- #1
Ranku
- 410
- 18
Does the CMBR contain the imprint of the entire expansion history of the universe or only of the last scattering ?
So when the Planck Survey of CMBR observed that space is flat, is that a measure of flatness of the present universe or during last scattering?Bandersnatch said:It's a snapshot of the state of the universe at last scattering. Its redshift contains information about the total amount of expansion over the remaining history of the universe, but not the details of how that expansion has happened.
The two can be combined into a model that tracks the entire expansion history, but that information isn't there in the light itself.
This is similar to observing a particular redshifted galaxy - the image is of the state at emission, modified (redshifted) by the amount of expansion undergone until reception.
CMBR stands for Cosmic Microwave Background Radiation. It is a remnant of the early universe, also known as the "afterglow" of the Big Bang. It is the oldest light in the universe, dating back to about 380,000 years after the Big Bang.
The CMBR carries information about the early universe, including its temperature and density. By studying this radiation, scientists can determine the rate of expansion of the universe and how it has changed over time. This is known as the expansion history of the universe.
The CMBR dipole anisotropy refers to the slight variations in the temperature of the CMBR across the sky. These variations are caused by the Doppler effect, as the Earth and our galaxy are moving through space. This anisotropy provides evidence for the expansion of the universe, as well as the direction and speed of our galaxy's motion.
The theory of inflation proposes that the universe underwent a rapid period of expansion in its early stages. This theory is supported by the uniformity of the CMBR across the sky, which suggests that the universe was once much smaller and more homogenous before undergoing a period of rapid expansion.
Aside from providing evidence for the expansion history of the universe, the CMBR also contains information about the composition of the universe. By studying the patterns of temperature fluctuations in the CMBR, scientists can determine the amount of dark matter and dark energy in the universe, as well as the overall curvature of space-time.