Your correspondent E M Izett's claim that alien visits to earth are not possible, just doesn't hold water. (Sun 7/1 ) He cites the vast distances and time require to get here as his proof. But Mr Izett's mind set is apparently locked in to 21st century thinking.
Can he not realize that any alien civilization, possibly hundreds or thousands of years more advanced than earthlings, would be light years ahead of us in terms of technology and would have solved the distance/time problem aeons ago.
Think nuclear energy or cold fusion for energy as examples. Think interdimensional travel or black holes for possible short cuts.
Remember mankind has gone from horse and cart to the moon in less than 100 years so it's unimaginable what could be achieved over several thousand years. Today's science fiction is tomorrow's reality.
Ian Lucas, Tauranga.