# What produces the velocity changes seen in some Earth flybys? · Earth flyby anomaly > Four answers have been proposed. An error or inconsistency in trajectory modelling and navigation software (reference frames, spheres of… leads, with… Source: https://mysteriesdept.com/mysteries/flyby-anomaly/questions/QST0CWYE98C43P6/what-produces-the-velocity-changes-seen-in-some-earth-flybys Publisher: Mysteries Department Licence: CC BY 4.0 (credit Mysteries Department and link the page) Updated: 2026-10-26T11:57:26+00:00 --- **0** # What produces the velocity changes seen in some Earth flybys? Asked 26 Oct 2026 by [**apollo** ](https://mysteriesdept.com/u/apollo)·4 answers·0·0 following **Most likely: an error or inconsistency in trajectory modelling and navigation software (reference frames, spheres of…** Ahead on the evidence, not yet confirmed. It needs two reviews to be accepted. ## Where it stands Four answers have been proposed. An error or inconsistency in trajectory modelling and navigation software (reference frames, spheres of… leads, with evidence 2 for, 1 against: partly supported by its tests. Three are still possible. Of the three narrower questions under it, none is answered yet. ## Why it matters The anomalies are small but far above the tracking errors, appear with both signs, and vanish in later flybys⁠[[1]](https://mysteriesdept.com/sources/SRC0CWYE07A1VKE/the-puzzle-of-the-flyby-anomaly)⁠[[2]](https://mysteriesdept.com/sources/SRC0CWYE16J6YDA/the-flyby-anomaly-a-multivariate-analysis-approach). Either spacecraft navigation is missing something, which matters for every gravity assist, or there is unrecognised physics near Earth. ## Answers 4 [**An error or inconsistency in trajectory modelling and navigation software (reference frames, spheres of…** ](https://mysteriesdept.com/mysteries/flyby-anomaly/answers/ANS0CWYEA7M1T1J/an-error-or-inconsistency-in-trajectory-modelling-and) Partly supported by its tests Evidence: 2 for, 1 against Most likely [**A real effect not described by current physics, tied to Earth's rotation or mass distribution.** ](https://mysteriesdept.com/mysteries/flyby-anomaly/answers/ANS0CWYEC645V23/a-real-effect-not-described-by-current-physics-tied-to) Failed a test; not refuted outright Evidence: 1 for, 2 against Disputed [**An unmodelled conventional force on the spacecraft, such as thermal recoil, drag, radiation pressure or a…** ](https://mysteriesdept.com/mysteries/flyby-anomaly/answers/ANS0CWYEB6W6YK9/an-unmodelled-conventional-force-on-the-spacecraft-such-as) Tested, but the results don't decide it Evidence: 1 for, 2 against Disputed [**None of these.** ](https://mysteriesdept.com/mysteries/flyby-anomaly/answers/ANS0CWYED5C5ED7/none-of-these) Not tested enough to call either way Evidence: none yet Still possible ## History 1. 1998[Antreasian & Guinn: the Moon, the Sun and relativistic effects were dismissed by the first analysts.](https://mysteriesdept.com/sources/SRC0CWYDZFW37Z1/investigations-into-the-unexpected-delta-v-increases-during)Against: An unmodelled conventional force on the spacecraft, such as thermal recoil, drag, radiation pressure or a… 1. 2008[Lämmerzahl et al. puts forward: an unmodelled conventional force on the spacecraft, such as thermal recoil, drag, radiation pressure or a…](https://mysteriesdept.com/sources/SRC0CWYDZZG6T0N/is-the-physics-within-the-solar-system-really-understood) 1. 2008[Anderson et al. puts forward: a real effect not described by current physics, tied to Earth's rotation or mass distribution.](https://mysteriesdept.com/sources/SRC0CWYDZQP6RHF/anomalous-orbital-energy-changes-observed-during-spacecraft) 1. 2008[Lämmerzahl et al.: atmosphere, tides, charge, magnetic moment, albedo pressure, solar wind and spin-rotation coupling were each…](https://mysteriesdept.com/sources/SRC0CWYDZZG6T0N/is-the-physics-within-the-solar-system-really-understood)Against: An unmodelled conventional force on the spacecraft, such as thermal recoil, drag, radiation pressure or a… 1. 2008[Anderson et al.: six flybys fit a formula with a constant equal to twice Earth's equatorial speed over c.](https://mysteriesdept.com/sources/SRC0CWYDZQP6RHF/anomalous-orbital-energy-changes-observed-during-spacecraft)For: A real effect not described by current physics, tied to Earth's rotation or mass distribution. 1. 2009[Turyshev & Toth puts forward: an error or inconsistency in trajectory modelling and navigation software (reference frames, spheres of…](https://mysteriesdept.com/sources/SRC0CWYE07A1VKE/the-puzzle-of-the-flyby-anomaly) 1. 2009[Turyshev & Toth: different teams with different software (JPL, ESA) found anomalies in different spacecraft.](https://mysteriesdept.com/sources/SRC0CWYE07A1VKE/the-puzzle-of-the-flyby-anomaly)Against: An error or inconsistency in trajectory modelling and navigation software (reference frames, spheres of… 1. 2009[Iorio: standard general relativity gives effects 10⁻⁵ to 10⁻² mm/s, far too small.](https://mysteriesdept.com/sources/SRC0CWYE25T261N/the-effect-of-general-relativity-on-hyperbolic-orbits-and)Against: A real effect not described by current physics, tied to Earth's rotation or mass distribution. 1. 2011[Rievers & Lämmerzahl: thermal recoil and Lorentz forces have been modelled in detail for flyby spacecraft.](https://mysteriesdept.com/sources/SRC0CWYE1P620CC/high-precision-thermal-modeling-of-complex-systems-with)For: An unmodelled conventional force on the spacecraft, such as thermal recoil, drag, radiation pressure or a… 1. 2013[Busack: an alternative formula that predicted the Rosetta nulls was taken by its author to support an error in older…](https://mysteriesdept.com/sources/SRC0CWYE0YR11F9/expected-velocity-anomaly-for-the-earth-flyby-of-juno)For: An error or inconsistency in trajectory modelling and navigation software (reference frames, spheres of… 1. 2017[Acedo: the later Rosetta flybys and Juno, processed with newer software, show no anomaly.](https://mysteriesdept.com/sources/SRC0CWYE16J6YDA/the-flyby-anomaly-a-multivariate-analysis-approach)For: An error or inconsistency in trajectory modelling and navigation software (reference frames, spheres of… 1. 2017[Acedo: the formula failed for Rosetta 2007 and 2009 and for Juno 2013.](https://mysteriesdept.com/sources/SRC0CWYE16J6YDA/the-flyby-anomaly-a-multivariate-analysis-approach)Against: A real effect not described by current physics, tied to Earth's rotation or mass distribution. 1. 26 Oct 2026Asked on this site ## Discussion 0 [Add to the discussion](https://mysteriesdept.com/signin?next=/mysteries/flyby-anomaly/questions/QST0CWYE98C43P6/what-produces-the-velocity-changes-seen-in-some-earth-flybys%23discussion) Help with this question [ **Propose an answer** Something the evidence could support or rule out ] [ **Propose an answer** Something the evidence could support or rule out ](https://mysteriesdept.com/signin?next=/mysteries/flyby-anomaly/questions/QST0CWYE98C43P6/what-produces-the-velocity-changes-seen-in-some-earth-flybys%23add-answer) [ **Add evidence** A result for or against an answer ] [ **Add evidence** A result for or against an answer ](https://mysteriesdept.com/signin?next=/mysteries/flyby-anomaly/questions/QST0CWYE98C43P6/what-produces-the-velocity-changes-seen-in-some-earth-flybys%23add-evidence) [ **Ask a sub-question** A smaller question that would help settle this one ] [ **Ask a sub-question** A smaller question that would help settle this one ](https://mysteriesdept.com/signin?next=/mysteries/flyby-anomaly/questions/QST0CWYE98C43P6/what-produces-the-velocity-changes-seen-in-some-earth-flybys%23add-question) [ **Add a source** A paper, archive record or image ] [ **Add a source** A paper, archive record or image ](https://mysteriesdept.com/signin?next=/mysteries/flyby-anomaly/questions/QST0CWYE98C43P6/what-produces-the-velocity-changes-seen-in-some-earth-flybys%23add-source) Where it fits Earth flyby anomaly **What produces the velocity changes seen in some Earth flybys?** Key question · you're here [Does the anomaly occur at other planets?](https://mysteriesdept.com/mysteries/flyby-anomaly/questions/QST0CWYE9ZT1W27/does-the-anomaly-occur-at-other-planets)Open · 3 answers, inconclusive [If the anomaly is real new physics, what kind?](https://mysteriesdept.com/mysteries/flyby-anomaly/questions/QST0CWYE9R02K3H/if-the-anomaly-is-real-new-physics-what-kind)Open · 4 answers, inconclusive [What decides which flybys show an anomaly?](https://mysteriesdept.com/mysteries/flyby-anomaly/questions/QST0CWYE9G65APR/what-decides-which-flybys-show-an-anomaly)Open · 5 answers, inconclusive [ Ask a question under this one ]