Entry 946, on 2009-02-16 at 22:57:23 (Rating 3, Science)
Recently I have been helping my wife, who is a teacher, prepare a teaching unit for astronomy. Its at a fairly basic introduction level so it doesn't get too advanced and I already had some material on the same subject I had prepared when she was doing teacher training about 15 years ago which I decided to update.
The thing that surprised me is how much astronomy has changed since then. The changes have been obvious but I never really noticed many of them while they occurred during that time but after 15 years the accumulated changes are far more obvious.
So what are some of these changes? Well, when I wrote the material Jupiter only had about 14 known moons and it now has 65. Pluto had no moons and it now has 3. We knew about nine planets then but now we have 8 (because Pluto has been re-assigned as a dwarf planet) but we now know about three more dwarf planets: Haumea, Makemake and Eris, plus Ceres (which was previous thought of as an asteroid) is also classified as one. There are also at least another 10 objects (Orcus, Ixion, Varuna, TX300, UQ513, Quaoar, OR10, UK126, QU182 and Sedna - the names are starting to get weird) which might be classified this way. The solar system is far more confusing!
The most advanced planetary lander was Viking and the most advanced spacecraft was Voyager. Since then two more missions have landed on Mars and other missions have been launched, such as Cassini which has returned amazing photos of Saturn. There was no Hubble Space Telescope then and no advanced digital imaging techniques, so the best photographs we had of space were hugely inferior to what we have today.
And things were even worse in cosmology. The inflation phase of the Big Bang hadn't even been theorised. The age of the Universe was only known approximately. The microwave background anisotropy was unknown. And dark matter and dark energy were either entirely unknown or even more mysterious than they are today (we didn't know or even suspect that the rate of expansion of the Universe was increasing).
So it would be tempting to say that astronomers didn't know what they were talking about back then. This is a common argument used by anti-science groups like creationists and global warming deniers who like to suggest that science was wrong then and could be just as wrong now (about the age of the universe or the warming of the planet for example).
Of course this argument is invalid because the vast majority of older theories were correct and still are. The new discoveries have been more about fine tuning and filling in detail than completely replacing older theories. For example, the Big Bang is still almost universally accepted even though it has been significantly affected by the discovery of inflation and dark energy. The age of the universe has only been modified by 20% at the most and it would need to change by 230000000% for creationism to be right!
So the argument that the way science is always changing shows it can't be trusted isn't a good one. I totally agree that we should always be open to the idea of new theories and information but its still safest to accept the current theories until clear new evidence is presented against them.
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