Xiang Zhu

Every spring, El Niño forecasts lose their edge, like a translator who gets distracted by every rustle in the room and turns a one-hour meeting into a two-hour one. Scientists call this the spring predictability barrier: in March and April, models that confidently predicted a warm phase in the Pacific back in January start making mistakes twice as often.

Light escaping a massive body loses energy: its waves stretch, and its color shifts toward the red. This is gravitational redshift, known since the work of Einstein.