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Do you know of any sources that rule out regular matter in between celestial bodies that would be sparse enough to be unobservable but massive enough when put t

Do you know of any sources that rule out regular matter in between celestial bodies that would be sparse enough to be unobservable but massive enough when put together? Like a bunch of cold electrons?

xenophonf 5y ago
We would see something like that against the cosmic microwave background. Instead, we see that about 5/6ths of the total matter of the universe interacts with the CMB only through gravity. Also, more hidden (somehow) baryonic matter would change our current theories surrounding Big Bang nucleosynthesis in ways that aren't supported by other observations, like the percentages of (visible) matter like helium and lithium.
littlestymaar 5y ago
If my physics class aren't too far: it cannot be charged otherwise it would radiate, it cannot be atoms because it would absorb radiations and it cannot be neutrons because they don't live long enough by themselves. Then it must be something else…
- ericbarrett 5y ago
  I believe the only two remaining candidates along these lines are MACHOs and relativistic neutrinos ("hot dark matter"), but I don't think either of them are considered likely among mainstream cosmologists anymore.
gerdesj 5y ago
I'm an IT consultant who's been reading New Scientist for 30 years, not an Astrophysicist! Now, you mention "matter ... sparse enough ... massive". I think you have answered your own question. The matter in question may be sparse but if there is enough of it, then it will become "massive" and hence detectible. Not sure what a "cold electron" is - it sounds unlikely. Dark Matter is postulated and not a "thing" per se. A lot of good science does seem to imply that 4/5ths of matter is unseen. The key thing I am trying to get across is that our human need to slap a name on something is not appropriate here but we do it anyway. The cool kids with massive budgets and impressive machines in space cannot yet tell you and I what the stuff is but for now we will call it "dark matter". It might sound a bit mad for people more used to dealing with certainties like Civil Engineering (lol - Britannia Bridge in London - resonance). I'm a Civ Eng grad. That's quite a long way of saying "no"!

xenophonf 5y ago

We would see something like that against the cosmic microwave background. Instead, we see that about 5/6ths of the total matter of the universe interacts with the CMB only through gravity. Also, more hidden (somehow) baryonic matter would change our current theories surrounding Big Bang nucleosynthesis in ways that aren't supported by other observations, like the percentages of (visible) matter like helium and lithium.

littlestymaar 5y ago

If my physics class aren't too far: it cannot be charged otherwise it would radiate, it cannot be atoms because it would absorb radiations and it cannot be neutrons because they don't live long enough by themselves. Then it must be something else…

ericbarrett 5y ago
I believe the only two remaining candidates along these lines are MACHOs and relativistic neutrinos ("hot dark matter"), but I don't think either of them are considered likely among mainstream cosmologists anymore.

gerdesj 5y ago

I'm an IT consultant who's been reading New Scientist for 30 years, not an Astrophysicist! Now, you mention "matter ... sparse enough ... massive". I think you have answered your own question. The matter in question may be sparse but if there is enough of it, then it will become "massive" and hence detectible. Not sure what a "cold electron" is - it sounds unlikely. Dark Matter is postulated and not a "thing" per se. A lot of good science does seem to imply that 4/5ths of matter is unseen. The key thing I am trying to get across is that our human need to slap a name on something is not appropriate here but we do it anyway. The cool kids with massive budgets and impressive machines in space cannot yet tell you and I what the stuff is but for now we will call it "dark matter". It might sound a bit mad for people more used to dealing with certainties like Civil Engineering (lol - Britannia Bridge in London - resonance). I'm a Civ Eng grad. That's quite a long way of saying "no"!