h2g2 The Hitchhiker's Guide to the Galaxy: Earth Edition

.....the concept of, if you could aim a telescope in the right directon, your could see the back of your head.....but that would be fractions of seconds after you had tried to look.

haha.

time travelling means a traveller reaches before his own death his destination in a defferent time period

not entirely correct.
a time traveler will live his/her lifespan.
the times they are in for a particular moment change when they travel.

may i recommend robert a. heinlein's 'time for the stars' novel ?

in it, a teenage boy travels to the stars, discovers planets and, when technology develops to bring him home to earth in hours, not the years he spent in space, he marries his grand-daughter and they supposedly live happily ever after. he's 40 and she's 20, but 80 years have passed on earth.
it doesn't make sense, but it is a fun idea to play with.