Somewhere deep beneath our feet, the Earth appears to be pulsing quietly and rhythmically, every 26 seconds. This faint tremor, too subtle for humans to feel, has baffled scientists for decades.

Learn to read your pulse for hidden heart problems. Rhythm irregularities and rate changes reveal cardiovascular issues.

While it may not always be a cause for concern, especially if there’s a known history of injury or surgery, it’s important to ...