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xdamage
07-29-2008, 01:38 PM
I look at it like this.

Suppose that stars lasted forever, emitted light forever AND suppose we could stop the expansion of the Universe. Also suppose we could stand outside the Universe, and had a common point of reference. If we could do all of that, we could say we see stars that are now 14 billion years old, and that are now 47 billion light years away from us.*

In reality those stars no longer exist, but because of my "supposes" above, if we wanted to send a message to one of those stars (i.e., a photon from us to them), now that the Universe is frozen, it would take 47 billion years for the message to arrive.

* And yep, it means that space is expanding faster then the speed of light. BUT as some have pointed out. The speed of a light is a limit on how fast light can move through space and time, but there is no such limit on how fast space can expand.

Golden_Rule
07-29-2008, 05:15 PM
Amazing. Thank you for posting.

Me too on that.

Its been quite an interesting read.

chop
07-30-2008, 04:40 AM
http://www.space.com/scienceastronomy/astronomy/universe_overview_010605-1.html

Another take on the subject from Docido's link.

Also a good read on the subject, although sometimes difficult to comprehend. Greene even takes on what we preceive as reality.
http://www.amazon.com/Fabric-Cosmos-Space-Texture-Reality/dp/0375412883

From a review of the book:
"His watchword is "reality" and his overarching idea is that reality is not as we intuitively think it is. (p. 5) This is one of the startling revelations from relativity and the quantum world: namely that our perceptions and concepts built up through evolutionary experience are NOT adequate to understand the world of the very small or the very large. The dual nature of the particle/wave is the most obvious example, and one that Greene examines at length. We have no way of intuitively appreciating the fact that elementary particles are not just particles but waves as well--actually probability waves. But there is also our notion of something and "nothing" that is being tested by modern physics. What appears to be empty space is in fact far from empty. Moreover, space itself has unsuspected qualities, as Greene demonstrates in his discussion of the postulated Higgs fields.

Particularly exciting was the way Greene makes inflation credible ("the universe could easily have expanded by a factor of 10 to the 30th, 10 to the 50th or 10 to the 100th or more" within a time frame "as short as ten to the minus 35th seconds" p. 284) by positing that before the Higgs field made its phase transition, all quanta had zero mass. It doesn't take much energy to move something with zero mass. (Or maybe something with zero mass can't be moved at all.) At any rate, very shortly after the big bang, space and presumably time, expanded enormously (faster than the speed of light, actually--but, as Greene, assures us, the speed limit on light does not apply to expanding space)."

xdamage
07-30-2008, 08:36 AM
...namely that our perceptions and concepts built up through evolutionary experience are NOT adequate to understand the world of the very small or the very large....

Perfectly said!

This is the key point. Our brains really are quite limited. They have evolved to solve certain kinds of problems, on earth, at a certain scale of the Universe, but they simply have not evolved any intuitive or innate abilities to understand everything, including reality at larger or smaller scales.

Which isn't to say we can't overcome our limits. Math is a tool (well a collection of tools) that we humans are developing to help us understand how our Universe really behaves. It is not intuitive. It does not come naturally to us. But fortunately in a huge population of billions born, occasionally some people are born who for various reasons, make significant contributions, who have unique new insights, who add a new tool or refine one.

We may never fully understand everything, but as long as scientists keep the creed of pushing back at each other hard, over time our collective knowledge will improve.

chop
07-31-2008, 04:18 PM
Perfectly said!

This is the key point. Our brains really are quite limited. They have evolved to solve certain kinds of problems, on earth, at a certain scale of the Universe, but they simply have not evolved any intuitive or innate abilities to understand everything, including reality at larger or smaller scales.

Which isn't to say we can't overcome our limits. Math is a tool (well a collection of tools) that we humans are developing to help us understand how our Universe really behaves. It is not intuitive. It does not come naturally to us. But fortunately in a huge population of billions born, occasionally some people are born who for various reasons, make significant contributions, who have unique new insights, who add a new tool or refine one.

We may never fully understand everything, but as long as scientists keep the creed of pushing back at each other hard, over time our collective knowledge will improve.

I have friends that seek understanding about the reality we live in through religion, philosophy, spirituality, etc. While I can't criticize their path for knowledge and understanding I can try to convey my amazement with "precieved" reality, the large and small universe we exist in, and our never ending quest to try to make sense of it. I find the study, even with my limited grasp, fullfilling. There are many good tutors along the way.

A couple of good reads for the amature astrophysicist (or scientist):

"E=mc2" by David Bodanis, a biography of the equation. Excellent read.

"A Short History of Nearly Everything" by Bill Bryson

Personally I never paid attention in science and math class. These books will challenge you to pay attention and the result will be more than rewarding. I've read each cover to cover several times; each time with facsination and a nagging dissapointment with the inability of public education to tell these stories with the wonder they deserve.

xdamage
07-31-2008, 07:07 PM
^^^

I forget which book it was I read that basically ends with the notion that what we are learning about reality is that the Universe is far more amazing (and stranger) than any fictions or religion that humans have dreamed up in their heads.

Jay Zeno
07-31-2008, 09:11 PM
"The Big Bang" by Simon Singh is quite good for a progressive read on this stuff, with good foundation for the graph line of knowledge from then to now.

Silverback
07-31-2008, 11:09 PM
I think this explains it better:

http://www.youtube.com/watch?v=JWVshkVF0SY