Scale-invariant dynamics in the Solar system

Indranil Banik*, Pavel Kroupa

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

3 Citations (Scopus)
2 Downloads (Pure)


The covariant scale-invariant dynamics (SID) theory has recently been proposed as a possible explanation for the observed dynamical discrepancies in galaxies. SID implies that these discrepancies - commonly attributed to dark matter - arise instead from a non-standard velocity-dependent force that causes two-body near-Keplerian orbits to expand. We show that the predicted expansion of the Earth-Moon orbit is incompatible with lunar laser ranging data at >200σ. Moreover, SID predicts that the gravitating mass of any object was much smaller in the past. If true, a low-mass red giant star must be significantly older than in standard theory. This would make it much older than the conventional age of the Universe, which, however, is expected to be similarly old in SID. Moreover, it is not completely clear whether SID truly contains new physics beyond general relativity, with several previous works arguing that the extra degree of freedom is purely mathematical. We conclude that the SID model is falsified at high significance by observations across a range of scales, even if it is theoretically well formulated.

Original languageEnglish
Pages (from-to)L62-L66
Number of pages5
JournalMonthly Notices of the Royal Astronomical Society: Letters
Issue number1
Early online date18 Jun 2020
Publication statusPublished - Sept 2020


  • Dark matter
  • Ephemerides
  • Gravitation
  • Moon
  • Space vehicles


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