GCSE›Edexcel GCSE Physics›Mind mapsCosmologyEdexcel GCSE Physics: Mind mapStudy pack PDFAlso for this subtopic:Revision notesFlashcardsSubtopic testCover factsRed-shiftDoppler effect: motion changes observed wavelengthSource moving away: wavelength up, frequency downLight shifts towards the red endSource moving towards: blue-shiftDistant galaxiesAlmost all show red-shiftSo they move away from usFurther away → greater red-shiftFurther away → moving away fasterSame in every direction: Universe is expandingBig BangBegan from one extremely hot, dense pointExpanding and cooling sincePredicted CMB radiationExplains red-shiftCosmologyorigin of the UniverseSteady StateUniverse has always existed and looked the sameMatter continuously createdAlso predicts red-shiftNo good explanation for CMBCMB evidenceFaint radiation from all directionsLeftover from the hot early UniverseIts discovery made Big Bang the accepted modelExam tipsRed-shift alone does not prove Big BangLink distance → red-shift → recession speedCMB decides between the two theories