Are Electric and Gravitational Fields the Same for Moving and Stationary Objects?

In summary: The only requirement is that the system is not accelerating with respect to an inertial frame. In fact, the theory of general relativity involves acceleration and gravitational forces. However, in SR, the concept of gravity is not included and it is not considered a force. In summary, Special Relativity (SR) does not consider gravity as a force and only deals with inertial frames that are not accelerating. Forces can still be involved in SR, as long as they are not associated with gravity. On the other hand, classical electromagnetism, which is a cornerstone of relativity, is fully relativistically covariant and can be applied to both stationary and moving objects.
  • #1
Silviu
624
11
Hello! I was wondering if the electric and gravitational fields are the same for a moving and a stationary object. The electric field (assume it is created by a stationary charge) is ##E = \frac{q}{\epsilon_0 4 \pi r^2}##, for a stationary observer, but it is higher for a moving one, as the r is getting smaller, while all the other are constant. Is this correct? For gravitational field, the formula would be ##G\frac{M}{r^2}##. The same reasoning can be applied here, only that in this case the mass M seems to increase. Are my reasoning correct? And if so, why does the electric and gravitational field behave differently, beside the math involved? Thank you!
 
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  • #2
The electric field is not the same for a moving and for a stationary charge. Not only does the electric field change, it also mixes with the magnetic field under Lorentz transformations.

There is no gravitation in SR.
 
  • #3
Orodruin said:
The electric field is not the same for a moving and for a stationary charge. Not only does the electric field change, it also mixes with the magnetic field under Lorentz transformations.

There is no gravitation in SR.
What do you mean by there is no gravitation in SR. You can still treat problems in SR when forces are involved. The nature of the force shouldn't matter, so it can be created by gravity, right?
 
  • #4
Silviu said:
You can still treat problems in SR when forces are involved.
Gravitation is not a force in relativity. Forces in relativity need to be local as action at a distance would violate causality. You cannot go about just assuming that nothing will change with the gravitational field and it is best to keep away from all considerations of gravity in SR.'

On the other hand, classical electromagnetism (in the form of Maxwell's equations) is fully relativistically covariant. It is in fact one of the cornerstones in how relativity was conceived.
 
  • #5
SR considers inertial systems. No force, no acceleration. Constant straight velocity.
 
  • #6
Thuring said:
SR considers inertial systems. No force, no acceleration. Constant straight velocity.
This is not correct, but a common misconception among laymen. It is perfectly possible to work with accelerated frames and forces in SR.
 

1. Are electric and gravitational fields the same for moving and stationary objects?

No, electric and gravitational fields are not the same for moving and stationary objects. They have different properties and behaviors, and are governed by different equations.

2. Can electric and gravitational fields be measured using the same units?

No, electric and gravitational fields use different units of measurement. Electric fields are measured in volts per meter (V/m) while gravitational fields are measured in newtons per kilogram (N/kg).

3. Do electric and gravitational fields interact with each other?

Yes, electric and gravitational fields can interact with each other. This is known as the gravitational-electric force, and it occurs when a charged object is placed in a gravitational field or vice versa.

4. How do electric and gravitational fields affect the motion of objects?

Electric and gravitational fields can both exert forces on objects, causing them to accelerate or change direction. The strength and direction of the force depends on the properties of the object and the field it is in.

5. Are there any real-world applications of electric and gravitational fields being different for moving and stationary objects?

Yes, there are many real-world applications of electric and gravitational fields being different for moving and stationary objects. For example, this concept is used in the design of particle accelerators, where charged particles are accelerated using both electric and magnetic fields. Additionally, the behavior of satellites and spacecraft in orbit is also affected by the differences in electric and gravitational fields for moving and stationary objects.

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