Revision 2

Accepted · core change · record

Changes against revision 1:

Title: Does antihydrogen fall with g to within 1 percent?
Plain: In 2023 the first direct experiment showed that antihydrogen falls down, not up, but only to about 20% precision. A 1% measurement would test whether antimatter feels gravity exactly like matter.
Precise · changed · core: Revision 1: ALPHA-g measured the vertical acceleration of antihydrogen as a_g = (0.75 +- 0.13 stat+sys +- 0.16 simulation) g (2023). Determine $a_g/g$ with total uncertainty below 0.01 and test whether it differs from 1.; Revision 2: ALPHA-g measured the vertical acceleration of antihydrogen as $a_g = (0.75 \pm 0.13 stat+sys \pm 0.16 simulation) g$ (2023). Determine $a_g/g$ with total uncertainty below 0.01 and test whether it differs from 1.
Settled by: A laser-cooled antihydrogen release or interferometric measurement (ALPHA-g, GBAR or AEgIS) reaching $1\%$ uncertainty on $a_g$.
Kind: well-posed
Answer type: value
References: (empty)
Literature status: open
Status note: No measurement of $a_g$ more precise than the 2023 ALPHA-g result has been published as of 2026; antihydrogen laser cooling (2021) is the stated prerequisite for the next step.
Posed since: (empty)

Decisions