4 ms·

> Consider the Bullet Cluster, which is two colliding galactic clusters. The gravitational center of mass is offset from the visible center of mass. This offset

> Consider the Bullet Cluster, which is two colliding galactic clusters. The gravitational center of mass is offset from the visible center of mass. This offset cannot be explained as potential energy of visible matter. There must be something else, invisible and massive, i.e. dark matter. i'd argue another possible explanation to add to your i.e. was addressed by the gp gp> then galaxies are not moving in the way we currently think they are. the movement of gyroscopes can alter a system's center of mass https://www.youtube.com/watch?v=n_6p-1J551Y https://www.youtube.com/watch?v=n_6p-1J551Y

dhimes 10y ago
The rotation is the gyroscope. And the meaning of your last statement (the movement of gyroscopes) is unclear. The video is cool, but well understood by the same physics that is being applied to the understanding of the galaxies.
- justifier 10y ago
  exactly, but the gp threw in the caveat gp> then galaxies are not moving in the way we currently think they are. so if our calculations already take into account the gyroscopic movement of the bodies within the system, still the gp's thought experiment accounted for this by saying the real nature of the motion of the bodies is different than the motion that we are currently using in our calculations just saying dark matter ignores the potential for other valid explanation for the phenomena instead of there being dm offsetting the center of mass the gyroscopic motion of the bodies within the system also could explain the offset 'not moving in the way we currently think' is a vague statement and could be a direction of rigor for the gp if thae wished to pursue the idea some underlying questions that need to be answered by anyone that suggests our current understanding is incorrect in this regard would need to address: how are they moving differently? how could we detect the difference? how can our incorrect perception be explained? my> the movement of gyroscopes can alter a system's center of mass the cube video was intended to show that yes, this is well understood, and exhibit how changing the nature of the rotation of the gyros: location, direction, speed; in the cube you could move the center of mass to wherever you'd like add another dimension allowing the gyros to move freely stead being fixed within a cube and even more freedom to alter the center of mass could be achieved https://www.youtube.com/watch?v=UnpLEnIqj_A https://www.youtube.com/watch?v=UnpLEnIqj_A i agree it is well understood.. that is why i was using it as naive evidence to defend the gp's thought experiment from being dismissed poorly
  - dhimes 10y ago
    add another dimension allowing the gyros to move freely stead being fixed within a cube and even more freedom to alter the center of mass could be achieved It's the fact that it is fixed within the cube that allows it to move the cm. That only happens because of the reaction force it can exert against the ground. In the absence of external forces the cm won't move (strictly, won't accelerate). In a sense this is a tautology. So it's not an uncalculated motion that can alter the motion of the c.m., it's an unaccounted for force. When "dark matter" arrived on the scene it was a catch-all for matter we couldn't see. It's only when the explanations for "normal matter hidden from view" fell one-by-one that dark matter took on exotic properties. (In other words, super-smart people have already done the math on hidden galaxies of brown dwarfs and neutron stars being the source of the gravity). I'm betting that if there is a revolutionary simplification to it all, it is because fundamental constants are changing with time. Thus redshift, as ars also speculates, isn't a true measure of velocity. But I understand that super-smart people are doing the measurements on this as well and are finding no changes.

dhimes 10y ago

The rotation is the gyroscope. And the meaning of your last statement (the movement of gyroscopes) is unclear. The video is cool, but well understood by the same physics that is being applied to the understanding of the galaxies.

justifier 10y ago
exactly, but the gp threw in the caveat gp> then galaxies are not moving in the way we currently think they are. so if our calculations already take into account the gyroscopic movement of the bodies within the system, still the gp's thought experiment accounted for this by saying the real nature of the motion of the bodies is different than the motion that we are currently using in our calculations just saying dark matter ignores the potential for other valid explanation for the phenomena instead of there being dm offsetting the center of mass the gyroscopic motion of the bodies within the system also could explain the offset 'not moving in the way we currently think' is a vague statement and could be a direction of rigor for the gp if thae wished to pursue the idea some underlying questions that need to be answered by anyone that suggests our current understanding is incorrect in this regard would need to address: how are they moving differently? how could we detect the difference? how can our incorrect perception be explained? my> the movement of gyroscopes can alter a system's center of mass the cube video was intended to show that yes, this is well understood, and exhibit how changing the nature of the rotation of the gyros: location, direction, speed; in the cube you could move the center of mass to wherever you'd like add another dimension allowing the gyros to move freely stead being fixed within a cube and even more freedom to alter the center of mass could be achieved https://www.youtube.com/watch?v=UnpLEnIqj_A https://www.youtube.com/watch?v=UnpLEnIqj_A i agree it is well understood.. that is why i was using it as naive evidence to defend the gp's thought experiment from being dismissed poorly
- dhimes 10y ago
  add another dimension allowing the gyros to move freely stead being fixed within a cube and even more freedom to alter the center of mass could be achieved It's the fact that it is fixed within the cube that allows it to move the cm. That only happens because of the reaction force it can exert against the ground. In the absence of external forces the cm won't move (strictly, won't accelerate). In a sense this is a tautology. So it's not an uncalculated motion that can alter the motion of the c.m., it's an unaccounted for force. When "dark matter" arrived on the scene it was a catch-all for matter we couldn't see. It's only when the explanations for "normal matter hidden from view" fell one-by-one that dark matter took on exotic properties. (In other words, super-smart people have already done the math on hidden galaxies of brown dwarfs and neutron stars being the source of the gravity). I'm betting that if there is a revolutionary simplification to it all, it is because fundamental constants are changing with time. Thus redshift, as ars also speculates, isn't a true measure of velocity. But I understand that super-smart people are doing the measurements on this as well and are finding no changes.