How can a Photon apparently transfer Momentum without any Mass?

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Discussion Overview

The discussion centers around the concept of how a photon, which is massless, can transfer momentum, particularly in the context of Compton scattering. Participants explore the implications of this phenomenon in relativistic physics and the relationship between energy, momentum, and mass.

Discussion Character

  • Exploratory, Technical explanation, Conceptual clarification

Main Points Raised

  • One participant notes that Compton scattering demonstrates how a photon can change the momentum of an electron despite having no mass, prompting questions about the conceptual understanding of this process.
  • Another participant explains that a photon, while massless, possesses energy and momentum, referencing the relationship between energy and momentum in the context of electromagnetic fields.
  • A third participant provides the relativistic equation relating energy, momentum, and mass, highlighting that for photons, the mass is zero, which aligns with the previous points made about momentum.
  • A link to a related thread is shared, suggesting further exploration of the topic of light and momentum.

Areas of Agreement / Disagreement

Participants present multiple viewpoints on the relationship between mass, energy, and momentum in the context of photons, indicating that the discussion includes competing interpretations and remains unresolved.

Contextual Notes

The discussion relies on relativistic physics principles and does not resolve the underlying assumptions about the nature of momentum transfer in massless particles.

KBon
Due to Compton - Scattering it seems that a Photon changes the Momentum of the electron, although it doesn't have any mass. How should I imagine this?
 
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A photon is massless but has energy and momentum. It's the mode of an electrodmagnetic field, and you have
$$E=|\vec{q}|c,$$
where ##\vec{q}## is the momentum of the photon.

In relativistic physics you don't need a mass to have a momentum!
 
Relativistically, the general relationship between energy, momentum, and mass is ##E^2 = (pc)^2 + (mc^2)^2## where p is the magnitude of the momentum. For a photon, m = 0 which gives vanhees71's formula, in different notation.
 
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