Is the universe infinitely large or finite in size?

how about the theory that our whole universe might be nothing more than a hologram...."In a larger and more speculative sense, the theory suggests that the entire universe can be seen as a two-dimensional information structure "painted" on the cosmological horizon, such that the three dimensions we observe are only an effective description at macroscopic scales and at low energies." some scientists also believe the human brain is a hologram. no one has ever figured out why the brain is capable of storing so much information and how it is able to recall it so quickly, and in such a small amount of space. a hologram based brain would make sense, because with it, the brain could communicate directly between different areas without the slight delay of sending the message thru a network of neurons. it is the same reason why nothing is said to be able to travel faster than the speed of light, yet subatomic particles can communicate instantaneously with each other, wether they are 10 feet apart or 10 billion light years apart.....wierd stuff.

Using a two dimensional example:

The universe is a ballon. The surface has only two dimensions - top/bottom and left/right. You are viewing it from a 3rd dimension. To anybody living on the surface there is no edge, and no up/down. If they travel far enough in any direction they eventually come back to where they began. This universe is finite, but unbounded.

Now suppose you draw a square on the surface of the ballon and make it exactly 1 inch square. Now you start adding air to the ballon to make the ballon bigger. From our 3 dimensional view we can see the drawn square getting bigger as the balloon gets bigger.

But to anybody living on the surface of the balloon nothing is happening. The yardstick they would use to measure the square is increasing at the same rate the square is increasing, so from their perspective their universe is not changing. It's not that things are moving farther apart, it's that space itself, including the space that their body occupies, is expanding and they can't tell.

That is basically what is happening in our universe. The balloon is a two dimensional construct that is warped through a 3rd dimension, anybody living in the 2 dimensions can't tell because of their perspective. Anybody living in 3 dimensions can easily tell.

Our universe is a 3 dimensional construct warped through a 4th dimension. Us living in the 3 dimensions can't tell just by looking, but anybody living in 4 dimensions could.

We know that our universe is expanding because of the dopplar shift in electromagnetic frequencies caused the objects moving towards us or away from us.

Let's not get into the arguement that the universe actually has 11 dimensions.

Does it really matter if it is infinite or not? I mean, who will travel to the edge that may or may not exist? The existence or absence of any edge affects this planet's inhabitants in no known way.

"...when you try to extrapolate the end of the universe, you say, if the universe is indeed infinite, then how - what does that mean? How far is all the way, and then if it stops, what's stopping it, and what's behind what's stopping it? So, what's the end, you know, is my question to you."

- David St. Hubbins

Yogi,

Not a bad start. I want to add a few things including the concept of inflation. Immediately after the big bang for a period of time that lasting less than a fraction of a second a process of inflation occurred that expanded the universe from, effectively nothing to approximately 90% of its size today. This inflation was caused by the incredible enthalpy (energy) present during the initial condition.

So over the past 13.7 billion years since this event the universe has expanded, at an accelerating rate, but is only about 10% bigger than one second after the big bang. This would indicate a radius of 120-130 Billion light years.

The argument for all this is derived from Einstein’s General Relativity and the observation that matter distorts space.

The concept of 11 dimensions is not that tough to picture if you imagine that 7 of them are curled up so tightly that they have been unobserved and ignored until the last 25 years. Only specialized mathematics techniques indicate that they are there at this point. These dimensions are very important as they form the fabric of space and enable almost all observable phenomena like:

The establishment of constant values for fundamental particle energy and masses.

The wave/particle nature of light is caused by its interaction with the fabric of space. This interaction occurs on a scale less than the Plank length (lp) transferring spin and vibration (EM spectrum), while regulating its velocity (c).

Racehorse, asking questions about where it all came from and where it’s all headed has given Physicist’s a greater insight into the “engine” that is driving nature now. If you think that has no practical application or minimal impact on our lives here on earth re-read the two examples described above. We are on the verge of huge discoveries in this field.