The surprising discovery that the universe is not just expanding but that the rate of expansion is increasing is what led to the idea of dark energy as the cause of that acceleration. But explaining in non-mathematical terms to a lay audience why dark energy leads to an accelerating expansion is not easy and introducing the idea that dark energy creates a negative pressure does not help much either. [Read more…]

Angular momentum is a hard concept to teach in introductory physics courses. This is partly because it is a quantity known as a vector that has both a magnitude and a direction, and adding and subtracting and multiplying vectors is more complicated than with scalars, like mass. Other things like force and velocity are also vectors but in those cases the directionality at least is intuitively obvious. The direction of the force vector is in the direction along which the force acts and the direction of the velocity vector is the direction in which the object is moving. [Read more…]

I was sorry to learn that Stanford professor Clifford Nass died unexpectedly this week at the age of just 55. He studied the ways in which technology and human beings interacted. [Read more…]

The ‘good news, bad news’ set up is often used in jokes. But apart from humor, I bet that almost all of us have at some point been asked by someone the above question when they were about to tell us something. I hate being asked it and would much prefer the person just tell me in whatever order they like. [Read more…]

A bicycle is a good example of something that is commonplace and yet quite extraordinary. It seems such an unlikely mode of transportation. One has to wonder how someone came up with the bizarre idea that by sitting astride a bar that connects two wheels one behind the other, one could propel oneself forward without falling. And yet everyone who has ridden a bike knows that it feels remarkably stable and as long as it is moving, it stays upright and seems to almost ride itself. ‘Look, no hands’ is the common exultation expressed by new learners as they discover for themselves that the bike can be ridden with minimal action on their part other than to keep it moving. [Read more…]

In a document obtained by Al Jazeera under the Freedom of Information Act, the NSA urges its officials to use 9/11 as a sound bite to deflect any questions about their snooping programs, giving them explicit language to use. And sure enough, NSA director Keith Alexander used it in his congressional testimony. [Read more…]

On Science Friday last week, I heard a segment about Cotard’s Syndrome, also known as the Walking Corpse syndrome. This is where some people are convinced that they are dead and actually tell other people so, saying things like “It is no use talking to me. I am dead.” [Read more…]

Carl Zimmer has an interesting article about attempts to estimate how many cells the average human body contains. It depends on how you do it and previous estimates over the past few centuries have ranged widely from two billion to 200 million trillion cells. [Read more…]

Developments in robotics that mimic living things are quite amazing. Here’s one robot designed to look and work like a pack mule that can go over rough terrain. [Read more…]