Key Takeaways on Earth's Inner Core Earth's inner core is solid and blistering hot. For decades, scientists have known ...

Of all Earth’s layers, the inner core is the most remote and mysterious. This solid sphere of iron and nickel is about 70% the size of the moon, with a radius of approximately 759 miles ...

Scientists have long thought Earth's inner core is like a huge solid metal ball. But an experiment revealed it may be a lot softer — more like butter, a lead scientist said.