With that in mind...
Hypothetically speaking, let's assume the nearest form of life is, say, 200 million light years away. Now, 1 light year = the distance light can travel in one year; or, about 6 trillion miles (5,878,630,000,000 to be exact). That would make our hypothetical alien world around 120 million trillion miles away. Okay. Cool.
Now, the speed of light is important, because of this: You can only see something when light is reflected back into your eyes from the object itself. Meaning, you can only see your wall in front of you right now because there is a light source in your room that is hitting that wall and bouncing back into your eyes. For a much bigger example, it takes light 8 minutes to get from the Sun to Earth. That means if the sun were to simply turn off, we wouldn't know about it until 8 minutes later. If you look up at the sky at night and see a star twinkle a few times and disappear, you just witnessed the death of a star... from millions of years ago. It just took the light that long to get to you. Crazy when you think about it.
So. That said, lets go back to our hypothetical aliens and assume can see our Earth from their planet using some super-amazing telescope technology. But they wouldnt see us, per se. Because they're 200 million light years away, they would only see a version of the Earth from 200 million years ago; With all the magma and and volcanoes and dinosaurs and swampy jungles, etc. Kind of like how when you're sitting at a baseball game and the player at the plate hits a ball but you dont hear the crack of the bat till a few seconds later. Even though it happened a few seconds prior, you're only hearing the sound now. Now imagine that sped up times 88,000. That's light. So the aliens 200 million light years away see Earth the way it was 200 million years ago. Okay.
Were closing in on my point here, so stay with me. They board their spaceship and rocket towards us as 200 million times the speed of light. But as they close the distance of Earth, they're also closing the distance of light coming from Earth to them. So in essence, they would suddenly be looking at Earth in fast forward. In just 6 months (the halfway distance mark) of their flight here they would see the Earth evolve 100 million years (the halfway time mark). At around 7 months in they would see the dinosaurs evaporate in a massive explosion that would last a fraction of a nano-second.
As they continued to close the gap and watch Earth speed up wildly, it would actually look pretty boring for a while. Kinda serene for 11 and a half months of their 1 year flight. At the speed they were traveling towards earth, they condensing 200 million years into 1 year. That comes out to them witnessing 54,795 earth years per day of their voyage (although I wasn't a math major in college, so forgive my napkin math).
|And on the 8th day, God sneezed.|
And on the start of Day #365, they would see civilizations forming.
A mere 6 hours from landing here, they would see would see Earth as it was 13,699 years ago: Small buildings and tribes popping up in certain corners of land.
Less than an hour from landing, if they tilted their telescopes just right, they would see the death of Jesus Christ.
15 minutes from landing - the year 1440 now - they would see a still largely untouched planet, with little wars between these creatures that inhabited pockets of the planet.
And in the final 4 minutes of their long, and arduous one year journey to visit a planet they discovered had life, they would see - in super fast forward - the humans explode in population all over the planet, and a frenzy of activity: The war of 1812, the civil wars, two world wars, the Nazis, nuclear bombs being dropped on each other, the industrial age, tanks, planes, the air grow dim from pollution, satellites and rockets shooting out from the planet, and massive swaths from the planet's surface cleared out to be swamped by more humans, racial genocide, oil spills, and chunks of the earth being blown up and dug into.
30 seconds from landing now. It's the year 1991. The Gulf war rages on. Missiles fly back and forth from land section to land section. The belt of rainforest vegitation around the equator gets eaten in half.
Fifteen seconds from landing. 2001. Two airplanes intentionally crash into two large towers in one of the most populated areas on earth, killing over 3000 beings. Another crashes into a pentagon-shaped building. Intentional as well.
T-minus five seconds till landing: War and terrorism rages on around the globe, and there is overall contempt and anger gripping the species due to politics and economy. Oil spills.
It's been a year-long journey full of hope for this once lush, green and blue planet they noticed had life so long ago. In the final 60 seconds of the alien's 200-million light year trek, the planet instantaneously rotted like an apple in fast forward right before their eyes.
4... seconds from landing...
2010: Lady Gaga appears.
The aliens turn around.