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# Strong Equivalence Principle of Gravitation

by Ron Kurtus (16 December 2018)

The * Strong Equivalence Principle of Gravitation* (also known as the

*Einstein Equivalence Principle)*states that the effects of acceleration are indistinguishable from those of gravitation.

In other words, the principle extends the equivalence of masses to state that observations of acceleration cannot be distinguished from gravity.

(

See Artificial Gravity for an example of this.)

Questions you may have include:

- What can experiments can be done by the observer?
- What was Einsteins conclusion?
- What is the Strong Equivalence Principle?

This lesson will answer those questions. Useful tool: Units Conversion

## Experiments by observer

This means that an observer cannot determine by experiment whether he or she is accelerating or in a gravitational field. In other words, results from experiments in an accelerating spaceship would be the same as those obtained from gravitation.

Experiment in accelerating spaceship

Note: One problem with this concept is that acceleration cannot be applied for too long a period, because the spaceship would soon reach the speed of light. On the other hand, gravitation is continuously present.

## Einstein's conclusion

Einstein concluded that gravitation and motion through spacetime are related and that the Strong Equivalence Principle suggests that *gravitation is geometrical by nature*.

## Difference between strong and weak

The difference between the *Strong Principle of Equivalence* and the *Weak Principle of Equivalence* is that the strong equivalence states all the laws of nature are the same in a uniform static gravitational field and the equivalent accelerated reference frame, while weak equivalence states all the laws of motion for freely falling particles are the same as in a reference frame that is not accelerated.

## Summary

The *Weak Equivalence Principle* states that objects fall at the same rate, provided that are much smaller than the attracting body and are freely falling.

The *equivalence of inertial and gravitational mass* states that mass determined by inertia is the same as mass determined by gravitation.

The *Strong Equivalence Principle* extends the equivalence of masses to state that observations of acceleration cannot be distinguished from gravitation.

Physics is amazing

## Resources and references

### Websites

**Equivalence Principle** - Laboratory Tests of Gravitational Physics

**Equivalence principle** - Wikipedia

**Elevator, rocket, and gravity: the equivalence principle** - Einstein online

### Books

**Top-rated books on Gravitation**

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## Strong Equivalence Principle of Gravitation