Consequences of the Equivalence Principle

In summary: Basically, light travels in a curved path relative to an accelerating frame of reference, and a straight line in an inertial (non-accelerating) reference frame.And the distinction is between "accelerating" and "non-accelerating" reference frames. The term "at rest" has no meaning except relative to a particular reference frame.
  • #1
unchained1978
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0
I was reading a book on SR and GR and it used the example of a falling elevator with a light beam traveling through it. Considering this setup leads to the conclusion that light bends in a gravitational field. My question is, would light bend as a result of any kind of acceleration given the elevator experiment. For example, if you were to accelerate an elevator magnetically and shine a light beam perpendicular to the direction of motion would not the light beam be curved to an onlooker outside of the elevator?
 
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  • #3
unchained1978 said:
bcrowell said:
I was reading a book on SR and GR and it used the example of a falling elevator with a light beam traveling through it. Considering this setup leads to the conclusion that light bends in a gravitational field. My question is, would light bend as a result of any kind of acceleration given the elevator experiment. For example, if you were to accelerate an elevator magnetically and shine a light beam perpendicular to the direction of motion would not the light beam be curved to an onlooker outside of the elevator?
Yes.

No! :tongue2:

To a non accelerating observer outside the accelerating elevator the light beam will appear to follow a straight path whether the source is outside the elevator or attached to the elevator because the observer outside the elevator is in flat space.

To an observer inside the elevator accelerating with the elevator, the light beam will appear to follow a curved path relative to a background grid painted on the walls of the elevator.
 
  • #4
Oops, sorry, yuiop was right and I was wrong. I didn't read the initial post carefully enough.
 
  • #5
yuiop said:
No! :tongue2:
To an observer inside the elevator accelerating with the elevator, the light beam will appear to follow a curved path relative to a background grid painted on the walls of the elevator.

How is this? Assuming a constant force is acting on the elevator how would you know if you were accelerating or at rest by the equivalence principle? And therefore, if you were unable to determine if you were accelerating or at rest, how could the light beam be curved inside the elevator but not outside?
 
  • #6
unchained1978 said:
How is this? Assuming a constant force is acting on the elevator how would you know if you were accelerating or at rest by the equivalence principle?
Use an accelerometer.
 
  • #7
unchained1978 said:
How is this? Assuming a constant force is acting on the elevator how would you know if you were accelerating or at rest by the equivalence principle? And therefore, if you were unable to determine if you were accelerating or at rest, how could the light beam be curved inside the elevator but not outside?
Whether the light beam is curved or not depends on whether the observer is accelerating, not on whether he's inside or outside the elevator. That's why yuiop specified that the observer inside was accelerating with the elevator, while the outside observer was not accelerating.

Basically, light travels in a curved path relative to an accelerating frame of reference, and a straight line in an inertial (non-accelerating) reference frame.

And the distinction is between "accelerating" and "non-accelerating" reference frames. The term "at rest" has no meaning except relative to a particular reference frame.
 
  • #8
If you accelerate the elevator magnetically, that means there is an accelerated charge, which means it will give off radiation, which means "the" light beam is ambiguous.
 

1. What is the Equivalence Principle?

The Equivalence Principle is a fundamental concept in physics that states that the effects of gravity cannot be distinguished from the effects of acceleration. This means that an observer in a uniform gravitational field will experience the same physical laws and effects as an observer in an accelerated frame of reference.

2. What are the consequences of the Equivalence Principle?

One major consequence of the Equivalence Principle is that it allows for the development of the theory of General Relativity, which describes how gravity works on a large scale. It also has implications for the behavior of objects in gravitational fields, such as the bending of light and the slowing of time near massive objects.

3. How does the Equivalence Principle impact our understanding of the universe?

The Equivalence Principle has greatly influenced our understanding of the universe, as it has allowed for the development of General Relativity, which is crucial in explaining the behavior of large-scale objects in the universe, such as planets, stars, and galaxies. It has also led to the discovery of phenomena like gravitational waves and black holes.

4. Are there any exceptions to the Equivalence Principle?

While the Equivalence Principle holds true in most situations, there are some cases where it does not apply. For example, at extremely small scales, the effects of quantum mechanics can overrule the Equivalence Principle. Additionally, in situations involving extremely strong gravitational fields, such as near a black hole, the Equivalence Principle may break down.

5. How is the Equivalence Principle tested and verified?

The Equivalence Principle has been tested and verified through numerous experiments and observations. One famous example is the Pound-Rebka experiment, which showed that light's frequency is affected by gravity in the same way as a clock's frequency. Other experiments, such as the Eötvös experiment, have also confirmed the Equivalence Principle's validity.

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