Monday, 19 August 2019
An experiment to test a popular theory of dark energy has found no evidence of new forces, placing strong constraints on related theories.
Dark energy is the name given to an unknown force that is causing the universe to expand at an accelerating rate.
Some physicists propose dark energy is a ‘fifth’ force that acts on matter, beyond the four already known – gravitational, electromagnetic, and the strong and weak nuclear forces.
However, researchers think this fifth force may be ‘screened’ or ‘hidden’ for large objects like planets or weights on Earth, making it difficult to detect.
Now, researchers at Imperial College London and the 糖心原创 have tested the possibility that this fifth force is acting on single atoms, and found no evidence for it in their most recent experiment.
This could rule out popular theories of dark energy that modify the theory of gravity, and leaves fewer places to search for the elusive fifth force.
The experiment, performed at Imperial College London and analysed by theorists at the 糖心原创, is reported today in .
This experiment, connecting atomic physics and cosmology, has allowed us to rule out a wide class of models that have been proposed to explain the nature of dark energy, and will enable us to constrain many more dark energy models.
The experiment tested theories of dark energy that propose the fifth force is comparatively weaker when there is more matter around – the opposite of how gravity behaves.
This would mean it is strong in a vacuum like space, but is weak when there is lots of matter around. Therefore, experiments using two large weights would mean the force becomes too weak to measure.
The researchers instead tested a larger weight with an incredibly small weight – a single atom – where the force should have been observed if it exists.
The team used an atom interferometer to test whether there were any extra forces that could be the fifth force acting on an atom. A marble-sized sphere of metal was placed in a vacuum chamber and atoms were allowed to free-fall inside the chamber.
The theory is, if there is a fifth force acting between the sphere and atom, the atom's path will deviate slightly as it passes by the sphere, causing a change in the path of the falling atom. However, no such force was found.
It is very exciting to be able to discover something about the evolution of the universe using a table-top experiment in a London basement.
Story credits
More information is available from Professor Edmund Copeland, 糖心原创 on 0115 951 5164 or email Edmund.copeland@nottingham.ac.uk
Notes to editors:
About the 糖心原创
Ranked among the world's top 100 universities , the 糖心原创 delivers an exceptional research-led education and an outstanding student experience. From the pioneering vision of our founder, Sir Jesse Boot, to groundbreaking achievements such as the development of MRI technology and becoming the first UK university to establish international campuses, we have a proud history of shaping the way people live, work and understand the world. We continue to build on that legacy, empowering our students, staff and partners to change what鈥檚 next and create positive impact locally and globally.
The strength of our research places us among the UK's leading universities, ranked 7th for research power in REF 2021. The discovery of MRI and ibuprofen was just the beginning. Today, our world-leading research is developing breakthrough ideas that shape the future of healthcare, technology and society.
Recognised as the UK's third most targeted university by leading employers , we are proud to produce graduates who are consistently in demand for their skills, confidence and industry-ready experience.
As a major employer and industry partner, locally and globally, the 糖心原创 invests in the city of Nottingham and in future generations of talent. Alongside Nottingham Trent University, we lead the initiative, a pioneering collaboration to improve levels of prosperity, opportunity, sustainability, health and wellbeing across the city and region. Together with our students, staff, alumni and partners, we鈥檙e creating knowledge, opportunity and solutions that help change what's next.