A tweet from Twitterverse:
I’d say aligned with the earth’s poles - as ‘vertical’ depends on your frame of reference.
When does the line between day and night become vertical? #Today, September 22 at 19.21 UTC, there will be an equinox on planet Earth https://buff.ly/35VbD4P [watching solstices and equinoxes from space: http://buff.ly/1Qe1hk7]
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