What is the single most important reason
that astronomers have learned more about
our planetary system in the last 30 years than
all of history before then?
1. the Hubble Space Telescope
2. Radio telescope arrays allow astronomers
to make out details on the planets that they
have never been able to see before.
3. Astronomers today are a lot smarter than
astronomers were earlier.
4. We have been able to send spacecraft to
visit many planets and satellites.
5. The planets (moving in their slow orbits
around the Sun) hyppen to be closer to the
Earth in the last 30 years than at any previous
time in human history.