A microwave signal is initially suspected to come from equipment on the Earth. After equipment faults and local sources are excluded, the signal is detected across the sky by independent instruments.
Which explains why these checks strengthen its use as evidence for the Big Bang?
They show that all microwave signals must come from distant galaxies.
They show that the Universe must create new matter as it expands.
They support a widespread background rather than a local source.
They support an unchanged Universe rather than an early hot state.
94 exam-style questions on Edexcel GCSE Physics 7.2 The Universe and red-shift, covering 7.2.1 Big Bang and Steady State theories, 7.2.2 Evidence for the Big Bang, 7.2.3 The Doppler effect and red-shift, 7.2.4 Red-shift as evidence for an expanding Universe, and 7.2.5 The CMB and the accepted model. Each one has a worked solution and a mark scheme showing where the marks go.