How much gravity do two adults generate when standing at opposite ends of the Earth?

It takes about 1 Newton of force to lift a 100-gram object.

The gravitational force generated by two adults standing at the two ends of the earth is approximately 10 to the negative 21st power Newton.

This is the force that the extremely weak force device at Zhijiang Laboratory can detect.

Nanoparticles

How can an extremely weak force device detect such a small force?

In a vacuum environment, a laser is used to capture and suspend a nanoparticle ball with a diameter of about one thousandth of a hair, and the size of the force it is subjected to is inferred from the movement and displacement of the ball.

This is the basic principle of the extremely weak force device.

And light is the key to this process.

When photons interact with matter, there is momentum exchange, which in turn changes the state of motion of matter. This process satisfies the law of conservation of momentum. Based on this light-momentum effect, scientists invented the optical tweezers technology, making light a tool that can manipulate microscopic particles.

Laser light path

Gao Xiaowen, deputy director of the Quantum Sensing Research Center of Zhijiang Laboratory, explained, "The ultra-weak force device uses optical tweezers technology to suspend nanoparticles and allow them to form intrinsic oscillations in the light field. If external signals cause changes in the movement of the particles, the magnitude of the force can be inferred by measuring this change."

In the microscopic world where nanoparticles exist, any tiny disturbance can cause a change in its state of motion.

"The disordered collisions of air molecules are a very large source of noise. Therefore, a high vacuum environment is a key to detecting extremely weak forces," Gao Xiaowen introduced.

After repeated optimization and improvement, the extremely weak force device team of Zhijiang Laboratory has reduced the vacuum limit of the extremely weak force device to 6×10 to the negative 7th power Pa (less than one billionth of the atmospheric pressure), which can provide excellent environmental protection for nanoparticles.

Members of the ultra-weak force device team are conducting an experiment

In order to stably separate, capture and control nanoparticles, Li Cuihong, a research expert at Zhijiang Laboratory, spent two years studying.

"Under high vacuum conditions, the noise of air molecule collisions is greatly reduced, but in this environment, particles can easily escape from the light trap, which requires us to scientifically screen, process and optimize the particles in the early stage," Li Cuihong introduced.

At present, the extremely weak force device team of Zhijiang Laboratory has established a unique method of particle identification and processing. The success rate of particle capture is close to 100%, and the force sensitivity of the device has reached the world's leading level.

Extremely weak force device part

What is the function of an extremely weak force device?

By using this device and the technology behind it, people will be able to detect high-frequency gravitational waves on a "desktop" and answer many cutting-edge scientific questions that remain to be explored, such as "non-Newtonian gravity" and "macroscopic quantum states."

Answering the unknown and satisfying curiosity are often the original driving force for scientific progress. Whether it is to understand the vast universe or to explain microscopic physical phenomena, the extremely weak force device is an excellent tool.

From chiseling the floor, to renovating the infrastructure, buying equipment, and setting up the platform, the Extremely Weak Force Device Team of the Zhijiang Laboratory transformed a computer room into a laboratory step by step, and achieved many firsts here:

The first time a particle was captured, the first time the system signal circuit was adjusted, and the first time a milestone node was passed for acceptance.

In three years, the extremely weak force device team of Zhijiang Laboratory has gone from being a follower in this technology to a leader.

Correspondent Xiao Le

Orange Interactive reporter Lin Jianan

Image courtesy of Zhijiang Laboratory