Radiation pressure

Definition

Radiation pressure is the pressure exerted by electromagnetic radiation on surfaces, resulting from the momentum transfer of photons when they collide with matter. This phenomenon plays a crucial role in various astrophysical processes, such as the behavior of stars and the expansion of the universe, particularly in relation to dark energy.

5 Must Know Facts For Your Next Test

1. Radiation pressure arises when photons hit an object and transfer momentum, which can have significant effects on objects in space, such as comets and asteroids.
2. In stars, radiation pressure counteracts gravitational collapse, balancing the forces that would otherwise lead to the star's destruction.
3. Dark energy is thought to be driving the accelerated expansion of the universe, and radiation pressure from various forms of radiation plays a role in this process.
4. The relationship between radiation pressure and gravity is critical in understanding the lifecycle of stars, influencing whether they will expand or collapse.
5. As the universe expands, radiation pressure from cosmic microwave background radiation diminishes, allowing dark energy to become more dominant over time.

Review Questions

• How does radiation pressure influence the lifecycle of stars?
  • Radiation pressure plays a vital role in a star's lifecycle by balancing against gravitational pressure. In the core of a star, nuclear fusion generates energy, creating radiation pressure that pushes outward. This balance prevents the star from collapsing under its own gravity during most of its life. When nuclear fuel runs out, however, gravitational forces can overpower radiation pressure, leading to various end states like supernovae or black holes.
• Discuss how radiation pressure is connected to dark energy and its effect on the universe's expansion.
  • Radiation pressure contributes to our understanding of dark energy by influencing cosmic dynamics during different epochs of the universe's history. Initially, radiation pressure was significant due to high-energy photons from primordial events. However, as the universe expanded and cooled, this radiation pressure weakened. Dark energy then became more influential in driving accelerated expansion, suggesting a shift in the dominant forces affecting cosmic evolution over time.
• Evaluate the implications of radiation pressure on small celestial bodies like comets and asteroids within the context of dark energy's role in cosmic evolution.
  • Radiation pressure has critical implications for small celestial bodies as it can alter their trajectories through space. When photons collide with these bodies, they exert a force that can push them away from the Sun or alter their orbits. In relation to dark energy's role in cosmic evolution, understanding how these small bodies interact with radiation pressure helps scientists predict their long-term stability and behavior as the universe continues to expand and evolve under the influence of dark energy.

Related terms

Photon: A photon is a quantum of electromagnetic radiation, which carries energy and momentum, influencing matter upon interaction.

Cosmological constant:

The cosmological constant is a term introduced by Einstein into his equations of general relativity, representing a constant energy density that fills space homogeneously and is associated with dark energy.

Gravitational pressure: Gravitational pressure is the force exerted by the weight of matter in a gravitational field, counteracting radiation pressure in stellar environments.