Introducing dark energy in the classroom using paradoxes

Abstract

The concept of dark energy, an active subject in current PHYSICS research, is related to cosmological models and supplies a mechanism to the recently discovered accelerated expansion of the universe. Modeling dark energy is usually done by considering Einstein’s cosmological constant which was introduced by him 100 years ago. In the present work, a speculative discussion on the effects that dark energy could have on everyday life on Earth is provided. It is targeted to first-year college students but arrangements for high school PHYSICS are also possible. Among its strange properties, dark energy acts contrary to gravity and can lead to counterintuitive situations. For instance, if the cosmological constant was big enough, objects left to themselves near the Earth’s surface could lift to the sky instead of falling down to the ground, contradicting the everyday experience. The proposed discussion uses basic concepts of Newtonian PHYSICS in a scenario where the cosmological constant value could counteract Earth’s gravity. It is shown that the problem can be reduced to the analysis of a one-dimensional potential energy diagram which is accessible to a first-year college student. An algebraic version of this problem can turn a modern PHYSICS concept into a classroom exercise on conservation of mechanical energy. The content of this contribution is aimed to the production of resources for different levels of PHYSICS teaching and instruction. Its main focus is not directly related to educational methodologies.