Cosmic Microwave Background Radiation (CMBR)
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16 Terms
What is cosmic microwave background radiation?
Electromagnetic radiation left over from the early Universe, now observed mainly as microwaves.
What does CMBR stand for?
Cosmic Microwave Background Radiation.
Where is CMBR detected?
From all directions in space.
Why is CMBR important?
It provides strong evidence for the Big Bang theory.
What was the early Universe like when the radiation that became CMBR was released?
It was hot and dense, but had cooled enough for atoms to form.
Why could light begin travelling freely when atoms formed?
Electrons combined with nuclei, so light was scattered much less frequently.
Why is the radiation now detected as microwaves?
The expansion of the Universe has stretched its wavelength.
What type of radiation was the CMBR originally?
Higher-frequency electromagnetic radiation, which has been red-shifted as space expanded.
What does CMBR tell scientists about the early Universe?
The Universe was once much hotter and denser.
Why does CMBR support the Big Bang theory rather than the steady state theory?
The Big Bang theory predicts relic radiation from a hot early Universe, whereas the steady state model does not adequately explain it.
What is the approximate temperature of the CMBR today?
About 2.7 K, just above absolute zero.
Why is the CMBR so cold today?
The expansion of the Universe has stretched its wavelengths and reduced its temperature.
Is the CMBR completely uniform?
No, it contains very small temperature variations.
Why are small variations in the CMBR important?
They provide evidence about early differences in matter density that helped structures form.
How does the CMBR provide evidence independently of galaxy red-shift?
It is relic radiation predicted by a hot early Universe, rather than a measurement of galaxies moving apart.
Why is the CMBR considered evidence rather than proof of every detail of the Big Bang theory?
It strongly supports the model, but some aspects of the Universe's earliest history remain uncertain.