A test of the Copernican principle

Area of Science:

• Cosmology
• Astrophysics
• Fundamental Physics

Background:

• The cosmic microwave background (CMB) radiation provides a unique probe of the early universe.
• The Copernican principle posits that Earth does not occupy a privileged position in the universe.
• Deviations from a perfect blackbody spectrum in the CMB could indicate large-scale structures or unusual cosmological conditions.

Purpose of the Study:

• To perform a modern test of the Copernican principle using the CMB spectrum.
• To constrain the possibility of our location within a large cosmic void.
• To investigate whether cosmic acceleration could be mimicked by residing in such a void.

Main Methods:

• Analyzing the blackbody spectrum of the CMB radiation.
• Utilizing the reionized universe as a reflective medium for CMB photons.
• Comparing CMB spectral measurements with theoretical models of large voids.

Main Results:

• Current spectral distortion limits exclude the largest voids that could mimic cosmic acceleration.
• A limit is placed on the possibility of occupying a privileged location at the center of a void.
• The Hubble diagram inferred from a void center might be misinterpreted as cosmic acceleration.

Conclusions:

• The CMB spectrum serves as a powerful tool to test fundamental cosmological principles.
• Sensitive CMB measurements are crucial to either confirm the Copernican principle or detect large-scale voids.
• Misinterpretation of cosmological data, such as cosmic acceleration, is possible without considering peculiar locations.