If you want to live longer, stay at ground level.
According to Einstein, time passes more slowly closer to a centre of mass. If you're basking in the heat of the Earth's core, you'll age less than someone who's sat on a flagpole (although both parties would probably have other things to worry about).
Now, the Lord Mayor of London has proved it so.
Rather than drill down into the infernal regions, he made use of the City's tallest skyscraper, 22 Bishopsgate.
With some rather significant help from the National Physical Laboratory, Lord Mayor Michael Mainelli was able to measure a difference between two super-accurate atomic clocks. The first was placed on the 61st floor of the 278-metre skyscraper. The other remained at NPL's headquarters in Teddington (roughly at sea level).
When the two clocks were compared, the one from the skyscraper was found to be 100±30 nanoseconds faster than its ground-based sibling. In press-release-copying words, the clock would have to sit atop the skyscraper for a million years to register a single second of difference*.
The skyscraper result agrees with Einstein's predictions that time travels faster as you get higher (i.e. further from a large centre of mass like the Earth) — an effect that's been measured many times over the past century, and is factored into the timekeeping of satellites.
The Lord Mayor is himself a scientist by background. The experiment is a stunt to promote his 'Connect to Prosper' initiative, to promote the Square Mile's knowledge and research credentials, and also coincides with British Science Week.
*You could increase the effect by moving still higher to the International Space Station — although then you'd also have to factor in the time-slowing effect of travelling at much greater speed. I'm only adding this sentence in to show that I've actually thought about this and am not just copying the press release like everyone else.
