The star Gliese 581 is positioned 20.3 light-years from the Earth, and is thought to have at least one planet in the habitable zone. A manned space-ship travels from Earth to Gleise 581 and back at the constant speed of 97% the speed of light. Determine how long does this roundtrip take (according to Newton)? According to Einstein’s special relativity, astronauts on the ship view distances contracted through a factor of 4.11. According to relativity, determine how long do the astronauts think the round-trip occurs?