Scientists from the Ioffe Physical-Technical Institute, the Konstantinov Petersburg Nuclear Physics Institute, and the St. Petersburg State Electrotechnical University "LETI" have established that the fundamental properties of matter remain unchanged across the disk of our Galaxy. The study was conducted using spectral observations of acetaldehyde and methanol molecules in interstellar clouds.
Acetaldehyde, which is toxic under terrestrial conditions, becomes a unique natural laboratory for testing the fundamental laws of the Universe on a cosmic scale. Scientists calculated the sensitivity of the spectral lines of this molecule to changes in the electron-to-proton mass ratio, and then compared laboratory data with astronomical observations. As a result, a new upper limit on the possible variation of the constant was established – no more than one hundred-millionth of a part.
Fundamental constants are fixed values that define the laws of nature and the structure of matter. As early as 1937, a hypothesis was put forward that their values could have evolved with cosmological time. According to another hypothesis, invisible dark matter or strong gravity can affect the fundamental properties of matter – for example, slightly changing the mass of the smallest particles. To test this, researchers compare the behavior of molecules in terrestrial laboratories with how they behave in distant space.
In this search, molecules act as ultra-precise natural clocks. Their internal oscillations are extremely sensitive to the mass of particles. If the mass of an electron or proton changes even slightly, the molecule's rhythm will be disrupted. To avoid confusing real changes in physics with measurement errors, scientists use a special method: they compare two different molecules that operate at the same frequencies but react differently to changes. For example, methanol has high sensitivity, while acetaldehyde has lower sensitivity.
For the experiment, scientists took an acetaldehyde molecule and compared its oscillation frequency in terrestrial laboratories with astronomical data obtained for three molecular clouds close to the Solar System. The results showed that the fundamental constant μ is stable and does not change even by one hundred-millionth of a part. This confirms that the basic laws of physics work very reliably.
Scientists plan to continue their research. Recently, when studying methanol in the center of the Galaxy, oscillations were observed that may indicate a change in physical constants. This could mean that dark matter or unknown particles are affecting the world around us. Researchers are currently preparing an application for targeted observations of sensitive acetaldehyde and methanol lines in the central part of the Milky Way.