Question

Evidence that the cosmic background radiation really is the remnant of a Big Bang comes from predicting characteristics of remnant radiation from the Big Bang and comparing these predictions with observations. Four of the five statements below are real. Which one is fictitious?

A) The cosmic background radiation is expected to have a temperature just a few degrees above absolute zero, and its actual temperature turns out to be about 3 K (actually 2.7 K).
B) The cosmic background radiation is expected to have a perfect thermal spectrum, and observations from the COBE spacecraft verify this prediction.
C) The cosmic background radiation is expected to contain spectral lines of hydrogen and helium, and it does.
D) The cosmic background radiation is expected to look essentially the same in all directions, and it does.
E) The cosmic background radiation is expected to have tiny temperature fluctuations at the level of about 1 part in 100,000. Such fluctuations were found in the COBE data.

Answer 1

The fictitious statement is that the cosmic background radiation contains spectral lines of hydrogen and helium. This is incorrect as the CMBR has a continuous blackbody spectrum without discrete spectral lines, supporting the Big Bang model.

Step-by-step explanation:

The statement that is fictitious is (C) The cosmic background radiation is expected to contain spectral lines of hydrogen and helium, and it does. This is not correct because the cosmic background radiation (CMBR) is not expected to contain spectral lines of hydrogen and helium. The CMBR is a relic from the time when the universe became transparent to radiation, hundreds of thousands of years after the Big Bang, and before the formation of hydrogen and helium atoms that could produce spectral lines. Instead, the CMBR has a continuous blackbody spectrum, as observed by the COBE spacecraft, with no discrete spectral lines.

The other statements (A, B, D, and E) are true characteristics of the cosmic background radiation as validated by observations. The CMBR has a temperature very close to absolute zero approximately 2.7 K, and it does have a nearly perfect thermal spectrum. This radiation is remarkably uniform in all directions, with only tiny temperature fluctuations. These characteristics provide compelling evidence for the Big Bang model of the universe's creation.