Accidental physics: Why mass has a split personality

MacGregor Campbell, contributor

We interact with the concept of mass every day. Without it, gravity wouldn't keep us firmly planted on Earth. But mass is also a component of inertia, making it hard, for example, to push a stalled car.

On the surface, inertia and gravity don't seem to have much in common. But in experiments, these two versions of mass always give the same results. Although we've been aware of the coincidence since Galileo's day, the only explanation, proposed by Einstein, has been much disputed.

In this video, we delve into the split personality of mass, exposing the conundrum that lies at the core of one of the most basic concepts in physics. For more on the topic, read our full-length feature article, "Sacrificing Einstein: Relativity's keystone has to go".

For more mind-bending animations, check out our previous explainers to find out, for example, how to change the past, or if space is really infinite.

Source: http://feeds.newscientist.com/c/749/f/10897/s/27cf7318/l/0L0Snewscientist0N0Cblogs0Cnstv0C20A130C0A10Caccidental0Ephysics0Ewhy0Emass0Ehas0Ea0Esplit0Epersonality0Bhtml0Dcmpid0FRSS0QNSNS0Q20A120EGLOBAL0Qonline0Enews/story01.htm

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