An observed increase in the wavelength of light from distant galaxies
The further away a galaxy is
The faster it is moving
The further away a galaxy is
The greater the observed increase in wavelength
Red-shift provides evidence that the universe is expanding
Red-shift supports the Big Bang theory
Big Bang theory
The entire universe started from a very small, hot and dense region in space
The galaxy that is further away
Is travelling faster
The observed red-shift
Is greater the further away it is
Scientists observed supernovae, which suggested that galaxies are moving away at an ever faster rate
Prior to observations of supernovae, the rate of expansion was expected to occur at an ever slower rate due to gravitational forces
The existence of energy and mass that we can't detect, known as dark matter and dark energy, could explain the universe's ever increasing rate of expansion
These ideas about dark matter and dark energy are still being developed by scientists and are not yet fully understood
