We've been sending out radio waves for about 80 years, and given that they travel at the speed of light, the nearest star that could hear them would be about 80 light years away. How many planets fall within that range?

I understand that there are two types of galaxies. Some have spiral arms and others an elliptical shape. What processes would form those two different types?

What determines the orbital distance from a star at which planetary material will coalesce? Is it just gravity?

If outer space is really cold, and the Sun is really hot, how close would you have to get to the Sun in order to be about room temperature?

Do all stars belong to a galaxy, or are there some stars which are orphans?

If what we term our universe was created by the big bang, does this mean that the whole universe was once a massive star that exploded, and if so could our universe be a small part of a bigger universe?

TV crime programmes often show DNA samples taken from suspects by swabbing the inside of their mouth. Human mouths are filled with bacteria, so the swab must collect non-human DNA as well as DNA from our food. How can human DNA be separated out from this?