Redshift, Earth's orbital speed, and the speed of light

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SUMMARY

The Earth orbits the Sun at approximately 30 km/s, with a yearly variation of about 60 km/s. Redshift measurements can reflect this orbital speed, potentially showing variations up to ±30 km/s. The Solar System's velocity around the Milky Way is estimated at 230 km/s, which, along with the Milky Way's motion through the universe, must be considered in redshift calculations. High-precision spectrometers, sensitive to about 1 m/s, are employed to measure these velocities, particularly in exoplanet research.

PREREQUISITES
  • Understanding of redshift and its implications in astrophysics
  • Familiarity with the principles of orbital mechanics
  • Knowledge of spectrometry, particularly in the context of astronomical measurements
  • Awareness of the cosmic microwave background and its relevance to cosmic motion
NEXT STEPS
  • Research the principles of redshift and its measurement techniques
  • Explore the functionality and application of high-precision spectrometers in astronomy
  • Study the effects of the cosmic microwave background on astronomical observations
  • Learn about the dynamics of the Solar System's motion within the Milky Way
USEFUL FOR

Astronomers, astrophysicists, and students of physics interested in the dynamics of celestial motion and the measurement of cosmic phenomena.

iantresman
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The Earth is moving around the Sun at around 30km/s, a change of 60km/s over the course of the year.
  1. Presumably, measurements of the speed of light would show a redshift up to ±30km/s? Are redshift measurements this accurate?
  2. Likewise, the speed of the Solar System around the Milky Way, is estimated to be about 230 km/s, and the Milky Way is moving at some speed through the universe. Do these need to be these factored into redshift measurements?
 
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iantresman said:
Presumably, measurements of the speed of light would show a redshift up to ±30km/s? Are redshift measurements this accurate?
It depends on the measurement. The best spectrometers are sensitive to about 1m/s for single stars, those are used to search exoplanets.
The orbit of earth, the rotation of Earth (still several hundred meters per second) and the influence of the moon (~10m/s) are well-known, so they are always taken into account where they are relevant.

iantresman said:
Likewise, the speed of the Solar System around the Milky Way, is estimated to be about 230 km/s, and the Milky Way is moving at some speed through the universe.
There is no "speed through the universe" as all motion is relative. We have some known velocity relative to the local cosmic microwave background, this is taken into account.
 

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