Archive for the ‘Accelerating Universe’ Category


July 31, 2017

If you look back in time, (up in the night sky, at the light emitted from galaxies billions of years ago), you are actually looking at an earlier version of the universe when it was smaller.


Due to the nature of how light moves through space, when you look back 14 billion years to the farthest reaches of the universe, you are actually looking at a very small volume. But the image, warped as it is, is spread out and fills the farthest regions of the sky, like a view through a concave lens. If you were able to look all the way back to the tiny point of the Big Bang, the image would be smeared and spread out across the 14 billion light-year shell, any detail of the event washed out by turning the fine detail of a tiny event into a picture the size of the universe.

So, when you look up at the night sky, everywhere you look in the blackness of deep space, 14 billion light years away, is actually the same small point.

Does this make sense? I’m trying to think of a good analogy for this, but it just isn’t coming to me. Maybe like starting with a tiny drawing on the surface of a tiny sheet of rubber, then stretching it out so that the sheet of rubber stretches all around you in a sphere, like the inside of a balloon, and then trying to figure out what the original picture looked like.

This, of course, begs the question of what physicists are calculating when they measure the accelerating expansion of the universe. If the universe was physically smaller 14 billion years ago, and now the remaining image of it is spread out over a sphere with a radius of 14 billion light years, that’s going to come off as an acceleration; the farther you look, the smaller the original volume and the more the image is spread out over the apparent warped view of the current volume. And, of course, 14 billion years ago, the universe actually was expanding a lot faster than it is now. It’s a double-whammy of accelerations. Most physicists are a hell of a lot smarter than me, so I’m guessing that both these accelerations have been calculated into the “accelerating expansion of the universe” equation. I can only speculate that there is a third element. I wish I could find out without wading through a lot of really obscure math.