Barriers to Interstellar Contact: Time Dilation, Energy Demands, and Earth's Atmosphere

To the point

Fike explains that some scientists think aliens stay away because interstellar travel would be slowed by time dilation, would require enormous energy to reach near-light speeds, and Earth's oxygen-rich atmosphere could be hostile to alien life, a view echoed by Carol Oliver of UNSW Sydney who also notes uncertainties about life beyond Earth but remains hopeful given the vast number of stars.