Question

How long have scientists been recording the strength of the Earth's magnetic field?

Answer 1

Since 1840 we have been accurately enough to tell how the magnetic feild works, every 300,000 years it flips that hasn't occurred for 800,000 years though, hope this helps.<span />

Answer 2

Explanation:

The strength of the magnetic field was first measured in 1835 by Carl Friedrich Gauss and has been measured numerous times since then, showing a relative decay of 10% in the last 150 years. Currently, satellites use magnetometers to probe the three-dimensional structure of the Earth's magnetic field.