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.