1st line: "Planets are for saying goodbye." Nice one.

Hooray, the journey through the random pulp novels finally turned up a good one!
This is just what I like in an SF novel; it takes a scientific idea and explores how it affects people.
The idea is this: we have invented a kind of teleporter that can instantly transport basically anything over many light years of distance. The problem, though, is that you can't transmit a transmitter, so in order to find new planets to colonize, there are ships of Explorers who travel close to light speed, bringing the transmitters to others can follow.
The result of this is that due to time dilation the Explorers only experience a few years of time while in the rest of the universe decades have passed. So, their ship becomes their whole world, and the crew is their family, and since the radiation of space makes them sterile, they have to adopt (or steal, or buy) babies to raise on the ship and continue the crew. Which makes the regular people very suspicious of them.

This was such an interesting and enjoyable book--I recommend it highly. ( )

Marion Zimmer Bradley is most famous for her Avalon fantasy books--which I don't care for, but I do love her Darkover science fiction. Even that is fantasy tinged though, featuring a clash between a technologically sophisticated space-faring civilization and a pseudo-medieval "lost colony" with a psychically talented aristocracy. So this collection of five connected stories is one of the few works of MZB that really is hard-science fiction, that falls into Space Opera. The basic premise is that there are "transmitters" that connect human colonies near-instantaneously across the galaxy. However, there's still a need for ships to explore space to find planets suitable for human habitation and set up those transmitters--and those ships are limited to relativistic sublight speeds. So for every year the "Explorers" spend in space, decades pass in ordinary space. Thus the first line and title of the first story: "Planets are for leaving." Home is the ship--Gypsy Moth. And there's another catch...

Now, yes, there are arguably better, or at least more famous books that use the time dilation of Einstein's theory to thought-provoking effect, such as Joe Haldeman's Forever War and Robert Heinlein's Time for the Stars or F.M. Busby's The Long View. Endless Universe isn't particularly thought-provoking nor stylistically remarkable. But it is an entertaining yarn I still remember decades after reading it as a teen. ( )

Endless Universe by Zimmer Bradley Bradley (1979)

Endless Universe by Zimmer Bradley Bradley (1979)