Observing the Universe

This lesson covers how astronomers observe and measure the universe — as required by the Edexcel GCSE Physics specification (1PH0), Topic 7: Astronomy. This is a Paper 2 topic. You need to understand the advantages of space telescopes over ground-based telescopes, how absorption spectra reveal what stars are made of, and key units of astronomical distance.

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Telescopes — Our Windows to the Universe

Telescopes are instruments that collect and focus electromagnetic radiation from distant objects in space. There are two main types based on their location:

Ground-Based Telescopes

These are telescopes located on Earth's surface. They are typically placed on high mountains in dry, remote locations to minimise atmospheric interference.

Feature	Detail
Location	On Earth's surface (ideally high altitude, dry climate)
Types	Optical (visible light), radio telescopes
Advantages	Cheaper to build and maintain; easier to repair and upgrade; can be very large
Disadvantages	Affected by atmospheric absorption and distortion; limited by weather, light pollution, and the day-night cycle
Famous examples	Very Large Telescope (Chile), Jodrell Bank (UK), Arecibo (Puerto Rico, now collapsed)