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The Discovery of the Radiation Belts

The belts of trapped radiation above the Earth's atmosphere, but within the magnetosphere, were first detected by James Van Allen in 1958. Therefore these belts are also known as Van Allen Belts.

When Sputnik I, the first spacecraft, was launched in 1957 by the Soviet Union, the Americans were anxious to respond. The Americans wanted to not only launch a satellite, but to learn something new!

Dr. James Van Allen had already been exploring the upper atmosphere of the Earth with balloons that could obtain information about radiation levels in the atmosphere. Van Allen and his team placed a Geiger counter and an altimeter on Explorer I, the first American spacecraft, to take radiation readings at different altitudes.

During the flight, radiation levels seemed to increase and then suddenly drop to zero and then again to increase, then suddenly drop to zero. What the team soon realized was that regions appearing as zero were really off the scale! These high-radiation regions were mapped and are now known as the Van Allen radiation belts.

Scientists recalibrated the Geiger counter for later flights, and Explorer III confirmed the existence of the Van Allen radiation belts.

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Radiation Belts

The Earth's radiation belts are one component of the larger and more complex system called the magnetosphere. The radiation belts of the Earth are made up of energetic, electrically charged particles or...more

Sputnik

The Soviet Sputnik program consisted of four satellites, three of which reached Earth orbit. Sputnik 1, launched on Oct.4, 1957, became the first artificial satellite to successfully orbit the Earth. It...more

The Earth's Magnetosphere

The Earth has a magnetic field with north and south poles. The magnetic field of the Earth is enclosed in a region surrounding the Earth called the magnetosphere. As the Earth rotates, its hot core generates...more

The Discovery of the Radiation Belts

The belts of trapped radiation above the Earth's atmosphere, but within the magnetosphere, were first detected by James Van Allen in 1958. Therefore these belts are also known as Van Allen Belts. When...more

Earth's Magnetic Poles

Earth has a magnetic field. If you imagine a gigantic bar magnet inside of Earth, you'll have a pretty good idea what Earth's magnetic field is shaped like. Of course, Earth DOESN'T have a giant bar magnet...more

Earth's North Magnetic Pole

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Altocumulus

Altocumulus clouds (weather symbol - Ac), are made primarily of liquid water and have a thickness of 1 km. They are part of the Middle Cloud group (2000-7000m up). They are grayish-white with one part...more

Windows to the Universe, a project of the National Earth Science Teachers Association, is sponsored in part is sponsored in part through grants from federal agencies (NASA and NOAA), and partnerships with affiliated organizations, including the American Geophysical Union, the Howard Hughes Medical Institute, the Earth System Information Partnership, the American Meteorological Society, the National Center for Science Education, and TERC. The American Geophysical Union and the American Geosciences Institute are Windows to the Universe Founding Partners. NESTA welcomes new Institutional Affiliates in support of our ongoing programs, as well as collaborations on new projects. Contact NESTA for more information. NASA ESIP NCSE HHMI AGU AGI AMS NOAA