The Big Bang Theory Unit: Space

Birth of a Theory Hypothesis: Educated Guess. Theory: Hypothesis that’s supported by consistent results & experimentation. Scientific Law: A rule that correctly describes a natural phenomenon; well established theory.

Light & the Doppler Effect Spectrum: Rainbow of colors passing through a glass prism. (spectra) Wavelength: Distance from crest of wave to crest of next wave. Each color spectrum has a wavelength. Light passes through prism  each wavelength is bent dif., resulting in spectrum.

Bright-Line Spectrum: Series of thin colored lines spaced at uneven intervals. Elements produce bright-line spectrums when heated. Every element has a unique bright-line spectrum.

Doppler Effect: - Used to determine an objects speed relative to an observer.

Doppler Effect: (continued) Blue Shifting Light/object moving toward observer  - shorter appearance of wavelength. - shift to shorter wavelength, blue end of spectrum; “Blue Shifting.” Red Shifting Light/object moving away from observer  - longer appearance of wavelength - shift to longer wavelength, red end of spectrum; “Red Shifting.”

Doppler Effect: (continued) The faster the light source, the greater the spectrum shift.

Evidence

Spectroscopes Used to determine what elements are in stars. Separates light into a spectrum of colors & wavelengths. Dif. chem. elements emit light of dif. colors when heated, so astronomers use this to examine light given off by stars (like the sun), when using spectroscopes. By determining the dif. colors of light emitted by a star, you can determine what elements it contains, it’s age, & it’s inside temp.

Spectroscope Evidence Starlight spectra gives us info. about Universe. Spectra of most galaxies (large systems of stars) show a shift toward red end of spectrum (Red Shift), indicating that almost all galaxies in universe are moving away from Earth. By examining degree of red shift, determine speed of traveling galaxies. Farthest galaxies, moving the fastest (most red shift). Conclusion, Universe is expanding= Big Bang Theory

Background Radiation Evidence Using radio telescopes, scientists detected low levels of energy (Background radiation), evenly distributed throughout the universe. The presence of evenly distributed energy convinced most scientists that the Big Bang Theory was correct.

Big Bang Theory Explained Billions of yrs ago, all matter & energy was compressed into extremely small volume. About 18 b.y.a. an event (Big Bang- cause: Gravity) sent all matter & energy outward in a giant cloud. As cloud expanded, some matter gathered into clumps, galaxies evolved. Today the universe is still expanding & galaxies continue to move away from each other, causing the red shift in the spectra of galaxies.

Big Bang Theory: All stars in universe appear to be moving away from same point. (balloon example) This is due to Doppler shifts (red/blue) in light emitted by stars, the distribution of stars throughout the universe, & the discovery of background radiation.

Misconception Galaxies are Not flying away from us, the space between them is growing

Limitations of the Big Bang Theory: Does not explain formation of galaxies, stars, etc. Can’t explain very early universe. Doesn’t answer where universe came from or what came “before” it.

PAST UNIVERSE - Compressed, Spaced closer together. - Hotter; only protons & electrons were present

End of the Universe: Two major Theories Heat Death the universe will stop expanding and everything will cool down to a temp. where no work can be done Steady State the universe will stop expanding and collapse upon itself and start over with a new Big Bang