
Chris Hadfield has conquered space. Now he's conquering the Internet, too.
A video of the Canadian astronaut singing David Bowie's "Space Oddity" from the International Space Station has been zipping around the Web at light speed since it was posted Sunday. The five-minute clip features Hadfield singing a modified version of the tune and strumming an acoustic guitar while floating through a space module, more than 200 miles above the Earth.
By Monday morning, it had more than 1 million views on YouTube, 3,000 comments on Reddit and was being widely shared across social networks.
By Elizabeth Landau, CNN
In some ways, it's just a number, but it's a big number with enormous implications.
For the first time, scientists measured an average concentration of atmospheric carbon dioxide of 400 parts per million in Mauna Loa, Hawaii, where the National Oceanic and Atmospheric Administration observatory is located, on Thursday.
"Most experts that really study CO2 amounts estimate that we haven't seen that amount of CO2 in our atmosphere in about 3 million years," said J. Marshall Shepherd, climate change expert and professor at the University of Georgia. In other words, modern humans have never seen carbon dioxide in these proportions before.
By Elizabeth Landau, CNN
Leave it all behind and start anew on a planet no humans have occupied - how does that sound? More than 78,000 people applied to go on a one-way trip to Mars, through Mars One, an organization aiming to put four people on the Red Planet by 2023.
Apparently, they are unfazed by the idea that they can never come back or that taking showers there would not be an option.
The applications came from more than 120 countries, although the United States led with 17,324 applications, the Dutch company said.
The International Space Station crew is preparing for a spacewalk to address the leak of ammonia from a cooling system, the commander said Friday.
NASA said the crew is preparing for a "possible" spacewalk and that a decision on whether to go ahead with it is likely to come late Friday.
Cmdr. Chris Hadfield of Canada announced the plan to venture outside the space station via his Twitter account.
"Good Morning, Earth! Big change in plans, spacewalk tomorrow, Chris Cassidy and Tom Marshburn are getting suits and airlock ready. Cool!" he posted Friday.
By Buzz Aldrin, Special to CNN
Editor's note: Buzz Aldrin, best known for his Apollo 11 moonwalk, holds a doctoral degree in astronautics and, at the age of 83, continues to wield influence as an international advocate of space science and planetary exploration. Aldrin’s new book "Mission to Mars: My Vision for Space Exploration," co-authored with space journalist Leonard David, is a blueprint and strategy for American-led presence of human beings from Earth on the Red Planet Mars. He is on Twitter at @therealbuzz.
We need to get the world excited again about space exploration and have the pioneering spirit to reach beyond our boundaries and current capabilities.
I want a new generation of space explorers to feel as I did when it was my privilege to take part in the Apollo program that landed the first humans on the surface of the Moon. This is important, not only for the USA but for the rest of the world.
Let me tell you why.

Buzz Aldrin's new book is called "Mission to Mars: My Vision for Space Exploration."
"The LAGEOS I, Laser Geodynamics Satellite, was launched on May 4, 1976 from Vandenberg Air Force Base, California. The two-foot diameter, 900-pound satellite orbited the Earth from pole to pole and measured the movements of the Earth's surface relative to earthquakes, continental drift, and other geophysical phenomena.
The mirrored surface of the satellite precisely reflected laser beams from ground stations for accurate ranging measurements. Scientists at NASA's Marshall Space Flight Center in Huntsville, Ala. came up with the idea for the satellite and built it at the Marshall Center."
Source: NASABy Meg Urry, Special to CNN
Editor's note: Meg Urry is the Israel Munson professor of physics and astronomy and chairwoman of the department of physics at Yale University, where she is the director of the Yale Center for Astronomy and Astrophysics
On April 27, NASA's Fermi and Swift satellites detected a strong signal from the brightest gamma-ray burst in decades. Because this was relatively close, it was thousands of times brighter than the typical gamma-ray bursts that are seen by Swift every few days. Scientists are now scrambling to learn more.
We already knew that when the biggest stars run out of fuel, they don't fade quietly away. Instead, they explode in a blaze of glory known as a supernova. These stellar explosions are often bright enough to be seen by us even though they are in galaxies billions of light-years from our own Milky Way galaxy home.
In very rare cases - such as GRB130427A (tagged with the date of its discovery) - astrophysicists are lucky enough to see energetic gamma-rays from hyperfast jets of outflowing material consisting of charged particles created during a massive star's violent death throes.
By Jacque Wilson, CNN
They emerge from the ground after 17 years, their worm-like bodies creating hundreds of peanut-sized holes near the base of your tree. As they begin to climb, their dark brown skin starts to shed. Two beady red eyes appear.
By the time they reach a steady branch their transparent wings have stretched, opened and closed. Within an hour their white bodies will turn black.
Soon the males will start to sing.

By Kelly Murray, CNN
From the darkest brown to the pastiest white and every shade in between, humans display a tremendous variety of skin colors. Human skin color is directly linked to our survival as a species as we lost our fur and developed a need for protection from the sun, and then migrated into cloudier regions of the globe. Over the course of evolution, scientists argue, skin color was influenced, among other factors, by our need for healthy bones.
To begin to explain this, we turn to Nina Jablonski, professor of anthropology at Pennsylvania State University. She is a well-recognized researcher in primate evolution, and specifically the evolution of human skin, and she was the subject of a Science Seat on CNN Light Years.
The story of human skin color begins with our furry ancestors about 6 to 7 million years ago in Africa, the last time that humans and chimpanzees shared an ancestor. Jablonski says that these ancestors, called Australopithecus, still had ape-like body proportions: fairly long arms and relatively short legs.
By Eoghan Macguire and Matthew Knight, CNN
Ever since it was discovered in 2004, graphene has been hailed as a natural wonder of the materials world destined to transform our lives in the 21st century.
Graphene's amazing properties excite and confound in equal measure. How can something one million times thinner than a human hair be 300 times stronger than steel and 1,000 times more conductive than silicon?
CNN Labs asked the head of MIT's graphene research department, Tomas Palacios, to explain why graphene is such a special material and what we can expect it to do for us in the future.

