Photon Decoupling Redshift

ATRONOMY – COMOLOGY (42) CALCULATOR Photon Decoupling Redshift A precise tool.
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What is the Photon Decoupling Redshift & How does it work?

Photon decoupling marks the moment when electrons and protons combined to form neutral hydrogen, allowing photons to travel freely for the first time. This event defines the surface of last scattering that we observe today as the Cosmic Microwave Background (CMB).

The redshift of photon decoupling, denoted z_*, can be estimated from the ratio of the temperature of the Universe at decoupling (≈3000 K) to the present CMB temperature (≈2.725 K). Because temperature scales with the cosmic scale factor as T ∝ 1/a, the relation (1+z) = T_dec / T_0 holds.

By inserting measured temperatures into this simple formula, we obtain a redshift of roughly 1100, indicating that the Universe was about a thousand times smaller when photons first decoupled from matter.

( (1+z) = frac{T_{mathrm{dec}}}{T_{0}} )
z = redshift at photon decoupling
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Frequently Asked Questions
What is photon decoupling in cosmology?
Photon decoupling is when electrons and protons combined to form neutral hydrogen, allowing photons to travel freely for the first time.
How do I calculate the redshift of photon decoupling?
Use the ratio of the temperature at decoupling (≈3000 K) to the present CMB temperature (≈2.725 K).
What is the significance of the Cosmic Microwave Background (CMB)?
The CMB is the surface of last scattering, representing the oldest light in the universe.
How does temperature scale with cosmic scale factor?
Temperature scales inversely with the cosmic scale factor, meaning as the universe expands, temperatures decrease.
What is the approximate temperature of the Universe at decoupling?
The approximate temperature of the Universe at decoupling is 3000 K.
What is the current temperature of the Cosmic Microwave Background?
The current temperature of the Cosmic Microwave Background is approximately 2.725 K.
Why is photon decoupling important in cosmology?
Photon decoupling marks a critical transition in the early universe, leading to the formation of neutral hydrogen and the first light we observe as CMB radiation.

Results are for informational purposes only and do not constitute professional advice.