Question

How did the earth come to have a molten iron core?

Asked by: Ralph Wiley

Answer

Four and a half billion years ago, Earth (and the other planets in the Solar System) formed when smaller bits of matter in solar orbit came together gravitationally. As a result of those multiple collisions the kinetic energy of motion was converted to heat energy, resulting in a hot, molten mass that would become our Earth.

While in this hot, fluid state, the denser, heavier material (iron and nickel) settled to the center and the less dense rocky material floated nearer the surface, resulting in today's iron/nickel core.

As the Earth radiated energy into space, the outer layers cooled first. The core, being insulated by Earth's outer layers, took longer to cool. That is not the complete story, however. In addition to the initial energy of formation, there are radioactive elements in the Earth with long half lives that continue to release energy. This energy cannot immediately escape into space either, and also accounts for the Earth's hot, molten interior.

Answered by: Paul Walorski, B.A., Part-time Physics/Astronomy Instructor

Search

Loading


Support Discovery Capsule - Anton's new project on Kickstarter.



Science Quote

'On the mountains of truth you can never climb in vain: either you will reach a point higher up today, or you will be training your powers so that you will be able to climb higher tomorrow.'

Friedrich Nietzsche
(1844-1900)
Science Sidebar | Science Education Articles
Cool Summer Science Projects

Why not make science a part of your family’s summer? Perhaps you can set aside one day a week for outdoor projects—maybe Mad Scientist Monday or Scientific Saturday? Here are a few ideas to help get you started. Continue reading ...

10 Ways to Keep Your Kids Interested In Science

Young children are natural scientists: they ask questions, pick up sticks and bugs outside, and are curious about the world around them. But as they get a bit older, many kids gradually lose their interest in science. They might see it as just another task at school, something that doesn't apply to their lives. Of course nothing could be further from the truth, so here are ten ways you can remind your kids that science is everywhere. Most of these are fun for adults, too! Continue reading ...

Top Selling

Here are our physics & astronomy bestsellers:
3D Magnetic Field Tube
Space Wonder Gyroscope
KonusScience 5 Way Microscope Kit
12 inch Galileo Thermometer
Solar Radiometer
Wood Grain Newtons Cradle
Brush Robot 4M Kit
Tin Can Robot 4M Kit
Electric Plane Launcher 4M Kit
Periscope

Sponsors

USC University of Southern California Dornsife College Physics and Astronomy Department McMaster University Physics and Astronomy Department