Starship Asterisk*

Markus Schwarz wrote:

neufer wrote:
Space-time curves convergently into local gravitation bodies and all free falling space coordinates (whether arbitrarily fixed to baseballs, the Earth or Voyager 1) are FORCED to be attracted to local gravitation bodies (i.e., they are constantly being sucked into such bodies).

What exactly do you mean by "space-time curves"? Do you mean the paths taken by particles or the coordinate lines?

Markus Schwarz wrote:
Since you emphasized the coordinates, keep in mind that these are precisely the quantities that have no physical meaning. What is physically meaningful are the paths taken by particles, all of which are affected by gravitation.

Markus Schwarz wrote:
Free falling coordinates are adopted for calculations of free falling particles. In these coordinates the metric components depend on time, since the infalling observer notices an increase in the gravitational pull.

Markus Schwarz wrote:
I go back to my question: how do you propose to build a "space-flow-o-meter",
which would measure the "flow of space"? All you can measure is the flow of particles.

neufer wrote: Definitions of space-time are highly arbitrary and
are mostly for calculations, bookkeeping & conceptualization.
What is NOT arbitrary (i.e., what is actually physically real) are the Ricci and Riemann curvature components of space-time.

neufer wrote: Space-time curves convergently into local gravitation bodies and all free falling space coordinates (whether arbitrarily fixed to baseballs, the Earth or Voyager 1) are FORCED to be attracted to local gravitation bodies (i.e., they are constantly being sucked into such bodies).

Chris Peterson wrote:

neufer wrote:
The most important point IMO is that no one should be left with the impression that the Earth curves around the Sun because space itself is curved. The Earth curves around the Sun because space is dynamic.

I would disagree completely with that assessment. The Earth moves in the path it does because of geodesics and the static curvature of space in this region. I have no idea what it even means to suggest that space (or spacetime) is "dynamic".

http://www.web-books.com/eLibrary/Medicine/Physiology/Skin/Skin.htm wrote:
<<The stratum corneum is the outermost layer of the epidermis, and is made up of 10 to 30 thin layers of continually shedding, dead keratinocytes. As the outermost cells age and wear down, they are replaced by new layers of strong, long-wearing cells. The stratum corneum is sloughed off continually as new cells take its place, but this shedding process slows down with age. Complete cell turnover occurs every 28 to 30 days in young adults, while the same process takes 45 to 50 days in elderly adults.>>

neufer wrote:The most important point IMO is that no one should be left with the impression that the Earth curves around the Sun because space itself is curved. The Earth curves around the Sun because space is dynamic.

Chris Peterson wrote:

neufer wrote:
Throw a ball up in the air and the ball follows a slightly curved space-time trajectory at the speed of light that falls back to Earth. What we perceive is a slow parabolic trajectory of the ball in space over time... but space itself can be thought of as actually falling back into the earth (carrying the ball with it).

If thinking of space that way provides an analogy that gives you a useful visualization tool, great. It doesn't seem to work for me, and from a more rigorous GR standpoint, I don't think the idea is physically meaningful. The distortion of spacetime is treated as a transformed coordinate system- the coordinates of one point in spacetime are not moving with respect to the coordinates of another point due to the presence of a massive body- which is what I'd consider to define the actual motion of spacetime.

neufer wrote:Throw a ball up in the air and the ball follows a slightly curved space-time trajectory at the speed of light that falls back to Earth. What we perceive is a slow parabolic trajectory of the ball in space over time... but space itself can be thought of as actually falling back into the earth (carrying the ball with it).

Chris Peterson wrote:

Markus Schwarz wrote:Interesting. Where did you get that?

I think he's just using the time it takes to fall 1 AU under the gravitational acceleration of the Sun.

Chris Peterson wrote:
As you say, that is how bodies with mass behave under gravitation, which is modeled as a distortion of spacetime. It doesn't describe the motion of spacetime itself. Indeed, as I understand GR, the motion of spacetime isn't even a defined concept. I don't know- physically or mathematically- what it means for "space to disappear" into a black hole or any other mass. Under GR, space is a coordinate system, not a physical thing.

• 1. A fold; a wrinkle; a collection of folds.
  2. A state of perplexity or anxiety; confusion; bother; agitation.

Markus Schwarz wrote:Interesting. Where did you get that?

neufer wrote: Space IS disappearing into black holes;

neufer wrote: The space around the earth falls into the Sun every 64 days (~ a year/sqrt(32)).

If the Earth were standing still (vis a vis the Sun) the Earth would join space in that plunge.

However, the Earth avoids that fate by leaving its space at ~30km/s.

Chris Peterson wrote:

Ron-Astro Pharmacist wrote:I think what I was curious about was," What effect would the loss of space around a black hole have on our galaxy?" And what effect would black holes, far from here, have on space in general if they did indeed get "sucked" or get pulled into the black holes - on large areas of, whatever it is that we call "space". Another question (and unfortunately I have plenty)," Where does the space and the matter pulled into the black hole go?" Into another universe?? Also, would the loss of space affect relativity? Sorry we amateurs know so little but are curious

Space isn't disappearing into black holes.

Ron-Astro Pharmacist wrote:I think what I was curious about was," What effect would the loss of space around a black hole have on our galaxy?" And what effect would black holes, far from here, have on space in general if they did indeed get "sucked" or get pulled into the black holes - on large areas of, whatever it is that we call "space". Another question (and unfortunately I have plenty)," Where does the space and the matter pulled into the black hole go?" Into another universe?? Also, would the loss of space affect relativity? Sorry we amateurs know so little but are curious :o

saturno2 wrote:NGC 922 has " high number of black holes"
Very intersting
More Interesting
In the link " somewhat surprising" there is a image of a dog ????
I don´t understand

Chris Kruskal wrote:

neufer wrote:
Black holes suck in space.

I think that interpretation is a stretch.

And any discussion of what happens inside a black hole is highly speculative.

• And I'm more than a little Szekeres to discuss it, myself.

http://en.wikipedia.org/wiki/Kruskal%E2%80%93Szekeres_coordinates wrote:

[b][color=#0000FF]Kruskal-Szekeres diagram. Each frame of the animation shows a blue hyperbola as the surface where the Schwarzschild radial coordinate is constant (and with a smaller value in each successive frame, until it ends at the singularities).[/color][/b]

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<<In general relativity Kruskal–Szekeres coordinates, named for Martin Kruskal and George Szekeres, are a coordinate system for the Schwarzschild geometry for a black hole. These coordinates have the advantage that they cover the entire spacetime manifold of the maximally extended Schwarzschild solution and are well-behaved everywhere outside the physical singularity.

Kruskal–Szekeres coordinates are defined, from the Schwarzschild coordinates, by replacing t and r by a new time coordinate V and a new spatial coordinate U:




for the exterior region r > 2GM, and:




for the interior region 0 <r <2GM.

neufer wrote:Black holes suck in space.

Ron-Astro Pharmacist wrote:
So tell me. Do if galaxies like this with lots of black holes in them just suck in lots of matter (if it happens to be around) or do they suck in space too?

Black holes suck in space

AND

Ron-Astro Pharmacist wrote:So tell me. Do if galaxies like this with lots of black holes in them just suck in lots of matter (if it happens to be around) or do they suck in space too? :roll:

APOD Robot wrote: The high number of massive black holes was somewhat surprising as the gas composition in NGC 922 -- rich in heavy elements -- should have discouraged almost anything so massive from forming. Research is sure to continue.

BDanielMayfield wrote:

starsurfer wrote:This is one of my favourite southern peculiar galaxies, look at all the star formation triggered by the initial interaction and subsequent merger!!! I don't like that "violent" language is used to describe galaxy collisions, to me its like galactic lovers in an embrace!

I agree starsurfer, collision is too violent a term for galactic mergers. And since the birth of many new stars is often the result, these mergers are rather procreative in nature, are they not?

As to the question raised in the Explanation, “Why so many black holes?” aren’t most large galaxies suspected of having numerous black holes in addition to the SMBHs at their centers, such as proposed intermediate BHs at the core’s of globular clusters? If that were the case couldn’t the merger be causing several otherwise undetectable BHs to light up in X-rays due to in-falling material (gas, dust, and rarely an unfortunate star) from the other galaxy?

Bruce

starsurfer wrote:This is one of my favourite southern peculiar galaxies, look at all the star formation triggered by the initial interaction and subsequent merger!!! I don't like that "violent" language is used to describe galaxy collisions, to me its like galactic lovers in an embrace!