That WMAP linked site says the universe is flat. Was this finding, when it was made, expected? How will the rate of expansion of the universe change over time?
That WMAP linked site says the universe is flat. Was this finding, when it was made, expected?
Yes
Quote:
How will the rate of expansion of the universe change over time?
It used to be thought that the expansion was slowing. Recent evidence indicates the expansion is accelerating. This is attributed to either Dark Energy or Einstein's Cosmological constant depending on whom you are listening too.
Hi, Mark. I in haste didn't phrase my question very well. From the WMAP site, there's about 23% dark matter, with some question as to the composition of it, e.g., baryonic, supermassive BHs, or even possibly new forms of matter. This discovery of 'intracluster light (ICL)', containing both stars and dust, seems to tip the scales towards mostly baryonic matter, but the discovery of Quasar HE0450-2958 may tip the scale towards BHs. In hindsight, it's probably a too-soon-to-tell question, but I'll gladly listen to any thoughts you might have about it. Thanks!
ChipperQ:
Are asking about which kind of mass is responcible for the gravity that is holding the cluster together? If so then I think the additional normal mass provided by the previously unseen stars will not change the ratio of normal to dark mass significantly.
Sorry, let me back up a step, and make sure I'm using terms properly. Interesting info from WMAP regarding the composition of the universe has 73% dark energy, 23% cold dark matter, and 4% atoms. Since the intracluster light is 1000x fainter than the night sky, would it be considered as part of the dark matter, or has it already been counted with the (more luminous) atoms?
Nobody knows what this is. Its existence is posited to explain the accelerating expansion of the universe.
Quote:
23% cold dark matter
Should be called non-baryonic, non-leptonic and non-photonic.
Again nobody knows what this is. Its existence is posited to explain discrepancies between the motion of stars and galaxies and the gravity due to normal matter.
The term cold dark matter is sometimes used to discribe non-luminous objects made up of mostly of normal matter but in this context such usage is inappropriate.
Quote:
4% atoms
The normal stuff we are familiar with. The value is determine by calculation of nuclear synthesis of element heavier the Hydrogen during the Big Bang. Not all of this matter is visible so some of is sometimes called dark matter. This leads some rather confusing terminology.
Quote:
has it already been counted with the (more luminous) atoms
Thanks, Mark. I was looking at the two images of the Virgo Cluster, along with the simulations, and I thought the ICL might be a reasonable explanation for some of the 'discrepancies between the motion of the stars and galaxies', since it apparently contains significant amounts of matter, despite being called 'light'. I'm a bit confused...
I thought the simulations were excellent insofar as they showed how filaments of ICL form between the clusters. From this, is it correct to say that all galaxies start out as globular clusters, and that spiral arms are formed only when clusters merge?
all galaxies start out as globular clusters, and that spiral arms are formed only when clusters merge?
Not according to what I have read. This may be out of date but as I understand it you start with irregular galaxies (which contain the clusters) these merge to form spirals which merge to form larger spirals or ellipticals. This topic has undergone a lot of change since I started studying such things and I think it is likely to undergo more change.
light between the galaxies
)
Wow! Not bad for ground based equipment. Do you think these observations will greatly impact calculations of dark matter ratio?
Probably not, the WMAP
)
Probably not, the WMAP results have fixed the amount of baryonic matter in the universe.
WMAP
That WMAP linked site says
)
That WMAP linked site says the universe is flat. Was this finding, when it was made, expected? How will the rate of expansion of the universe change over time?
RE: That WMAP linked site
)
Yes
It used to be thought that the expansion was slowing. Recent evidence indicates the expansion is accelerating. This is attributed to either Dark Energy or Einstein's Cosmological constant depending on whom you are listening too.
Hi, Mark. I in haste didn't
)
Hi, Mark. I in haste didn't phrase my question very well. From the WMAP site, there's about 23% dark matter, with some question as to the composition of it, e.g., baryonic, supermassive BHs, or even possibly new forms of matter. This discovery of 'intracluster light (ICL)', containing both stars and dust, seems to tip the scales towards mostly baryonic matter, but the discovery of Quasar HE0450-2958 may tip the scale towards BHs. In hindsight, it's probably a too-soon-to-tell question, but I'll gladly listen to any thoughts you might have about it. Thanks!
ChipperQ: Are asking about
)
ChipperQ:
Are asking about which kind of mass is responcible for the gravity that is holding the cluster together? If so then I think the additional normal mass provided by the previously unseen stars will not change the ratio of normal to dark mass significantly.
Sorry, let me back up a step,
)
Sorry, let me back up a step, and make sure I'm using terms properly. Interesting info from WMAP regarding the composition of the universe has 73% dark energy, 23% cold dark matter, and 4% atoms. Since the intracluster light is 1000x fainter than the night sky, would it be considered as part of the dark matter, or has it already been counted with the (more luminous) atoms?
RE: 73% dark
)
Nobody knows what this is. Its existence is posited to explain the accelerating expansion of the universe.
Should be called non-baryonic, non-leptonic and non-photonic.
Again nobody knows what this is. Its existence is posited to explain discrepancies between the motion of stars and galaxies and the gravity due to normal matter.
The term cold dark matter is sometimes used to discribe non-luminous objects made up of mostly of normal matter but in this context such usage is inappropriate.
The normal stuff we are familiar with. The value is determine by calculation of nuclear synthesis of element heavier the Hydrogen during the Big Bang. Not all of this matter is visible so some of is sometimes called dark matter. This leads some rather confusing terminology.
Yes, more or less.
Thanks, Mark. I was looking
)
Thanks, Mark. I was looking at the two images of the Virgo Cluster, along with the simulations, and I thought the ICL might be a reasonable explanation for some of the 'discrepancies between the motion of the stars and galaxies', since it apparently contains significant amounts of matter, despite being called 'light'. I'm a bit confused...
I thought the simulations were excellent insofar as they showed how filaments of ICL form between the clusters. From this, is it correct to say that all galaxies start out as globular clusters, and that spiral arms are formed only when clusters merge?
RE: all galaxies start out
)
Not according to what I have read. This may be out of date but as I understand it you start with irregular galaxies (which contain the clusters) these merge to form spirals which merge to form larger spirals or ellipticals. This topic has undergone a lot of change since I started studying such things and I think it is likely to undergo more change.