Two ways of detecting absolute motion

In summary: The first method is unworkable because the speed of light is the same in any reference frame. That means that if you measure the speed of an object using two different reference frames, the two measurements will always be the same.
  • #1
avito009
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There are two ways by which absolute motion might be detected: by measuring motion with respect to a beam of light, and by making use of inertial effects that arise when an object is accelerated. So why MichelsonMorley experiment showed the first method to be unworkable? Einstein's special theory of relativity explained why.

Correct me if I am wrong. Special relativity proved that no matter the position or speed with which a person is moving, the speed of light will be the same. Is this correct? otherwise how does SR prove that the first method is unworkable?
 
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  • #2
Absolute motion relative to what? That's not a joke; all motion is relative.
 
  • #3
Special relativity didn't prove that the speed of light is the same, it started with the assumption (Einstein's second postulate) that it was.

We choose to make this assumption because:
- It agrees with all the experimental evidence we have (including the Michelson-Morley experiment).
- It is consistent with the laws of electricity and magnetism, which were solidly established more than a half-century before the discovery of relativity.
- The conclusions that follow from that assumption can be tested, and when we test them they are confirmed.

That doesn't mean that it's right, but it does mean that any alternative that doesn't do all of the above has to be wrong.
 
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  • #4
avito009 said:
There are two ways by which absolute motion might be detected: by measuring motion with respect to a beam of light, and by making use of inertial effects that arise when an object is accelerated.
You can't use acceleration detect absolute motion because per Newton's first and second Laws of Motion, acceleration works the same regardless of your current state of motion.
 
  • #5
avito009 said:
There are two ways by which absolute motion might be detected: by measuring motion with respect to a beam of light, and by making use of inertial effects that arise when an object is accelerated. So why MichelsonMorley experiment showed the first method to be unworkable? Einstein's special theory of relativity explained why.

Correct me if I am wrong. Special relativity proved that no matter the position or speed with which a person is moving, the speed of light will be the same. Is this correct? otherwise how does SR prove that the first method is unworkable?

Since the speed of light is the same in any reference frame measuring your speed using it as a reference will always produce: ta-da, the speed of light.
 

FAQ: Two ways of detecting absolute motion

What is the difference between absolute and relative motion?

Absolute motion is the movement of an object in relation to an unmoving, fixed reference point, such as the Earth's surface. Relative motion, on the other hand, is the movement of an object in relation to another moving object.

How can we detect absolute motion?

There are two main ways to detect absolute motion: using an external reference frame, such as the Earth's surface or the stars, or using an internal reference frame, such as an accelerometer or gyroscope.

What is the principle behind using an external reference frame to detect absolute motion?

The principle is based on the fact that the Earth is constantly rotating and orbiting the sun, providing a fixed reference point for measuring absolute motion. By observing the movement of objects in relation to this fixed reference point, we can determine their absolute motion.

How do accelerometers and gyroscopes work to detect absolute motion?

Accelerometers measure changes in acceleration, which can then be used to calculate absolute motion. Gyroscopes, on the other hand, measure changes in orientation and can also be used to determine absolute motion.

What are the advantages and disadvantages of each method of detecting absolute motion?

The advantage of using an external reference frame is that it is a more accurate and precise method. However, it may not be feasible in all situations, such as when traveling in space. Internal reference frames, such as accelerometers and gyroscopes, are more portable and can be used in various environments, but they may be less accurate and susceptible to errors.

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