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SWilhelm
2007-Jan-08, 09:08 PM
Beats me.

We talk about it so often, but what exactly is it? In the Big Bang episode Dr. Gay gave the analogy of raisin bread, and how space is the bread between the raisins. This helps, but it doesn't explain what space is. As far as I know, space is just the area between mass and/or energy, therefore isn't space actually nothing? How can nothing expand? Would it be more accurate to say that all massive objects are moving apart?

If space is nothing, then what is outside of the universe? More nothing? Wouldn't that just mean that the universe is infinitely large? Wouldn't the universe just be defined as a collection of objects of mass and energy?

We talk about gravity bending space, but what does that mean? Is space like dark matter, in that we can't actually see it but we see it's effects? Am I asking unanswerable questions?

My head hurts.

-Scott

squid
2007-Jan-08, 11:05 PM
Just a few more questions that I think fit with the ones above...

Okay, I'm quoting my older brother here (he said this when he was three)
"If the universe goes to infinity, and the universe is always expanding, is infinity getting bigger?"
So yeah, as far as I knew/previously thought, I thought that the universe was supposed to be infinitely large. However, if the universe is still expanding from the big bang, how can it be infinitely big and still be getting bigger?

morlankey
2007-Jan-11, 07:27 AM
I don't think the Universe is actually infinitely big. If you think of the fact that nothing can travel faster then the speed of light and the fact that the universe is about 13.7 billion years old, the universe can be no larger then 13.7 billion light years across.

I like to look at the universe as a bubble containing everything inside it, including our dimensions. At the moment, even in a complete vacuum, it is still possible to figure out your position. If we were somehow able to get outside our universe, there would be no dimensions. We wouldn't be able to tell one point from another. There wouldn't even be a dimesnion of time.

... or, it's possible that if we were to exit our universe, there would be more dimensions. Who knows? Whatever it is, it'd be so completely different that it's completely unimaginable.

Mrs B
2007-Jan-11, 02:10 PM
I totally agree! No one will ever know because if a universe does not assume fundamental constants of nature that can sustain life and the development of intelligence, no one will ever be able to report on its traits/characteristics. That's the reason why our universe makes so much sense to us, it's perfectly adapted to us. Or "We live in the best of all possible worlds" to put it in Voltaire's words. If you go search the internet on the anthropic principle, it will give you hours of mindbending reading to plough through.
But I on the other hand do not believe the universe will expand for ever. I think the total universe-gravity thing will stop and regress the expansion of the universe and we will all be compressed together right back to the singularty where we came from.
Does this make sense or do I need to take my tablets now nurse?

luckynate
2007-Jan-15, 01:45 PM
Beats me.

We talk about it so often, but what exactly is it? In the Big Bang episode Dr. Gay gave the analogy of raisin bread, and how space is the bread between the raisins. This helps, but it doesn't explain what space is. As far as I know, space is just the area between mass and/or energy, therefore isn't space actually nothing? How can nothing expand? Would it be more accurate to say that all massive objects are moving apart?

space is not actually 'nothing', in fact it isn't really 'empty' anywhere. there is a background of microwave energy that fills the entire observable cosmos, which is a remnant of the big bang. It would however be more accurate to refer to universal expansion as "all massive objects that are unbounded by mutual gravitational attraction which exceeds the negative pressure of the dark energy are moving apart"


If space is nothing, then what is outside of the universe? More nothing? Wouldn't that just mean that the universe is infinitely large? Wouldn't the universe just be defined as a collection of objects of mass and energy?
The universe can be finite in size and yet have no edge, like the surface of the earth. or it can be infinite in size. Which ever view you take, the meaning of something being "outside" the universe is undefined, and can have no effect on what we observe. This is what is meant by the term "non-existant".


We talk about gravity bending space, but what does that mean? Is space like dark matter, in that we can't actually see it but we see it's effects? Am I asking unanswerable questions?
The answer to your first question is actually quite simple. Think of a laser. When fired this light will travel in a "straight line", meaning a geodetic path through the shape of the universe (the shortest possible path). When the laser beam travels close to a massive body, its path will appear curved to a distant observer. This effect has been experimentally confirmed to be true. The point is that the light is still taking the straightest path, but moving through a curved space! The movement of the moon around the earth is another example of the curvature of space. If not for earth the moon would move in a euclidian straight line, but the earth's gravitation curves the space near it so that the path of the moon is bent around it, giving the appearance of orbit. The moon is still moving straight, again through curved space. The reason light escapes most gravity (except black holes) is that its speed is very high compared to the moon. In fact if the moon were to somehow speed up, it would escape from the earth's gravitation, just as light would.

My head hurts.
-Scott

eric_marsh
2007-Feb-08, 02:32 AM
That's the reason why our universe makes so much sense to us, it's perfectly adapted to us. Or "We live in the best of all possible worlds" to put it in Voltaire's words. If you go search the internet on the anthropic principle, it will give you hours of mindbending reading to plough through.

As a follower of the weak anthropic principle I would argue that the univers is not perfectly adapted to us. I find it to be terribly egocentric to say the universe has adapted to us, just as it is/was to take a geocentric perspective. Rather, we adapted to the universe around us. We are able to observe the universe because the universe is capable of supporting us.

Personally I think this is a good argument for a multiverse.

squid
2007-Feb-09, 02:51 AM
...the total universe-gravity thing will stop and regress the expansion of the universe and we will all be compressed together right back to the singularty where we came from.

So basically what you are suggesting/hinting at is that once the universe gets recompressed back into the singularity there will be another big bang and there will be a second (assuming that we are in the first) age of our universe? That would be so weird, yet so incredible.

Uranu5
2007-Feb-14, 12:04 AM
Oooohhh.... well we want to represent space as an object and not as... NoThInG!!! so thats where dark matter comes into play really, also since everything in science is converted into "information" its impossible to get information from nothing therefore there has to be somthing filling the gap, the space; so dark matter is that somthing. And with the moving away of the galaxies from each other the information holds strong :surprised :surprised

Uranu5
2007-Feb-14, 12:13 AM
As a follower of the weak anthropic principle I would argue that the univers is not perfectly adapted to us. I find it to be terribly egocentric to say the universe has adapted to us, just as it is/was to take a geocentric perspective. Rather, we adapted to the universe around us. We are able to observe the universe because the universe is capable of supporting us.

Personally I think this is a good argument for a multiverse.

We are exploring the universe on our terms, not of the true universes for we cannot predict everything that has happened during these 13 billion years of the universes life. reletive to the life time of the universe we will be wiped out of existance very shortly...but u can best belive were gonna get sum info about our lil doomsday before it occurs

Ziggy Stardust
2007-Feb-14, 07:54 PM
There was a classic philosophical debate between Newton and Leibniz on this subject (they seriously hated each other). Newton believed that space is absolute (so if you took all the matter out of the universe there'd still be something called 'space' left over). Leibniz thought space was nothing more than the relations between different objects. So they would debate stuff like if you were the only object in the universe could you spin? (ie. Newton would say yes because you can spin around relative to 'space', Leibniz would say no because there's nothing you can spin relative to).

spent
2007-Feb-15, 06:30 AM
This topic is cool. I find it really cool how many folks think of the same thing.
Even though opinions differ.

I think Space can possibly be very large. Large enough that if we could travel far enough to pass everything from the big bang we may "TRAVEL" in a "SNOWBLIND" manner, thinking we are traveling in the same direction we were but kind of not really nowing cause we can't make heads or tails out of where anything is. (because we past everything that shines light and our eyes can't see it. Like getting stuck in the arctic and seeing nothing but snow (white) but opposite (black).

Now we may after passing everything , travel for billions of year and then once again find matter such as stars and planets. We may have returned to the point we left. Like traveling around the world. chicago to chicago.

Or.........

Just meeting up with matterial from yet another big bang that went off.

We are probably just one of billions of big bangs going off because size is relative too. "Big Bang" the same as a star that goes supernova just on a larger scale.

I like to think of it as a REALLY BIG pool table and the rack is the big bang before it went off. What's cool is that all the balls don't actually move away from every other ball. Though if you lived on the the one ball that goes all the way down the table it would appear (To you) that everything was.

However, If you lived on one of the balls that collided with another ball, it would appear (to you) as if that ball was getting too close for comfort and heading toward you before you collided. Like apophis is heading toward earth. Or andromeda heading for us.

Sometimes one ball travels in the same direction but slower than the one behind it. But from both balls perspective they are heading toward each other.

Uranu5
2007-Feb-17, 12:51 AM
Theres a book called "Zero" and its really tight, its about the# zero and infinity and the philosofhys behind it....excuse the speeling :).......but there was one professor during the time of the great greek philosofers that stated a fast runner could not pass up a turtle that is right infront of him...and by segmenting the time in halfs each time did this become the reality...
just like cuting a penny in half... andthen cuting the same piece in half...and over and over and over and over u will never be able...litterally get rid of that penny....untill u get to the size of protons and neutrons....but nobody cares about them :D

EvilEye
2007-Feb-17, 03:39 AM
I think people confuse the universe with space.

But space itself is a part OF the universe. It is distance between particles, between planets, between your finger and your nose.

It is very hard to comprehend that the universe is a group of things that actually has a border, but there is no outside of that border.

There is no "nothing" as stated before. But also, there is and edge. Just like there is an edge to the ouside of an orange. Then you (inside the orange) say, "well what stops the orange"? The question is moot again. Nothing stops the orange. It is all there is of the orange and that is the end. Period.

Your mind wants to think that if there is a bubble (universe), that there has to be something to contain it. But in "space" it doesn't work that way. It can grow infinately larger, but it is still finite. There is an edge. There just isn't anything at all beyond that edge. No space, no time. No distance.

SWilhelm
2007-Feb-21, 07:17 PM
There is no "nothing" as stated before.


There is an edge. There just isn't anything at all beyond that edge. No space, no time. No distance.

Heh, see this where I get confused, but it's starting to make more sense.

There is no "nothing" inside the universe, for even space is "something," even if we can't see it. I think my problem is that I am trying to visualize "nothing." "Nothing" can't really be comprehended because it is, after all, nothing.

Thanks for all the responses guys, so much more than I was expecting. :D

Coincidentally, right after I started this thread I got my newest edition of Wired magazine, where they had a whole section devoted questions categorized as "What We Don't Know." The main article was entitled "What's the Universe Made Of?"

http://www.wired.com/wired/archive/15.02/bigquestions.html?pg=3#universe
It was "answered" by Brian Greene.

-Scott

EvilEye
2007-Feb-22, 12:53 AM
I think I finally got it through my son's head. And this is very simplistic, but it worked.

There was a package of Chips on the table, and about a foot away, there was his plate.

I asked him.... if there were no space (or nothing) between your plate and the chips, where would the chips be?

He answered, "Right next to the plate."

And if you wandered beyond the bag of chips, what is there? ....he replied (and he is 13).... "no more chips and no plate."

The whole point is that if you have nothing with which to gauge distance, there is no time or space.

If you were magically placed into empty nothing and you were the only thing in it, you could walk forever, and you would be exactly where you were when you started. Take away the space (which requires at least two objects) and you are everywhere at once.

chasepreuninger
2007-Feb-26, 02:19 PM
I have a Google group about astronomy is anybody is interested. Here is the link: http://groups.google.com/group/neat-astronomy?hl=en to apply for membership (I will pretty much accept anyone right now since I don't have many users.) Click "apply for group membership" link on the right hand side of the page. Sign into your Google account or create one, and follow the steps from their. Or just email me and I will invite you. chasepreuninger@gmail.com

KingNor
2007-Apr-05, 12:07 AM
can't you think of the "edge" of our universe as sort of being everywhere?

I think of it like this, as i sit here typing i'm comfortably sitting in our universe. but now i want to move out of our universe.

so just by being here i take up our normal demensions. height, length and depth. i'm a 3 dimensional guy sitting in a 4 dimensional universe if you count time. right?

ok. so i hold up my hand and... i move it into the 5th dimension so i can pull myself through. except i can't do that because i'm bound by my four dimensions. so basicly now i'm at the edge of our universe, trying to get out but can't because there is no where to go.

that's how i try to visualize it, does that make any sense at all??