10.1 Spectroscopy and the Big Bang

Electromagnetic Spectrum

Stars & Light When visible light from a star hits the Earth, all the colours are combined. A spectroscope is a device for splitting starlight into its separate colours (like a prism does) PRISMSPECTROSCOPE Spectrum = the pattern of colours seen through a spectroscope (plural: spectra)

Spectra from stars are not just a rainbow of colours; they also have black lines on them. Absorption Spectrum

The lines are created when elements in the outer atmosphere of the star absorb some of the star’s light before it leaves.  The lines tell which elements are in the outer atmosphere of the star.

Spectroscopy can tell if a star is moving! FACT: A wave made by an object may change in wavelength if the object is moving E.g., Sound waves: pitch of sound goes up when noisy object is moving towards observer pitch of sound goes down when noisy object is moving away from observer E.g., Light waves: Light spectrum of stars changes when star is moving towards or away from Earth Red Shift: When a star is moving away from Earth, absorption lines shift toward red because the light’s wavelength’s have gotten longer Blue Shift: When a star is moving towards Earth, absorption lines shift toward blue because the light’s wavelengths have gotten shorter This tells scientists which way a star is moving

SUMMARY A “red shift” means: the lines on the star’s spectrum have shifted towards red the wavelength of the starlight is getting longer the star is moving away from Earth A “blue shift” means: the lines on the star’s spectrum have shifted towards blue the wavelength of the starlight is getting shorter the star is moving closer to Earth

The Big Bang Theory Once astronomers realized everything in the universe seemed to be moving away from everything else, they thought the universe might have originated from a single point. The Big Bang theory: – An unimaginably tiny speck suddenly “exploded” to an immense size, forming all the matter and energy in the universe – It all happened in the tiniest fraction of a second – It happened approximately 13.7 billion years ago. Biggest Evidence for the Big Bang theory: 1.The universe expanding 2.Cosmic Background Radiation

Cosmic Background Radiation: – The Earth is constantly being hit by microwave radiation coming equally from all directions in the universe – This is called cosmic background radiation, or cosmic rays – The Big Bang theory has an idea of why this background radiation might exist: It might be energy left over from the Big Bang Map of cosmic background radiation made by space probes (COBE and WMAP explorations)

Still, just a theory: – The Big Bang theory is ~80 years old – There is no way to scientifically confirm for sure how our universe started – Big Bang theorists do not know how or why the Big Bang happened, or what existed before the Big Bang – There are other scientific theories about how the universe was formed, though the Big Bang theory is the most dominant one today – Some also believe in a God/Creator, and some in a combination of God and the Big Bang