Keith S. Taber
Sophia was a participant in the Understanding Science Project. When I interviewed her in her first year of secondary school (Y7 in the English school system). I asked her about what she remembered about the science she had studied in primary school. She told me about she had studied the topic of space.
So what did you learn about space?
All the planets, and –
(pause, c.2 s)
So how many planets are there?
Nine.
Nine, okay. Do you know them all?
No (laughs)
Do you know some of them?
Erm. Pluto, Jupiter, Venus, Uranus, Earth, the Sun, the Moon – (pause, c.2s) hm.
[This was a few years back, and I think was before Pluto was demoted from full planet status in the scientific community.] So, Sophia seemed to have an alternative conception of what would be considered a planet, and she was counting both the moon and the sun among the planets. After a little further conversation about other candidates we came up with a list of more than nine planets.
So how many does that make?
(Sophia laughs)
(Pause, c.6s)
Is there eleven?
Well you said there was nine, didn't you?
Yeah. (laughing)
How could that be, how could we get these extra two?
(Pause, c.4s)
… So, Mercury, is that a planet?
Hm.
Okay, Venus?
Yep.
Earth?
Uh hm.
Mars?
Yeah.
The Moon?
Hm, yeah.
Yeah, Jupiter?
(Pause, 2.s)
Saturn?
(Pause, 2.s)
The Sun?
I'm not sure about the Sun.
Not sure about the Sun.
I think so.
Neptune?
Uranus?
Yep.
Pluto?
Uh hm.
So Sophia was not entirely sure the sun should be considered as planet, although she seemed more confident about the moon. The earth and moon are not technically considered as a double planet system, even though the moon is unusually large satellite compared the the planet it orbits, as the system's centre of mass is within the earth. (Strictly, the earth, as well as the moon, orbits their joint centre of mass.)
As Sophia thought the sun might be a planet, I asked her what a planet was, and the difference between planets and stars. She suggested that some stars are closer to us than the planets.
[Read 'Some stars are closer than the planets']
Not considering luminosity to be a factor, Sophia did not consider the sun to be a star:
What's the closest planet to you?
Erm – the Sun?
Yeah?
If it is a planet.
I think that might there might have been a trick question there. Which is the closest planet to you?
To me?
Yeah.
Earth.
