There are only a few pleasures like super-science space opera from people who seem at some point to have encountered actual science but not to have any particularly deep interest in it, eg, John W Campbell's Invaders From The Infinite. So Arcot, Wade, and Morey set off for a kerspillion light-years away to meet aliens from another dimension or something. I don't mean to be vague, but they talk of the surprisingly small number of lifeforms in the many universes, but seem to be going around galaxies. When these stories were written galaxies were still sometimes called island universes, and probably if I read carefully I could figure it out but does it matter? Even if I did pin down a detail the characters, who are always busy when off-camera thinking up new rays, would whip up another ray and escape the narrative block anyway.
Our Heroes end up 80,000 years in the past by some accident probably involving rays, but they zip ahead with only a few pauses to set off the legends of Hercules and the Egyptian gods. They get really excited about how they could see the First Battle of Bull Run if only they knew just when it was. (Engineers. Tch. Without leaving my bedroom I think I could set my hand on four books giving the dates for both battles.) Certainly if you could drop in at any event in human history 1st Bull Run is a natural point of interest. After that catastrophic battle it was only three more years until the Union realized the Civil War was going to be long and difficult, and four years for the Confederacy to realize the same.
And nobody in Our Heroes' native time finds it odd they accidentally travelled back 80,000 years. These things just happen. You get the feeling everyone in this world always wears inertio-fluxation jet-packs to leap out a window and fly to other floors rather than wait for the elevators, which are out of service four times a week due to molecular vibrations from the 62nd dimensional universe galaxy anyway. It'd be a fun universe to live in if there weren't so many billions casually killed. But hey, a normal trip to another universe could get you a chance to see the First Battle of Bull Run, isn't that at least as good as avoiding unspeakably massive civilian deaths? Somebody call Brainaic-5 and see if he's stopped Computo yet.
Trivia: Gemini VI-A got its radar lock on Gemini VII at a distance of 268 miles. Source: Deke! Donald K Slayton, Michael Cassutt.
Currently Reading: Invaders From The Infinite, John W Campbell.