By definition a constant is something that does not change, but in physics one cannot be certain. Over the lifetime of the Universe it is theoretically possible that certain constants have changed, and if this happened, important theories, such as the General Theory of Relativity, would be thrown into doubt. Fortunately though researchers at the VU University of Amsterdam and the Max Planck Institute for Radio Astronomy have recently confirmed at least one of these constants has not been changed by time.
The mass ratio of protons and electrons is critical to many phenomena but is not an easy thing to test, especially when your target is seven billion light years away. Luckily parts of the spectrum of methanol, the simplest alcohol, are extremely sensitive to this ratio, and researchers have recently determined why. An internal rotation of the molecule involves a quantum tunnel effect which is affected by the mass ratio.
Careful examination of the spectral data from a distant galaxy has revealed that the mass ratio of a proton and electron has changed at most by a factor of 10-7 or 0.00001% in the past seven billion years. With that result this value can rightly call itself a universal constant.