What Is Space? (1964)

This is a 1964 British reprint of a 1961 U.S. book (under the same title).

This is another in the "Collins Pageant of Knowledge series."  It has many colorful illustration and some pretty heady contents for "ages up to 11".

Kane, Elmer R and Fellger, Merrill C. Illustrated by Tiedemann, Berthold. What is Space? London: William Collins Sons and Co. Ltd. (47 p.) 21 cm. Cloth. 

This next section about the shape of the universe is pretty interesting for a children's book:

It goes on to talk about space exploration:

Then about human exploration of space:

 How about expansion of Time as you travel closer to the speed of light?

 This next section is the updating from the 1961 publication

 The book ends with a "space glossary". All in all a knowledge-rich space book for the under 12 set.