Contrary to what Einstein proclaimed, time is not an illusion. The linearity of time may actually be the only constant of physics accross multiple universes.
Time travel nevertheless is a reality. But not with a technology that would propel matter at velocities faster than the speed of light. Because matter desintegrates long before it moves that fast.
On the other hand, information is really comfortable at that rate of movement. Because information in every computer travels at the speed of electricity, which is the speed of light.
Time travel doesn’t move matter backwards on a scale of linearity. Time travel resolves matter into information and transfers it to a current position.
A peculiarity of time is that while monodirectional linear, it is of endless width. The number of events that can happen simultaneously is unlimited.
So, whenever time travel copies and reconstructs a reality of the past based entirely on information for the time traveler to be inserted, this then creates a parallel now, with its own future, in its own universe.
To answer Stephen Hawkins question as to where the tourists from the future are: well, time travel isn’t round trip journeys. Once a past time that has been recaptured and transformed in a present time, in its new universe, the time traveler cannot normally be aware of a future in the universe from where he departed, and he can’t go back there. Rather, the new parallel universe has its own future. No grandfather paradox here.
However, for humans who already have arrived in the future, traveling to the past may not be an attractive option. What would that be good for? Sightseeing? There are better technologies for this purpose, with predictable outcome, such as 3D history tours. Time travel into the past robs any individual of the amenities of the future, including time travel technologies.
But at the core, time travel is the same as modifying the past for a better present. Not as Orwellian propaganda, but for real.
Because any time the past is modified, the presence is a new bubble universe, with its own, distinct future.