Where Does Space End? It Must End Somewhere!

[Martin]

martin,I like the stuff you write

 

There's a link saying "(say thanks for this post)" at the bottom of each post. Use it ! He deserves it, and it'll have even more effect

 

I appreciate both your kind comments. It's nice to get positive feedback especially when I can see what post you are responding to, so I can guess what I'm doing right.

 

The same goes for everybody else I think.

 

What Moo is talking about is the link at the bottom where it says "add". If you use it, it gives you a chance to say who the thanks is coming from (which can be helpful to know)

 

we all respond more or less to positive comment whether it comes through the "add" button or simply when someone says thanks in a post.

[mooeypoo]

What Moo is talking about is the link at the bottom where it says "add". If you use it, it gives you a chance to say who the thanks is coming from if you want to say (which can be nice for the person to know)

Oops, I keep forgetting I use the new "experimental" template

Same same, and we should all use it

[devrimci_kürt]

There's a link saying "(say thanks for this post)" at the bottom of each post. Use it ! He deserves it, and it'll have even more effect

I appreciate the advice:-)

 

)

[XxFar0wxX]

I think space is kinda like on Scooby Doo when they are being chased by the creepy guy they met in the beginning that is actually the bad dude they are after that is trying to run everyone off so he can take the hidden gold money for himself, but during the chase the run thru a door, and come out thru the door acroos the hall, just to run back thru the same door again. Think of it as a continues loop, or if you are standing in front of door looking in a dark room, with the exact same door behind you. You then throw a ball into the door in front of you, and it hits you in back of the head. Either that, or I am in a drug induced Dr. Seuss nightmare.

 

that makes scene, So picture space as earth So earth = space and everything beyond earth or space is in the 4th dimension ... or something like that.

 

Back in the day everyone thought the earth was flat

seems like most people think space is flat

(i tried to explain it best i could...)

but it gets bigger as the sun does

[Airbrush]

I can never get used to the balloon analogy unless the thin skin of the balloon was so thick it was thicker than the observable universe.

 

If space was very curved, would that mean that if you looked at an area of space on the very edge of our visual horzon, you would see the same constellations of quasars and ancient galaxies by looking 180 degrees the opposite direction?

[Martin]

I can never get used to the balloon analogy unless the thin skin of the balloon was so thick it was thicker than the observable universe.

...

 

the way to use the balloon is as a 2D analogy for 3D space. analogy, not direct straightforward representation.

 

in other words, concentrate on the surface of the balloon as having zero thickness and being a purely 2D toy model of the 3D reality

 

analogies are tools to help your mind imagine.

 

so to use this balloonsurface 2D toy model analog, to train your mind to imagine living in the 3D version (called a hypersphere)

you first think a while what it would be like to be a purely 2D creature (no thickness) sliding around in the 2D balloonsurface.

 

If it wasn't expanding you might eventually make your way all the way around, just by going in one direction. So you could figure out that your world was finite and curved. (I mean curved as experienced from the inside because there is no outside to the universe, all existence is concentrated on the balloon surface as far as you the flatski creature know.)

 

You could also discover internal or intrinsic curvature in your world by making triangles and discovering that the sum of angles was bigger than 180 degrees. In fact by doing this you could learn how to estimate the circumference of your world without having to make a tour. If you assumed it was uniform, then you could sit in one place and study triangles and estimate how big all of space was.

 

So think about the experience of a 2D flatski in a 2D balloonsurface world and then try to project by analogy what it would be like as a 3D creature in a 3D hypersphere world.

[Airbrush]

Would the 2-D creatures living on the surface of the balloon be able to see beyond very close objects? Or would their field of vision curve all the way around the balloon?

[Sisyphus]

Would the 2-D creatures living on the surface of the balloon be able to see beyond very close objects? Or would their field of vision curve all the way around the balloon?

 

It would "curve." I use quotation marks because going around the balloon is a straight line in this universe. Much like, if our universe is finite but unbounded in a similar way, travelling in a straight line would in theory get you right back where you started (although the sheer size of the universe, the limited speed of light, and the rate of expansion would make that impossible).

[Airbrush]

If the universe was flat then would the balloon analogy not apply? The balloon analogy only works for a curved finite universe?

[Martin]

Would the 2-D creatures living on the surface of the balloon be able to see beyond very close objects? Or would their field of vision curve all the way around the balloon?

 

In every geometry there is an idea of straightness proper to that geometry.

Straight lines are called geodesics, by analogy with great circle lines on earth.

Between nearby points, straight follows the shortest distance.

 

Light goes along shortest distance routes. So it follows geodesics. In the 2D balloonsurface toymodel the flatski can see something that is halfway around the balloon from him. Unless the balloon is expanding so fast the light never makes it.

 

If the universe was flat then would the balloon analogy not apply? The balloon analogy only works for a curved finite universe?

 

Correct. But a very large expanding balloon is experienced approximately like an infinite flat 2D.

So it is a good mental exercise to think a lot about the balloon analogy and the 3D hypersphere case and get to understand it. How some distances between things are increasing at a faster rate than c, and so on. How expansion affects what you can see.

 

And then when you have learned what you can, just enlarge the picture and get the infinite flat case in the limit. A lot of the intuitive understanding carries over.

[XxFar0wxX]

I can never get used to the balloon analogy unless the thin skin of the balloon was so thick it was thicker than the observable universe.

 

If space was very curved, would that mean that if you looked at an area of space on the very edge of our visual horzon, you would see the same constellations of quasars and ancient galaxies by looking 180 degrees the opposite direction?

 

anything that has gravity Bends space and if you look at the right side of the sun you are actually looking behind it rather then straight. Also Gravity bends time so the more gravity there is the slowing you time travel Jupiter time is slowing then ours on earth so you'd live long there (assuming it was like earth there) and if you lived in space, you would age faster then if you lived on earth.

[mooeypoo]

Actually, correct me if I'm wrong here, but technically you would age SLOWER in space because your relative speed is higher.

 

The time issue is not about gravity, it's about velocity... Martin?

[Martin]

...

The time issue is not about gravity, it's about velocity... Martin?

 

It's really hard to tell what XxFar is saying, and so to figure out what the real issue is here.

XxFar, your post really needs grammatical sentences with punctuation. It isn't fair to the others to make it so confusing.

 

Anyway, in my opinion the big issue here is gravitational time-slowdown.

This is a really practical thing that engineers have to allow for and correct for. Clocks really do run faster at the top of a building than at the bottom, the same identical clock.

 

So the GPS satellites each have a very accurate clock on board---atomic clock actually---and that helps them send out signals that help someone on the ground locate themselves. And those GPS satellite clocks actually run a little bit FASTER than the same clocks would on the ground. It had to be allowed for in designing the system.

 

Because being deeper down in a gravity well slows your time. And we down here on the surface are down in a potential energy well, so we are slowed, our chemical reactions and everything, compared with people living out in space.

 

And this is actually very simple to visualize and not hard to understand if you first think about the gravitational redshift. If someone at the top of a building shines a green light down at someone on the ground the light will gain a little energy and be imperceptibly blue shifted by the time it gets down. If the groundster shines the same green light up at the topster, the light will be a little redshifted by the time it gets to him or her. It will have lost a little energy. This isn't perceptible but it's real. And it is measurable if the gravitational field is strong and the difference in altitude is large.

 

Well the ticking of a clock is analogous to the vibrations of a lightwave.

So if you are high up in a gravity field and you look down at some groundster and his clock, you have to see his clock moving slower! Because it is just like he sent you light of a certain frequency and it was redshifted to a lower frequency when it got to you.

 

 

the factor of gravitational redshifting is the same factor as that for gravitational time-slowing (technically called gravit'l time-dilation).

 

DH, Swansont, Atheist and I forget who else are all very good on this.

 

It might be good to call on them sometime just to share the fun, and as insurance (in case I'm mistaken I appreciate getting straightened out).

 

BTW that Cylon Six is dazzlingly beautiful.

Edited March 22, 2009 by Martin

[Mr Skeptic]

Anyway, in my opinion the big issue here is gravitational time-slowdown.

This is a really practical thing that engineers have to allow for and correct for. Clocks really do run faster at the top of a building than at the bottom, the same identical clock.

 

Unless they are pendulum clocks, which run faster the more gravity they have. But that is because gravity is part of their functioning, not due to time itself. I'd suppose that they would run a little itsy bitsy bit faster than they should by Newtonian standards when there is less gravity --not that they'd be even close to accurate enough to measure this.

[Martin]

Unless they are pendulum clocks, which run faster the more gravity they have. .

 

You are right! I was thinking of electric oscillator or atomic clocks. That was a keen observation Mr. S.

 

The pendulum clock at the top of a tall building would run slower than his brother on the ground floor because of less pull on his pendulum.

[XxFar0wxX]

You are right! I was thinking of electric oscillator or atomic clocks. That was a keen observation Mr. S.

 

The pendulum clock at the top of a tall building would run slower than his brother on the ground floor because of less pull on his pendulum.

 

So then gravity does effect time in a noticeable difference?

Edited March 23, 2009 by XxFar0wxX

[cameron marical]

just for a pendulum, because theres different gravity farther up or lower down.

 

not for things like atomic clocks, or us.{timewise, though im sure different gravity would change your body, but not the same way as the twins paradox}

[moth]

not to be a nitpicker, but doesn't gravity affect time not effect it?

i just think the difference leads to misunderstanding.

[NowThatWeKnow]

So then gravity does effect time in a noticeable difference?

 

It depends on what you call noticeable. (GPS satellite - Altitude 12,000 miles) Our Earth clocks are slower by 45 microseconds per day. It would take a black hole to be really noticeable. When Martin said "The pendulum clock at the top of a tall building would run slower than his brother on the ground floor because of less pull on his pendulum." He was referring to a pendulum clock only. Normally less gravity will cause a clock to run faster.

[Cap'n Refsmmat]

http://blogs.scienceforums.net/swansont/archives/6

 

Especially this link.

[Martin]

It depends on what you call noticeable. (GPS satellite - Altitude 12,000 miles) Our Earth clocks are slower by 45 microseconds per day. It would take a black hole to be really noticeable. When Martin said "The pendulum clock at the top of a tall building would run slower than his brother on the ground floor because of less pull on his pendulum." He was referring to a pendulum clock only. Normally less gravity will cause a clock to run faster.

 

Good! That's the kind of thing I should have said when Moo asked for help. I want to deputize you.

 

Instead of just yakking you injected relevant quantitative fact.

 

Thanks also to C.R. for the links.

[Mr Skeptic]

So then gravity does effect time in a noticeable difference?

 

Yes, but the effect with the pendulum clock is a flaw in the pendulum clock, not a slowdown in time itself nor any other type of clock. However, the pendulum clock would slow down far more than a relativistic time increase from less gravity.

[jersincl]

In simple terms,for us simple folks.

The energy used to create space and time can be measured, however more information on this initial singularity will be forth coming by the launch of the NGST. The correlation between dark energy and the singularity energy I believe will be in concert with the expansion and creation point of our dimension in the multiverse theory.

If we can learn and understand the Macro energy involved in multiverse creation theory we can perhaps harness that energy and use it to advance our civilization to a type 1 civilization or even a type 2 civilization.

We really need to get beyond this restrictive one universe thinking. It should probably take another 1000 years of primitive behavior before this can be accomplished. Man I wish I could jump to the year 3009 A.D. What technological achievements will we have and people looking back and saying,"Look how primitive they were in 2009 A.D." So in closing your honor, I'd just like to say, "Find the distributing factor in singularity energy used for universe and dimension creation and the answer for where space ends will be a null question". I believe the intelligence used is exponentially beyond our present day capacity.

[RobertDonaldson]

In response to the original question a good few years ago "Where Does Space End? It Must End Somewhere! "

 

This question is used by people wanting to quantify their existance and have a meaning, the truth behind it is we are are miniscual compared to our galaxy of which it is one of 200 billion plus. People talk about whats at the end of our universe, say a vacuum of a sort or just empty space..whos to say that are universe isnt the equivalent of 1 galaxy in our universe! if anything this is alot more likely, and so you say what about at the end of that..pheraps its like looking into a mirror with a mirror behind you..never ending ! pheraps its circular, dimensions, pheraps what is at the end is too incomprehensible for a race that is still very much primitive in our intellectual capacity !

 

This is the true way too look at things, but it can be hard for educated people to admit they have no real significance and so you come full circle to the statement "this question is used by people wanting to quantify their existance and have a meaning".

[mooeypoo]

In response to the original question a good few years ago "Where Does Space End? It Must End Somewhere! "

 

This question is used by people wanting to quantify their existance and have a meaning, the truth behind it is we are are miniscual compared to our galaxy of which it is one of 200 billion plus. People talk about whats at the end of our universe, say a vacuum of a sort or just empty space..whos to say that are universe isnt the equivalent of 1 galaxy in our universe! if anything this is alot more likely, and so you say what about at the end of that..pheraps its like looking into a mirror with a mirror behind you..never ending ! pheraps its circular, dimensions, pheraps what is at the end is too incomprehensible for a race that is still very much primitive in our intellectual capacity !

 

This is the true way too look at things, but it can be hard for educated people to admit they have no real significance and so you come full circle to the statement "this question is used by people wanting to quantify their existance and have a meaning".

That's a very good point, but that does not mean we can't estimate or perform educated guesses (as long as we are aware that their value is no more and no less of an educated guess), and these *are* valuable.

 

Our knowledge of the universe might be limited, but we do know and see how things operate and behave in it, and that allows us to estimate many hypothetical properties (including its hypothetical shape). Such estimations then allow us to go on with further theories and devise more ways to explore things we do - and don't - know.

 

For that matter, if we go into a forest and see a stump of a tree and the rest of the tree lying on the ground next to it, we assume that the tree fell. Can we know for certain? No. But when we take into account everything we know about physics and the physical world, and trees, and the trees we did see fall, we can safely assume it did fall. For all intended purposes, the tree fell down, whether we saw it or not.

 

That assumption allows us to continue on to more valuable assumptions or experiments that might show us more things that we wouldn't have otherwise explored.

 

It's very wise to remember where the limits of our knowledge end, but that doesn't mean we can't still use assumptions and estimations for our beneft, we just need to remember that they're not as "valuable" as facts and observations.

 

~moo