On March 22, 2015, one astronaut took on an out-of-this-world mission for one particular reason – to see how he ages onboard the International Space Station (ISS). Astronaut Scott Kelly traveled to the ISS for 342 days while his twin brother, Mark, stayed on Earth. At the end of the experiment, Scott returned to Earth both younger and older than his brother. How? Because time runs slightly faster on the ISS due to a weaker gravitational pull, and the effects on the human body in space are slightly more damaging, Scott aged faster. At least, that’s what this particular experiment concluded. Do we really age faster in space than on Earth? What variables determine this?
Location, Location, Location
How fast time flies, and the rate at which you age are dependent on your location in our solar system. If you were to go to a different planet, say Mercury, you would be at the mercy of that particular planet’s gravity. Since Mercury has a deeper gravitational pull than Earth, time passes slower. The distance between Mercury and the Sun also plays an important role in what would cause humans to age slower than they do on Earth.
It can also get a little complicated. If humans travel to the International Space Station, like astronaut Scott Kelly did, time works in both directions. They’re floating about 260 miles above, where Earth’s gravitational pull is weaker than it is at the surface. That means time should speed up for them relative to people on the ground. But the space station is also whizzing around Earth at about nearly five miles per second. This means time should also slow down for the astronauts relative to people on the surface. In this case, time is almost working against itself.
How Do We Determine ‘Age’ for Space Travelers?
In the case of someone on the International Space Station, we determine the way they age by looking at exposure to radiation (cosmic rays), dietary habits, and changes to the person’s cellular makeup (telomeres). Telomeres are sections of DNA found at the end of every chromosome in your body. They help keep the ends of your chromosomes together. Every time a cell replicates itself and copies its DNA, these telomeres get shorter and shorter. Once the cells stop replicating, due to the telomeres getting too small, replication stops. On Earth, this mostly happens to older people, but in space, this can occur because of the more rapid rate they are traveling.
By comparing the data of an astronaut’s biological changes in space to those of someone on Earth of the same age (like the Kelly twins), provide at least some clues as to how much damage life in space can do. Keep in mind, there have not been many studies on this theory, although there are many clues that help prove it. Through more experiments and data collection, we will be able to determine more definite rates at which we age in space.