The green bars are called "error bars." They indicate the range of uncertainty that scientists have about the data on the graph. (Note: Not all error bars are shown.)
Why do you think these error bars are smaller near the year 2000 than in the 1890s?

This graph shows data up to about 2010. So it couldn't have been drawn before 2010. OF COURSE the data from only 10 years earlier was more reliable than the data that was 120 years old ! It wasn't even measured the same way back then as it is now.

Error bars are used to show the error in a reported measurement. The reason why the error bars are smaller near the year 2000 than in the 1890s because the ways of measuring have changed majorly over the past 100 years. The ways of measuring 100 years ago were probably not as accurate as the ways of measuring today.

Best of Luck!

a charge 3q is at the origin, and a charge −2q is on the positive x axis at x=a. part a where on the x-axis would you place a third charge so it would experience no net electric force? enter an expression for the exact answer, which will involve a square-root sign. (do not enter an approximate decimal answer.)