Space colonization remains the only long-term option for humanity: A reply to Torres

2019 https://www.scopus.com/inward/record.uri?eid=2-s2.0-85055671541&doi=10.1016%2fj.futures.2018.09.006&partnerID=40&md5=01392f6acd3890ed53f5bde34d6915b9