IRA FLATOW: This is Science Friday. I’m Ira Flatow.

We begin with a consideration of human mortality pretty apt time to do that. Average global life expectancy rose by five years between 2000 and 2015, continuing our general trend of living longer as medicine advances in the fight against disease and infant mortality is making progress. But what about the limits of our lifespans?

Harvard researcher David Sinclair said, the first person to live to 150 has already been born. But new research published in Nature this week is a little less optimistic. Here with this story and other headlines is Popular Science senior editor Sophie Bushwick. She joins us in our QNE studios. Welcome back, Sophie.

SOPHIE BUSHWICK: Thanks.

IRA FLATOW: So let’s talk about it. How long have I got?

SOPHIE BUSHWICK: Well, so when they talk about this particular study, it’s distinct from average human life span. Like you said, average human lifespan has been increasing due to a lot of breakthroughs. But when you look at maximum human lifespan, that’s a different factor.

And so what these researchers did was looked at maximum human lifespan over time. And they found that it increased fairly steadily through from the 1970s through the 1990s, and then it sort of plateaued. And it’s been plateaued ever since. And this has led them to conclude that about 115 is probably the cap on maximum lifespan.

There will be exceptions. So the woman that we know of who has lived the longest lived to age 122. She died in 1997. But the researchers say, this is probably an exception. There’s going to be a few exceptions, but in general, the odds of someone living past age 120, any human on Earth, is going to be like one in 10,000.

IRA FLATOW: Wow. So she was an outlier, as they would say in statistics.

SOPHIE BUSHWICK: Exactly.

IRA FLATOW: Is this because of anything we’re eating, our nutritional habits or food or anything like that?

SOPHIE BUSHWICK: No. So what happens for a lot of the people who live to the longest amount of time, they tend to have survived the era when a lot of other people die of cancer or of a lot of diseases that strike the elderly. But the issue is that, as you age, your cells get worse at repairing themselves. And your body, in general, accumulates wear and tear and is just not as good at recovering from that.

And so when you die, it’s sort of death by 1,000 papercuts almost. Your body just reaches that point. And that’s what they think is causing people to die at 115. And that can’t really be fixed by eating a healthy diet.

IRA FLATOW: Could it be fixed if you have better genes, maybe, right?

SOPHIE BUSHWICK: Well there are other researchers who say, if we could have a breakthrough in treating that particular type of wear and tear and making the cells better at repairing themselves, that sort of medical breakthrough could increase that age.

IRA FLATOW: Let’s talk about something that’s on everybody’s mind this week. And hurricane Matthew, it reached Florida yesterday after killing lots of people in the Caribbean. It was briefly the first category 5 hurricane in the Atlantic since 2007. Why is this storm so deadly? And how do you rate this storm compared to others?

SOPHIE BUSHWICK: So the hurricane– yeah, it reached category 5, which has to do with wind speed. So the speed of the wind is what puts it in the category. And categories 4 and 5, at those wind speeds, it can cause devastation to– even well-built houses can be destroyed by wind moving at that speed. It’s now a category 3, and I think they’ve got maximum sustained winds of about 120 miles per hour, which can still do a ton of damage, but they’re actually expecting most of the damage is going to come from the storm surge caused by the hurricane.

That’s what caused most of the damage in Haiti. And that’s especially an issue, because the hurricane isn’t just moving onto land, it’s moving up the coast, it’s moving parallel to the land. So it can cause storm surge over a much longer stretch of shore.

IRA FLATOW: Makes me wonder, well, why don’t they include storm surge in the category rating? We have wind, maybe it’s storm surge if it does most of the damage. They should adjust those readings to include storm surge.

SOPHIE BUSHWICK: Yeah, maybe. I think it depends. Because this particular storm, again, moving parallel to the coast, that’s not the type of thing they would have a category 4. They predict how far up it will go, but they don’t– maybe they should start categorizing like what the length of shoreline that it damages will be.

IRA FLATOW: This is a very powerful storm, maybe it does conform to the climate change global warming models of maybe fewer hurricanes but more powerful ones.

SOPHIE BUSHWICK: It’s really hard, with those models, to tie any individual storm definitively to global warming. But yeah, it’s true that models of what happens– when the whole globe gets warmer, it affects a ton of different things around the planet. And yes, one of those is storms.

IRA FLATOW: Let’s talk about, this week was big for the 2016 Nobel Prize winners. We had medicine chemistry, and physics. You want to pick one out?

SOPHIE BUSHWICK: Well, I thought the medicine prize was really interesting. That went to a researcher who studies autophagy, which is– that literally means self-eating. And it has to do with how cells deal with damaged or unused parts. They can break them down, and they can use them to rebuild themselves or use them as food.

And so the really cool thing about that is, that’s controlled by genes. This researcher was looking at how genes affect autophagy. And to go back to the story about longevity, autophagy is one of the things that contributes to aging. And so learning more about it could, maybe, lead to the medical breakthrough that researchers are hoping will push up our maximum age.

But it also has to do– it’s involved in diseases, such as diabetes and, I think, Parkinson’s as well.

IRA FLATOW: Let’s just talk about chemistry. Anything of note?

SOPHIE BUSHWICK: Chemistry is really cool. OK. So chemistry is basically like very, very tiny machines made out of molecules. So it’s a molecule that, say, if you stimulate it with an electric current, it’ll start rolling across a surface. That example makes it sound more like a party trick, but these things are incredible. That can be used to find HIV, they can be used to target and kill cancer cells, they can be used in smart materials. These are materials that might be able to be self-healing. So there’s a ton of different really cool applications for them.

IRA FLATOW: Because we forget that chemistry is molecules, actually little objects.

SOPHIE BUSHWICK: Yep.

IRA FLATOW: That can move around and do sorts of stuff like that. And physics.

SOPHIE BUSHWICK: Yeah. So physics went to researchers who use a mathematical concept called topology to study these materials like superconductors and superfluids. So the superconductors a material where it’s got zero resistance when electrical current– electrical current can flow through it with zero resistance. And a superfluid is sort of like the fluid version, it’s a fluid that can flow with zero friction.

And by using topology to study them, the researchers have learned more about what makes a material transition into becoming a superconductor, becoming a superfluid.

IRA FLATOW: Yeah. Well, exciting stuff. I love topology, because it’s the science of why a donut is the same as a teacup.

SOPHIE BUSHWICK: I like that one too, yeah.

IRA FLATOW: It’s got one hole. All right. Thank you, Sophie.

SOPHIE BUSHWICK: Thanks for having me.

IRA FLATOW: Sophie Bushwick is a senior editor at Popular Science.

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