Localization by the doppler effect

In summary: MBR is not "isotropic" (the same in every direction) -- it is anisotropic (has different values in different directions).In summary, the conversation discusses the possibility of finding out one's speed and direction while being hypothetically enclosed in a box that blocks outside influences. The idea of using the Doppler effect and the microwave background radiation to measure velocity is also mentioned, but it is concluded that it would not work due to the MBR not being isotropic.
  • #1
disregardthat
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I have heard that if one is hypothetically placed in a box completely solid, whith a shield that leaves everything that would have entered a normal box, like light, or neutrinos, out of it. If you sent that in a certain speed, with nothing affecting it, just traversing through space, the person inside it could not in any way find out where he is, or what speed he is going in.
Or something similiarly, i don't explain it that good.

Anyway, my question is, that you COULD find out what your speed is, if you originally know what for example what frquenzies glowing hydrogen gas sent out. Then you measure the frequenzie of it in all directions. Let's say (i don't know anything about it, just as an example) normal hydrogen gas sent out light in frequenzies of 5, then the doppler effect would have made the frequenzy higher the way the box is moving. if the box is moving half the speed of light, the frequenzy would be doubled, since the light waves are compressed. on the opposite side the light frequenzy would be halfed.

so theoretically wouldn't they say something about what speed, or at least what direction they are moving in? Or have i misunderstood the doppler effect?
 
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  • #2
The H gas frequencies as seen by the receiver moving with the source would not see any Doppler shift. Doppler shift is seen by a receiver moving relative to the source.
 
  • #3
doppler and velocity measurement

Jarle said:
I have heard that if one is hypothetically placed in a box completely solid, whith a shield that leaves everything that would have entered a normal box, like light, or neutrinos, out of it. If you sent that in a certain speed, with nothing affecting it, just traversing through space, the person inside it could not in any way find out where he is, or what speed he is going in.
Or something similiarly, i don't explain it that good.

Anyway, my question is, that you COULD find out what your speed is, if you originally know what for example what frquenzies glowing hydrogen gas sent out. Then you measure the frequenzie of it in all directions. Let's say (i don't know anything about it, just as an example) normal hydrogen gas sent out light in frequenzies of 5, then the doppler effect would have made the frequenzy higher the way the box is moving. if the box is moving half the speed of light, the frequenzy would be doubled, since the light waves are compressed. on the opposite side the light frequenzy would be halfed.

so theoretically wouldn't they say something about what speed, or at least what direction they are moving in? Or have i misunderstood the doppler effect?

You can measure other's velocity using radar echo. Experiments confined in a given inertial reference frame do not offer infoirmation about its velocity.
 
  • #4
Jarle said:
hypothetically box completely solid, whith a shield that leaves everything that would have entered a normal box, like light, or neutrinos, out of it. ...
...you COULD find out what your speed is, if you originally know what for example what frquenzies glowing hydrogen gas sent out. Then you measure the frequenzie of it in all directions. -- Doppler effect --
The Doppler effect would apply only to light coming in from outside the box. -- But you defined your box as being shielded form allowing entry of anything outside, not even the MBR.

To ask your question in a different way, for those not in such a box: Could the MBR (Microwave Background Radiation) define a "Preferred Reference Frame" to base measurements from as the classical Newton would have wanted?
My expectation is NO; due to 'Hubble Expansion'
 

Related to Localization by the doppler effect

1. What is localization by the Doppler effect?

Localization by the Doppler effect is a method used in science and engineering to determine the location of a moving object using the change in frequency of a wave, known as the Doppler effect. This change in frequency is caused by the relative motion between the source of the wave and the observer.

2. How does localization by the Doppler effect work?

Localization by the Doppler effect works by measuring the change in frequency of a wave as it travels from the source to the observer. This change in frequency is then used to calculate the relative velocity between the source and the observer. By knowing the velocity and direction of the source, the location can be determined.

3. What types of waves can be used for localization by the Doppler effect?

The Doppler effect can be applied to any type of wave, including sound waves, light waves, and radio waves. However, it is most commonly used with sound waves, as they are easier to measure and can travel through different types of media, such as air and water.

4. What are some real-world applications of localization by the Doppler effect?

Localization by the Doppler effect has many practical applications, such as in radar systems, sonar systems, and medical imaging. It is also used in traffic speed cameras and in determining the speed and direction of weather patterns, such as hurricanes and tornadoes.

5. Are there any limitations to localization by the Doppler effect?

While localization by the Doppler effect is a useful tool, it does have some limitations. It is most accurate when the source is moving directly towards or away from the observer, as any lateral motion can affect the measured frequency. Additionally, the accuracy can be affected by environmental factors, such as wind or background noise.

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