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Fed
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we all know of positive / negative mass, could the theorized "Dark Matter" actually be "Neutral" Mass?
just a thought:)
just a thought:)
I have no idea what is meant by "negative mass".Fed said:we all know of positive / negative mass
There is nothing which does not interact with the gravitational field.SimonRoberts said:Surely 'neutral mass' by definition means massless. i.e, not interacting with the gravitational field.
Don't confuse dark matter with dark energy. And even w/o dark energy there are well-known cosmological solutions which do not collaps in a big crunch singularity. And btw. the collaps is not to be confused with a black hole. The later one exists within spacetime whereas the universe is spacetimeFed said:... that they/we believe dark matter to be part the reason the universe has and will forever continue to expand rather than collapse into a black hole
DE acts like a "negative gravitation force", but is does not "repel" normal matter. And as I said before - DE and DM are totally different concepts.Fed said:this would mean DM repels normal matter.
tom.stoer said:There is nothing which does not interact with the gravitational field.
SimonRoberts said:As I understand it, one piece of evidence for dark matter is the rotation rate of a galaxy as a function of distance from the centre. After a certain point, whereas the rate would be expected to fall of with radius, it stays the same. Or at least, it doesn't fall off as much as it would. This indicates the presence of what we call 'dark matter'. However, as I understand it, if present, it is evenly distributed outwards with radius. Quite how the neutrino explanation would fit with this requirement I am not sure.
Exactly. In addition the DM hypothesis is supported by gravitational lensing and other astrophysical observations.SimonRoberts said:As I understand it, one piece of evidence for dark matter is the rotation rate of a galaxy as a function of distance from the centre. After a certain point, whereas the rate would be expected to fall of with radius, it stays the same. Or at least, it doesn't fall off as much as it would. This indicates the presence of what we call 'dark matter'. However, as I understand it, if present, it is evenly distributed outwards with radius. Quite how the neutrino explanation would fit with this requirement I am not sure.
Neutrinos are no reasonable candidates for DM as they are too light; they will not come into thermal equilibrium with normal matter = they will stay too hot. Candidates are light SUSY particles, probably neutralinos. LHC will tell if there is something like that ...sanman said:Well, if neutrinos have rest mass, then as they travel outward from a galaxy they are going to be decelerated gradually by that gravitational pull, leaving only their tangential velocity components. So they will orbit their galaxy, providing uniform distribution wrt radius.
Dark matter is a hypothetical form of matter that is believed to make up approximately 85% of the total matter in the universe. It is called "dark" because it does not emit, absorb, or reflect any electromagnetic radiation, making it invisible to telescopes. Its existence is inferred through its gravitational effects on visible matter. Understanding dark matter is important because it plays a crucial role in the formation and evolution of galaxies and the overall structure of the universe.
Dark matter is different from regular matter in several ways. It does not interact with light, making it invisible, and it does not interact with regular matter through the electromagnetic force. It only interacts with regular matter through gravity, which is why it is difficult to detect. Dark matter is also believed to be non-baryonic, meaning it is not made up of the same particles as regular matter, such as protons and neutrons.
Scientists study dark matter through various methods, such as observing its gravitational effects on visible matter, using computer simulations to model its behavior, and searching for particles that could make up dark matter. They also use telescopes and other instruments to detect radiation that could be emitted from interactions between dark matter and regular matter.
There are several theories about the nature of dark matter, but the most widely accepted one is the Cold Dark Matter (CDM) theory. This theory proposes that dark matter is made up of non-baryonic particles that were formed shortly after the Big Bang. Other theories suggest that dark matter could be made up of exotic particles or even small black holes.
Dark matter and dark energy are two separate and distinct concepts. While dark matter makes up the majority of matter in the universe, dark energy is believed to be a mysterious force that is responsible for the accelerated expansion of the universe. Both concepts are still not fully understood and are the subject of ongoing research and scientific debate.