I took it as the sphere staying in the same place and the Earth moving to its previous place seven days prior, then gravity would pull the sphere back to earth.
The sphere at a minimum has some kind of thrusters since they used them in the space episode and stabilizers in general (which is the whole point of him flying the needles so there is a good/survivable landing).
Most Time Travel stories, are not entirely accurate when it comes to time travel itself... Probably to keep viewers from being confused...
The Earth is is constant motion revolving around the Sun. It takes 365.25 days to complete one orbit. Gravity keeps us all from floating away.
Seven Days ago, the Earth was located in a different location in space.
If I recall the show correctly...
When the Sphere travels back in time, it does NOT travel in space. It stays in the same location as today...
(As compared to what is seen in most other science fiction movies, where time machines DO travel in space, as they travel in time, and arrive at the same location.)
This is why Frank always wears a "Pressure Suit" If the Sphere decompresses during the journey through time, he will survive.
Also...Again...If I recall the show correctly...
The Sphere creates it's own gravity field...
Flying The "Needles" with the control stick, somehow manipulates this field, giving the sphere a type of propulsion... (And there may also be some maneuvering thrusters too) ...and hopefully moves the sphere toward Earth.
If everything is perfect, which rarely happens, the sphere exits it time travel journey back at NNL.
Unfortunately, as pointed out in the show, sometimes it lands inside the Earth, Underwater, or Ends up in space. If the Chrononaut is lucky, he'll just land halfway around the Earth, but on the surface.
In one known case, he was coming in like a shooting star, and passed through an airliner...
I guess the gravity field, keeps him from crashing to Earth in a giant crater and going splat!
So NO, the sphere really does not travel into space, the Earth moves away from the sphere, and the Chrononaut "relocates" the sphere to the coordinates of where the Earth was Seven Days Ago.
The sphere definitely travels out into space, like in the Time Gremlin episode the sphere travels to a wormhole "beyond the Hydra star system." It probably is in an arc out from where Earth is when he leaves ending where Earth was 7 days ago.
Well, it makes sense, but it doesn't appear the writers thought it out that much as the Sphere does travel in space. Not only is it seen more than once flying up in space, lingering momentarily and dropping back to Earth, but the opening of the pilot shows a failed backstep with the sphere in orbit of Earth, the hatch blown off and flying around, and a dead backstep pilot with his helmet broken open. And like another user pointed out, it got sucked into a space anomoly in one episode. Then I'll also add there was another episode where they not only travel back in time, but while up there in space the sphere docked with the International Space Station.
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