Assertion: space elevator | /r/HasProperty | built
Facets:
Source sentences:
text: Once a first space elevator is built, the second one and all others would have the use of the previous ones to assist in construction, making their costs considerably lower.
text: During the second half of the 20th century and the early 21st century, multiple concepts were proposed, but it was not until almost three hundred years later that the first space elevator would be built.