Spin Gravity & Space Hotels
By 2050 there will be a space station with a section under rotation to produce artificial gravity by centrifugal spin. The first one is likely to simulate either Moons or Mars gravity to test the long term health effects of low gravity, and likely be partially funded by or later converted over to a space hotel. While commercial travel to space will include a space hotel to allow people to experience zero-gravity, most people will find lower gravity more appealing after initially experiencing weightlessness and prefer to take their rooms in low rather than no gravity. The number of people traveling to space in any given year will exceed the total number of astronauts to visit space in the entire 20th century.