- #1
TerranIV
- 26
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I was just curious if there were any known (theoretical) particles with zero inertial mass that don't travel at light speed. Is this even possible?
Particles w/ 0 Inertial Mass Traveling Faster than Light?
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Discussion Overview
The discussion revolves around the theoretical possibility of particles with zero inertial mass traveling at speeds other than the speed of light. Participants explore the implications of zero inertial mass on particle velocity, particularly in the context of relativity.
Discussion Character
- Exploratory
- Technical explanation
- Debate/contested
Main Points Raised
- Some participants question whether it is possible for particles with zero inertial mass to travel at speeds other than light speed.
- Others assert that particles with zero inertial mass must travel at the speed of light, citing the relationship between energy, momentum, and mass.
- One participant provides a formula relating speed to momentum and energy, indicating that if mass is zero, then speed must equal c.
- Another participant suggests that having zero inertial mass and traveling at c are fundamentally linked due to the geometry of spacetime.
- A later reply introduces a hypothetical scenario where a particle could have zero energy, momentum, and mass, leading to an undefined velocity, and humorously notes that such a non-existent particle need not travel at c.
- One participant references a classical mistake in topology, adding a philosophical perspective to the discussion.
Areas of Agreement / Disagreement
Participants express disagreement regarding the possibility of zero inertial mass particles traveling at speeds other than c. While some assert that it is impossible, others explore hypothetical scenarios that challenge this view.
Contextual Notes
Some statements rely on specific definitions of mass and energy, and the discussion does not resolve the implications of these definitions on the nature of particles.
- #2
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No.TerranIV said:
- #3
TerranIV
- 26
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Orodruin said:
Do we know why having 0 inertial mass causes particles to HAVE to travel at c?
I know it's true, but it doesn't seem intuitive to me. It makes sense why only zero inertial particles CAN travel at c, but I don't understand why they MUST travel at c.
- #4
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The speed of a particle is given by ##v = pc^2/E##, where ##p## is the momentum and ##E## the total energy. For a general particle ##E^2 = m^2 c^4 + p^2 c^2##. If ##m = 0## then ##E = pc## and therefore ##v = c##.
- #5
PeterDonis
Mentor
- 49,902
- 25,951
TerranIV said:
Because they're the same thing: having zero inertial mass (actually "invariant mass" is a better term) is traveling at c. The geometry of spacetime forces them to be the same.
- #6
PeterDonis
Mentor
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Moderator's note: Thread moved to relativity forum.
- #7
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As a funny exception, one can have energy, momentum, and mass all be zero. Then velocity is not necessarily c. It is undefined. One may describe this as saying that a massless particle that doesn't exist, need not travel at c.
- #8
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For all particles that don't exist, it is vacuously true that they travel at ##c##.PAllen said:
- #9
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The classical mistake in topology is to forget about the empty set ...
"All open sets in ##\mathbb R## have an infinite number of elements."
"All open sets in ##\mathbb R## have an infinite number of elements."
- #10
OCR
- 996
- 936
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