Let’s start with a fact: Suni Williams, one of the two astronauts recovered after 288 days by the ISS with the Space X capsule, made a sensation because it appeared incredibly aged and weak, and on some social networks they also pulled out Einstein’s relativity, which in this case has nothing to do with it.
Indeed, orbit around the land at a speed of 28000 thousand kilometers per hour, at a height of 400 km, for 288, the time for her has passed more slowly, more or less will have gained almost a second of life. To have an effect in which we actually return to rejuvenation we should orbit at least an hour around a huge mass, like a black hole. But here we are not surprised because it is rejuvenated (that second would not notice it), but because it is very aged, the opposite. He could not even stand, which is common to those who remain a lot of time in microgravity.
In fact, in conditions of microgravity the muscles weaken and atrophize quickly. Astronauts make many physical exercises, linked to belts and elastic bands to simulate body weight and run, for example, on a treadmill, but are not enough. They also lose bone density and muscle mass. The same thing that happens to the elderly, faster though.
Then there are cosmic radiation, of course: they are lethal for the human body, but not on the ISS, because it is still protected by the earth’s magnetic field. However, it is not exactly the maximum for health, given that a further protective screen is missing, which is the atmosphere. Cosmic radiation are the main reason for the continuous references of human travels on Mars, where the Earth’s magnetic field is no longer there on the trip or once landed on the red planet. Admitted to get there without tumors (with nine months of travel), you would remain very little alive. Not for another Elon Musk who will land on his starship on Mars on Mars will be a robot. For a human expedition, beyond the effect ads (always postponed), it will take a long time, and the main problem is precisely this.
As if that were not enough, without gravity (or rather in conditions of absence of gravity, because gravity on the ISS would be only 5% less than the terrestrial one: it is as if it were not there because it “falls” towards the earth without ever falling, which means being in orbit), the heart is also atrophic, which works less to pump the blood, and think of the pressure problems when you return to the earth. “Doctor, I have the pressure on the ground.” “What did Madam did?” “Well, I was just two hundred days without gravity.”
Also consider that there is no high and low, it’s all the same. Although the ISS designers, and in general of the spacecrafts, tend to give a sense of high/low to the environment, purely illusory. Being upside down or straight is the same thing. In addition to the muscles, in conditions of microgravity, the cerebrospinal fluid moves differently to our body, compromising balance and coordination once they are returned. The body struggles to get back to having a weight. Just as sleep deprivation and stress cause other problems.
But I go to the last element, connected to stress: Suni Williams also came white hair! In addition to the causes listed above, add another one: he had to stay on the ISS ten days, and
There is due to remain in spite of himself a year. To whom, waiting for them to decide to come back, wouldn’t come white hair? That in any case no, they are not those of Einstein and the theory of relativity.