The discussion revolves around the relationship between dark matter and energy, specifically whether dark matter can be related to energy in a manner similar to ordinary matter through the equation E=mc^2. Participants explore the distinctions between dark matter and dark energy, the nature of dark matter particles, and the potential naming of the energy associated with dark matter.
Participants generally agree on the weak interactions of dark matter and its similarities to ordinary matter, but there is no consensus on the naming of the energy associated with dark matter or the specifics of its interactions.
The discussion includes assumptions about the nature of dark matter and its interactions, which remain unresolved. The potential for dark matter to interact through the weak nuclear force is also noted as uncertain.
The equation E = mc^2 is a statement of what we mean when we talk about mass: the equation states that mass is the energy in the internal degrees of freedom of an object. For example, if I have a potato, and I heat it up (add energy internal to the potato), then I increase its mass.PhanthomJay said:If ordinary matter is related to energy per E=mc^2, then can dark matter also be similarly related, and if so, is there a name for this energy? I understand that "dark energy" (the cosmological constant in the expanding universe) and "dark matter" bear no relationship, so I'm wondering that if dark matter = E/c^2, has a name been coined for "E" to distinguish it from the existing definition of dark energy.
There is no fundamental difference between dark matter and 'ordinary matter'. Ordinary matter can also interact weakly. I'm not pointing this out to be critical, but only because the confusion about dark matter is deep and rampant in these forums. We need to be careful!AleLucca said:Dark matter differs from ordinary matter only in the way it interacts with stuff. Dark matter is now believed to be made of massive particles that interact only weakly.
I think the point is that like neutrinos, dark matter does not interact with either the strong nuclear force or electromagnetism. (If it interacted electromagnetically, it would behave like normal matter on cosmological scales. If it interacted with the strong nuclear force, we would have detected it long before now.)bapowell said:There is no fundamental difference between dark matter and 'ordinary matter'. Ordinary matter can also interact weakly. I'm not pointing this out to be critical, but only because the confusion about dark matter is deep and rampant in these forums. We need to be careful!
Chalnoth said:I think the point is that like neutrinos, dark matter does not interact with either the strong nuclear force or electromagnetism. (If it interacted electromagnetically, it would behave like normal matter on cosmological scales. If it interacted with the strong nuclear force, we would have detected it long before now.)
Bear in mind that they are not necessarily posited to interact through the weak nuclear force. They may, but it isn't clear at this time. Obviously we hope that they do, so that direct detection is more likely.AleLucca said:You are both right. Dark matter particles are believed to interact only through the weak and gravitational force, so they are not different from neutrinos in this aspect. If so, there is no fundamental difference between dark and ordinary matter
Chalnoth said:I think the point is that like neutrinos, dark matter does not interact with either the strong nuclear force or electromagnetism. (If it interacted electromagnetically, it would behave like normal matter on cosmological scales. If it interacted with the strong nuclear force, we would have detected it long before now.)
Chalnoth said:Bear in mind that they are not necessarily posited to interact through the weak nuclear force. They may, but it isn't clear at this time. Obviously we hope that they do, so that direct detection is more likely.