The universe

• Scientists have tried to work out the density of the universe to answer if the universe will expand forever or if there will be a “Big Crunch”
• Dark energy


  Accounts for 68% of the universe and is responsible for expansion
• Dark energy


  Responsible for the accelerating expansion of space
• Dark matter


  Invisible to scientific instruments and is accountable for 27% of the universe
• Dark matter is responsible for the gravitational attraction
• Cosmic Microwave Background Radiation (CMBR)


  Remains of thermal energy from the Big Bang spread across the whole universe
• CMBR is evidence of the Big Bang theory
• The Big Bang theory is the idea that the universe began 13.8 billion years ago and expanded outwards
• Red-shift is proof of the universe expanding
• Emission spectra


  Elements in a star absorb some of the emitted wavelengths
• Dark lines in the spectrum represent star emissions
• Dark lines are shifted towards the red end of the spectrum
• More red-shifted dark lines means galaxy is moving away faster