The order of magnitude is correct: https://www.wolframalpha.com/input/?i=(diameter+of+blood+cell+in+meters)++*+(size+of+solar+system+in+km)%2F+(size+of+earth+i

The order of magnitude is correct: https://www.wolframalpha.com/input/?i=(diameter+of+blood+cell+in+meters)++*+(size+of+solar+system+in+km)%2F+(size+of+earth+in+km) https://www.wolframalpha.com/input/?i=(diameter+of+blood+cel... (convert erythrocyte | diameter to meters)×(convert diameter of Neptune's orbit to kilometers)/(convert Earth | average radius to kilometers) = 11 meters edit: Of course you could argue with this calculation in all kind of ways - widths vs volume vs mass ... but I think for such a silly analogy this is good enough to say: It is not totally unreasonable.