1. Electromagnetic Spectrum
Radio telescopes make use of the wave nature of light to image the cosmos.

2. Radio light waves are a million times weaker than optical light waves.
Yet they can travel right through walls and immense dust clouds in space.
need giant telescopes and very sensitive electronic receiver/amplifiers
1 second energy output of a light bulb  100 Joules
Energy received by a radio telescope in 1 second  Joules
Optical and radio (blue) views of the nearby galaxy Centaurus A

3. Polarized Waves
Linearly polarized electromagnetic wave moving through space. Red is the electric field, blue is the magnetic field.
Linearly polarized wave: electric field oscillates in the vertical direction

4. Green Bank Radio Telescope, West Virginia, US
100 m diameter

6. Cellphones, wifi, satellite TV spoil radio astronomy!

7. Hubble Space Telescope

9. Interstellar dust clouds make stars behind them look redder and fainter

10. Sunsets

11. Why do you think the dust around these stars looks blue?

12. Polarized light from a giant dust cloud around a young star 800 light years away. Someday this dust may turn into planets!
Radio telescope (ALMA) image of HD142527

13. Black Hole at our Galactic Center
Event Horizon Telescope