The scale of the known Universe

[CRTGAMER]

Is the Universe limitless? We have a limited range of view because of the time it takes for an image reaches us. If you follow the big bang theory as exceeding the speed of light, there are galaxies that we will never see, moving faster away then the image reflected back to us. A galaxy say 100 light years away, the image we see is from 100 years ago. What about if one is situated at a hypothesized edge of the entire Universe, what could be seen at that edge?

Okay gotta cut down on the coffee. For just a small area, that is a lot of galaxies!

http://www.dailymail.co.uk/sciencetech/ ... z0tXPPzn6J

Hubble's "deep-field" view offers a glimpse of the Universe from 13 billion years ago.

Looking through the telescope, Hubble's sensors reach back almost 13billion years and brings us back an image from the dawn of time. The photo, re-released as part of the NASA telescope's 19th anniversary, shows an image of the universe from when it was less than a billion years old. What an active place it was - with the picture showing us a bewildering variety of galaxies that give important clues to understanding the evolution of the universe.

The picture shows several hundred never-before seen galaxies in what is called a "deep-view" of the universe. The full image - taken over ten days in December 1995 - shows just a portion of the sky no larger than looking at a a coin placed 74 feet away, and NASA used 342 separate exposures to produce the finished article.

19th birthday: The Hubble Space Telescope is having one final makeover before retirement. It shows at least 1,500 galaxies at various stages of evolution, helping show how early on galaxies formed following the Big Bang, the theory which states that all matter in the universe was once compressed into an area smaller than a pinhead before rapidly expanding in an explosion 13.7 million years ago.

Harry Ferguson, one of the Hubble Deep Field astronomers, said: "One of the great legacies of the Hubble Telescope will be these deep images of the sky showing galaxies to the faintest possible limits with the greatest possible clarity from here out to the very horizon of the universe."

The "deep field" image can be seen as the equivalent of digging a core sample of the Earth's crust - as the telescope peers further into the distance, it is digging deeper into the past picking up radiation and light from earlier and earlier in the universe's existence.

More than 1,000 never-before-seen galaxies are visible in this "deepest-ever" view of
the universe, called the Hubble Deep Field, made with NASA's Hubble Space Telescope

[MrPopo]

Is the Universe limitless?

You have no idea just how profound that question is. Based on observations all the observable objects of a given distance X are moving away from us at velocity Y. Essentially, you can think of it as us being stationary and everything else rushing away from us. Of course, we're not actually in the center of the universe; from the perspective of any of those other galaxies they're the center with everything rushing away from them. Think of the old balloon metaphore; as you blow it up and focus on one dot it makes that dot the center, because what's actually happening is that space itself is expanding. And due to the nature of this expansion the far reaches of the universe expand faster than light can travel, leading to the aforementioned edge of visible space. Again using our crude 2D analogies, the Universe could be a sheet or it could be a sphere; in one case there's an edge and in the other if you went in one direction you would eventually wrap around back to your starting point. But due to the nature of the expansion of space it's impossible to verify one way or another.

[CRTGAMER]

Looking at Earth's entire 4 ½ Billion year history, man barely a blink in time.
Dinosaurs = 160 million years, a lot of zeros
Man = only 195,000 years

http://en.wikipedia.org/wiki/Geologic_time_scale

The BIG pic.
http://upload.wikimedia.org/wikipedia/c ... remake.png

[elvis]

Checking back over the thread, I see that Jesus Christ has not posted to it.

Nobody uses their real names on the internet.

Is the Universe limitless?

How much nothing can you fit into an unconfined space? (Not that I'm admitting to "nothing" actually being "nothing", nor the universe being unconfined either).

Either way, it is somewhat amusing seeing humans constantly strive to wrap finite definitions around infinite things. (Less amusing, because I do it regularly as well). We're somewhat constrained by our constant need for definitions and boundaries due entirely to our finite existence.

Sucks to be us, sometimes.

[J T]

.

[Pulsar_t]

[J T]

Big Bang, more to follow.

Weird. I just saw this diagram for the first time ever at an observatory about a week ago. It leaves me with questions though. I thought the big bang exploded out in all directions from a singularity? The diagram makes it look like it moves in one direction out from the point. Unless, I'm reading it wrong. I see time is on the X-axis, I just can't tell if that's how many light years away from the starting point we are, or if each area is supposed to be a slice of time. Trying to understand the space-time continuum makes my head feel funny.

Also, we can observe that the boundaries of the universe extend away from us in all directions. But that seems peculiar if we are not near the center of the bang, which we should be far away from by now. Does that mean that planetary bodies closer to the center of the universe are moving at a slower velocity than us on Earth and planetary bodies farther away from the center point are moving at a faster velocity than us on Earth, so we only have the perception that they are expanding out, when in fact we are all accelerating and it only looks like those closer to the center of the universe are expanding away from us because we are actually accelerating away from them? If we are accelerating, then what is propelling us outward away from the big bang starting point now?

[Ivo]

Why the heck am I in this joke (genuinely curious, I'm guessing it is not actually me though).

Ivo.

[Ivo]

JT,

The plot shown is an artist impression - going to the right is time. Going "radially" is space, so as the thing is sort of cylindrical / conical it represents going out in all directions.

It is meant to illustrate that there was a LOT of expansion spatially in a very short time in the very start (inflation), and then it continued expanding, but as the "slope" is a upward curve instead of a line the expansion is accelerating again.

Furthermore, if the Big Bang theory holds, the idea is that everything is expanding in relation to everything else. Imagine painting dots on a balloon and inflating it - the dots move away from each other (that is a good way to "picture" it I think). There is not really anything "closer" to the center in that way as in the balloon you are considering only dots on the surface of it, not anything inside it (which would indeed move slower if it was closer).
Our universe is apparently flat (or very closely flat) so it is not appropriate to consider it a N-dimensional ball, but lets imagine it was a ball. If you are considering it a 3-dimensional ball you must not think of a sphere surface (which is a 2-dimensional ball) nor of a solid sphere, but as the surface of a 4-dimensional sphere. In any number of dimensions in this type of construction there is no "special" point nearer to a center, they are all equal to each other (think of the line that encloses the solid circle or the surface that encloses the solid sphere). So it seems to be (in a very macroscopic or cosmological scale) with our Universe, although it isn't curved like a ball is.

As for what is actually "propelling" us outward, if there was no acceleration we could say it is just inertia from the initial point (don't ask about the starting conditions as no one really knows so far). As the expansion is accelerating however, that can't be just inertia. We know gravity would decelerate the expansion if there was enough stuff to "pull" back the expansion, but there isn't, but in order to actually push outwards it is something that we don't really know. We represent our ignorance by saying there is "dark energy", which is something that has the weird property of having negative pressure (positive pressure is what everyone knows as pressure - pressure that goes inside; negative pressure goes outside). There is one good way of physically explaining a positive pressure, through a specific type of, shall we say, particle - a scalar - that in certain situations can give such outwards pressures. Unfortunately, if it was a scalar doing it we would expect the acceleration to be much, much, much stronger (by 120 zeros stronger) than what we see. It is thought that it was precisely a scalar pushing out that did the part called Inflation, and you can imagine how much faster that accelerated expansion was.

Any more questions let me know, I'm not exactly an expert on Cosmology but I should be able to field most questions from people here.

Ivo.

Weird. I just saw this diagram for the first time ever at an observatory about a week ago. It leaves me with questions though. (...)

[Ack]

Why the heck am I in this joke (genuinely curious, I'm guessing it is not actually me though).

Ivo.

"The universe revolves around me."