Physicists watch quantum particles tunnel through solid barriers. Here's what they found.

[Jim__]

24. I was referring to a paragraph in the article.

Subatomic particles all have magnetic properties and when magnets are in an external magnetic field, they rotate like a spinning top. The amount of rotation (also called precession) depends on how long the particle is bathed in that magnetic field. Knowing that, the Toronto group used a magnetic field to form their barrier. When particles are inside the barrier, they precess. Outside it, they don't. So measuring how long the particles precess told the researchers how long those atoms took to tunnel through the barrier.

Specifically to these 2 sentences: When particles are inside the barrier, they precess. Outside it, they don't.

The way I read those sentences, the particles will not precess unless they pass inside the barrier. It was that paragraph that raised the question with me.