By peering at alcohol molecules in a distant galaxy, astronomers have determined that a fundamental constant of nature has hardly changed at all over the age of the universe.
The constant — the ratio of the mass of a proton to the mass of an electron — has changed by only one hundred thousandth of a percent or less over the past 7 billion years, the observations show.
The scientists determined this by pointing the Effelsberg 100-m radio telescope at a distant galaxy that lies 7 billion light-years away, meaning its light has taken that long to reach Earth. Thus, astronomers are seeing the galaxy as it existed 7 billion years ago. The telescope looked for special light features that reflect the absorption of methanol, a simple form of alcohol that contains carbon, hydrogen and oxygen.
If the ratio of the mass of the protons and electrons inside those atoms were different than it is here and now in our own galaxy, the scientists would be able to detect this in the properties of the light.
"This idea makes the methanol molecule an ideal probe to detect a possible temporal variation in the proton-electron mass ratio," astrophysicist Wim Ubachs of VU University Amsterdam said in a statement. "We proposed to search for methanol molecules in the far-distant universe, to compare the structure of those molecules with that observed in the present epoch in laboratory experiments."
Their observations confirmed that the proton-electron mass ratio has changed by no more than 10E-7 over the past 7 billion years. The universe itself is 13.7 billion years old.