When astronomers find a redshifted celestial object, they say that the object is moving away from Earth. Can the redshift be interpreted as the Earth moving away from the celestial object?
Sure
No, the redshift of a celestial object cannot be interpreted as the Earth moving away from the object. When astronomers observe a redshift in the light emitted from a celestial object, it is due to the Doppler effect caused by the object moving away from Earth. The Doppler effect is a well-known phenomenon in physics that occurs when there is relative motion between the source of waves (in this case, light) and the observer (in this case, the astronomer on Earth).
The redshift is a shift towards longer wavelengths, which corresponds to a decrease in the frequency and energy of the light. This occurs because the object is moving away from Earth, stretching out the wavelength of the light as the source and observer move apart.
If the Earth were the source of the observed redshift, it would imply that the entire universe is expanding away from Earth, which is not the case. In reality, it is the space between galaxies that is expanding, with the galaxies themselves being carried along with the expansion. This is known as the metric expansion of space, and it is responsible for the observed redshift of distant galaxies.
To determine whether a celestial object is moving away from Earth or not, astronomers rely on spectroscopy, which involves analyzing the light emitted by the object. By studying the redshift or blueshift (a shift towards shorter wavelengths) of certain spectral lines, astronomers can precisely determine the velocity at which the object is moving away or towards Earth.