The International Space Station,   or ISS, has been swinging above humanity’s  collective heads for almost three decades.

But it won’t be up there forever. Details are still a little vague,  but we’re all going to have to say Goodbye to the ISS sometime around 2030.

Personally, I will be buying a fifth  of bourbon and trying not to cry as the remnants of its metallic corpse crash into Earth’s spaceship graveyard in the South Pacific. But if the bourbon can’t console me, I can always think of all the weird  things the ISS taught us about reality. It turns out a lot of things don’t work  the same up there as they do on Earth.

From human cells, to spiders, to  goodness gracious small balls of fire… because safety first, people! So let’s break down five of the weirdest  discoveries we’ve made thanks to the ISS. [♪ INTRO] Scientists have a particular interest  in knowing what kinds of life can and can’t survive outer space environments. Horror movies are, sadly, not a reliable resource.

For example, they might focus  entirely on the lack of air or the extreme temperatures, and not at all on the cancer-causing radiation  that isn’t getting blocked. If humanity ever wants to try setting  up a colony somewhere as inhospitable as Mars…let alone terraforming it…we’re  gonna need to know where to start. Which kinds of life will have  the best chance of survival, to help give us the best chance?

Well, in a study published in 2025,  one research team attempted to answer this question by slapping a  bunch of moss to the outside of the ISS. I’m only kind of exaggerating. The team chose the species Physcomitrium patens, which is a cute little  kinda-palm-tree-looking plant that is used quite a bit  for scientific experiments.

It’s physiologically simple. We’ve sequenced its full genome. It’s known to be pretty dang good at  dealing with environmental stress.

What’s not to like? The team also chose to investigate  three different forms of the moss, representing three different life stages. First, there’s protonemata,  which are chains of cells from very early in the reproductive process.

Then, brood cells, which act like spores. And finally, sporophytes:  reproductive structures that basically “give birth” to spores. All these mossy cells were placed in a small, box-like container with a  mesh window for exposure, and attached to a special platform  outside the station’s module called KIBO.

Not with a spacewalk, but with  the space station’s robot arm! Then, they were left out in space for nine months. Different samples were  subjected to different aspects of a standard space environment…  like the general vacuum of it all, the extreme heat and cold, and perhaps most  damaging of all: ultraviolet radiation.

And while neither the protonemata nor the  brood cells survived the full experiment, a significant number of the sporophytes did. A full 99% survived the vacuum of  space, 81% survived the freezing cold, 36% survived the high heat, and 27%  survived the ultra-damaging UV-C rays. You can’t even get UV-C rays  down on Earth’s surface.

They’re the ones our atmosphere blocks out. Which is why your sunscreen only  worries about the A and B types. But that’s not all.

After the surviving sporophytes  were brought back to Earth, 80% of the spores cocooned inside them germinated. Not only did they live, they lived  enough to carry on a new generation! Now, granted, even multiple generations of moss aren’t the most complex life forms in the world.

They’re not even the most complex  plants we’ve brought to space. In fact, humanity’s done a lot  of research on plants in space. It’s mostly crop plants, because if we ever  intend to live anywhere other than Earth, or take really long space journeys,  we’ll need crops to feed ourselves.

But because of their simplicity,  mosses can help scientists set a solid baseline for how plants in general  may fare in a spaceship’s tiny garden… or on the surface of another planet. Certain mosses are also  quite hearty here on Earth, so they have the potential to  survive in more hostile environments than complex plants like crops and trees. So if we can’t get a crop growing on  our first fancy lunar research base, we could at least ship some  moss up to help make oxygen.

But even if we never wind up  colonizing the solar system, this research isn’t useless. Testing plants’ hardiness in space  can help researchers figure out how resistant they can be to the  effects of climate change on Earth… which you may have noticed  has become a bit of a problem. So wherever future humans have to live, today’s space moss can teach us how to  survive whatever tomorrow’s deal is.

Unless tomorrow reveals we’re  living in a horror movie, and the monster is space-mutated moss. Stem cells are the building blocks and  maintenance crews of almost all our tissues. Not only are they great at  making more of themselves, but they basically start as blank slates.

Then when given the right chemical signal…BAM! They transform into a new,  more specialized type of cell. If scientists can harness that  power for medical treatments… say, to regrow a patient’s damaged organ… we could have an absolute  game changer on our hands.   Now, the stem cells inside of you right now aren’t as blank slate-y as you’d find in a newborn baby.

After all, the latter ones just got  done cooking, metaphorically speaking. For example, a newborn’s cardiovascular  progenitor cells, or CPCs, can create a greater variety of  cardiovascular cells than adult CPCs. But what if we could convince  those adult CPCs to dream bigger?

Not necessarily all the way to the  true blank slates you find in embryos… which have to build a body from scratch… but at least regain the  options of a newborn’s CPCs? Space could help with that. According to a paper published in 2021,  if you bring adult CPCs to the ISS, and let them chill in microgravity for a month, they will change to resemble something  closer to that newborn state.

Thanks to all kinds of pathways for  chemical reactions and signals opening up, the cells got even better  at replicating themselves and differentiating into  other cardiovascular tissues. One might say the stem cells got even stemmier. Now, do we know for sure why this happened?

Unfortunately, no. Scientists have a few ideas,  and they observed some related genes getting turned on and off. But there’s no concrete answer yet.

We also don’t know how to replicate this on Earth, to bring about a revolution  in stem cell treatments. But maybe, if scientists can figure out  what exactly makes those genes flip on and off, they could make progress on growing  replacement organs from cell cultures. After all, it’d be great  to circumvent the crucial, but frustrating bottleneck that is organ donation.

If this study is the first  step, we’ll be on a path to sci-fi space organ replacements in no time. Now just like the ISS, SciShow  needs funding to keep running. So here’s a quick ad.

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Brilliant’s also given our viewers 20%  off an annual Premium subscription, which gives you unlimited daily  access to everything on Brilliant. You’ve probably heard of the three main  states of matter: solid, liquid, and gas. You’ve also likely heard  of a fourth state: plasma.

The Sun kind, not the blood kind. But scientists have identified  way more states than four. Including Bose-Einstein condensates, or BECs.

A BEC emerges when some gas gets so cold, the weirdness of quantum physics starts  playing out on macroscopic scales. What do I mean by that? Well, in quantum physics, each  particle has its own quantum state, which has nothing to do with the states of matter.

Basically, a particle’s quantum  state is a complex math equation that describes everything about that  particle, like its position and its spin. Meanwhile, all particles of the same  type…such as every single electron… are interchangeable with one another. So if you collect a bunch of the same  particles that are also sharing the same state, they’ll wind up amplifying the  quantum behaviors of just one of them.

In a BEC, instead of thousands of separate atoms, they all collectively act like one large atom. And scientists can use them to observe  some weird fundamentals of reality, like how each bit of matter  is both a particle and a wave. But creating and maintaining a  BEC is easier said than done.

For one thing, when I said “cold”, I meant “hovering just above absolute zero,”  which is tricky to achieve on Earth. For another, after you’ve got your BEC,  one standard experiment requires you to then monitor its particles during free fall. And when you’re in a lab on Earth, you’ve got like 1 second of observation time, max.

Lucky for scientists, the ISS  has the Cold Atom Lab onboard, which solves both those problems. The Cold Atom Lab is sometimes called  the “coldest spot in the universe”. And it’s a multi-step process to get it that way.

It starts with laser cooling:  trapping atoms in the middle of six lasers until they stop vibrating so much. It’s kind of like how if you push  a kid on a swing at the wrong time, they’ll slow down instead of picking up speed. Then, the lab switches off the  lasers and turns on a magnetic trap to hold the newly chilled atoms,  which is carefully tuned to allow the hottest of those  uber-cold atoms to evaporate away.

Finally, it turns down the  intensity of the magnetic trap, and allows the atoms to spread  out and get even colder. In the microgravity environment of the ISS, scientists can push this  further than they can on Earth. They can cool things down to less  than one billionth of one Kelvin… all from the remote comfort of NASA’s Jet Propulsion Laboratory in Pasadena, California.

Meanwhile, microgravity also helps  the atoms to stay in free fall longer, giving scientists much more  time to study their behavior. We don’t just want to study BECs to better understand quantum shenanigans, of course. There are potential practical applications, too.

Like inside superconductors that  transmit electricity without energy loss, or the lasers in atomic  clocks that keep everything from the clocks on your phones  to GPS working properly. But for even more shenanigans, let’s move on to our next subject of  scientific investigation: spiders. You may personally have issues with spiders, but I think they’re cool even when they  aren’t giving teenagers superpowers.

And just like Spider-Man in  1972’s Marvel Team-Up #54, several real spiders have  been launched into space. Technically, the bad guys were  trying to launch the Hulk into space, and Spidey was just there to stop them. Don’t worry; he got rescued, eventually.

For a long time, scientists  have known that spiders decide how to orient their webs using gravity. But they wanted to test if gravity  was the only guide they used. Hence, the sending of spiders to a space station.

Which, much like studying a  BEC, is easier said than done. The first spider astronauts arrived  at NASA’s Skylab station back in 1973. But someone forgot to pack  any food for the spiders, so the human astronauts couldn't  tell if the weirdly shaped webs were because the spiders were in  microgravity, or just starving.

Researchers tried again in 2008,  bringing two spiders to the ISS. The experiment featured one adult  spider and a juvenile backup, along with colonies of fruit  flies for them to munch on. Unfortunately, the backup  spider somehow escaped its cell, and joined the first spider so no  one could tell whose web was whose.

Not that it even mattered, because the  fruit flies wound up reproducing so fast, the sheer mass of them blocked  the view inside the cell. But finally, in 2011, scientists  got their spider experiment to work. They took two golden silk orb weavers to the ISS, leaving two more on Earth as controls.

The species they picked is  known to make asymmetric webs, which would make it easier to notice  any differences in orientation. By the way, the astronauts who  took care of the two spiders nicknamed them “Esmeralda” and “Gladys.” The experiment setup was improved to avoid both cross contamination and fruit fly overload. And after a 2-month observation  period…and 56 space-based webs… the team learned that in the absence of gravity, spiders will use light to orient  both their webs and themselves.

The spiders seemed to treat the direction  of light as “up” and the other as “down,” implying they instinctively  knew that light meant “up.” While it might sound weird for spiders to  have a Plan B for when gravity seemingly disappears, remember that bodies are  fallible…be they human or spider bodies. It makes sense they evolved another  system that can take over if the gravity-sensing one fails, or to  work in tandem for extra support. However, a whopping two space-faring  spiders is a pretty small sample size.

We’ll need a lot more if we want to  make certain this is a real “thing”... and not just an Esmeralda and Gladys thing. To be fair, pretty much everything  acts weird in microgravity. Including fire.

Which apparently burns cold. In a 2012 experiment called FLEX, astronauts set small droplets of heptane fuel on  fire and let them burn themselves out. The goal was to better understand  how to extinguish fires, and they chose heptane because:  1) it’s relatively simple, 2) it’s very well-studied,  and 3), at least for a while, scientists thought it may have been  a good ingredient in some kind of substitute…or “surrogate”, to use the  technical jargon... for gas or diesel fuel.

How this work will transfer  to other fuels, we don’t know. But you gotta start somewhere. During the experiment, the crew saw  the burn, and then saw the extinction… but their instruments revealed  there was an invisible flame that kept going until it  finally snuffed itself out.

It turns out, the camera was  capturing a kind of burning known as cool-flame chemical heat release. Which isn’t really that cool  from a human perspective. A cool flame burns around 600 degrees Celsius, but that’s nowhere near the roughly  2000 degrees you can measure in a flame burning your typical hydrocarbon fuel.

Under ideal conditions, at least. While scientists knew heptane  could produce a cool flame before the much hotter visible flame, getting  one after was a complete shock. This sparked a whole bunch of excitement  around space-based cool flames, and in 2021, researchers  were able to get a gas-fueled cold flame to burn in space for the first time.

One day, cold-flame research  could lead to more efficient and less polluting engines, turning the  same amount of fuel into more power. And of course, understanding  how fuel is secretly burning will keep astronauts safer, as fires  can get very dangerous very quickly in the tight quarters of a space station  floating in an empty sea of death. With so much weird and wonderful  science coming from the ISS, it's a bummer that we have to  say goodbye to it in a few years.

But there's still plenty of time for  scientists to make even weirder discoveries. [♪ OUTRO]