Keith S. Taber
My interest was piqued by an item in the BBC Radio 4 news bulletin broadcast at 17.01 today (Wed 1st July 2020). Science reporter, Paul Rincon, reported:
Giant planets like Jupiter and Saturn have a solid planetary core beneath a thick atmosphere of gas, but no one has ever been able to see what these solid cores are like.
Item on BBC Radio 4 PM News on 1st July 2020
Now a team of astronomers has found an object that fits the description, orbiting a star like the sun that's 730 light years away.
The team knew the object must be the core of a giant planet,
because it is unusually dense for its size. It's about three and a half times bigger than earth, but thirty nine times heavier.
Objects with these properties are thought to draw gas in to form giant planets. Astronomers are planning more observations which could test ideas about how planets form.
Some years back I wrote a Reflection on Teaching and Learning Physics column called 'Documentaries can only mean one thing', as a response to my frustration about how science in the media was presented. Even quality science programmes that I really enjoyed, such as Horizon documentaries, would commonly include the phrase "this could only mean".
This was seldom, if ever, justified. What was meant was that the scientist concerned considered one particular interpretation to be convincing. The scientists themselves were unlikely to ever claim that there was only one possible interpretation of the data – but the writers and journalists clearly thought that viewers needed certainty.
This is important, of course, because we try to teach young people about the nature of science – and that means that all theories are underdetermined by evidence, and that scientific knowledge is technically provisional – open to being revisited in the light of new evidence or a new perspective that makes better sense of the data. Science involves argumentation to seek to persuade the community, and even when consensus is reached, the community can later revisit the issue.
So any suggestion that "this can only mean [whatever]" belongs in a different domain to the natural sciences – perhaps logic or mathematics. Any journalists who insist on presenting science in this way are undermining the work of school science teachers charged with teaching young people about the nature of science. So my question here is:
[did] the team know the object [that is, the object believed to be 730 light years away] must be the core of a giant planet?
No, of course not. This might be their current preferred interpretation, but it is not something they know for certain.
Because, they are not ideologues, or prophets, but scientists.
And the one thing a scientist can know for certain, is that scientific knowledge is never certain.