Looking for a specific children's time and space travel book 50s or 60s

Question

Children's book 50s or 60s, in which time travel gives accidental space travel to moons of either Jupiter or Saturn as the time machine is fixed at a point in space, and the movement of the solar system over time 'moves' the earth away from it. It is a sealed machine with oxygen, so this is not fatal.

The author's name would begin with a letter between G and Q based on where in the library it was shelved (which I can remember). I read it around 44 years ago. It was a hardback.

It may have starred two children and a professor who built the machine.

I read it around 1974 from Garston Library, Liverpool.

It is not a conflation of the suggested Heinlein books, both of which I also read as a child, but later.

Following more research, it's more like (but I don't think it is) a cross between Danny Dunn and the Anti-Gravity Paint and Danny Dunn, Time Traveler. I still think it's a real separate single book by a different author than the Danny Dunn series whose authors have names beginning A, & W, but in tone it would have been more like the Danny Dunn than Heinlein.

Answer 1

This sounds very much like a conflation of two juvenile novels by Robert A. Heinlein -- Tunnel in the Sky, in which the gate that takes people to the stars is discovered accidentally when the inventor was attempting to build a time machine (he thinks he's opened a gate to the Jurassic, but when he crawls through, finds himself in the rain forest exhibit of a botanical garden), and Farmer in the Sky, most of which takes place during colonization of Ganymede (but uses spherical torch ships for interplanetary travel).

Tunnel in the Sky had a single (teen male) protagonist, who goes on a survival class field trip, but his older sister (already a colony guide) figures prominently in an early scene, giving him a knife that winds up being his only survival tool after he's robbed by another student. Farmer in the Sky involved the (teen male) protagonist's whole family, including two younger siblings (a boy and a girl, as I recall), one of whom dies when a technology failure causes a period of extreme cold.

Both books were written in the 1950s, Heinlein would have been shelved in the correct part of the fiction section in your library, and the titles are similar enough to make them easy to conflate.