why don't more mainstream scientists think aliens exist? Nothing moves faster than the speed of light: 186,000 miles per second. The faster thing ever made by humans (voyager) moves at 11 miles per second. It would take voyager over 70k years to reach the closest star. Surely the conditions that provided for life sustainability on earth must have been present somewhere else in the vastness of space. In the billions of galaxies throughout the universe, there must be at least a couple of planets just like earth where life exists.