Question: my brother says that if you take all the blood cells out of your body it would go all around the world twice true or false if true how is it possible

Eoin McEvoy answered on 6 Mar 2018:

There are more than 20 trillion red blood cells in an average adult body. These cells have a diameter of around 0.006 mm. So, if we lined them up end to end, they would cover a distance of ~ 20 trillion x .006 mm = 120 (x10^9) mm = 120,000 km. To go around the world, you need to cover a distance of around 40,000 km.

Therefore, all the red blood cells in the body lined end to end could go around the world 3 times!