Physics

Physicists measure gravitational time warp to within one millimeter

Physicists measure gravitation...
A 1-mm cloud of strontium atoms suspended in a laser lattice helped physicists measure the effect gravity has on the flow of time more precisely than ever before
A 1-mm cloud of strontium atoms suspended in a laser lattice helped physicists measure the effect gravity has on the flow of time more precisely than ever before
View 1 Image
A 1-mm cloud of strontium atoms suspended in a laser lattice helped physicists measure the effect gravity has on the flow of time more precisely than ever before
1/1
A 1-mm cloud of strontium atoms suspended in a laser lattice helped physicists measure the effect gravity has on the flow of time more precisely than ever before

The flow of time isn’t as consistent as we might think – gravity slows it down, so clocks on the surface of Earth tick slower than those in space. Now researchers have measured time passing at different speeds across just one millimeter, the smallest distance yet.

The idea that time would be affected by gravity was first proposed by Albert Einstein in 1915, as part of his theory of general relativity. Space and time are inextricably linked, and large masses warp the fabric of spacetime with their immense gravitational influence. This has the effect of making time pass more slowly closer to a large mass like a planet, star, or, in the most extreme example, a black hole. This phenomenon is known as time dilation.

Here on Earth, time dilation effectively means that time moves more quickly at higher elevations. So for instance, time passes faster on the summit of Mount Everest than at sea level, but it applies over smaller distances too – someone living in a 10th floor apartment will age faster than someone on the first floor, and your head ages faster than your feet.

Of course, the differences in the passage of time across these distances are so tiny as to be unnoticeable, but they can be measured using atomic clocks, which keep time very precisely using the reliable ticks of atoms. By comparing atomic clocks on satellites and planes to those on the ground, scientists have been able to measure time dilation over distances of up to thousands of kilometers. But in a new study, researchers at JILA have measured time dilation over the smallest distance yet – just one millimeter.

To make this measurement, the team used an atomic clock composed of an ultracold cloud of about 100,000 strontium atoms. The clock’s “ticking” comes from the atoms switching back and forth between two energy levels, which they do at an extremely reliable frequency. Through careful control of these energy states, the team was able to make all the atoms in the cloud tick in perfect unison for 37 seconds, a record length of time.

Currently, the force of gravity can’t be explained in terms of quantum physics, but being able to measure its effects on smaller and smaller scales could unlock its secrets and perhaps reveal the missing link between quantum and classical physics.

In this particular atomic clock, the atoms were loaded into an optical lattice, which arranges them into several thin layers like a stack of pancakes. Once the atoms were ticking in unison, the scientists used extremely precise imaging techniques to measure the ticking in the top of the stack compared to the bottom.

And sure enough, they detected a difference between the two regions, due to the time dilation. The shift in frequencies was of course tiny, only 0.0000000000000000001, but it was measurable.

The team says that this work could not only help make atomic clocks 50 times more precise than they are now, but it could open up new tools to probe the mysteries of physics. Currently, the force of gravity can’t be explained in terms of quantum physics, but being able to measure its effects on smaller and smaller scales could unlock its secrets and perhaps reveal the missing link between quantum and classical physics.

“The most important and exciting result is that we can potentially connect quantum physics with gravity, for example, probing complex physics when particles are distributed at different locations in the curved space-time,” said Jun Ye, lead author of the study. “Being able to measure the time difference on such a minute scale could enable us to discover, for example, that gravity disrupts quantum coherence, which could be at the bottom of why our macroscale world is classical.”

The research was published in the journal Nature. The team explains the work in the video below.

Einstein, Time, and Very Small Things - with Jun Ye

Source: NIST

7 comments
7 comments
Pierre Collet
Gravity has no influence on the speed at which time ticks... Time DOES NOT pass faster on the top of Mount Everest than at sea level...
If you take two identical devices that flash a light precisely every second, and you place one at sea level and the other on top of Mount Everest, then, the lights will still flash exactly every second on top of Mount Everest and at sea level.
HOWEVER, people at sea level looking up will see the flashing light from Mount Everest flash at intervals shorter than 1 second, and people on top of Mount everest looking down to sea level will see the flashing light at sea level flash at intervals longer than 1 second... but for each of them, one second is still exactly one second...
If it takes 209.3746374374662 seconds to read this article at sea level, reading it on top of Mount Everest will still require exactly 209.3746374374662 seconds, unfortunately...
Aaron Robinson
together
Entropy is defined as the movement of energy is to dissipate evenly over space
energy itself is a field if you look at the combined sum of gravity chemical and nuclear potential and kinetic energy as a whole
Expansion of space is what generates time. Space defined dimension “d”expansion can be measured by velocity. Therefore time is simply a function of the expansion of d . T = d/v
So the rate of change of time is proportional to the velocity of the expansion of the universe.
Gravity warps space and time as it directly affects the localized expansion of parts of the universe. As gravity can reverse the expansion it can therefore can slow down time. There are limits to this effect as nothing can exceed the velocity of light.
FB36
The correct way to look at the problem is (IMHO), how quantum particles (at micro-scale) could really create spacetime (at macro-scale) (as an emergent property)!
(& so explain gravity as just bending of that created spacetime!)
& fortunately, it is already wellknown that spacetime of GR can be explained as a (super)fluid:
(By the way, all kinds of fluids are actually emergent properties!)
From Wikipedia:
"In general relativity, a fluid solution is an exact solution of the Einstein field equation in which the gravitational field is produced entirely by the mass, momentum, and stress density of a fluid."
Then realize, the problem is actually similar to explaining how water is created by water molecules!
(Actually a much better analogy would be, how air fluid (weather at macro-scale) is created by air (gas) molecules (at micro-scale)!)
Also realize, none of known real particles of SM could possibly be the source that creates spacetime!
& so, only realistic physical possibility could possibly be is, virtual particles (of quantum vacuum), which are already wellknown/proven to be exist everywhere (as a gas-like medium)!
Username
I've been saying for a long time that they seem to be confusing what they are measuring with the instrument used for the measurement. In this case Time and clocks. Time doesn't slow down, clocks do. Time can't have a speed since time is a component of speed. Speed is distance over time, which would mean that the speed of time would be distance(which makes no sense here) over itself (time).
Douglas Rogers
This is an incredible level of verification for general relativity!
Daveb
I like Username’s comment, I was also thinking that the clock was being affected by gravity, or at least that it hadn’t been shown otherwise. Also excellent point about the circular definitions, would love to hear the refutation of that
Lamar Havard
Maybe the reason the results of quantum experiments are changed by the mere presence of an observer is due to the gravity produced BY the observer?

And Pierre, you disproved your statement, because even though the people at both places experience the same length of time, when the people on the mountain come down, their watches or phone clocks will still be behind the sea level people's clocks...proving gravity DOES influence time.