Question

On the atomic level, there is some free space between the electrons and nucleus of atoms (and between the protons and neutrons in the nucleus itself). What 'material' fills these spaces? Dark matter?

Asked by: Jeff

Answer

The empty space between the atomic cloud of an atom and its nucleus is just that: empty space, or vacuum. That's the simple answer, but there are a few subtleties:

1) Sub-atomic particles such as electrons, protons and neutrons need to be treated as quantum objects. Thus they have a wavefunction which can be *thought of* as the 'spread' in the particle's location. Electrons are thus 'spread out' quite a bit in their orbits about the nucleus. In fact, the wave-functions for electrons in s-orbitals about a nucleus actually extend all the way down into the nucleus itself. In this sense, then, the space between the electrons and the nucleus isn't really 'empty.'

2) The electrons and the protons/neutrons are constantly interacting, either electromagnetically or through the weak force. In quantum field theory we would say that these particles are constantly exchanging photons (in the case of electromagnetism) or heavy gauge bosons (in the case of the weak force). Thus you might say that the otherwise 'empty' space between the electrons and nucleus is 'filled' with these quanta carrying forces.

Despite these two quantum-mechanical subtleties, it's still correct to say that the space between the electrons and nucleus in atoms is truly empty space. As for dark matter, if only it were sitting inside the atom -- then maybe we would have discovered it by now! Despite the mysterious name 'dark matter,' we actually know quite a lot about what the particles that might make up dark matter can and cannot be. One thing we know is that it isn't likely to be interacting strongly with protons, neutrons and electrons. That means it isn't likely to be found in atoms -- and if any dark matter exists in our planet at all, it would have to be down at the very core of the planet where it has been drawn by the force of gravity. Needless to say, that makes searching for it rather difficult!

Answered by: Brent Nelson, M.A. Physics, Ph.D. Student, UC Berkeley

Search

Loading






Science Quote

'Our loyalties are to the species and the planet. We speak for Earth. Our obligation to survive is owed not just to ourselves but also to that Cosmos, ancient and vast, from which we spring.'

Carl Sagan
(1934-1996)
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:
KonusScience 5 Way Microscope Kit
3D Magnetic Field Tube
Space Wonder Gyroscope
Revolving Multi-Color Fiberoptic Light
Periscope
Deluxe Water Rocket Set
Wood Grain Newtons Cradle
Brush Robot 4M Kit
Solar Radiometer
12 inch Galileo Thermometer

Sponsors

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