gravity generators can generate fields that are almost earth-normal, but they’ll never quite be perfect - especially if they have to compensate for the different species of alien on board, who may well be used to completely different gravitational strengths on their homeworld. it’s not uncommon for a crew, after a long voyage, to step back onto their homeworld and experience temporary feelings of excessive heaviness or lightness. “gravity hangovers” are common, especially among ensigns and those from worlds where gravity is more extreme.

the air onboard starships and stations is highly concentrated and purified, recycled through a series of filters to make it suitable for the inhabitants of the vessel. many dormant allergies develop post-voyage, and crews of all ages and levels of experience dread the “station sickness” that sometimes results from exposure to less sterilized air after a long period stationed in space.

lighting and sound is also different; many veterans report difficulty sleeping without the sound of the ships’ engines to lull them to sleep; or the piercing, painful brightness of the midday sun after so long stationed out in the impenetrable void, with only the light of the stars as an external source of illumination.

it’s no wonder that those who journey into space rarely want to leave, are so desperate to get back out there when they do.