Abstract
To explain rotation curves of spiral galaxies through Newtonian orbital models, massive halos of non-baryonic dark matter (NBDM) are commonly invoked. The postulated properties are that NBDM interacts gravitationally with baryonic matter, yet negligibly interacts with photons. Since halos are large, low-density gaseous bodies, their postulated attributes can be tested against classical thermodynamics and the kinetic theory of gas. Macroscopic models are appropriate because these make few assumptions. NBDM–NBDM collisions must be elastic to avoid the generation of light, but this does not permit halo gas temperature to evolve. If no such collisions exist, then the impossible limit of absolute zero would be attainable since the other available energy source, radiation, does not provide energy to NBDM. The alternative possibility, an undefined temperature, is also inconsistent with basic thermodynamic principles. However, a definable temperature could be attained via collisions with baryons in the intergalactic medium since these deliver kinetic energy to NBDM. In this case, light would be produced since some proportion of baryon collisions are inelastic, thereby rendering the halo detectable. Collisions with baryons are unavoidable, even if NBDM particles are essentially point masses. Note that <0.0001 × the size of a proton is needed to avoid scattering with γ-rays, the shortest wavelength used to study halos. If only elastic collisions exist, NBDM gas would collapse to a tiny, dense volume (zero volume for point masses) during a disturbance—e.g., cosmic rays. NBDM gas should occupy central galactic regions, not halos, since self-gravitating objects are density stratified. In summary, properties of NBDM halos as postulated would result in violations of thermodynamic laws and in a universe unlike that observed.
Highlights
Following Rubin and Ford’s [1] discovery that the rotation curves (RCs, measurements of tangential velocity v as a function of equatorial radius r) of the many billions of stars distributed in spiral galaxies do not exhibit a Keplerian orbital pattern as do the few tiny planets of our Solar System, spherical halos of dark matter (Figure 1a) have been proposed to account for the mass discrepancy (e.g., [2,3]).The concept of dark matter (DM) traces to the 1930s and efforts of Zwicky and others, and originally denoted material that was neither visibly detected nor luminous
We find that non-baryonic dark matter (NBDM) halos cannot exist without violating some laws of thermodynamics
The mathematical constructs used to fit rotation curves in Newtonian orbital models (NOMs) assume a spherical distribution of NBDM about the galactic center (Figure 1a), which is required for the halo to serve as the central point mass under Newtonian physics
Summary
Following Rubin and Ford’s [1] discovery that the rotation curves (RCs, measurements of tangential velocity v as a function of equatorial radius r) of the many billions of stars distributed in spiral galaxies do not exhibit a Keplerian orbital pattern as do the few tiny planets of our Solar System, spherical halos of dark matter (Figure 1a) have been proposed to account for the mass discrepancy (e.g., [2,3]). Because no halo matter was detected and laboratory experiments show that ordinary matter (e.g., baryons) interacts with EM radiation, the description of halo material evolved to become non-baryonic dark matter (NBDM) sometime in the 1990s. In this thought experiment, we adopt the postulated NBDM properties (Table 1) as truth, and derive behavior expected for NBDM halos in view of (1) classical thermodynamics (the theory of heat), in combination with (2) the experimentally confirmed equivalence of heat and light in dilute media (gas or the “vacuum” of space), and (3) kinetic descriptions of ideal point-mass gases [32] and real gases [33] Put: motions of matter cannot exist without producing heat, which is intimately linked to both temperature and light production
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