# MythBusters – a tree is 90% air

Dear Mythbusters. I hope you know that I think you are awesome. I know you are not scientists, but rather master robot builders. I respect that. I envy your robot-building abilities. Please forgive me for pointing this out – but even if a tree is 90% air, that does not mean a ball has a 90% probability of passing through it.

For those of you who are unaware, in the last episode of MythBusters, they explored the idea that a golf ball should pass through a tree 90% of the time. What if they were to test following alternative myth:

*A golf ball has a 90% chance of passing through something that is 90% air.*

Here is my test object:

It is a steel box with air inside. I did not give the dimensions, but you can imagine it would not be difficult to make this 10% steel and 90% air. What would happen if I hit a golf ball at this? I think there were would be a 0.000000000000000000001% percent chance of it going through (smaller than that – but I think you get the idea).

What is really important is the scattering cross-section, not the density.

1. #1 Starr Astronomer
October 13, 2008

Interesting post !! very well said. found your name in a comment on Bad Astronomy . And checked out your site .

2. #2 jason
January 21, 2009

The problem is really 3 dimensions versus 2, right?

They are viewing the scattered cross section in 3 dimensions, but not accounting for how in a cross sections those points form something that is much more dense.

3. #3 lol
November 2, 2009

another thing, when they said it was a 90% chance of a ball passing thu(let’s say it was true)it would not mean that 90 out of 100 balls would have to pass, it would mean EACH ball would have a 90% chance, that means you could have 100 balls pass the tree or 100 balls not passing it, get wat i meen?

4. #4 marco
November 30, 2011

I came upon this post while looking deeper thoughs about that particular experience.
I’m not such a pure scientist guy…I’m a management engineer to be clear but the first thing that came to my mind is:

You can’t shoot shoot with the same angularity with a cannon versus a tree…in this way ur simply demonstrating that u found a hole in the vegetation ….not that the tree is made by 90%of air or whatever…

Pure statistic thought …