I don't understand it. Can someone please explain it to me?
When you look into the sky and see the stars, you are seeing the stars as they were ten years ago if the star were ten light years away because it took the light ten years to get to us. When we see something, we are really seeing the light that it gives off or reflects, but we don't think about it much on Earth because light can travel around the earth seven and a half times a second, so the effects are negligible on Earth. The Sun is 8 light minutes from Earth, so right as you read this the sun could burn out and you wouldn't know it for eight minutes.
So basically what this is saying that the light given off from Earth one million years ago would travel to the mirror, bounce back, take one million years to travel back and arrive at the telescope in the present day, so the result is that we'd be seeing light given off two million years ago.
Now the problem with this though is that the Earth doesn't give off or reflect near enough light for this to work (leaving the improbability of a massive mirror out of the equation). This is a picture of the Earth from 3.7 billion miles away.
Now, one light year is 9.461×10^15 miles, or 9,461,000,000,000,000 miles for the scientific notation impaired. From Pluto (which isn't anywhere close to a light year away from the sun) the sun isn't even the brightest object in the sky. So, light from the Earth just wouldn't work for doing this.
It's an interesting idea, though.
