Zircon was one of the first minerals to solidify on Earth, it resists weathering and melting, and it holds on to uranium well, so it’s a good candidate for dating old rocks.
The team found that, while most of their samples had similar uranium ratios, some were wildly different.
They found that the half-life is just 68 million years, 30 per cent shorter than thought.
That means that every rock dated by samarium-146 decay – which include some of the oldest on Earth and the moon, and even some Martian meteorites – formed 20 million to 80 million years earlier than thought.
In many cases it is quite difficult to prove whether one method is superior to another: and in this regard, the only way of doing so is to closely examine how each method works and try to find fault with it.