## Abstract

For disk galaxies the fourth power of the circular velocity v^{4}_{c} of stars around the core of the galaxy is proportional to the luminosity L, v^{4}_{c} ∝ L (Tully-Fisher law). Since L is proportional to the mass M of the galaxy, it follows that v^{4}_{c} ∝ M. Newtonian mechanics, however, yields v^{2}_{c} = GM/r for a circular motion. In order to rectify this big difference, astronomers assume the existence of dark matter. We derive the equation of motion of a star moving in the central field of a galaxy and show that, for a circular motion, it yields a term of the form v^{4}_{c} ∝ GMc/τ, where G is Newton's gravitational constant, c is the speed of light, and τ is the Hubble time. This puts in doubt the existence of halo dark matter for galaxies.

Original language | English |
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Pages (from-to) | 1397-1404 |

Number of pages | 8 |

Journal | International Journal of Theoretical Physics |

Volume | 39 |

Issue number | 5 |

DOIs | |

State | Published - 1 Jan 2000 |

## ASJC Scopus subject areas

- General Mathematics
- Physics and Astronomy (miscellaneous)