New data supports theory of dark matter, but suggests inexplicably that it acts differently depending on the galaxy’s mass
The uncertainty of science: Astronomers analyzing twelve small and faint galaxies have determined that the existence of some form of mysterious undetected dark matter is necessary to explain the motions of their stars, and that another theory dubbed MOND that would make dark matter unnecessary fails to explain the data.
The authors found that the galaxies’ internal gravitational fields cannot be explained by visible matter alone, and that MOND predictions fail to reproduce the observed behaviour. They then compared their results with theoretical models that assume instead that these galaxies are surrounded by a massive halo of dark matter. Run on the UK’s DiRAC National Supercomputer facility, these dark matter models gave a much better match to the data.
Sounds good, eh? Not so fast. The research also found that large and small galaxies inexplicably interact with gravity and dark matter differently.
The research, published in Astronomy & Astrophysics, also challenges a long-standing assumption about how galaxies behave. Astronomers have long believed there is a simple link between the amount of visible matter in a galaxy and the strength of the gravitational pull it produces – known as the “radial acceleration relation.” While this relationship still holds for larger systems, the new study shows that it starts to break down in the smallest galaxies.
In other words, we don’t know enough yet to really explain the formation and behavior of galaxies. This really isn’t surprising, considering the time scales involved (billions of years) and the distances (millions to billions of light years).
On Christmas Eve 1968 three Americans became the first humans to visit another world. What they did to celebrate was unexpected and profound, and will be remembered throughout all human history. Genesis: the Story of Apollo 8, Robert Zimmerman's classic history of humanity's first journey to another world, tells that story, and it is now available as both an ebook and an audiobook, both with a foreword by Valerie Anders and a new introduction by Robert Zimmerman.
The print edition can be purchased at Amazon or from any other book seller. If you want an autographed copy the price is $60 for the hardback and $45 for the paperback, plus $8 shipping for each. Go here for purchasing details. The ebook is available everywhere for $5.99 (before discount) at amazon, or direct from my ebook publisher, ebookit. If you buy it from ebookit you don't support the big tech companies and the author gets a bigger cut much sooner.
The audiobook is also available at all these vendors, and is also free with a 30-day trial membership to Audible.
"Not simply about one mission, [Genesis] is also the history of America's quest for the moon... Zimmerman has done a masterful job of tying disparate events together into a solid account of one of America's greatest human triumphs."--San Antonio Express-News
The uncertainty of science: Astronomers analyzing twelve small and faint galaxies have determined that the existence of some form of mysterious undetected dark matter is necessary to explain the motions of their stars, and that another theory dubbed MOND that would make dark matter unnecessary fails to explain the data.
The authors found that the galaxies’ internal gravitational fields cannot be explained by visible matter alone, and that MOND predictions fail to reproduce the observed behaviour. They then compared their results with theoretical models that assume instead that these galaxies are surrounded by a massive halo of dark matter. Run on the UK’s DiRAC National Supercomputer facility, these dark matter models gave a much better match to the data.
Sounds good, eh? Not so fast. The research also found that large and small galaxies inexplicably interact with gravity and dark matter differently.
The research, published in Astronomy & Astrophysics, also challenges a long-standing assumption about how galaxies behave. Astronomers have long believed there is a simple link between the amount of visible matter in a galaxy and the strength of the gravitational pull it produces – known as the “radial acceleration relation.” While this relationship still holds for larger systems, the new study shows that it starts to break down in the smallest galaxies.
In other words, we don’t know enough yet to really explain the formation and behavior of galaxies. This really isn’t surprising, considering the time scales involved (billions of years) and the distances (millions to billions of light years).
On Christmas Eve 1968 three Americans became the first humans to visit another world. What they did to celebrate was unexpected and profound, and will be remembered throughout all human history. Genesis: the Story of Apollo 8, Robert Zimmerman's classic history of humanity's first journey to another world, tells that story, and it is now available as both an ebook and an audiobook, both with a foreword by Valerie Anders and a new introduction by Robert Zimmerman.
The print edition can be purchased at Amazon or from any other book seller. If you want an autographed copy the price is $60 for the hardback and $45 for the paperback, plus $8 shipping for each. Go here for purchasing details. The ebook is available everywhere for $5.99 (before discount) at amazon, or direct from my ebook publisher, ebookit. If you buy it from ebookit you don't support the big tech companies and the author gets a bigger cut much sooner.
The audiobook is also available at all these vendors, and is also free with a 30-day trial membership to Audible.
"Not simply about one mission, [Genesis] is also the history of America's quest for the moon... Zimmerman has done a masterful job of tying disparate events together into a solid account of one of America's greatest human triumphs."--San Antonio Express-News