We need to sleep for a host of reasons, but what exactly is happening in our brains while we’re unconscious? We've only scratched the surface of understanding all that happens during sleep, but we do know that while our bodies are resting, our brains are very busy.

The Solar Impulse, an airplane traveling across the United States using only solar power, is in Phoenix today, after reaching Arizona from California Saturday. It took the plane about 20 hours to travel from Mountain View, Calif., near San Francisco.

The aircraft is capable of flying at night as well as in daytime; the plane had about 75 percent of its battery power remaining when it landed in Arizona.

Same-sex marriage got huge headlines at the Supreme Court last month, but in the world of science and medicine, the case being argued on Monday is far more important. The lawsuit deals with a truly 21st century issue — whether human genes may be patented.

Adding some details to an initiative he announced during his latest State of the Union address, President Obama on Tuesday said that federal agencies plan to spend $100 million to jump start an effort to map the human brain. It's research that could lead to breakthroughs in the treatment and prevention of brain disorders.

To err is human.

So is refusing to apologize for those errors.

From toddlers and talk show hosts to preteens and presidents, we all know people who have done stupid, silly and evil things, then squared their jaws and told the world they've done nothing wrong.

CDC/ Amanda Mills

A brother and sister team of young scientists from Westwood High School are finalists in a national science competition.

Priya and Naveen Arunachalam are both finalists in the Exploravision contest. The contest attracted nearly 16,000 students nationwide in a competition to design future technologies that could change the world.

Dr. Andrea Alu, UT

Update: Harry Potter fans and Muggles alike may be one step closer to getting their own invisibility cloaks, if researchers at the University of Texas can help it.

According to the New Journal of Physics, they’ve created a thin material called a “mantle cloak.” Right now the cloak can only make things invisible in a certain range of light waves. It also doesn’t look like a cloak you would wear. It’s a thin tubing made from polycarbonate film, wrapped with copper tape.

Tonight is one of a few chances Austinites will have to see a passing comet.

The PAN-STARRS comet, or C/2011 L-4 as it’s known by stargazers, will make its way across the Austin skies around 30 to 40 minutes after sunset tonight – which is at 7:37 p.m, according to the National Weather Service.

courtesy NASA

First it was a music festival, then a film festival, then an interactive festival. Since then, South by Southwest has added education, the environment and venture capital to its repertoire. Could SXSW Space be far off?

Update at 8:10 p.m. ET: Problem Fixed, Arrival Delayed

SpaceX says the problem with its unmanned craft carrying supplies for the International Space Station has been fixed.

Scientists from Colombia believe they have pinpointed the origin of the giant meteor that smashed into a remote region of Russia earlier this month, injuring more than 1,000 people.

The meteor that caused at least 1,000 injuries in Russia after a startling and powerful daytime explosion one week ago has been identified as a chondrite. Russian scientists who analyzed fragments of the meteor, whose large size and well-documented impact made it a rarity, say that its composition makes it the most common type of meteor we encounter here on Earth.

University of Texas at Austin

A University of Texas chemist has been honored with a $500,000 prize for inventing a key technology used to produce virtually all modern computer chips. The Japan Prize is awarded annually to people who make major contributions to the fields of science and technology. 

C. Grant Willson, along with a colleague and a grad student, figured out how to print complex computer circuits on silicon wafers. Chris Mack, an expert in lithography, says Willson’s work is everywhere.

We all think we know what happy means. But when you get down to it, how would we actually define it? Raj Raghunathan has tried. He teaches marketing at UT’s McCombs School of Business. He studies, among other things, consumer behavior, decision theory, and happiness. Raghunathan says different people define happiness differently, but a couple of traits are universal. It’s a positive emotion, and we want to experience it. But, he says, pursuing society’s most common markers of happiness won’t actually get us there.

We start with a pool of oil. We turn on a magnet. The oil travels up a superstructure and blossoms into a tree. Turn off the magnet, the branches, the needles, the tree melt away. It's a puddle again.

The perfect tree for an oil billionaire, no?

Filipa Rodrigues for KUT News

Former president Bill Clinton was in Austin today to speak at Dell's annual business and technology conference. He touted Dell’s announcement of a partnership with the Clinton Global Initiative University – and also recalled a forehead-slapping a moment with a former Texas Senator.

NASA/ESA/Andrew C. Fabian

Scientists at the University of Texas say they’ve discovered the most massive black hole ever identified.

It sits in the center of a galaxy called NGC 1277. It has a mass equivalent to about 17 billion suns.

Doctor Karl Gebhardt is an astrophysicist at UT, and a member of the team that made the discovery. He says their finding could help us better understand the way galaxies are formed.

Amanda Mills, Centers for Disease Control

The San Antonio-based Texas Biomedical Research Institute has applied for a patent for a new genetically engineered HIV vaccine. This new vaccine would provide lifelong protection from the disease with a single dose.

The vaccine is designed to target the cells that line the body’s surface structures. which are the point of entry into the body in approximately 90 percent of HIV cases. Once HIV enters the body through these cells, it quickly spreads to the lymph nodes and other organs, where it replicates throughout the body. The new vaccine would stimulate the body’s outer layers and cells to generate cells that produce antibodies to HIV. 

In case you missed it this weekend, here is harrowing video of the Austrian skydiver Felix Baumgartner stepping off a capsule at the edge space. He then plummets toward Earth at :