What does it mean when light hits something? Is light “hitting” the air around you? If so how can you see at all?
For light to measurably change when it interacts with a particle or group of particles, there has to be a separation of electrical charges. The light also has to be close to the energy of an available energy state transition. There’s lots of diffferent types, but remember electron orbitals? Most visible light interactions involve electrons jumping to higher energy orbitals or falling to lower energy orbitals. There are only very specific interactions that are possible with specific wavelengths of light. Fortunately, visible light spans a wide range of wavelengths that interact very strongly with the forms of matter that surround us.
There are lots of things that won’t interact with light at all. Nuetrons and neutrinos don’t have a charge separation and don’t interact with light at all. You could shine very strong lasers through a cloud of neutrinos, and as far as the beam path would indicate, it would be identical to vacuum. They have to be studied by how they interact with other matter that does interact with light. It may sound counterintuitive, but single free charges like a bare hydrogen nucleus or free electron also don’t absorb or emit photons. It is only when charges can interact with eachother that we get light interactions.
So nothing measurable happens when light propagates through a volume where dark matter is. There is no mechanism by which the two can interact, except gravitational lensing.
What does it mean when light hits something? Is light “hitting” the air around you? If so how can you see at all?
For light to measurably change when it interacts with a particle or group of particles, there has to be a separation of electrical charges. The light also has to be close to the energy of an available energy state transition. There’s lots of diffferent types, but remember electron orbitals? Most visible light interactions involve electrons jumping to higher energy orbitals or falling to lower energy orbitals. There are only very specific interactions that are possible with specific wavelengths of light. Fortunately, visible light spans a wide range of wavelengths that interact very strongly with the forms of matter that surround us.
There are lots of things that won’t interact with light at all. Nuetrons and neutrinos don’t have a charge separation and don’t interact with light at all. You could shine very strong lasers through a cloud of neutrinos, and as far as the beam path would indicate, it would be identical to vacuum. They have to be studied by how they interact with other matter that does interact with light. It may sound counterintuitive, but single free charges like a bare hydrogen nucleus or free electron also don’t absorb or emit photons. It is only when charges can interact with eachother that we get light interactions.
So nothing measurable happens when light propagates through a volume where dark matter is. There is no mechanism by which the two can interact, except gravitational lensing.