Probably was one of my least favorite in Heinlein's "Scribner's Juniors" "series". Like the others it's really a stand-alone story amongst a series of similar tales. (Young adults leading scientific adventures).

This one is about two teenage twin boys finishing school and invited to a symposium by the "long range foundation" a private non-profit company that can focus on funding endeavors that don't have to make investors happy with quick returns, nor be at the will of fickel politicians, they can work on projects that will be years, decades or centuries before a return, if any occurs.

The project the LRF is now working on is to deal with the overpopulation of the planet. The 1954 written book is very concerned that in the future (maybe 200 years from now?) the world population is unsustainable with over 4.5 billion people (never mind that 75 years from when ti was written we are doing just find with 8 billion).

In order to explore what planets beyond or solar system may be suitable for habitation they need to find a way to communicate back to earth that is faster than the near light speeds of the ships. Ta-da the proof of telepathy that distance cannot substitute, primarily available between identical twins.

A little far-fetched but certainly interesting. I appreciate how Heinlein brings about theoretical ideas including those like over taxing large families etc.

Some of the story is pretty unbelievable though, like giant sea monster attacks in space, that could have been prevented with encoded messages from light years away being approved to be sent 2 days earlier.

The ending was anticlimactic to say the least, but all and all I still liked it.