Across
- 6. The range of wavelengths that trigger brightness and color perception in humans.
- 8. The strength and vitality required for sustained physical or mental activity.
- 9. A system of millions or billions of stars, together with gas and dust, held together by gravitational attraction.
- 11. A colorless, odorless, highly flammable gas, the chemical element of atomic number 1.
- 12. The wavelength of the light is stretched, so the light is seen as 'shifted' towards the red part of the spectrum.
- 13. The branch of science that deals with celestial objects, space and the physical universe as a whole.
- 14. An English astrophysicist and advocate of the steady state theory of cosmology.
- 15. The displacement of the spectrum to shorter wavelengths in the light coming from distant celestial objects moving toward the observer.
- 16. An American physicist and radio astronomer.
Down
- 1. The cooled remnant of the first light that could ever travel freely throughout the Universe.
- 2. An American astronomer who played a crucial role in establishing the fields of extragalactic astronomy and observational cosmology.
- 3. An apparatus for photographing or otherwise recording spectra.
- 4. All existing matter and space considered as a whole; the cosmos.
- 5. How astronomers explain the way the universe began.
- 7. The range of all types of EM radiation.
- 10. An American director and playwright of experimental theater. He also worked as a choreographer, performer, painter, sculptor, video artist, and sound and light designer.
- 11. The chemical element of atomic number 2, an inert gas which is the lightest member of the noble gas series.
- 13. German-born physicist and activist.