Negative Rest Mass: Faster than Light?

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SUMMARY

The discussion centers on the theoretical implications of negative rest mass and its relationship with faster-than-light travel. It is established that negative masses, while they can be manipulated mathematically using Newton's law of gravitation, do not travel faster than light under normal conditions. Instead, objects with imaginary masses, known as tachyons, are the entities that can theoretically exceed the speed of light. The conversation also highlights the importance of distinguishing between different types of mass, such as inertial and gravitational mass.

PREREQUISITES
  • Understanding of Newton's law of gravitation
  • Familiarity with concepts of inertial and gravitational mass
  • Knowledge of tachyons and their theoretical properties
  • Basic grasp of conservation of momentum principles
NEXT STEPS
  • Research the properties and implications of tachyons in theoretical physics
  • Explore the mathematical modeling of negative mass scenarios
  • Investigate the distinctions between inertial, active, and passive gravitational mass
  • Examine current theories on faster-than-light travel and their scientific basis
USEFUL FOR

Physicists, theoretical researchers, and students interested in advanced concepts of mass and relativistic physics.

Daedalus_
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Theoretically, if an object were to have negative rest mass, would it travel faster than light?
 
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Daedalus_ said:
Theoretically, if an object were to have negative rest mass, would it travel faster than light?

Which kind of mass are you talking about -- inertial mass, "active" gravitational mass, or the "passive" gravitational mass?

Generally, when considering negative masses, it is assumed that they fall with the same acceleration as as positive masses, and conservation of momentum is valid. They do not travel faster than light.

By putting '-m' in place of m in Newton's law of gravitation, you can play around a bit with the concept of negative mass. Note that negative masses move in the opposite direction of the applied force on it. Can you figure out what will happen when a mass m and a mass '-m' are just left close to one another?

To answer your question, objects with imaginary masses, which are called tachyons, travel faster than light.

EDIT: There is already a lot of discussion going on in https://www.physicsforums.com/showthread.php?t=66852, which I had somehow missed.
 

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