- Time crystals repeat patterns in time, unlike ordinary crystals repeating in space
- NYU researchers made time crystals from Styrofoam spheres levitated by sound waves
- Sound waves create unbalanced forces between particles, defying Newton's third law
Isaac Newton's Third Law of Motion teaches that for every action, there is an equal and opposite reaction. This simple rule explains many everyday things, from walking and a baseball bouncing to rockets launching into space. However, researchers at New York University (NYU) have discovered something unusual that does not follow this law. They have created a new kind of "time crystal" that can float in mid-air on a cushion of sound, reported Newsweek.
Ordinary crystals, such as diamond or common salt, are solids in which atoms are arranged in a fixed and repeating pattern.
Time crystals are different. They repeat patterns not in space but in the dimension of time. They are quantum systems in which particles continuously move back and forth in a fixed cycle.
The concept of time crystals was proposed in 2012 by Nobel Prize-winning physicist Frank Wilczek of the Massachusetts Institute of Technology. Scientists hope to use them in future fields such as data storage and advanced quantum computing.
NYU physicist David Greer, author of the study, said that time crystals are extremely interesting not only because of their potential uses but also because of their unique and complex nature. He also explained that the system they created is special because it is so simple.
Experimental Procedure
The time crystals the scientists created are made from small Styrofoam spheres, commonly used in packaging. These spheres were floated in the air between two speakers placed approximately six inches apart.
To create this new type of time crystal, the particles were first stabilised in mid-air using sound waves.
NYU researcher and co-author Mia Morrell explained that sound waves can exert forces on particles, much like pond waves propel a floating leaf. She explained that by placing objects in a sound field called a "standing wave," they can be lifted into the air, defying gravity.
As particles float in this sound field, they interact with each other through scattered sound waves.
Larger particles scatter sound more than smaller ones, causing them to have a greater impact on smaller ones. This causes an unbalanced interaction between them.
Morrell explained this by analogy with two boats of different sizes approaching a dock. Both create waves in the water, which push against each other, but their size causes the effects to differ.
The researchers say that the interactions between these airborne particles do not obey Newton's third law. The forces are not equal and opposite, instead, the particles move unevenly, impacting each other.
According to the team, this discovery not only advances understanding of time crystals but could also help understand natural processes like circadian rhythms, which regulate our body's biological clock.
They explained that some biochemical systems in the body, such as the digestive processes, also interact in a similar unbalanced manner, just like these airborne time crystals.
