It’s really quite obvious. Everything we do and say is projected into space at the speed of light. So in theory, we’d be able to see our past if we had a massive mirror launched deep into the universe and reflected back towards us. And we wouldn’t even need a suped-up DeLorean. Though this method comes packaged with plenty of limitations. We’d only be able to look 2,000,000 years in the past of the current time. There would be no picking and choosing.
Of course the logistics of this would be damn near impossible. Space junk, other celestial bodies, the reflecting light of the Sun and other stars. In theory, it could work in absolute perfect conditions, but unfortunately, that’s not the sort of universe we’re living in.[via]