The yellow dots are aircraft.
It is a 24 hour observation of all of the large aircraft flights in the
world, condensed down to about 2 minutes. You can tell it was summer
time in the north by the sun's footprint over the planet. You could see
that it didn't quite set in the extreme north and it didn't quite rise in
the extreme south.
Notice that as evening approaches, the traffic is predominantly from the US
to Europe and when daylight comes, the traffic switches and it
is predominantly from Europe to the US.
World Air Traffic 24 Hour Period