reasons mostly.

Q: What would rational cannabis policy based on science in America look like to you?

A: I think three or four things: We have to do research to find out what (marijuana) really does. Nobody is exactly sure what tetrahydrocannabinol does. No one’s exactly sure what cannabidiol does. But perhaps because of a genetic configuration, certain people become addicted to it. Then there’s also substantial evidence that young people’s brains are modified by smoking a lot of dope. And there’s no question that men’s sperm is affected by marijuana smoking.

Then I, as taxpayer and voter, would very much like to have some way to assess or evaluate driving while high.

You’re intoxicated in a different way than alcohol. Does it make you drive slowly, as every standup comic would have you believe? Or does it make you react slowly, which would be bad for traffic writ large. That needs to be researched. No one knows.

I will say also as a taxpayer and voter, I hope it doesn’t become so readily accepted that people smoke all the time the way they used to smoke cigarettes, and the smell of marijuana smoke is in everything the way it used to be when I was growing up.

Q: Did you have any personal experience with cannabis growing up?

A: I smoked it once, and I didn’t get high. I haven’t learned to smoke anything very well. ... I just was too uptight to have anything happen.

Q: Did you get to go into any dispensaries for this season?

A: I went online and got a license in California, and I went to a dispensary and bought dope on camera. It went fabulous. Got advice from a sales associate, and somehow the question came up of whether a pothead would like this type or that type of marijuana, and I asked her, “What is a pothead?” And she said, “Anyone who doesn’t know how much marijuana they consume.”

Q: Did the dispensary experience meet your expectations?

A: Yeah. The room is very secure. You have to pass through sort of an airlock to get in and out, there’s cameras everywhere and security guards, and it’s a for-profit business — wow, the amount of tax dollars. On the episode, we have a guy from the Washington state Liquor and Cannabis Board, and his message was, “We legalized it in Washington state in 2012, but the sky hasn’t fallen.”

Q: What about these days — do you enjoy a glass of wine or ...

A: Yeah, yeah, but there’s some difference between alcohol and marijuana, because you can test for alcohol. Because it’s so “missible” — as we say in chemistry — in water, you can test for alcohol a day later and, except for liver damage, there will be no readily apparent effects of it. It’s not detectable in your blood whereas marijuana is in your blood apparently for two weeks at least. And then if you’re a regular user, it’s longer than that. Is that good or bad? I don’t know. They need to study it. I mean, DDT is in my system apparently because I breathed a lot of it as kid and look, I’m fine.

Q: How did the Kevin Smith panel go?

A: Kevin Smith tells his daughter that she’s only going to smoke with him and the weed that he buys. I don’t know if that’s good or bad, it’s just certainly a well-intending father. ... This ones going to be like the sexuality episode from the last season: Everybody is going to be talking about it.

Q: What do you hope people take away from the episode on marijuana?

A: That we need to study it more. It’s not well-understood. We’re passing laws or not passing laws because of presumptions and assumptions about marijuana — some of which have just got to be wrong.

Q: Are there any parallels with other politicized science in America these days?

A: It’s different than climate science, which has been suppressed by the fossil-fuel industry because they want to keep burning fossil fuels. They’ve introduced the idea that there’s doubt about the science of climate change, whereas marijuana laws are passed because of certainty about the science of marijuana. But as Mark Twain said, “It’s not the things that you don’t know that get you. It’s the things that you’re absolutely sure of that can lead to trouble.”

David Downs is The San Francisco Chronicle’s cannabis editor. Email: ddowns@sfchronicle.com Twitter: @davidrdowns

“Bill Nye Saves the World”: Talk show. Season two available Friday, Dec. 29, on Netflix.