Yes for earth-mass black holes, but no for the asteroid-mass range. Also, microlensing constraints are sensitive to the degree to which the black holes are clustered, which is a topic of ongoing study.

Dark matter's local density is about 0.4 GeV/cm^(3), which is about 10^-25 times the average density of the earth. So for example, if the dark matter were earth-mass black holes, they would reside inside the earth only 1/10^25 of the time, on average. Even asteroid-mass black holes (~10^20 grams = 10^-8 earth masses) would reside inside the earth only 1/10^17 of the time.

At typical velocities (200-300 km/s), a black hole would pass through the earth in ~30 seconds. If the dark matter were black holes of mass 10^20 grams, they would thus encounter the earth roughly every 10^17 * 30 seconds = 100 billion years, which is longer than the age of the universe.

If dark matter is a particle, then it's constantly passing through the earth, very similarly to neutrinos. Without nongravitational interactions, it can't really get trapped in (or on) the earth. But we are conducting an array of searches for this dark matter. We haven't found anything, which suggests that dark matter must interact very weakly with ordinary matter.

(If dark matter is massive, e.g. primordial black holes, then it's sparse enough that collisions with the earth are extremely rare. Then we can say that there is no dark matter in/on the earth.)

It can be radiated away as light.

Collisions involving molecules can excite vibrational or rotational modes, which is probably what you are getting at. Such modes gradually decay by emitting light. Collisions could also excite electronic states, which also later decay by emitting light.

Ordinary matter and dark matter both exert gravitational forces on each other, so they influence each other collectively. However there is essentially no momentum exchange between individual particles. Such gravitational collisions are possible (e.g. the slingshot effect), but their importance scales inversely with the number of particles in the system. In the context of galaxies, the individual dark matter particles and ordinary matter particles (whether they be stars or atoms) are far too numerous for gravitational collisions to be important.

(Incidentally, you said dark energy, not dark matter. In case that was intentional, I'll note that we currently have no evidence that dark energy is capable of clustering, but that is an active research topic.)

Sure, it holds for almost every dark matter model that we consider, including

• cold dark matter
• warm dark matter
• fuzzy dark matter (which is so light that quantum effects are important)
• primordial black holes or other massive objects
• self-interacting dark matter (with elastic collisions)

There are, however, "dissipative" dark matter models that are capable of losing energy through inelastic collisions. In those models, there would be a tendency to form disks over very long time scales. Since we know that dark matter halos are much more broadly extended than galaxies, the time scale for dark disk formation must be a lot longer than the time scale to form galactic disks, though.

Also, a dark matter particle that has a significant nongravitational interaction with ordinary matter could be dragged along with the disk. It's hard to reconcile this possibility with (1) absence of dark matter direct detection and (2) absence of dark matter creation in colliders, though.

> to my knowledge there isn't even strong evidence of where its located.

We have a fairly precise picture, e.g. https://academic.oup.com/mnras/article/494/3/4291/5821286

Since they are both subject to the same gravitational forces, dark and ordinary matter at the same location orbit at similar average speeds. However, dark matter has a much broader distribution of velocities, both in magnitude and direction.

Basically, ordinary matter is able to cool via inelastic collisions, causing it to lose energy but not angular momentum. Thus it tends to settle into configurations that reduce the ratio of energy to angular momentum, like disks. Note that collisions alone don't suffice for this; energy loss is needed. Within a disk, particles have largely coherent velocities with only a small spread. For example, material within our section of the disk orbits at roughly 220 km/s, but its velocity dispersion is only in the tens of km/s. (The velocity dispersion is the root-mean-squared deviation from the average velocity.)

In contrast, dark matter has no coherent motion, instead moving in random directions with a wide spread of speeds. The local dark matter velocity dispersion is something like 270 km/s.

(It should be noted, though, that many galaxies don't have disks. Only gas cools; stars are essentially collisionless, just like dark matter. So for example, if a galaxy's mass gets significantly redistributed, perhaps due to a merger, after it has converted its gas into stars, then the stars will not reform a disk.)

Assuming dark matter wasn't created cold enough to cluster on those scales, then yeah, that's a fair interpretation. However it should be noted that on galactic scales, the temperature of the dark matter was not the limiting influence on when structures began to form. That was set by the initial amplitude of variations in the density of the universe and the details of how they grew over time (which are determined by certain aspects of the history of the universe).

Since the dark matter temperature was not the limiting influence, we actually have no clear evidence what its temperature initially was. However, by probing dark matter halos at smaller and smaller scales, we might be able to determine it. The impact of temperature becomes more important at smaller scales.

Not necessarily. Dark matter cools in the early universe due to cosmic expansion (it's the same phenomenon as cosmological redshift, but it's even more efficient for nonrelativistic particles). The fact that dark matter clusters in galaxies does give us information about what dark matter could be, though! For example, it can't be primarily composed of ordinary neutrinos (which are technically dark matter), because they would be too hot to reproduce the observed clustering.

In the early universe, both the gas and the dark matter were cold. With little thermal motion, both components were able to participate in the gravitational clustering that formed galaxies. Consequently, there are comparable amounts of dark matter and ordinary matter in galaxies. That means dark matter contributes significantly to gravitational dynamics.

When material falls into galaxies, it gains kinetic energy, becoming too hot to participate in further gravitational clustering. Gas can cool, e.g. through inelastic collisions, but dark matter cannot. Star systems, which form inside galaxies, thus form in an environment where the dark matter is hot but the gas is cold. That means the gas can participate in the gravitational clustering but the dark matter cannot. Consequently, star systems have much more ordinary matter than dark matter, so the contribution of dark matter to gravitational dynamics is negligible.

The smoothness of the dark matter isn't the full explanation. A completely uniform distribution of dark matter would affect planetary orbits if there were enough of it. It would source a harmonic oscillator potential.

The main reason dark matter does not significantly affect planetary orbits is that there is simply not enough of it. Stars and star systems form when gas cools and condenses. Since dark matter does not cool, it does not participate in this process. Consequently, whereas the average density of the solar system within Neptune's orbital radius is about 3*10^12 GeV/cm^3, the average density of dark matter in our neighborhood is about 0.4 GeV/cm^(3), ten trillion times smaller.