TED Conversations

This conversation is closed. Start a new conversation
or join one »

My observable universe

I've been stretching the ol' grey matter recently tackling- how the universe is expanding in all directions, that wherever you are in the universe it will appear to be expanding in all directions etc etc
I understand that in whichever direction we look the universe appears to be homogeneous, and that my perceivable universe is limited by the amount of it that I can actually observe - that the further I look the longer I look back in time and the farthest viewable points away are those whose light has only just reached me here on Earth.
Does that mean then that if I were somehow able to look beyond the furthest images I can see that I would see a black sky where lights would blink on over time as the light from those objects reached me?
Also, if the universe if expanding faster than the speed of light, meaning I will never see the farthest objects as they are travelling away from me quicker than the light can make it back to me to observe, will I eventually reach a point where I can see so far that I can see no more? Are there any guess-timates to this threshold (if indeed it exists)?

0
Share:

Showing single comment thread. View the full conversation.

  • Apr 7 2013: That would certainly be a good trick.
    You are always looking back in time the further you look away. That is because the speed of light is a fixed value.
    So, it takes 8 minutes and 20 seconds for light from the sun to get to the earth. Therefore the sun you are looking at is 8 minutes and 20 seconds back in time vis a vis its actual condition right now. I could have blown up 4 minutest and 10 seconds ago and you will not know about it for another 4 minutes and 10 seconds.
    Extrapolate that to the outer planets. There you are look back hours.
    The nearest star, over 4 years ago.
    You have probably heard the theory that alien races if they exist may just be getting our first radio and tv transmissions and watching I love Lucy without even getting the DejaVu channel.
    From their point of view, they are looking at the earth back in time.

Showing single comment thread. View the full conversation.