Instant takeaway: ETH Zurich and the Paul Scherrer Institute (PSI) have produced a “cold” μ-sodium-like beam of mu-atom matter—nearly matched in speed and almost parallel—paving the way for the first test of Earth’s gravity using a second-generation (anti-)matter interferometer.
According to an ETH press release (2026-09-15) and a Nature Physics paper (2026-09-14, online): positive and negative muons are injected into an ultra-thin superfluid helium layer cooled to near absolute zero. After forming neutral muonium, they are “shot” out of the liquid surface by chemical potential. With the old source, the particles flew in all directions, making precision experiments hard; the muon lifetime is only about 2.2 microseconds. Next comes an interferometer—to see whether gravity shifts the interference fringes by even a tiny amount. The method is expected to be tested this year, while a complete gravity experiment will likely take another two or three years.
Independent verification: PSI’s press release the same day uses the same wording—using the CHRISP facility to obtain high-intensity ultra-cold muonium beams, aiming to check whether the universality of free fall also holds for second-generation particles.
First, let’s be clear: what has been completed so far is beam preparation—not the result that has already “challenged Einstein.”
Figure: Markus Fischer / PSI; experimental assembly ETH Zurich / Anna Soter
Data as of: Nature Physics 2026-09-14; ETH / PSI press releases 2026-09-15
#物理 #particle
According to an ETH press release (2026-09-15) and a Nature Physics paper (2026-09-14, online): positive and negative muons are injected into an ultra-thin superfluid helium layer cooled to near absolute zero. After forming neutral muonium, they are “shot” out of the liquid surface by chemical potential. With the old source, the particles flew in all directions, making precision experiments hard; the muon lifetime is only about 2.2 microseconds. Next comes an interferometer—to see whether gravity shifts the interference fringes by even a tiny amount. The method is expected to be tested this year, while a complete gravity experiment will likely take another two or three years.
Independent verification: PSI’s press release the same day uses the same wording—using the CHRISP facility to obtain high-intensity ultra-cold muonium beams, aiming to check whether the universality of free fall also holds for second-generation particles.
First, let’s be clear: what has been completed so far is beam preparation—not the result that has already “challenged Einstein.”
Figure: Markus Fischer / PSI; experimental assembly ETH Zurich / Anna Soter
Data as of: Nature Physics 2026-09-14; ETH / PSI press releases 2026-09-15
#物理 #particle