The City of London’s tallest building, 22 Bishopsgate, has been used for a science experiment—to display a curious quirk of Einstein’s theory of general relativity.

22 Bishopsgate skyscraper (c) ianVisits

It’s all to do with time and how gravity affects time — the stronger the pull of gravity, the slower time proceeds. If you stand on the ground, gravity is stronger than if you’re in a plane, so time in the plane is faster than if you’re on the ground (time literally flies), albeit by such a minuscule amount that it requires very clever machines to measure the effect.

There are other minuscule effects on time, even on the ground. For example, time in London is marginally faster than time in New York because New York is built on dense rock, which has a stronger gravity than London’s clay.

Back to London, though – and the National Physical Laboratory (NPL) synchronised two exceptionally accurate clocks at their offices in Teddington, and then one was taken to the Horizon 22 viewing gallery at the top of the 22 Bishopsgate skyscraper.

Not your average clock (c) NPL

When the two clocks were reunited, the time on the clock that was at 22 Bishopsgate was measured to have gained an additional 100±30 nanoseconds compared to the clock that stayed at NPL, entirely in agreement with Einstein’s prediction that time does travel faster the higher up you are.

However, the difference is so slight that a person would need to live on the top floor of the skyscraper for around a million years to have aged just one second more than a person living on the ground floor.

But the time dilation effect was proven – so yay science!

If it sounds a bit niche, science has practical implications – as satellites in space are sufficiently far from the earth, gravity is much weaker, and time flows faster in space. So much so that the internal clocks inside GPS satellites have to tick at a slower speed than clocks on the Earth to account for the difference.

Without understanding how gravity affects time, the GPS location in your phone would get progressively less accurate until you end up in the wrong location.

The demonstration at 22 Bishopsgate was part of the Lord Mayor of London Alderman Professor Michael Mainelli’s mayoral theme, ‘Connect to Prosper’.

The demonstration was the first in a series of showpiece exercises, which will run for the duration of the Lord Mayor’s tenure. The Experiment Series seeks to showcase innovation and invention in the City of London and promote and celebrate the many ‘knowledge miles’ within the Square Mile.

London’s buildings have played unexpected roles in off-worldly science before, such as when a neutrino detector was installed in Holborn tube station.


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  1. Andrew says:

    Neat, but 100+/-30 is barely over three sigma so hardly a ringing endorsement. Particle physicists usually insist on at least five sigma.

    Satellites also move fast, several kilometres per second, so experience time slowing down (compared to an observer “at rest”) due to special relativity. But that is overwhelmed by the effect of gravity and general relativity making their clocks faster than those on the ground, which is several times larger.

    • Flywheel says:

      What exactly is a “ringing endorsement”? The very notion of a variation in time – however miniscule – was what the project set out to explore; there’s no “endorsement” in that, simply a practical application to a theoretical construct.

    • Craig Booth says:

      Oh, thanks 😉

    • Nicole Therez says:

      I loved how you explained this it was easier for me to grasp the concept. I especially liked how you clearly explained Einstein’s theory , time gets faster the higher up you are. That was profound for me I never could understand the concept before . Thanks for the read

    • Jonathan Collet says:

      Sorry posting this here, I don’t know where to post a new message. Precisions about the beginning on the article: time goes faster for someone in space observing life on earth because even if the gravitation field is weaker, acceleration takes over several orders of magnitude if it’s a geosynchronic orbit. Observer’s time actually goes slower compared to ppl on Earth who are observed going / acting faster than usual.

  2. Ron Striebig says:

    The two Einstein equations of special relativity 1906 and general relativity 1916 are use to accurately set such atomic clocks on Earthand on the satellites
    As the great mathematician Erdos said occasionally God let’s us glimpse at his great book of mathematics
    Ron Striebig B.Sc Physics hons London M.Sc Mathematics King’s college London

  3. Ron striebig says:

    Good article
    If you stayed on a satellite for 100 years you would lose 0.5 seconds of your life

  4. Roz Roseman says:

    Just thank you for the “visits.”

  5. Amarachukwu Achara says:

    Doesn’t this have something to do with how those (mechanical or electronic) clocks measure moments? Would this gravitational effect be the same for clocks that measure time differently (perhaps by instruments that don’t depend on gravity to record moments)?

    • ianVisits says:

      The NPL clocks are not mechanical — and the link between gravity and time still happens even if you don’t measure it.

    • Tom says:

      This is basically the big deal with relativity – we all assume time is an absolute constant passing at the same rate everywhere, Einstein worked out the only way to explain some things we observe in the universe is if that’s not the case. It’s not that the clock is measuring time wrong, it is actually passing at a different rate.

  6. Vince Pirillo says:

    Does this affect the way we measure distance between earth and stars, measured in light years?

  7. Marcus Rongonui says:

    Assigning qualities to quantitative numeric entities, may imply a contradiction * .

    * Mathematictan Wildberger draws attention to dilation from accelerating a measuring rod relative to another one, implies that a coordinate system is logically impossible.

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