So how long or far is forever?

[fullnelson9999]

On the topic of the immense size of the universe, or space and time, I usually try to avoid thinking about it.

Things like that tend to make me sick to my stomach. Literally.

[GibbsFactor]

Watch this video about the most important picture ever taken in the history of mankind.

http://www.gizmodo.com.au/2009/08/the-most-amazing-photo-ever-taken-now-in-3d/

[Soup]

Forever is a form of time and not distance right? I think I'm right

IF that is true than forever is just perception and thus relative

[Prosperity]

http://www.youtube.com/watch?v=AUUkjWsNC9k

Scale: powers of 10

from the particles that make up particles to the galaxies that make galaxy clusters

[Ignatius J.]

I'm going to assume that this isn't just a thread about the dangers of smoking pot.

Q: How can space be finite? Does that mean that there is a wall beyond the edge of space?

A: Remember pacman. Was the amount of area that pacman could move around on infinite? No, it was the size of one screen. But did it have any edges? Boundaries that pacman could not move past? Absolutely not. If pacman went past the edge of the screen to the right, then he showed up on the left and vice versa. Finite space CAN work in the same way. Also, think about the surface of the earth, it has a finite size but it also has no boundary. Such spaces are called closed. Now it's easy to imagine a two dimensional closed space because we can just embed it in a three dimensional space. No such luck for three dimensions (and what about the fact that our universe is really four dimensional, 3 space + 1 time?) Turns out that's actually not a big complication. It certainly is possible that the universe is closed, but that doesn't mean it has a boundary.

I could link to this:

http://www.mathpages.com/rr/s7-01/7-01.htm

but that probably does more harm than good.

Anyway, space is probably not closed, which means that its open. What does open mean? Well it means that it goes on forever, and well, that's a hard concept to grasp.

But that brings up an interesting point, how does infinite space expand, and what does that mean? Well, it means that if i pick two points in the universe and mark them with a red dot, then if I wait a while, those two dots are further apart. Now, how do we observe this, we can do it in two ways.

Option 1 - observe the matter. Pick two stars watch them for a while and they should move apart from each other if the universe is expanding. If all the matter in the universe is generally moving away from all the other matter than this should indicate some kind of exapansion right? But not so fast, this just means that the matter content is expanding. you would expect the same thing if all the matter started at one point in the universe and just explodedc out into the universe. That's not the same thing as saying the UNIVERSE is expanding. So we need a different check.

Option 2 - Cosmic microwave background. LEts say you're traveling at 50 miles an hour down the freeway, and the guy in front of you is traveling at 50 miles an hour down the freeway, what happens to the distance between the two of you? It stays the same right? But suppose space is expanding, then the distance between the two cars would increase even if you were traveling at the same speed. This is the effect we need to observe. Luckily we know from the michelson-morley experiment that light ALWAYS travels at the speed of light. So if we watch two photons traveling and the distance between two photons traveling in the same direction increases, then space must be expanding.

The way we observe this is that light is a wave, so if you stretch out the space between the crests of a wave, you see that the wavelength increases. As you may remember from high school, the wavelength of light is realted to the color, the longer wavelength light looks red, and the shorter wavelength light looks violet. If we start with a light wave of a certain color then in an expanding universe, the color is going to become redder over time. This phenomenon is referred to as the red-shift and is why we study the cosmic microwave background. This is essentially all the random light out there in space. We ask what the frequency of the random light out in space is (I know it looks dark but it's not TOTALLY dark) and then try to see if it has been red-shifted.

Anyway, all that is basically physics we knew about in 1925, einstein's general theory of relativity. No string theory, no quantum mechanics, nothing fancy. I don't know if that's understandable or helpful, but at the very least it's mostly a representation of how we talk about expanding universes and what the evidence is.

[[[ghost]]]

"Forever" is just an easy way of saying "beyond the limits of human comprehension". No point in worrying about things you absolutely cannot comprehend.

Simple, Wise, and To the point.

[Prosperity]

But that brings up an interesting point, how does infinite space expand, and what does that mean? Well, it means that if i pick two points in the universe and mark them with a red dot, then if I wait a while, those two dots are further apart. Now, how do we observe this, we can do it in two ways.

why don't the dots themselves expand?

[WVUforREDSKINS]

Did you eat the entire 1/8th of shrooms before you started this thread?

lol I was thinking the same thing.

Because I was thinking about this exact thing once when I took some mushrooms. It was not a very good trip and I never need/will do any drug like that again.

[matty dread]

Time, the universe, death, life, it will all trip you the F out if you really think about it, or try to at least.

[LaxBuddy21]

Think of it this way. take two points A and B. Now go half way from A to B. Then go half way again. And again. Keep doing this until you reach point B. You will never get there. Think of the opposite of that concept and you get the concept of the universe and infinite space.

[sly]

http://www.gizmodo.com.au/2009/08/the-most-amazing-photo-ever-taken-now-in-3d/

The picture of all those galaxies has been my desktop wallpaper for a few months now. It's honestly just incredible... and can cause you to seriously put life, death, and this tiny little planet in the middle of nowhere into a completely new perspective.

I really wish in my lifetime we'll finally be able to say for certain we're not alone in this galaxy... with billions of other galaxies, how can we be alone? Pretty incredible concept. I wonder if they've invented football, too?

[NOLASKINSFAN]

Would it be a giant wall? Don't think so.

In fact there is a wall, Chuck Norris is the only one to ever see it. He counted to infinty on his way out, and then again on his way back.

[No Excuses]

You must have had one hell of a trip.

[GibbsFactor]

The picture of all those galaxies has been my desktop wallpaper for a few months now. It's honestly just incredible... and can cause you to seriously put life, death, and this tiny little planet in the middle of nowhere into a completely new perspective.

I really wish in my lifetime we'll finally be able to say for certain we're not alone in this galaxy... with billions of other galaxies, how can we be alone? Pretty incredible concept. I wonder if they've invented football, too?

Using the concept of infinity, there is an infinite amount of complex life in our universe.

[HRNY4ZRNY]

Watch this video about the most important picture ever taken in the history of mankind.

http://www.gizmodo.com.au/2009/08/the-most-amazing-photo-ever-taken-now-in-3d/

Hey thanks for the link I thought it was really incredible. I had never seen it. I showed my chick and she was like eh'

I thought it was funny that they put so much money time and work to get that pic and someone could be like eh'

Anyways thanks for the link

For the record I havent smoked pot in years

[Corcaigh]

It's longer or farther than you can think.

[The Sir]

every thousand years

this metal sphere

ten times the size of Jupiter

floats just a few yards past the earth

you climb on your roof

and take a swipe at it

with a single feather

hit it once every thousand years

`til you've worn it down

to the size of a pea

yeah I'd say that's a long time

but it's only half a blink

in the place you're gonna be

[Spec138]

From 3.7 trillion miles away, I present my favorite picture ever taken:

"Look again at that dot. That's here, that's home, that's us. On it everyone you love, everyone you know, everyone you ever heard of, every human being who ever was, lived out their lives. The aggregate of our joy and suffering, thousands of confident religions, ideologies, and economic doctrines, every hunter and forager, every hero and coward, every creator and destroyer of civilization, every king and peasant, every young couple in love, every mother and father, hopeful child, inventor and explorer, every teacher of morals, every corrupt politician, every "superstar," every "supreme leader," every saint and sinner in the history of our species lived there – on a mote of dust suspended in a sunbeam.

The Earth is a very small stage in a vast cosmic arena. Think of the rivers of blood spilled by all those generals and emperors so that, in glory and triumph, they could become the momentary masters of a fraction of a dot. Think of the endless cruelties visited by the inhabitants of one corner of this pixel on the scarcely distinguishable inhabitants of some other corner, how frequent their misunderstandings, how eager they are to kill one another, how fervent their hatreds.

Our posturings, our imagined self-importance, the delusion that we have some privileged position in the Universe, are challenged by this point of pale light. Our planet is a lonely speck in the great enveloping cosmic dark. In our obscurity, in all this vastness, there is no hint that help will come from elsewhere to save us from ourselves.

The Earth is the only world known so far to harbor life. There is nowhere else, at least in the near future, to which our species could migrate. Visit, yes. Settle, not yet. Like it or not, for the moment the Earth is where we make our stand.

It has been said that astronomy is a humbling and character-building experience. There is perhaps no better demonstration of the folly of human conceits than this distant image of our tiny world. To me, it underscores our responsibility to deal more kindly with one another, and to preserve and cherish the pale blue dot, the only home we've ever known."

~ Carl Sagan

Now for my favorite composite image, also from the Voyager space craft.

[HRNY4ZRNY]

every thousand years

this metal sphere

ten times the size of Jupiter

floats just a few yards past the earth

you climb on your roof

and take a swipe at it

with a single feather

hit it once every thousand years

`til you've worn it down

to the size of a pea

yeah I'd say that's a long time

but it's only half a blink

in the place you're gonna be

I dont get it, it sounds interesting though