Question

What is cosmic radiation? Is it dangerous?

Asked by: George T.

Answer

Cosmic radiation is a collection of many different types of radiation from many different types of sources. When people speak simply of 'cosmic radiation' they are usually referring specifically to the cosmic microwave background radiation. This consists of very, very low energy photons (energy of about 2.78 Kelvin) whose spectrum is peaked in the microwave region and which are remnants from the time when the universe was only about 200,000 years old. There are also very old remnant neutrinos in the cosmic radiation. Neutrinos pass through just about everything with no effect so they are harmless. The photons are too low in energy to be dangerous.

On top of these there are higher energy particles that are being created constantly by all luminous objects in the universe. Photons of all different energies/wavelengths are being created by our sun, other stars, quasi-stellar objects, black-hole accretion disks, gamma-ray bursts and so on. These objects also produce high-energy massive particles such as electrons, muons, protons and anti-protons. These higher energy particles are potentially dangerous, but most of these particles never make it to the earth. They are deflected by magnetic fields between us and the source, or they interact with other particles, or they decay in flight.

The particles that do make it to the earth interact with our atmosphere, which acts as a 'radiation shield.' The high-energy cosmic rays bombard us all the time, but they interact quickly, producing particles of much lower energy which impact the earth harmlessly. If this was dangerous to us, we wouldn't be here to discuss these things! Some particles, like neutrinos and high energy muons, are passing through us all the time, but they interact so weakly that they have no effect on our bodies. Of course, if we were in space without the protection of our atmosphere then we would need some other type of shielding from the radiation (spacesuits and protective covering on our spacecrafts).

The radiation to worry about, of course, is the 'cosmic' radiation produced by our sun. There is only one type of cosmic radiation known to adversely affect us and that's UV radiation from our sun, which causes skin cancer in millions of people every year.. Again, our atmosphere serves as a shield, but ultraviolet photons do make it through -- and without that protective ozone layer which blocks these photons we're all going to need a lot more sunscreen!

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

Search

Loading






Science Quote

'I beseech you to take interest in these sacred domains so expressively called laboratories. Ask that there be more and that they be adorned for these are the temples of the future, wealth and well-being. It is here that humanity will grow, strengthen and improve. Here, humanity will learn to read progress and individual harmony in the works of nature, while humanity's own works are all too often those of barbarism, fanaticism and destruction.'

Louis Pasteur
(1822-1895)
Science Sidebar | Science Education Articles
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:
Magnetic Levitator - Classic
12 inch Galileo Thermometer
Cricket, Locust, Beetle and Crab
Solar Radiometer
Weather Station 4M Kit
3D Magnetic Field Tube
Clean Water Science 4M Kit
Revolving Multi-Color Fiberoptic Light
Periodic Table of Elements Poster - Laminated
Solar Science 4M Kit

Sponsors

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