Currently Online 
Mnementh on 22 March 2019
| SvennoJ said: I guess they are see through, or will these (probably rather large balloons) cast shadows? These things coming down every 100 days, that's not much of a permanent solution. |
Looks quite transparent. But this high up I doubt it is relevant even if not transparent, the shadow will be obscured by scattered light over distance.
https://en.wikipedia.org/wiki/Loon_(company)
