| Red-shift | EMISSION SPECTRA:
Light from a star doesn't contain all wavelengths of the EM spectrum as elements in the star absorb some of the emitted wavelengths (so dark lines are present when the spectrum's analysed). Different elements produce different patterns of dark lines.
SPECTRA FROM DISTANT GALAXIES:
When astronomers observe light from distant galaxies, they can see it is different to the light from the sun. The dark lines in the spectra from distant galaxies show an increase in wavelength. The lines are moved or shifted towards the red end of the spectrum - Red-Shift
RED-SHIFT & SPEED:
Astronomers see red-shift in virtually all galaxies, its a result of the space between the Earth and the galaxies expanding. This expansion stretches out the light waves during their journey to us. shifting them towards the red end of the spectrum. The more red-shifted the light from a galaxy is, the faster the galaxy is moving away from Earth |
| Big Bang Theory | About 13.8 B years ago, the whole universe was v/small, v/hot & dense region, from this point it expanded out to what it is today |
| The future of the Universe | If scientist could find out the density of the universe, they'll have an answer to if the Universe will expand forever, or if gravitational attraction between all objects will eventually slow to a stop, attracting everything back together in a 'Big Crunch'
DARK ENERGY:
- Since 1998, astronomical observations of supernova have suggested that distant galaxies are moving away increasingly faster (accelerating)
- Dark energy is thought to cause the Universe to expand faster all the time
- This would mean dark energy must account for 68% of the Universe
DARK MATTER:
- galaxies seem to rotate too quickly for the mass of their stars, this suggests that there is mass in the Universe that is invisible to the instruments used by scientists
- Scientists only know it is there because it has gravity that affects objects nearby
- Astronomers have calculated that 27% of the Universe must be made of this dark matter |
