Cosmic Horizons main content.
Cosmic Horizons
Part of Curriculum Collections.
Educator Materials
Case Study: Friedrich Bessel and the Companion of Sirius
Bessel discovered Sirius' unseen companion star long before technology allowed us to see Sirius B and even longer before quantum...
Educator Materials
Case Study: Gerard Kuiper and the Trans-Neptunian Comet Belt
A dusty snowball orbiting the Sun, trailing gas and dust as it melts—a poetic and highly accurate way to describe a comet. Find out...
Educator Materials
Case Study: John Michell And Black Holes
Imagine gravity so strong that even light is contained by its force. When a country parson first described black holes in 1783, the...
Educator Materials
Case Study: Fossil Microbes on Mars?
A meteorite that escaped from Mars 16 million years ago was found recently in Antarctica. Does it, or doesn't it, hold evidence that...
Educator Materials
Case Study: Neutrino Observatories
Update your image of astronomers. Today they spend most of their time peering into computer screens rather than through the eyepiece...
Educator Materials
Case Study: The Cosmic Microwave Background Radiation
At this distance in time and space, can we prove that the universe was created with a single explosion? See how scientists have detected...
Educator Materials
Profile: Ernst Chladni and Rocks from the Sky
Today, we accept the notion that enormous rocks exist within our solar system and that some of them fall to Earth. A little over...
Educator Materials
Profile: Georges Lemaître, Father of the Big Bang
When a Catholic priest—cosmologist first proposed that the universe began as a "primeval atom," it seemed preposterous....
Educator Materials
Profile: Cecilia Payne and the Composition of the Stars
What are the stars made of? At 25, Cecilia Payne answered this fundamental question in her Ph.D. thesis. Her pioneering work also...
Educator Materials
Profile: Ole Roemer and the Speed of Light
While studying one of Jupiter's moons, Ole Roemer happened upon the first good estimate of the speed of light. Before his 1676 discovery,...
Educator Materials
Profile: Vera Rubin and Dark Matter
For every visible star in the observable universe, there are nine masses that are invisible and unidentified. Learn more about the...
Educator Materials
Profile: Carl Sagan and the Quest for Life in the Universe
Cosmos, Contact, Icarus and Billions and Billions—from TV and movies to professional journals and best-selling books, Carl Sagan's...
Educator Materials
Profile: Lyman Spitzer and the Space Telescope
The idea of launching a telescope into orbit was first suggested in 1923, but the idea wasn't realized until nearly 70 years later....
Educator Materials
Profile: Fritz Zwicky's Extraordinary Vision
Astronomer Fritz Zwicky was the first person to conceive of supernovas, neutron stars, dark matter, and gravitational lenses. So...
Educator Materials
Profile: Harold C. Urey
This Nobel Prize–winning chemist contributed to several scientific fields. His remarkable body of work spanned chemistry, geochemistry,...