Last year I was writing questions for an Australian Years 9-10 Science textbook when I first came across the "gamma decay" problem.
The textbook authors stated that there are 3 types of radioactive decay: alpha, beta and gamma (which is kind of OK for Year 9 or 10 science). They wanted to provide an isolated example of each type, that is, an example of alpha decay, an example of beta decay, and an example of gamma decay. Which is where the problem lies. Giving an example of alpha or beta decay is easy, just ignore any other possible radiations when you do it, which is the "traditional" method for teaching nuclear decay to Years 9 or 10, or indeed Year 11 chemistry (and yes, physics teachers are probably horrified, and rightly so, IMHO). But, you can't do this for gamma decay unless you want to talk about "excited states".
Which brings us to version 9 of the Australian Curriculum for Year 9 Science which states,
"describing in simple terms how different unstable isotopes decay such as radon-222 releasing an alpha particle, iodine-131 releasing a beta particle and cobalt-60 releasing gamma radiation to form stable atoms"
Alpha decay of radon-222 and beta decay of iodine-131 ... OK, can do.
Gamma decay of cobalt-60 ? Problem! Cobalt-60 decays by emitting a beta particle to produce an excited state nickel-60 atom. Excited state nickel-60 loses energy by emitting high energy gamma ray and relaxing back to a ground-state nickel-60 atom. But, we can't use this as an explanation because the introduction to excited states won't occur 'til, possibly, year 10 (when they do flame tests).
Has the Australian Curriculum been proof-read?
I think not. Further evidence of the writer's (or writers') slipshod approach to "science" is evidenced in this "interesting" extract (also for Year 9)
"investigating how radiocarbon and other dating methods have been used to establish that First Peoples of Australia have been present on the Australian continent for more than 60,000 years"
Problem 1: radiocarbon dating is pretty useless for anything older than about 40,000 years old, so it would be worse than useless for artifacts said to be 60,000 years old.
Problem 2: where is the SCIENTIFIC evidence that Australia has been inhabited by humans for "more than 60,000 years"? Surely if you are going to make a statement like this, and force SCIENCE teachers to teach it, you need to support the statement, just a link a two, some references, to some SCIENTIFIC studies would be useful.
So, here's what I think I know ... Mungo man/mungo woman are thought to be about 40,000 years old (give or take a few thousand). Blackened rocks at Moyjil are thought to be about 125,000 years old, but not linked to human habitation (that I'm aware of). The Pilbara petroglyphs have a wide range of dates depending on who provides them, but they also seem to be scientifically dated between 40,000 and 50,000 years.
My problem is that I'm not an anthropologist, I know a little bit about chemistry (Chemical Sciences), a bit less about geology (sorry, Earth Sciences), even less about physics (AKA physical sciences), and practically nothing about biology (sometimes called a science), and hence I am NOT in a position to either a) know how long Australia has been inhabited for, or
b) to teach anything about this
... and I suspect most SCIENCE teachers in Australia would fall into the same category.
AC: Australian Curriculum or Australian C_ _ p?
