According to NASA a "perfect" Solar storm could happen in 2013. Which could possibly make alot of GPS, ATC, Power grids and eletrical products have great trouble functoning and cause possibly trillions of loss to the economy.
On the bright side there would be aurorae all over the Earth...
The Combine knew about the base for ages because of Mossman, its just that Breen got tired of waiting and decided to go ahead and attack Black Mesa East and capture Eli
I'm not to sure about the CP though
The trouble is that the signal came from a star group that is over 220 lightyears away.So even if the Voager 2 probe started to head its way and never run out of battery it would take over 1 million years. The vastness of space is what stops us from discovering alien life
Less of a moon and more of a Quasi-satellite (A quasi-satellite's orbit around the Sun takes exactly the same time as the planet's, but has a different eccentricity)