用适当的短语完成句子。
hear about, millions of,  try doing sth. go around,
more than, send sb.(a) message(s), try to do sth.?
1. I haven't seen Tom for a long time, so I ______ him ______ .?
2. The earth is a planet and it ______ ______  the sun.?
3. There has been life on earth for ______ years.?
4. There is ______  one galaxy.?
5. They have ______  send information to us.?
6. —Tom, I've just heard that scientists have sent a spacecraft to Mars.?
    —Really?I haven't ______  this yet.