Comparison of even-toed ungulate and cetaceans genetic material has shown that the closest living relatives of whales and hippopotamuses is the paraphyletic group Artiodactyla. Dan Graur and Desmond Higgins were among the first to come to this conclusion, and included a paper published in 1994.
Definition of roundâtrip. : a trip to a place and back usually over the same route.
Time Travel. Time travel is commonly defined with David Lewisâ definition: An object time travels if and only if the difference between its departure and arrival times as measured in the surrounding world does not equal the duration of the journey undergone by the object.here are also investigations of the logical possibility of time travel, the physical possibility of time travel, and the technological practicality of time travel. The most attention is paid to time travel that is consistent with current physical theory such as Einstein's general theory of relativity.