To find out how many pennies weigh as much as the Earth, we can divide the weight of the Earth by the weight of a penny.
Given:
- Weight of the Earth = \( 5.972 \times 10^{24} \) kg
- Weight of a penny = \( 3.1 \times 10^{-3} \) kg
Now, we can perform the following calculation:
\[ \text{Number of pennies} = \frac{\text{Weight of the Earth}}{\text{Weight of a penny}} = \frac{5.972 \times 10^{24}}{3.1 \times 10^{-3}} \]
To simplify this calculation, we can divide the coefficients and subtract the exponents:
\[ \text{Number of pennies} = \frac{5.972}{3.1} \times 10^{24 - (-3)} = \frac{5.972}{3.1} \times 10^{24 + 3} = \frac{5.972}{3.1} \times 10^{27} \]
Now we calculate the coefficient \( \frac{5.972}{3.1} \):
\[ \frac{5.972}{3.1} \approx 1.925 \]
Now, rounding this to a whole number gives us approximately 2, so we can write:
\[ \text{Number of pennies} \approx 2 \times 10^{27} \]
Thus, the answer in scientific notation is:
\[ \boxed{2 \times 10^{27}} \]