The discussion centers on measuring the Doppler-shifted 21 cm emission line, which is crucial for understanding astrophysical phenomena. It highlights that the 21 cm line serves as a probe for redshifts up to 150, contrasting with the Cosmic Microwave Background (CMB) which is redshifted by approximately 1100 times. The contamination of the 21 cm signal from other emissions poses significant challenges, necessitating careful observational techniques. The Wikipedia article on the hydrogen line in cosmology provides a comprehensive overview of these redshift effects.
PREREQUISITESAstronomers, astrophysicists, and researchers focused on cosmology and the study of cosmic background radiation will benefit from this discussion.
The statement is incorrect. The observations of 21cm line is an useful probe for redshifts up to 150, while CMB (which is more correct to call "first light") is redshifted by ~1100 times.atomiclaser said:Summary:: 21 cm was considered as the first light after big bang. How does people measure this emission ?
we know that all emission from asctrophysical context is doppler shifted. So, how to make sure the doppler shifted 21 cm not contaminated by some other emission?