# Thread: Basic Astronomy Question 101

1. ## Basic Astronomy Question 101

Another example of rampant scientific illiteracy!

FC

2. ## Basic Astronomy Question 101

Don't knock dumkoff atheistic nutjobs until you've tried one. I
understand that they can be quite rewarding, especially if the dumkoff
atheist takes out her dentures first.

Let's hear it for the big bang theory! Yay!

3. ## Basic Astronomy Question 101

Anonymous wrote:

Lookup the resupts from the COBE and WMAP data. These 'telescopes'
measured the background glow from the big bang and fit it to the Big
Bang model of the universe including 'inflation'. The data confirms the
Big Bang theory and sets limits to the size, shape, geometry, and age
of the universe. The data indicates that the universe if 12.7 BYO +/-
0.2 BY.

The age of the universe and the size of the universe are not that
closely related. The size of the universe is on the order of 90 B light
years and much of it is beyond our horizon.

No, the universe is isotropic (to a high degree of precision) and the
earth is no closer to the center than anything else! The universe is so
large (and still expanding) that everything we can see with large
telescopes can all be considered the center of the universe with equal
presision.

4. ## Basic Astronomy Question 101

On 27 Sep 2005 07:41:38 -0700, MitchAlsup@aol.com wrote:

I'm not sure how you meant this, but to avoid confusion: the reason that
any point (or really, no point) can be considered the center of the
Universe has nothing to do with its size. It is a consequence of the
fact that an object with more than three dimensions (the Universe) has
no center that can be represented by a three-dimensional point.

_________________________________________________

Chris L Peterson
Cloudbait Observatory
http://www.cloudbait.com

5. ## Basic Astronomy Question 101

This is getting a bit away from Basic Astronomy 101.

Chris L Peterson wrote:

There's no such thing as a three-dimensional point. And even
interpreted as "a point in three dimensions," it's still unclear.
I *think* you mean that any space that is curved into more than three
dimensions cannot have a center within that space (not that it can't
have a center in three dimensions). Technically, that's not always
true, but for the usual 3-manifolds under discussion, I think it is.

By analogy, there are 2-manifolds that contain their centers--centers
both in the sense of an expansion fixed point, and in the sense of
geometric center. However, the 2-sphere (curved into three dimensions)
is not one of them, and that's the sort of shape we usually mean in
these discussions.

In ordinary English, a sphere is like a flat surface curved into three
dimensions, and although it has a center, that center lies nowhere on
the surface itself. That means that all points *on the surface* can
equally well (or equally poorly, depending on your point of view) be
considered as the center of that surface.

--
Brian Tung <brian@isi.edu>
The Astronomy Corner at http://astro.isi.edu/
My Own Personal FAQ (SAA) at http://astro.isi.edu/reference/faq.txt

6. ## Basic Astronomy Question 101

In article <kaoij1pnev0cd6e81qjvrd7ta87gm2ruhp@4ax.com>,
Chris L Peterson <clp@alumni.caltech.edu> wrote:

The observable universe has only three observable physical dimensions.
However, since the physically observable universe is embedded in a
higher dimension, the observable matter in the universe may not have
a center inside of itself. Depending on the embedding, the universe
may have a center in the higher dimension.

Here is a two-dimensional analog. Consider an ant on an inflating
balloon with grape juice spilled on it. The ant crawls around in any
direction and finds pools of grape juice contracting under surface
tension yet each pool is moving away from the others because of the
inflation of the balloon. No pool of grape juice could be considered
the center of the grape juice universe.

If the ant were to follow the inflation of the balloon back to when it
was extremely small, it would find the center of the balloon in space-
time was the time when the inflation of the balloon began. However,
since all the surface of the balloon at that time was essentially in
one place, the ant would not be able to specify the center on the
surface of the balloon.

If we extrapolate the ant's two physical dimension universe to our
three physical dimension universe, the center of the universe is at
the time of the Big Bang, but at every spatial point since all the
spatial points were at the same place.

Rob Johnson <rob@trash.whim.org>
take out the trash before replying

7. ## Basic Astronomy Question 101

If no cat has 8 tails, but every cat has one more tail than no cat, then all
cats have 9 tails.

And that is just about as clear as anything else.

--

The Lone Sidewalk Astronomer of Rosamond
http://home.inreach.com/starlord
Astronomy Net Online Gift Shop
http://www.cafepress.com/astronomy_net

"Rob Johnson" <rob@trash.whim.org> wrote in message
news:20050927.092537@whim.org...

8. ## Basic Astronomy Question 101

Rob Johnson wrote:

Just a minor quibble.

Although it is most natural for us humans to think of the universe
as being embedded in a higher space, there is no need for that to be
the case. The universe can exhibit the metric characteristics of
being curved without possessing the *geometric* characteristics of
being curved.

In other words, it is possible for GR to predict the behavior of the
fabric of space-time, including all of its space and time warping
effects, without the universe being physically curved into a further
dimension. There's no easy visual analogy for this; the very term
"curvature" practically denies one. But one can go through the
mathematics just the same.

Current TOEs mention large numbers of "extra" dimensions with finite
and small extent. It is worth noting that they are supported in large
part by symmetry arguments, which are convincing from an elegance
perspective but hardly ironclad. I'm not sure whether they speak
directly to embedding.

--
Brian Tung <brian@isi.edu>
The Astronomy Corner at http://astro.isi.edu/
My Own Personal FAQ (SAA) at http://astro.isi.edu/reference/faq.txt

9. ## Basic Astronomy Question 101

In article <dhbuom\$d2n\$1@zot.isi.edu>,
brian@isi.edu (Brian Tung) wrote:

True, Gauss's Theorema Egregium says that irrespective of embedding,
the curvature of a surface can be determined purely from the intrinsic
metric <http://mathworld.wolfram.com/GausssTheoremaEgregium.html>.

However, in order to speak of a center to the universe, I made the
probably unsupportable assumption that our space-time is embedded in a
higher dimension, mainly to show that even if we are embedded, there
might be no point currently that could be considered the center of the
universe.

Rob Johnson <rob@trash.whim.org>
take out the trash before replying

10. ## Basic Astronomy Question 101

If no cat has 8 tails, but every cat has one more tail than no cat,
then all cats have 9 tails.

And that is just about as clear as anything else.

***************************

Isn't polysemy wonderful?

Page 1 of 5 123 ... Last

#### Posting Permissions

• You may not post new threads
• You may not post replies
• You may not post attachments
• You may not edit your posts
•