Extra-terrestrial life is the existence of life outside of the Earth. Are we alone in the universe? So far the only life we know about inhabits our planet – Earth – but there are planets that orbit other stars in a similar way to how the Earth orbits the Sun.

Download the answers to the quiz here.

For more information about the electromagnetic spectrum see the resource "It's what's inside that counts".

Telescopes are used to detect radiation from the whole electromagnetic spectrum.

Radiowaves - radio telescopes need to be large to account for the long wavelength of radiowaves. They are often large dishes and several of them can be used together to increase resolution. The SKA (square kilometre array) will be a series of radio telescopes that cover a square kilometre. Radio telescopes are used to collect "images" from most astronomical objects that emit radiowaves including stars, galaxies, nebulae and planets.

Infrared - these telescopes have to be positioned high above the ground or in space to avoid interference form the infra-red radiation on the Earth. They also need to be above as much of the water vapour in the atmosphere as possible. Water vapour will limit the amount of infrared radiation that reaches the surface of the Earth, so the higher the better.

Visible light - They use lenses and/or mirrors to reflect or refract light to form an image which can be seen by the human eye.

These are the types of telescope that the public can buy in the shops. Much larger ones are used by astronomers.

UV light - UV telescopes have to be even higher than infra-red telescopes as the Earth's atmosphere blocks out some UV light. They are often positioned outside the atmosphere (in space). It is the ozone in the atmosphere that blocks UV light - and this is beneficial for the existence of life on Earth, as UV light is dangerous in large quantities (eg causes sunburn).

X-rays & gamma-rays - the best results come from telescopes on satellites orbiting the Earth.

Curriculum links

Data, evidence, theories and explanations 1a. how scientific data can be collected and analysed
Energy, electricity and radiations
7c. radiations, including ionising radiations, can transfer energy d radiations in the form of waves can be used for communication.
Environment, Earth and universe 8c. the solar system is part of the universe, which has changed since its origin and continues to show long-term changes.

Scottish Curriculum

Science - Curriculum for Excellence level 4 SCN 4-06a. Planet Earth - Space: By researching developments used to observe or explore space, I can illustrate how our knowledge of the universe has evolved over time.
SCN 4-11b. Forces, electricity and waves - Vibrations and waves: By carrying out a comparison of the properties of parts of the electromagnetic spectrum beyond the visible, I can explain the use of radiation and discuss how this has impacted upon society and our quality of life
SCN 4-20a. Topical Science: I have researched new developments in science and can explain how their current or future applications might impact on modern life
SCN 4-20b. Having selected scientific themes of topical interest, I can critically analyse the issues, and use relevant information to develop an informed argument
Physics National 4 & 5 Potentially relevant to modules: Space (solar system and its exploration)


SETI uses radio telescopes to search for patterns in radio signals from space.

gamma ray mapRadio telescopes have also allowed astronomers to "see" things in the space between the stars which looks empty. They allowed astrochemists to identify water, carbon-monoxide and ammonia as well as more complex molecules containing carbon. We now know there are over 100 different types of molecules in the space between the stars. The field of astrochemistry is explained here: an exhibition as part of The Royal Society's Summer Science Exhibition in 2004.

Image: A map of Mars as measured by gamma rays.

Other types of telescopes can be used to look for other things in the universe. Researchers in Durham and Namibia are using telescopes to detect gamma rays from space. They hope by finding out where gamma rays come from they can find out more about cosmic rays. Cosmic rays are high energy particles, such as protons and electrons, that enter our solar system from far away in the galaxy. They provide information from outside our solar system but they are difficult to detect. Gamma rays are produced when cosmic rays are accelerated through space and these are easier to detect. You can find out more about this project and watch a short video "Astronomy at the end of the rainbow" here.

Different types of telescopes look at different parts of the electromagnetic spectrum. For more information and images of the Milky Way taken using different telescopes, have a look at NASA's website here.



Test your telescopic knowledge!

Take the online quiz here,

Or download the pdf worksheet.