- #1
ScienceNerd36
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How can a photon exist if it has no mass? I've always found this concept hard to grasp. (Rhyming not intended)
How can a photon exist if it has no mass?
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Discussion Overview
The discussion centers around the existence of photons in the context of their mass, exploring the implications of masslessness in quantum mechanics and relativity. Participants examine foundational concepts in physics related to energy, mass, and the nature of photons.
Discussion Character
- Exploratory, Technical explanation, Debate/contested
Main Points Raised
- One participant expresses difficulty in understanding how a photon can exist without mass.
- Another participant explains the relationship between energy, mass, and momentum, referencing the equation E^2 = (mc^2)^2 + (pc)^2, and notes that photons can have energy and momentum despite having zero mass.
- A question is raised about the necessity of mass for existence, suggesting a philosophical inquiry into the nature of existence itself.
- One participant asserts that a photon does have mass, distinguishing between rest mass and the concept of mass in motion, while questioning the relevance of rest mass for a photon that is never at rest.
- A later reply humorously acknowledges the contentious nature of the topic, indicating that it may lead to further debate among participants.
Areas of Agreement / Disagreement
Participants express differing views on the concept of mass as it relates to photons, with some asserting that photons do not have mass while others argue that they possess mass in a different context. The discussion remains unresolved with multiple competing perspectives.
Contextual Notes
Participants reference concepts from both classical and quantum physics, indicating potential limitations in understanding based on differing interpretations of mass and energy. The discussion does not resolve the philosophical implications of existence and mass.
- #2
jtbell
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We're not in classical physics any more. Photons are quintessentially relativistic and quantum-mechanical. The general relation for energy, mass and momentum is
[tex]E^2 = (mc^2)^2 + (pc)^2[/tex]
(This uses what is often called "rest mass", not "relativistic mass".) An object can have zero mass but still have nonzero energy and momentum.
Note that even in classical electrodynamics, electromagnetic waves carry energy and momentum without having mass.
- #3
malawi_glenn
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Why does everything that exists have to have mass? Is there an a priori reason??
- #4
tiny-tim
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Hi ScienceNerd36! 
(erm
… rhyming not achieved)
mass is energy, energy is mass
a photon does have mass
(it has no rest-mass, but why should that matter when a photon is never at rest?
)
(erm
… rhyming not achieved)mass is energy, energy is mass
a photon does have mass
(it has no rest-mass, but why should that matter when a photon is never at rest?
)- #5
malawi_glenn
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tiny-tim said:Hi ScienceNerd36!
(erm
mass is energy, energy is mass
a photon does have mass
(it has no rest-mass, but why should that matter when a photon is never at rest?
oohh now you have started this war again Timmy, prepare for battle
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