There’s a magic rock in France. It defines our standard of mass, and scientist would like to get rid of it.
Holding Measurements To A Higher Standard
Our measurements of the universe require a standard basis of units. Defining those standards poses certain challenges. After all, how to you measure something that is used to define your measurements?
How Do We Know Gravity Is Constant?
Could the strength of gravity have been different in the past? How can we tell that gravity has never changed?
Rock of Ages
A natural fission reactor allows us to look at physical constants over time, and through it we can put astrophysics to the test.
Gravity Check
Yesterday I wrote about how we test whether unitless constants such as alpha (α) change over the history of the universe. You might also have noticed that I said if such constants did change, then it would mean either fundamental physical constants change or there is some exotic physics going on. We looked at the physical constants yesterday, so today let’s look for exotic physics.
Variables of Nature
Within physics there are certain physical quantities that play a central role. These are things such as the mass of an electron, or the speed of light, or the universal constant of gravity. We aren’t sure why these constants have the values they do, but their values uniquely determine the way our universe works. For example, if the mass of electrons were smaller, atoms would be smaller. If the gravitational constant were larger, you’d need less mass to create a black hole, and neutron stars might not exist.
Gravitational Constant
Astrophysics works with the assumption that the laws of physics are the same everywhere. That’s a huge assumption given that our most distant space probe has barely left the solar system. So how do we know our assumption is valid?
Here and There
When Isaac Newton proposed his universal law of gravity, he was actually making a rather bold claim, specifically that the distant stars and planets are governed by the same physical laws that govern the Earth. This was a radical split from the traditional Aristotelian view that the heavens were fundamentally different from terrestrial physics.