Reference Pages
02 April 2014, 04:19 AM ET
Where are the aliens? That is the question that the Fermi Paradox seeks to answer. Given our solar system's relatively young age, the theory says that aliens should have visited us already.
01 April 2014, 02:18 AM ET
Astronomers say there are 100 billion to 200 billion galaxies in the universe. But accurately counting the number of galaxies depends on several factors.
28 March 2014, 05:35 PM ET
A look at the U.S. Air Force's unmanned X-37B space plane, which has flown three secret, long-duration missions in Earth orbit to date.
26 March 2014, 03:55 AM ET
The Drake Equation is used to estimate the number of communicating civilizations in the cosmos, or more simply put, the odds of finding intelligent life in the universe.
21 March 2014, 11:31 PM ET
The Hubble Constant is the unit of measurement used to describe the expansion of the universe. The cosmos has been getting bigger since the Big Bang kick-started the growth about 13.82 billion years ago.
19 March 2014, 12:59 AM ET
The Big Bang Theory is the leading explanation about how the universe began.
17 March 2014, 10:45 AM ET
Gravitational waves are the "smoking gun" of the Big Bang. Predicted by Albert Einstein's theory of general relativity in 1916, a massive object like Earth distorts space-time around it like a bowling ball dropped on a trampoline.
04 March 2014, 02:05 AM ET
NASA's Kepler Space Telescope is an observatory in space dedicated to finding planets outside our solar system.
28 February 2014, 08:39 PM ET
Yes, the moon rotates on its axis. The moon's rate of rotation nearly matches its orbital period, which keep the same side facing Earth.
28 February 2014, 08:34 PM ET
Space is the zone above and around our planet where there is no air to breathe or to scatter light. Space is a vacuum, but it is far from empty.
27 February 2014, 11:57 PM ET
Scientists have calculated that Earth is 4.54 billion years old, with an error range of 50 million years.
27 February 2014, 12:53 AM ET
Artificial satellites from Earth have only populated space since 1957, but there are now hundreds of thousands of objects from our planet in orbit.
13 February 2014, 10:27 PM ET
If you wanted to pay a visit to the red planet, how long would it take? The answer depends on a number of things …
13 February 2014, 10:53 AM ET
Ganymede would easily be classified as a planet if were orbiting the sun rather than Jupiter.
12 February 2014, 07:34 PM ET
Edmond Halley is best remembered for predicting the orbit of the comet that was later named after him. Besides astronomy, he also made significant discoveries in the fields of geophysics, mathematics, meteorology and physics.
11 February 2014, 05:00 PM ET
The Gemini program tested docking, rendezvous, spacewalks and long-duration spaceflight in preparation for the moon missions of the late 1960s.
10 February 2014, 06:50 PM ET
Mercury was a NASA program to prove that astronauts could function effectively in space for minutes to hours at a time.
04 February 2014, 03:11 PM ET
NASA's Lunar Atmosphere and Dust Environment Explorer (LADEE) launched in September 2013. Here is everything you need to know about it.
31 January 2014, 11:48 PM ET
Gordon Cooper had the longest flight among the original Mercury astronauts.
31 January 2014, 12:46 AM ET
Scott Carpenter, one of the original Mercury astronauts, explored space and later the sea.
30 January 2014, 12:49 AM ET
Deke Slayton was selected for the Mercury program, but had to wait more than a decade to fly in space after concerns about an erratic heartbeat pulled him out of the flight rotation.
29 January 2014, 01:45 AM ET
Wally Schirra, one of the original Mercury Seven astronauts, was the only one who flew in the Mercury, Gemini and Apollo programs.
28 January 2014, 01:46 AM ET
Gus Grissom, one of the original Mercury Seven, also flew on a Gemini mission. He died during training for the first Apollo mission.
27 January 2014, 10:44 PM ET
When stars can't handle their nuclear fuel, they explode in a brilliant burst of light.
22 January 2014, 01:00 PM ET
Ceres is a dwarf planet, the only one located in the inner reaches of the solar system. It is the largest object in the asteroid belt.
15 January 2014, 10:29 PM ET
The density of the universe determines its shape. It could be spherical, saddle-shaped or flat.
06 January 2014, 01:22 PM ET
Kepler-69c, also known as KOI 172.02, is a planet candidate discovered by the Kepler space telescope. It is a "super-Earth" that could hold water on its surface.
02 January 2014, 06:53 PM ET
The rocky planet Kepler-62f could be covered in water, as long as there is enough cloud around the planet to warm the surface below.
31 December 2013, 07:13 PM ET
Kepler-62e is an alien planet that is believed to be in the habitable zone of its red dwarf parent star.
31 December 2013, 06:53 PM ET
Kepler-22b is an alien planet that's a bit larger than Earth, but it's in the habitable region of its star.
30 December 2013, 06:04 PM ET
A do-it-yourself Galilean telescope makes an excellent and inexpensive starter telescope — or science fair project.
24 December 2013, 12:36 AM ET
Based on what we can observe, the universe appears to be almost 28 billion light-years in diameter. However, it is far larger than that.