Question

Patterns of emission or absorption lines in spectra can uniquely identify individual atomic elements. Explain how positive identification of atomic elements can be used as one way of testing the validity of the cosmological principle discussed in Chapter 1

Answer 1

When we pass a light through a spectrograph (for cosmological purposes) , many of the wavelengths get absorbed. This will create a pattern unique to each cosmic body .It means when looking at a distant planet, an astronomer can take the light emitted, run it through a spectograph, and be able to tell what elements the planet is composed of based of the absorption spectrum obtained.

Furthermore Each element will absorb or emit light of a particular wavelength due to the energy needed to bump an electron up to a higher level (absorption) or drop an electron down to a lower level (emission). These light frequencies identify which gasses are present, what is the composition and surface temperature and so many things.

There are many possible electron transitions for each atom. Each transition has a specific energy difference. This collection of transitions makes up an emission spectrum. These emission spectra are as distinctive to each element as fingerprints are to people.Thus, scientists can use atomic spectra to identify the elements in them.

One most relevant example would be DNA which is uniques to an individual.