The Blackbody force is a newly discovered force that attracts atoms and molecules to hot, opaque objects emitting blackbody radiation. Under certain circumstances, the new force is stronger than gravity.
Blackbodies are opaque, non-reflective objects, and they emit electromagnetic radiation based on their temperature. When sufficiently hot, this electromagnetic radiation falls into the visible spectrum, and is responsible for why very hot objects glow, like wooden embers in a fireplace or molten glass. In fact, blackbody radiation emanating from soot-particles are responsible for why fire glows, and in a sense, the sun itself is a giant blackbody, radiating electromagnetic waves in the green-yellow and ultraviolet spectrum. Blackbodies are everywhere around us, but it has taken until now to discover a secret property they contain.
The secret is a brand new fundamental force, called Blackbody force. Until recently, blackbodies were thought to have a net-repulsive effect on nearby bodies due to radiation pressure, but the new force has been theoretically shown to be attractive, and strong enough to overcome the radiation’s repulsive effect. Even more surprising, the new force may be stronger than gravity itself. The scientists who made the discovery, Sonnleitner, Ritsch-Marte and Ritsch from the University of Innsbruck, have published a paper on the new force and believe it may lead to a re-examining of several physical phenomena.
The underlying causes of the force have been known for nearly fifty years: Blackbody radiation causes a change in energy level to nearby atoms and molecules. This is known as a “Stark shift” and is more powerful the hotter the blackbody is. What wasn’t realized until recently is that under most conditions, the Stark shifts create an attractive optical force on the atoms, pulling them closer to the Blackbody.
Artist’s conception of the force between atoms and a blackbody
“The most important result is that we point out that radiation forces typically associated with lasers in the lab also exist for every source of thermal radiation,” explains Sonnleitner, “The interplay between these two forces,a typically attractive gradient force versus repulsive radiation pressure, is routinely considered in quantum optics laboratories, but it was overlooked that this also shows up with thermal light sources.”The blackbody force has a few interesting properties: The force decays proportionally to the third power of the distance from the blackbody. In addition, it’s more powerful for smaller atoms, and more powerful for hotter blackbodies… to a point. Once temperatures reach a few thousand Kelvin, the force suddenly becomes repulsive. Since gravity depends upon the mass of the objects involved, the blackbody force can be stronger than gravity under certain circumstances. For a speck of cosmic dust at 100K, the force is indeed stronger than gravity, but for a star at 6000K, it is much weaker.
“Since the forces are very weak, they beat gravity only for small particles such as cosmic dust,” Sonnleitner said. “These sub-micron-sized grains play an important role in the formation of planets and stars or in astro-chemistry. Apparently there are some open questions on how they interact with surrounding hydrogen gas or with each other. Right now we are exploring how this additional attractive force affects the dynamics of atoms and dust.”