Comparing Gravity to Other Forces in Physics

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SUMMARY

The discussion centers on the comparative analysis of gravity and other fundamental forces in physics, highlighting the significant disparity in their strengths. Physicists regard the relative weakness of gravity, quantified as 40 orders of magnitude less than electromagnetic forces, as a major unsolved problem. The conversation emphasizes the importance of using natural units to facilitate accurate comparisons between forces, specifically focusing on the coupling constants 'G' for gravity and 'e_0' for electromagnetism. This approach allows for a more coherent understanding of the forces at play.

PREREQUISITES
  • Understanding of fundamental forces in physics
  • Familiarity with natural units in theoretical physics
  • Knowledge of coupling constants, specifically 'G' and 'e_0'
  • Basic grasp of particle physics, including mass and charge
NEXT STEPS
  • Research the concept of natural units in physics
  • Study the role of coupling constants in force interactions
  • Explore the implications of gravity's weakness in theoretical frameworks
  • Investigate the four fundamental forces and their comparative strengths
USEFUL FOR

This discussion is beneficial for physicists, students of physics, and anyone interested in the fundamental forces and their interactions, particularly those exploring the theoretical implications of gravity's relative weakness.

waveicle
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I've often heard physicists say that the relative weakness of gravity is 'one of the greatest unsolved problems in physics'. When physicists talk about how puzzling it is that gravity is so much weaker than the other forces, how are they comparing the two? Isn't the unit of charge (Coulomb) and the unit of mass (kilogram), fairly arbitrary?
And if we Compare the two based on the smallest possible unit (charge of electron, mass of a quark or whatever), why should we EXPECT them to be related in the first place?
 
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waveicle said:
Isn't the unit of charge (Coulomb) and the unit of mass (kilogram), fairly arbitrary?
Yes

And if we Compare the two based on the smallest possible unit (charge of electron, mass of a quark or whatever), why should we EXPECT them to be related in the first place?
You wouldn't necessarily expect them to be similar - but 40 orders of magnitude is difficult to fit into a theory!
 
When we speak of comparing forces, we mean to compare the (force-mediated) *coupling* between two objects- that is, not 'm' or 'q', but 'G' and 'e_0'.

More precisely, using natural units for the four forces:

http://en.wikipedia.org/wiki/Fundamental_force

allows one to compare them in an 'apples to apples' manner.
 

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