With an estimated price tag between a hundred and forty and a hundred and sixty billion dollars, the fifteen year old International Space Station is, without a doubt, the most expensive thing ever built. Measuring a hundred and eight by seventy two meters, larger than an American football field, it is also easily the largest artificial satellite having taken sixteen nations more than thirteen years to build. But while we get a lot of so-called 'news' from the ISS, like about mission scientists playing Angry Birds in low gravity, or playing David Bowie covers, we don't hear a whole lot about the terrific science that's being done up there. But that changes today: here are just three of the many discoveries made aboard the ISS that you should know about.

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One of the most recent, and maybe most important discoveries, came in April 2013, when scientists announced that the space station's cosmic ray detector had observed particles that may confirm the existence of dark matter.

Dark matter, which appears to take up a great deal of the universe but we don't know what it is, has been perplexing scientists since its existence was first inferred in the 1930s. It's thought to make up about twenty three percent of all the mass energy in the universe, but it's never been directly observed because it doesn't emit or reflect light, and it's not composed of protons and neutrons like other matter is. Enter the Alpha Magnetic Spectrometer, or AMS, one of the final pieces of equipment installed on the ISS.

In just two years of operation, the AMS has detected billions of cosmic ray particles, particularly electrons and their antimatter counterparts, positrons. What scientists have discovered is that the AMS is detecting more positrons than electrons, and they're coming from all directions, not just from one particular place. This not only confirms that there's tons of antimatter out there, but it may also support the theory that positrons are formed not from specific places, like pulsars or other stuff that we can see, but by collision of dark matter particles everywhere, which we can't see.

Scientists have said that this may be the most important discovery in physics to be made on the ISS, but another obvious function of the space station is to study the long-term effects of living in space.

Space life has many pitfalls, and astronauts have been found to lose lots of bone density and muscle mass to the low gravity environments. But thanks to the ISS NASA has now learned that extended stays in space also places lots of stress on the eyes.

Researchers found that sixty percent of astronauts who have been in space for six months or more have suffered vision problems that got worse with time. Thankfully in most cases the problems went away once they were back on Earth, but doctors now suspect these and other ailments are caused by pressure on the eyes and optic nerves. Without normal Earth-like gravity keeping things moving, spinal fluid seems to build up in the brain, pressing on nerves and flattening the backs of eyes.

In early 2015 two crew members will begin a year-long stay on the space station to better understand long-term health effects, and because of this new finding, these and other astronauts may undergo regular eye scans and test out special eye glasses, to find out how future crews can keep seeing clearly.

And of course the final frontier of space is also meeting the final frontier of medicine: cancer research.

A lot of oncology studies have taken place aboard the ISS, thanks again to the unique micro-gravity setting. And much of it has focused on the technology of micro-encapsulation, which creates tiny tiny tiny tiny biodegradable balloons that can be filled with drug treatments or imaging dyes, and injected right at the spot of a tumor. This, unsurprisingly, has been found to work a lot better than sending stuff through a patient's entire body and hoping it lands in the right place.

Work in the ISS lab revealed that in low-gravity different fluids contained in these balloons can kinda hang together intact, instead of rubbing up against each other. This discovery has led to all kinds of patentable inventions that NASA has developed to reproduce this process on Earth, and it's now being used to manufacture the next generation of cancer treatments.

So a hundred and sixty billion dollars in thirteen years - nice to see that we're getting a return on that investment.

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