Question to the Astronomers

[GoinAllTheWay]

Ok, I was watching perhaps one of the deepest, trippiest shows I have ever watched last night. It was on at about midnite and had to do with the expansion of the universe and what is causing it. LOVE shows like this but the one thing that I didn't full understand I'm hoping can be answered here.

So basically, the universe is currently expanding due to the big bang. I guess the jist of the show is they were trying to figure out if it's speeding up or slowing down and what would cause either effect. The got into the whole dark matter/dark energy thing and concluded that the rate of expansion in the universe is in fact accelerating. Which got me to thinking. Everything we see in the sky is basically a large debris field from the big bang which to me suggests the size of all this debris field could be somewhat estimated. Does that mean beyond all the stars/cosmic dust/planets is just really empty space?

Anyone else see this show? Really wish I saw the name of the show as it was really very good.

[JohnnyFlame]

It is slowing down just like everything else but Obama and Gore have /are going to put a package together to stimulate expansion. It's being funded by Walmart who keep hoping there are some new markets out there.

[GoinAllTheWay]

lol

[PsYcNeT]

There are some fairly good estimates as to the universes rough size (tough to estimate as it is likely still expanding), but what lays beyond the 'edge' of the universe...

...well lets just say there are more theories than a pimp can shake whatever at.

[MarchHare]

According to the theory of general relativity, gravity is a curvature of space-time caused by objects with mass. Because the universe is so massive, it actually curves back in upon itself, so there isn't an "edge" in the traditional sense. If you could fly a spaceship in a straight line forever, you'd eventually come back to your starting point, similar to an ocean liner or aircraft circumnavigating the Earth.

Pretty confusing, right? I took two semesters of university-level astronomy/astrophysics, and I still can't wrap my mind around some of this stuff. :/

[JohnnyFlame]

Originally Posted by MarchHare

According to the theory of general relativity, gravity is a curvature of space-time caused by objects with mass. Because the universe is so massive, it actually curves back in upon itself, so there isn't an "edge" in the traditional sense. If you could fly a spaceship in a straight line forever, you'd eventually come back to your starting point, similar to an ocean liner or aircraft circumnavigating the Earth.

Pretty confusing, right? I took two semesters of university-level astronomy/astrophysics, and I still can't wrap my mind around some of this stuff. :/

No I understand it. When I was a teenager my buddies and I would go down to Chinatown and do a straight line straight to the buffet. We would eat like pigs and then go to the bathroom and puke. Whereupon we would come back and start over at the buffet table thus returning to our starting point.

I just didn't know it had to do with gravity. Thought it was the mushrooms we had before heading down the hill but you live and learn every stinkin day!!!!!!!!!!!!

[flip]

I can't answer your question but the show was called "Death of the Universe" and was on National Geographic channel 828 on bell.

[Flamesoholic]

Originally Posted by GoinAllTheWay

Anyone else see this show? Really wish I saw the name of the show as it was really very good.

Yes, it's called "Naked Science" and the episode was called "The Death of the Universe". It's not on a totally regular schedule but my PVR is set to record it when ever it comes on. It's on Discovery 35, National Geographic 116, the National Geographic and Discovery HD channels 214/215. I love this show. I don't have HD so I can only imagine how awesome this episode would have looked in HD.

[GoinAllTheWay]

/\/\/\

Sweet, thanks!

[Flamesoholic]

You're welcome. Just a heads up there is another one on at 8am on Wednesday morning called "Saturn's Secrets" about what lies beneath Saturn's atmosphere.
Also, the Discovery channel had another show on a week ago or so that you might like if it ever comes on again. It was a 2 hour documentary called "Journey to the Edge of the Universe". It was set up like a travel log or something that pretended you were the passenger on a ship or a satellite and you travelled from Earth all the way out to the edge of the universe, stopping at all of the "hot spots" on the way. It was really awesome, even on my regular SD tv.
http://www.discoverychannel.ca/Article.aspx?aid=14316

[photon]

Originally Posted by GoinAllTheWay

So basically, the universe is currently expanding due to the big bang.

Actually the big bang is the term used for the observation that the universe is expanding (or more precisely the big bang refers to the history of the universe, that it was once very dense and very hot, and now it's less dense and very cool).

The expansion is due to dark energy.

Originally Posted by GoinAllTheWay

I guess the jist of the show is they were trying to figure out if it's speeding up or slowing down and what would cause either effect. The got into the whole dark matter/dark energy thing and concluded that the rate of expansion in the universe is in fact accelerating. Which got me to thinking. Everything we see in the sky is basically a large debris field from the big bang which to me suggests the size of all this debris field could be somewhat estimated. Does that mean beyond all the stars/cosmic dust/planets is just really empty space?

The big bang is really a misnomer, it's not really an explosion in the sense that one would imagine an explosion. It's just something getting bigger.

But yeah you can look at the debris field (all the galaxies) and how fast they are moving, run everything backwards and come back to a point where everything was on top of each other.

But as far as we know there's no "beyond" all the galaxies and such. Think of the surface of a balloon, if you live on the surface of it there's no such thing as beyond the surface of it, but the surface can get bigger by expanding in all directions, there's no beyond.

Originally Posted by MarchHare

According to the theory of general relativity, gravity is a curvature of space-time caused by objects with mass. Because the universe is so massive, it actually curves back in upon itself, so there isn't an "edge" in the traditional sense. If you could fly a spaceship in a straight line forever, you'd eventually come back to your starting point, similar to an ocean liner or aircraft circumnavigating the Earth.

That's only one solution for GR though, there are other solutions which involve a flat universe or a universe curved the other way so that it's unbounded (you could fly in one direction forever).

There's dark matter and dark energy to consider now as well.

From experiments space appears quite flat, but it's unlikely it's actually flat since that would be a very specific solution to GR for Λ (lambda, the cosmological constant).

I think we know that the universe, if it is curved inwards, is bigger than the observable universe though since we don't see patterns being repeated in galaxies or the CMBR, which we would see if the universe was smaller than the observable universe.

But it could very well be infinite spatially.

I don't know if we'll ever know for sure because the speed of light puts constraints on how much we can observe.

You really want to make your brain melt? Try to imagine how a universe that is (and would have always been then) infinite spatially could once have been dense and has since expanded..

Hope that helps until the real astronomer shows up and corrects me.

[GoinAllTheWay]

Ya, wow, this is getting painful. This was not the greatest show to watch right before going to bed. Intensley interesting but my puny brain is far to small to comprehend it all.

I understand exactly what you are getting at with the expaning balloon example but would it not be more accurate to say we are living within that balloon and that the space inside the balloon is also expanding? To say we are living on the surface of it would suggest that the real world equivalent would be like living on the extreme edge of the expanding matter?

[photon]

Originally Posted by GoinAllTheWay

I understand exactly what you are getting at with the expaning balloon example but would it not be more accurate to say we are living within that balloon and that the space inside the balloon is also expanding?

No! That's exactly wrong

The problem with our brains is we are not equipped to think beyond our experiences, so trying to think of taking something 3 dimensional like space, and say now think of that curved, just doesn't work.

So what is often done to try and help communicate things is to reduce things down one level.

So take our entire 3 dimensional universe and squish it to 2 dimensions, only width and only length, no height.

So the surface of the balloon represents the universe. You can only move freely in two dimensions, the third dimension (up and away from the balloon or down and towards the inside of the balloon) makes no sense.

Now glue coins onto the balloon, these are galaxies. Now as it blows up, the coins are all getting further from each other; space between the coins is getting bigger.

EDIT: If it helps, ignore the balloon and think of a flat rubber sheet of infinite size that can be stretched in all directions, the analogy holds.

The universe isn't expanding "into" anything, it's just getting bigger. If you could create a faster than light ship, you couldn't travel really fast and find an edge, because there isn't one*.

Now take that analogy and try to imagine it being translated into more dimensions. The "surface" is 3 dimensional space.

*I say there isn't one, but origins of the universe (and thus the properties of the universe beyond what we can see and back "before" the big bang) is something that is mostly speculation, some ideas have the universe being regions of inflation in a much bigger universe in which case there would be an "edge" to our universe, but that edge would just be more universe.

To say we are living on the surface of it would suggest that the real world equivalent would be like living on the extreme edge of the expanding matter?

Not quite sure what you mean here, the surface of the balloon is everything that exists, the inside and outside of the balloon in the analogy don't even exist.

[GoinAllTheWay]

Originally Posted by photon

No! That's exactly wrong

Really? Crap, I have a lot to try to figure out then.

The part of about the balloon was kinda based on when you said:


run everything backwards and come back to a point where everything was on top of each other.

I think this is were I'm getting into trouble. Imagine all matter in space is gone. Now insert a chunk of rock the size of say, a soccer ball. In the middle of the soccer ball is an eplosive, set off that explosive and you will create a debris feild that travels in all directions. Now freeze that debris field and I kinda figured it would still resemble a sphere. Hope you are following me here. Unfreeze that and everything continues to travel in all directions kinda like a balloon filling with air. In the middle of that balloon is where the exposion originally took place.

Am I way off with that? I assumed when you said the surface of the balloon, you were reffering to the exteme edge of that debris feild. Clearly this is the part I'm not getting my head wrapped around.

**edit**
Hmm, just saw your edit with refference to the rubber sheet. Makes a bit more sense but need to learn more.

[photon]

Originally Posted by GoinAllTheWay

Really? Crap, I have a lot to try to figure out then.

The part of about the balloon was kinda based on when you said:


run everything backwards and come back to a point where everything was on top of each other.

I think this is were I'm getting into trouble. Imagine all matter in space is gone. Now insert a chunk of rock the size of say, a soccer ball. In the middle of the soccer ball is an eplosive, set off that explosive and you will create a debris feild that travels in all directions. Now freeze that debris field and I kinda figured it would still resemble a sphere. Hope you are following me here. Unfreeze that and everything continues to travel in all directions kinda like a balloon filling with air. In the middle of that balloon is where the exposion originally took place.

That's why I said the explosion idea is a really bad one, the big bang is nothing like an explosion.

If you explode the soccer ball, you're still exploding that soccer ball in an existing space, and the pieces are moving outwards in an existing space.

In the big bang, space itself is getting bigger. That's why I use the surface of the balloon, because the surface represents everything that exists.

Originally Posted by GoinAllTheWay

Am I way off with that? I assumed when you said the surface of the balloon, you were reffering to the exteme edge of that debris feild. Clearly this is the part I'm not getting my head wrapped around.

Sorry yeah.. There's no "edge" of the debris field because the debris fills the universe equally everywhere.

When the universe was very dense there was no matter, only energy, so that energy filled the universe pretty much uniformly. As the universe expanded it cooled, and eventually matter could form. It would form pretty much uniformly across the whole universe.

The Cosmology Tutorial is pretty good:

http://www.astro.ucla.edu/~wright/cosmo_01.htm

[GoinAllTheWay]

I see. I guess where I'm really not thinking straight is reading into the big bang part to literally. I thought the theory once stated that all matter in the universe was once all formed up into a ball. Boom! The whole thing flys apart, eventually it will slow down and then start pulling back with all matter smashing back into a ball and them BOOM, the whole process repeats.

I think that is how the whole show started and then went on to say, much to their surprise all matter was actually accelerating away. Show ultimatley concluded that the universe would either tear itself apart or matter would become so far apart , everything would eventually cool off to the point where all stars are dead and space is just filled with cold icy rocks.

[MarchHare]

Originally Posted by GoinAllTheWay

I thought the theory once stated that all matter in the universe was once all formed up into a ball. Boom! The whole thing flys apart, eventually it will slow down and then start pulling back with all matter smashing back into a ball and them BOOM, the whole process repeats.

That's only one possibility. Cosmologists are still unsure if the universe will eventually contract (big crunch/big bounce), continue to expand forever, or reach an equilibrium state.

[CaptainCrunch]

I think the universe will eventually accidentily be bumped off of gods bookshelf by god's slightly cross eyed cat Rufus, and life as we know it will come to an end when it hits the floor and shatters like a cheap sno globe.

God will then sweep whats left of the universe up, toss us in the trash and order a new universe on ebay.

[Hemi-Cuda]

Originally Posted by CaptainCrunch

I think the universe will eventually accidentily be bumped off of gods bookshelf by god's slightly cross eyed cat Rufus, and life as we know it will come to an end when it hits the floor and shatters like a cheap sno globe.

God will then sweep whats left of the universe up, toss us in the trash and order a new universe on ebay.

except Edmonton, he'll realize his first mistake and won't waste the money on that feature again

[photon]

Originally Posted by GoinAllTheWay

I see. I guess where I'm really not thinking straight is reading into the big bang part to literally. I thought the theory once stated that all matter in the universe was once all formed up into a ball. Boom! The whole thing flys apart, eventually it will slow down and then start pulling back with all matter smashing back into a ball and them BOOM, the whole process repeats.

It isn't just all the matter in the universe that was very dense, it's the universe itself that was small. Not just matter, but the fabric of space-time itself.

Originally Posted by GoinAllTheWay

I think that is how the whole show started and then went on to say, much to their surprise all matter was actually accelerating away. Show ultimatley concluded that the universe would either tear itself apart or matter would become so far apart , everything would eventually cool off to the point where all stars are dead and space is just filled with cold icy rocks.

Yup, like MarchHare said they're not sure, though the current expansion and acceleration of expansion would suggest that things will just move apart forever.

Sounds like the show was starting from an older view of cosmology and then moved up to a more recent view.

Gotta remember this whole idea of the universe expanding and the expansion accelerating is very new, like 10-20 years!