First, calculate the total number of seconds in a day: Seconds in a minute = 60 Minutes in an hour = 60 Hours in a day = 24 Total seconds in a day = $24 \times 60 \times 60 = 86400$ seconds. To find the order of magnitude, express the number in scientific notation: $86400 = 8.64 \times 10^4$. For a number written as $N \times 10^p$, where $1 \le N < 10$, the order of magnitude is $10^p$ if $N \sqrt{10} \approx 3.16$, we round up the power of 10. Therefore, the order of magnitude is $10^{4+1} = 10^5$.