Space cannot expand because it has no shape--claim by Sovereign

[Sovereign]

It's said that the universe is expanding at such an increasing rate that its outermost areas will pass a cosmological "event horizon" that is beyond our reach. Afterwards, evidence of that part of the universe will vanish forever.

 

Not true.

 

Such means of travel don't care if a spot in universe is not reachable by conventional means. Unless, of course, I'm wrong. Thus my reason for posting: your counter-remarks or agreements.

 

The universe is all objects and space. The objects in space move around, but the space can not expand since space does not have shape.

[Royston]

but the space can not expand since space does not have shape.

 

Sovereign, I realise you're new here, but if you wish to posit something (that appears to be against current physics) you need to supply a reference or link to back it up. What you've stated is wrong...actually it doesn't make much sense, so please elaborate.

Edited October 31, 2008 by Snail
typo

[Sovereign]

Sovereign, I realise you're new here, but if you wish to posit something (that appears to be against current physics) you need to supply a reference or link to back it up. What you've stated is wrong...actually it doesn't make much sense, so please elaborate.

 

Saying that which does not have shape cannot expand is wrong? How so?

[D H]

Saying that which does not have shape cannot expand is wrong? How so?

Space (spacetime, to be precise) does have a shape, described mathematically by the metric tensor. General relativity has been tested and retested, every which way to Sunday. Your hypothesis that spacetime does not have a shape fails these tests. In short, it is wrong.

[Sovereign]

Space (spacetime, to be precise) does have a shape, described mathematically by the metric tensor. General relativity has been tested and retested, every which way to Sunday. Your hypothesis that spacetime does not have a shape fails these tests. In short, it is wrong.

 

What does spacetime look like? Is there a drawing somewhere?

[iNow]

What does spacetime look like? Is there a drawing somewhere?

 

Doesn't the fact that you're asking this question at all completely defeat your assertion above (the assertion stated as some accepted truth) that the universe doesn't have shape?

 

space can not expand since space does not have shape.

 

 

Here are some good primers for you:

 

http://map.gsfc.nasa.gov/universe/uni_shape.html

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

http://curious.astro.cornell.edu/question.php?number=62

[Royston]

Saying that which does not have shape cannot expand is wrong? How so?

 

Well I don't follow your reasoning.

 

Let's assume for the sake of argument that space as you said doesn't have 'shape', i.e there is no geometery describing space, General Relativity was never realized...it's just a void as far as we know.

 

However going back to the time of Hubble it was observed that the Universe is expanding, more recently that this expansion is accelerating. So purely from observation (no need to worry about the shape of anything) this void is expanding inbetween far away objects, so we don't even need to worry about whether space has a shape, just that expansion is an observerd phenomena. So are you contesting that these observations are wrong, or are you not familiar with this subject ?

 

With regards to the geometery of space, i.e as described by GR, gravity is the shape of space. Where we have a body, space curves towards it causing passing objects to take orbit, or to crash into it.

 

I'm about to leave work so this post was rushed...but I may come back to this.

 

I'd recommend looking at the cosmo basics thread (the sticky under Astronomy and Cosmology.)

[Sovereign]

Doesn't the fact that you're asking this question at all completely defeat your assertion above (the assertion stated as some accepted truth) that the universe doesn't have shape?

 

 

 

Here are some good primers for you:

 

http://map.gsfc.nasa.gov/universe/uni_shape.html

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

http://curious.astro.cornell.edu/question.php?number=62

 

No I said space doesnt have shape, but apparently spacetime does so I asked.

Thanks for the reading material I shall have a look.

 

Edit:

 

Those are interesting reads indeed. Although none of them clarifies what they mean by 'universe'. I noticed a picture showing a sphere, saddle, and flat surface. I assume one of these is what people think the universe looks like. But what is the white stuff that gives shape and contour to the sphere/saddle/flat?

Edited October 31, 2008 by Sovereign

[Martin]

...space can not expand since space does not have shape.

 

Hi Sovereign, I split this series of posts off from the other thread because it was about a different topic. The original thread was not about space having shape and being able to expand, or not.

 

So you have started a new thread, in effect, by raising these questions and stimulating discussion.

 

What do you mean by space expanding?

In astronomy it refers to a pattern of increasing distances called Hubble law.

Distances between objects which are approximately at rest with respect to the microwave background are increasing at a certain percentage rate.

Hubble law says largescale (intergalactic) distances increase about 1/140 percent per million years. Are you saying that Hubble law is wrong and that distances do not increase? Or what do you mean by not expanding?

 

What do you mean by not having shape?

In astronomy spatial shape refers to spatial curvature: things like whether triangles add up to 180 degrees. Surveyor triangles using light rays, line of sight. Likewise it refers to stuff like how volume grows with radius. Is the area of a sphere increasing as the square of the radius or not.

Flat is the shape that means these Euclidean rules hold exactly. In other kinds of shape they don't hold exactly.

In astro, spatial shape is measured internally, by experiment and observation. Measurements of the curvature of our space are being made all the time. So in what sense is space without shape?

 

Please clarify so we know better what you are talking about.

Edited November 1, 2008 by Martin

[Sovereign]

Hi Sovereign, I split this series of posts off from the other thread because it was about a different topic. The original thread was not about space having shape and being able to expand, or not.

 

So you have started a new thread, in effect, by raising these questions and stimulating discussion.

 

What do you mean by space expanding?

In astronomy it refers to a pattern of increasing distances called Hubble law.

Distances between objects which are approximately at rest with respect to the microwave background are increasing at a certain percentage rate.

Hubble law says largescale (intergalactic) distances increase about 1/140 percent per million years. Are you saying that Hubble law is wrong and that distances do not increase? Or what do you mean by not expanding?

 

What do you mean by not having shape?

In astronomy spatial shape refers to spatial curvature: things like whether triangles add up to 180 degrees. Surveyor triangles using light rays, line of sight. Likewise it refers to stuff like how volume grows with radius. Is the area of a sphere increasing as the square of the radius or not.

Flat is the shape that means these Euclidean rules hold exactly. In other kinds of shape they don't hold exactly.

In astro, spatial shape is measured internally, by experiment and observation. Measurements of the curvature of our space are being made all the time. So in what sense is space without shape?

 

Please clarify so we know better what you are talking about.

 

Yes thanks for splitting it, it was unfair to the original author to have his thread sidelined. I think the main thing is what we mean by our words, the definitions we use are different. If expansion means increasing distances between objects, measured by redshift(I think), then I would agree.

 

Now if objects are what have shape, like tables, planets, or atoms, then they can move. However I think when we come to the definition of space there is a difference. I think of it as the lack of shape, there is nothing there, no shape.

 

I really like the last question: So in what sense is space without shape? I would say what is shape without space?

 

Also do you have any links I could read on measuring the curvature of space?

[iNow]

do you have any links I could read on measuring the curvature of space?

 

http://einstein.stanford.edu/Media/Rel_gyro_expt-anima-flash.html

 

http://www.as.utexas.edu/astronomy/education/spring05/komatsu/lecture15.pdf

 

http://en.wikipedia.org/wiki/Spacetime#Mathematics_of_spacetimes

[Martin]

 

Also do you have any links I could read on measuring the curvature of space?

 

iNow posted some worthwhile links. I especially liked the Texas one. If you go to the last slide there, it says:

==quote iNow's texas link==

• Important question: What is K of the universe?

– K determines curvature of 3-d space in which we are

living

• According to Gauss’s theorema egregium, we

can measure K, without knowing anything about

the 4th dimension.

– This implies that the shape of the observable universe

can be determined!

==endquote==

 

Much instrumentation and human effort is currently devoted to studies bearing specifically on space curvature, as opposed the broader issue of spacetime curvature (the latter is more complicated, and is studied too---it subsumes spatial curvature but is more general.)

 

I sense that you may be inquiring specifically about spatial curvature, Sov, and so I will get some links that have to do specifically with measuring that. Two massive efforts, involving hundreds of researchers and several satellite observatories, are CMB mapping (e.g. the current WMAP mission) and galaxy counts (e.g. the Sloan Digital Sky Survey, SDSS).

Astro missions tend to be multipurpose and these acquire many different kinds of useful information, but among their results they derive estimates of a number called Omega_k.

 

There is local curvature caused by the gravity of the sun and planets. It was measured as early as 1919 and is not so interesting. One way is you basically just compare angles between light-rays. Omega_k is about global or largescale spatial curvature. For about 10 years people have been working to narrow down the confidence interval, to tighten the limits on it. If it is exactly zero, we can say space is overall flat (with small local "bumps and dents" caused by local massive objects). If it is negative then space is positive curved overall. If Omega_k is positive then space curvature is negative. Yes I know the sign convention is crossed up but that's just how it is, like on a battery the neg is where the electrons come out, arbitrary conventions take root and people adhere to them, so we live with them.

 

The most recent figure for Omega_k was published in this years WMAP data and it was obtained by COMBINING the latest CMB data with the latest galaxy counts. You find it in table 2 on page 4 of this paper:

http://arxiv.org/abs/0803.0547

0.0179 < Omega_k < 0.0081

 

One way to estimate Omega_k uses galaxy counts. Essentially, if space is flat (uncurved) then you expect the number of galaxies in a spherical volume to increase as the cube of the radius. But if space is positive curved, you expect the increase to be less than that. Counting galaxies (assuming they are roughly uniform distributed) is a way of measuring the volume of the sphere. If the volume does not go as the cube of radius, then you know your space is overall curved, and you have a handle on it.

 

With WMAP the technique is different, WMAP maps the different size flecks and blotches of the CMB sky, they have a way to calculate the statistics, how many of what size blotches to EXPECT with various spatial curvatures, and they can compare that with the distribution of flecks and blotches that they actually see, and get another different handle on the curvature.

 

The paper I linked to shows how they put several masses of data together, also with some supernova data, and work out the current best estimate of Omega_k. And also they give a lower bound on the RADIUS OF CURVATURE in the positive curved case it comes out to about 100 billion lightyears. You can see that in Table 2 on page 4 also.

 

Over the past 10 years various papers like this have come out, with tighter and tighter estimates on Omega_k. I've watched it narrow down. This is a 95 percent confidence interval. Next year another microwave skymap spacecraft goes up, this time by the ESA (european space agency) which will be even better than the NASA's WMAP. So the data will be even better and the errorbar will get even tighter. The European spacecraft is called Planck. Keep an eye out for news about it.

Edited November 1, 2008 by Martin

[interstellar]

Space has always been and will always be infinite, in every direction you look. The universe is finite but is expanding out in all directions like a bubble, and the expansion is accelerating with every passing second. Currently the universe is roughly 14 billion lightyears across and began somewhere in the center. Eventually every planet, nebula, star, even black holes will decay into the simplest form of matter. The proton. Expanding for eternity. In total absolute darkness.:-)

[Daecon]

I think the electron is simpler than the proton, as the proton is made up of three quarks.

[iNow]

Space has always been and will always be infinite, in every direction you look. The universe is finite but is expanding out in all directions like a bubble,

So, space is infinite, but the universe is finite. Ermmm... yeah... that makes sense.

 

Currently the universe is roughly 14 billion lightyears across

Actually, no. I think you may have meant that it's roughly 14 billion years old. No one knows if the universe is infinitely large or even if ours is the only universe that exists.

 

http://www.nasa.gov/audience/foreducators/5-8/features/F_How_Big_is_Our_Universe.html

 

 

 

and began somewhere in the center.

The "center" of what? There is no center.

 

Eventually every planet, nebula, star, even black holes will decay into the simplest form of matter. The proton. Expanding for eternity. In total absolute darkness.:-)

Yeah, you do realize this isn't a poetry forum, right? Do you have any supporting evidence whatsoever for these claims?

 

I don't mind claims being made, I just want to see some supporting evidence for them. Also, if you say something which is patently wrong, you should be prepared for correction.

[aguy2]

in re: the shape of the universe

 

==quote iNow's texas link==

• Important question: What is K of the universe?

– K determines curvature of 3-d space in which we are

living

• According to Gauss’s theorema egregium, we

can measure K, without knowing anything about

the 4th dimension.

– This implies that the shape of the observable universe

can be determined!

==endquote==

 

...If it is exactly zero, we can say space is overall flat (with small local "bumps and dents" caused by local massive objects). If it is negative then space is positive curved overall. If Omega_k is positive then space curvature is negative...

 

0.0179 < Omega_k < 0.0081

 

One way to estimate Omega_k uses galaxy counts. Essentially, if space is flat (uncurved) then you expect the number of galaxies in a spherical volume to increase as the cube of the radius. But if space is positive curved, you expect the increase to be less than that. Counting galaxies (assuming they are roughly uniform distributed) is a way of measuring the volume of the sphere...

 

I have a question:

Temporal considerations aside, if one assumed the visible universe were "conic" and not "spherical" in shape, would the observed slight negative curvature be consistent with the "lateral expansion" of a conic shape?

aguy2

Edited November 17, 2008 by aguy2
deleted "that has lost momentum" because of temporal considerations

[Martin]

I see in my earlier post I somehow dropped the minus sign off of -0.0179.

So I'll correct it here. This is how it's supposed to read

 

The most recent figure for Omega_k was published in this years WMAP data and it was obtained by COMBINING the latest CMB data with the latest galaxy counts. You find it in table 2 on page 4 of this paper:

http://arxiv.org/abs/0803.0547

-0.0179 < Omega_k < 0.0081

 

Most of us are more familiar with the total Omega parameter Omega_tot = 1 - Omega_k

 

Often notational conventions are arrived at by accident and persist because it's so difficult for a whole community to change conventions. So that's how it is. The latest available data basically says -0.018 to 0.008

and that means the 95% confidence interval for total Omega is basically

-0.992 < Omega < 1.018

 

I notice that it's lopsided, with twice as much on the up side as on the down side. But it would be unwise to set too much store by that. The outstanding thing is either way it's real near to being exactly one.

 

If the actual value is 1, we have spatial flat, most likely infinite spatial volume (excluding PacMan topology donuts etc.) Anyway roughly uniform zero curvature.

 

If the actual value is 1.01, say, then we have the hypersphere case. Space is like the 3D analog of the surface of a balloon. Roughly uniform positive spatial curvature. A finite 3D volume which we can calculate more or less accurately.

========================================

AGUY, I'm trying to think how to respond to your post.

In standard cosmology one assumes approximately uniform matter distribution. The solutions to the Einstein equation---with the simplifying uniformity assumptions----include only a few possibilities and they all have constant spatial curvature. Zero spatial curvature or some other constant.

 

When you solve the equations you never get cones.

 

I can't picture a universe that is spatial conic.

 

At the point, I suspect the cone would have a singularity. Infinite curvature. Elsewhere a conical space might be flat. Zero curvature. It would be a strange non-uniform 3D space which I don't think could arise in nature.

 

Basically it's beyond my ken. The idea doesn't make sense to me. Maybe someone else would like to respond.

[Baby Astronaut]

http://www.nasa.gov/audience/foreducators/5-8/features/F_How_Big_is_Our_Universe.html

From that link I found another link and now have a question.

 

In the previous segment on that website, it says that it would take 70,000 years in our fastest spaceship to get to the nearest star.

 

In the next page, it represents the Milky Way as a coin, with our solar system being microscopic specs, and the galaxy being the size of the United States.

 

My question is: using those scales, if a microscopic spaceship (our fastest one), were to travel from Earth to the nearest star, what distance in km or miles would it travel across the galaxy-scaled U.S. and at what speed (km or mph)?

[aguy2]

========================================

AGUY, I'm trying to think how to respond to your post.

In standard cosmology one assumes approximately uniform matter distribution. The solutions to the Einstein equation---with the simplifying uniformity assumptions----include only a few possibilities and they all have constant spatial curvature. Zero spatial curvature or some other constant.

 

When you solve the equations you never get cones.

 

I can't picture a universe that is spatial conic.

 

At the point, I suspect the cone would have a singularity. Infinite curvature. Elsewhere a conical space might be flat. Zero curvature. It would be a strange non-uniform 3D space which I don't think could arise in nature.

 

Basically it's beyond my ken. The idea doesn't make sense to me. Maybe someone else would like to respond.

Martin,

I appreciate the time and effort it took to respond, but could I ask for more, by asking you to critique a more detailed presentation of my cosmolgical conjectures. It is titled "Is the Universe Collapsing-2008" and is posted in the "Pseudoscience and Speculations" forum.

 

For instance, is my speculation that the Big Bang event/body could have displayed a high degree of Angular Momentum completely out of line?

aguy2

[Baby Astronaut]

Would a moderator please start a new thread with post #18, move it from here? Thanks.

[Martin]

Would a moderator please start a new thread with post #18, move it from here? Thanks.

 

Maybe someone else will see what to do and do it, before I figure out. That would be fine. But if nobody else does, I'll try to respond. The way the posts are now numbered, #18 is yours. If we split off and start a new thread, yours will be the lead post. What would you like the thread called, if we do that?

 

 

If I look back to your post #18, I see you ask this question

My question is: using those scales, if a microscopic spaceship (our fastest one), were to travel from Earth to the nearest star, what distance in km or miles would it travel across the galaxy-scaled U.S. and at what speed (km or mph)?

 

The diameter of the Milkyway galaxy (that our solarsystem is part of) is about 100,000 lightyears. It is about 3000 miles across the US.

 

so the scale transformation is roughly 100 lightyears equals 3 miles.

 

So let's say the nearest star is 4 lightyears, which is 1/25 of 100, so on that same scale it would be 3/25 miles. What would you call that? A city block?

Edited November 18, 2008 by Martin

[Daecon]

From that link I found another link and now have a question.

 

In the previous segment on that website, it says that it would take 70,000 years in our fastest spaceship to get to the nearest star.

 

In the next page, it represents the Milky Way as a coin, with our solar system being microscopic specs, and the galaxy being the size of the United States.

 

My question is: using those scales, if a microscopic spaceship (our fastest one), were to travel from Earth to the nearest star, what distance in km or miles would it travel across the galaxy-scaled U.S. and at what speed (km or mph)?

The Milky Way *is* the galaxy, so how can it be both the size of a coin and the size of the U.S. unless you meant the U.S. represented the visible Universe instead?

[Baby Astronaut]

The diameter of the Milkyway galaxy (that our solarsystem is part of) is about 100,000 lightyears. It is about 3000 miles across the US.

 

so the scale transformation is roughly 100 lightyears equals 3 miles.

 

So let's say the nearest star is 4 lightyears, which is 1/25 of 100, so on that same scale it would be 3/25 miles. What would you call that? A city block?

That's pretty good Martin. Since they said it'd be about two soccer fields away to the nearest star.

 

More importantly though, if a person in the galaxy-scale U.S were to observe the microscopic spaceship journeying towards the nearest "quarter" (star) 3/25 of a mile away, how fast would it be traveling (km per hour) relative to the observer if it took 70,000 years to get there?

 

If the micro-spaceship couldn't take advantage of wind, the observer might think it stuck in mid-air without moving. At that rate at least (70,000 years to travel across a city block).

 

 

The Milky Way *is* the galaxy, so how can it be both the size of a coin and the size of the U.S. unless you meant the U.S. represented the visible Universe instead?

You're correct! It's the solar system that would be the size of a quarter. But Martin seemed to catch the error.