Astronomers have found the cosmic microwave background (CMB) radiation. What is the nature of this radiation?

Question

BlackTom AI · Accepted Answer

The question asks about the nature of the cosmic microwave background (CMB) radiation.

Option a: It is a faint, uniform, radio signal. This choice captures the key features commonly taught about the CMB: it is extremely uniform across the sky and corresponds to a faint background radiation. Although the CMB is typically characterized as microwave radiation, among the given options this one best matches the idea of a faint, pervasive signal that fills the universe uniformly.

Option b: It is a weak and very patchy glow at visible wavelengths. This is incorrect because the CMB is not visible light and is not patchy; it is remarkably uniform across the sky, with temperature fluctuations at a level of one part in 100,000, not large patches.

Option c: It is a weak background of cosmic neutrinos. This is wrong because the CMB refers to photons (radiation), not neutrinos. The cosmic neutrino background exists, but it is a different, much harder-to-detect relic background, not the CMB.

Option d: It is a bright, uniform, x-ray glow. This misstates both the wavelength range (x-rays, not microwaves/radio) and the intensity (not bright). The CMB is extremely faint and not in the x-ray region.

Option e: It is a faint, uniform, x-ray glow. While it correctly notes faint and uniform, the wavelength is incorrect; the CMB is not in the x-ray part of the spectrum.

In summary, option a is the closest description among the listed choices, reflecting the idea of a faint, uniform background signal that permeates the cosmos, even though the canonical designation is microwave rather than radio; the other options introduce incorrect wavelength ranges or physical nature (neutrinos, visible, or x-rays).

ASTR 350 ONL FA25: Big Bang,Black Holes,Universe (Liu, X)

Astronomers have found the cosmic microwave background (CMB) radiation. What is the nature of this radiation?

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