February 29, 2012

What is a Leap Year?

What is a leap year and why do we have them? Why does February 29th, or leap day, only appear on the calendar every four years? These are questions that many people ask every four years, so here is the reason for the periodic appearance of February 29th.

The calendar system used in most of the world is called the Gregorian calendar, and this calendar is not perfectly in sync with the actual rotation of the earth around the sun. In other words, seasons and related astronomical movement do not correspond to the days on the calendar. Contrary to what we all learned in school, the earth does not circle the sun every 365 days. Instead, the earth travels around the sun in just under 365.25 days. To keep our man-made calendar systems from drifting too far out of sync with this reality, an extra day is inserted every four years to re-sync the Gregorian calendar with what is actually happening in our solar system. The result is that every fourth year we count 366 days instead of 365. Years with 366 days are called Leap Years and years with 365 days are called Common Years.

As a point of interest, the Hebrew calendar, also known as a lunisolar calendar, has a different compensation system. It adds an extra month seven times every nineteen years.

February 25, 2012

Preventing Bone Loss in Space-Dwellers

Astronaut exercising in zero gravity
Photo courtesy of NASA
"Use it or lose it" is a saying that applies to most of our body parts, including bones. Bone density loss is a well-documented problem among astronauts who spend significant amounts of time in space. In fact, even brief periods of time spent in zero gravity tends to result in the loss of bone density and muscle mass. Exercise, resistance training in particular, has been shown to help slow the decay of bone and muscle tissue, but not enough. Now, the construction of the International Space Station has increased the urgency of finding a solution to bone loss among astronauts.

According to NASA, humans living in space lose one to two percent of their bone mass per month, even with exercise. To combat the bone loss, the crew of the space station is currently using a combination of nutrients and workout equipment that is specially designed to work in zero gravity. Meanwhile, scientists are running various studies aboard the station to try and better understand the fight the accelerated bone and muscle deterioration. Bisphosphonates are currently being investigated as a possible solution to the problemThe Human Research Program at NASA's Johnson Space Center, along with the Japanese Space Agency, or JAXA, work together on this study to see if the medicine's ability to block the breakdown of bone will help astronauts to retain bone density while on orbit. Seven astronauts from the United States, Canada, and Japan took part in this investigation. Participants ingested one 70 mg alendronate pill per week prior to and during space flight, along with vitamin D supplements and routine workouts. For comparison, the study also includes crew members who use exercise only. "Since exercise alone has not been entirely successful in preventing bone loss in astronauts during long duration missions, we hope to determine if a combination of anti-resorptive drugs, in this case oral alendronate, and in-flight exercise will reduce bone loss and renal stone risk." said Adrian LeBlanc, Senior Scientist at Universities Space Research Association in Houston, Texas. "Bisphosphonate medication is used to reduce bone breakdown in osteoporosis patients on Earth. Its use in space was a logical extension, since space flight increases bone breakdown."

Studies of this nature could result in new solutions to bone-loss challenges for those living on the International Space Station, as well as those of us living here on earth. Also, remember to get your free NASA ap for your Android phone.

February 5, 2012

The Ant Colony Excavation

In the breathtaking video below, researchers pour 10 tons of concrete into a giant ant hill and then slowly, carefully excavate the site to reveal the amazing size and complexity of the underground structure. The result is an intricate sculpture, equivalent in labor to humans building the Great Wall of China and then some. Of course, humans filled the anti hill with concrete (think of Mr. House and Vault 21). The ants probably didn't appreciate that, even in the name of science.