OK I'm sure this has been asked before but I can't get it out of head. A long time ago I heard about galaxies spinning so fast that gravity alone should not be able to hold them together. Has an answer to this come about?
Yep.
I believe the answer was "Crap, I forgot to cary the 9!"
But seriously, I've seen that claim made by cranks, but I've never seen any reputable source for it. It's certainly not on any list of unsolved mysteries in physics that I've ever seen, and I've seen quite a few such lists, from the 60's to modern day.
I believe the answer was "Crap, I forgot to cary the 9!"
But seriously, I've seen that claim made by cranks, but I've never seen any reputable source for it. It's certainly not on any list of unsolved mysteries in physics that I've ever seen, and I've seen quite a few such lists, from the 60's to modern day.
QUOTE
Beer w/Straw Posted: Apr 11 2008, 10:23 PM OK I'm sure this has been asked before but I can't get it out of head. A long time ago I heard about galaxies spinning so fast that gravity alone should not be able to hold them together. Has an answer to this come about?
was it the discovery of HVC 127-41-330 ?
the proposed answer to the problem of what is holding HVC 127-41-330 together nicely explains the galaxy rotation problem also ie dark matter.
Well that article is 2003 so I can't say for sure.
"It appears to be rotating so fast it would fall apart unless it contains a strong, hidden source of gravity. The researchers therefore argue that the cloud must be at least 80 per cent dark matter, the hypothetical invisible substance whose gravity is supposed to explain why many objects in the cosmos move as fast as they do."
It was a long time ago but thanks for the reply.
"It appears to be rotating so fast it would fall apart unless it contains a strong, hidden source of gravity. The researchers therefore argue that the cloud must be at least 80 per cent dark matter, the hypothetical invisible substance whose gravity is supposed to explain why many objects in the cosmos move as fast as they do."
It was a long time ago but thanks for the reply.
...
Also MOND I think is an idea besides dark matter,
http://www.americanscientist.org/template/...l/assetid/16363
I learned something new today ... theoretically
http://www.americanscientist.org/template/...l/assetid/16363
I learned something new today ... theoretically
Galaxies still rotate faster than matter we can account for explains.
Not a few special galaxies, but every single one we have good data of - for instance our very own one.
Standard explanation is that galaxies have more mass than we can see up to now, and this mass is not made up of dead stars, brown dwarves, nor neutral gas.
This mass missing in galaxies is only a part of the mass missing between galaxies.
Have a look at "Wimps" for an explanation attempt. "Machos" were also considered but look less seducing today.
Alternately, gravity laws could be modified - have a look at MOND for instance. But since gravitational microlensing has shown mass outside the debris of two colliding galaxies, MOND is much less fashionable than Wimps.
Not a few special galaxies, but every single one we have good data of - for instance our very own one.
Standard explanation is that galaxies have more mass than we can see up to now, and this mass is not made up of dead stars, brown dwarves, nor neutral gas.
This mass missing in galaxies is only a part of the mass missing between galaxies.
Have a look at "Wimps" for an explanation attempt. "Machos" were also considered but look less seducing today.
Alternately, gravity laws could be modified - have a look at MOND for instance. But since gravitational microlensing has shown mass outside the debris of two colliding galaxies, MOND is much less fashionable than Wimps.
QUOTE (Enthalpy+Apr 17 2008, 12:47 AM)
Galaxies still rotate faster than matter we can account for explains.
Not a few special galaxies, but every single one we have good data of - for instance our very own one.
Standard explanation is that galaxies have more mass than we can see up to now, and this mass is not made up of dead stars, brown dwarves, nor neutral gas.
This mass missing in galaxies is only a part of the mass missing between galaxies.
Have a look at "Wimps" for an explanation attempt. "Machos" were also considered but look less seducing today.
Alternately, gravity laws could be modified - have a look at MOND for instance. But since gravitational microlensing has shown mass outside the debris of two colliding galaxies, MOND is much less fashionable than Wimps.
If you have a link or something to this, I would be interested.
Not a few special galaxies, but every single one we have good data of - for instance our very own one.
Standard explanation is that galaxies have more mass than we can see up to now, and this mass is not made up of dead stars, brown dwarves, nor neutral gas.
This mass missing in galaxies is only a part of the mass missing between galaxies.
Have a look at "Wimps" for an explanation attempt. "Machos" were also considered but look less seducing today.
Alternately, gravity laws could be modified - have a look at MOND for instance. But since gravitational microlensing has shown mass outside the debris of two colliding galaxies, MOND is much less fashionable than Wimps.
If you have a link or something to this, I would be interested.
now, if galaxies are 80% dark matter, wouldn't we run into it? i mean were happily whizzing around in space then, BAM. we get pulverised by a gob of invisable meteors.
QUOTE (roam+Apr 17 2008, 01:03 PM)
now, if galaxies are 80% dark matter, wouldn't we run into it? i mean were happily whizzing around in space then, BAM. we get pulverised by a gob of invisable meteors.
not if ur in star trek. you can just reconfigure sensors to detect it
not if ur in star trek. you can just reconfigure sensors to detect it
QUOTE (roam+Apr 17 2008, 06:03 PM)
now, if galaxies are 80% dark matter, wouldn't we run into it? i mean were happily whizzing around in space then, BAM. we get pulverised by a gob of invisable meteors.
Road kill of the Milkey Way
Road kill of the Milkey Way
QUOTE
roam Posted: Yesterday at 4:03 AM now, if galaxies are 80% dark matter, wouldn't we run into it?
no. dark matter's interaction with ordinary matter is limited to gravitational interaction ie it does not interact electromagnetically.
dark matter, may be passing through us all right ....now
PhysOrg scientific forums are totally dedicated to science, physics, and technology. Besides topical forums such as nanotechnology, quantum physics, silicon and III-V technology, applied physics, materials, space and others, you can also join our news and publications discussions. We also provide an off-topic forum category. If you need specific help on a scientific problem or have a question related to physics or technology, visit the PhysOrg Forums. Here you’ll find experts from various fields online every day.
To quit out of "lo-fi" mode and return to the regular forums, please click here.