Expanding Faster?Really?

This is one for CR4's Jorrie, among others.

I am sure your explanation is valid, it just has not sunk in yet.It seems to me ( an ignorant man in things of this nature), that the further back we look, the closer to the "Big Bang" we see, and I would expect the initial expansion rate to be faster than it is now. Did it initially expand, then contract (or slow expansion), then start accelerating expansion again?Are they inferring distance by redshift measurement, or vise versa or do they have a reference independent of redshift for measuring distance? An error in distance(time) calculation could give a error in redshift prediction.

I need to sleep on this awhile.

The expansion rate is proportional to the slopes that you see on those graphs above. Right after the BB, the expansion rate was tremendously fast (an almost vertical slope). The slopes of the two graphs show you how the expansion rates developed over time (for the two scenarios).

Distance had originally to be found by means other than redshift. Once you have distance for a good number of objects (with their redshifts), you know the Hubble constant. You can then use redshift with the Hubble constant to find the distance of other galaxies or quasars.

-J

Jorrie, two questions that are a little off target, but...

1. We know that supermassive black holes have such strong gravity that nothing can escape the space-time (space curvature ?) of the Black Hole. We believe that the Big Bang happened when all the matter / energy of the Universe was concentrated at nearly infinite density in a singularity or similar. How did matter/energy escape such an infinitely dense (thus infinite gravity) particle??

2. Agreed that the Universe is expanding. What is the Universe expanding into? Do we assume that there is an edge / border to the expanding Universe? (What is "space"?).

Hi C7,

Space itself is not subject to the limits posed by the speed of light and hence cannot be contained by black holes. It is only things (including light) that cannot move faster than light through space. Given enough energy inside space itself, it can expand at any rate whatsoever and it is allowed to carry light and matter with it.

"What is space" is not really answerable by science. The best answer I know of was given by Werner Heisenberg: "Space is blue and birds fly through it"!^[1]

My perception of what space expands into is biased by my preference for the hyper-spherical model (the cosmic balloon), where space expands because the balloon expands into a 5th dimension (a hyper-dimension). Check out my cosmic balloon threads if you like.

-J

[1] Felix Bloch (Physics, 1952), recalls an encounter with his mentor, Dr. Heisenberg, which is recorded for posterity in Physics Today, December 1976, Vol. 29, No. 12, pp. 23-27. Said Bloch, "I have discovered that space is a matrix of linear forces." Bloch had just read a book entitled Space, Time & Matter. "Nonsense!" replied Heisenberg. "Space is blue, and birds fly through it."

There are at least four different ways astronomers estimate the distance to galaxies they then compare their redshifts and see a relationship between redshift and distance.

Look up the recent work done with the mighty Hubble estimating the age of the universe.

Our visible universe is a sphere surrounding us in all directions.It is limited by our ability to receive weak signals,be it light, rf, etc.Some matter may have redshifted into invisiblilty,and we could never know.There is much more to the universe than what we observe, dark matter and energy aside.

If everything originated from a single point, then if we run the film backwards, there will be a center where everything began.Therefor the universe must still have a center somewhere,but it is beyond our observational abilities.We cannot point our telescopes toward "center" because of the form that space time has now assumed.We are like a photon in a fiber optic cable, we must follow the contours of space time like the photon follows the fiber.The fiber could be curved in many directions, but to the photon, it seems just like a straight line.To escape the waveguide(fiber) (spacetime in our case), is impossible, at least with current technology and knowledge.

We could be trapped between two concentric spheres, expanding in unison, our universe existing in the space between and dark energy created between the two "shells"

EZStreet

Hi EZStreet, you said: "If everything originated from a single point, then if we run the film backwards, there will be a center where everything began. Therefor the universe must still have a center somewhere,but it is beyond our observational abilities."

Yes, but there is no problem observing it - it is right where we are today!

Run time backwards and every galaxy will approach us until they are almost on top of us and then, well, they will all disappear, leaving only radiation and other particles...

I suppose it also depends how you define center. If the universe is hyper-spherical, as is reasonably possible, then there is a hyper-center where it all began, but it is outside of our observational ability - in a different dimension. In normal space there is no center today. This is the most fundamental truth that you must try and wrap you head around.

I also suggest you read some of the material that StandarsGuy pointed you to. Speculation on these things may be an interesting exercise, but will rarely bring you closer to reality.

-J

"Expanding Faster?Really?"

Yes, that is the conclusion obtained by measurements from about 2003 until now.

For more enlightenment look here, here, and here.