[samanator]

You can't use cancellation or heavenly bodies:

"He is far away, or in some strange location, and he cannot see anything we can see. For instance, we cannot say, “Look at Ursa major; now see how those stars are arranged. What we mean by ‘right’ is …” We are only allowed to telephone him."

[Modified3019]

Ah good catch, I somehow still assumed same galaxy.

Thinking about it, ironically I think the direct mention of Ursa Major might have played a part in that.

[noworld]

"imagine that we were talking to a Martian"

[indoordin0saur]

I think by Martian he just meant "alien". Obviously if you're on Mars you could use all sorts of celestial bodies to demonstrate chirality.

[verzali]

" he cannot see anything we can see. For instance, we cannot say, “Look at Ursa major; now see how those stars are arranged"