If aliens ever visit us, I think the outcome would be much as Christopher Columbus first landed in America, which didn't turn out very well for the Native Americans.

If aliens visit us, the outcome would be much as when Columbus landed in America, which didn't turn out well for the Native Americans.... We only have to look at ourselves to see how intelligent life might develop into something we wouldn't want to meet.

Space creatures might not be visiting Earth with peaceful intentions.

In some histories space-time will be so warped that objects like rockets will be able to travel into their pasts.

To my mathematical brain, the numbers of planets in the universe make thinking about aliens perfectly rational.

A possible way to reconcile time travel with the fact that we don't seem to have had any visitors from the future would be to say that such travel can occur only in the future.

It is a waste of time to be angry about my disability. One has to get on with life and I haven't done badly. People won’t have time for you if you are always angry or complaining.

The increase of disorder or entropy with time is one example of what is called an arrow of time, something that distinguishes the past from the future, giving a direction to time.

One, remember to look up at the stars and not down at your feet. Two, never give up work. Work gives you meaning and purpose and life is empty without it. Three, if you are lucky enough to find love, remember it is there, and don’t throw it away.

One of the most serious consequences of our actions is global warming brought about by rising levels of carbon dioxide from the burning of fossil fuels. The danger is that the temperature increase might become self-sustaining if it has not done so already.