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Tuesday, February 16, 2010

Psych FAIL.

I love the show Psych. For those who don't know the show, it's about a guy named Shawn Spencer (actor James Roday) whose uncanny powers of observation allow him to convince the Santa Barbara Police Department that he's a psychic. He's adorable, eccentric, and totally awesome in mostly every way. But I found myself yelling at my television (ok, my computer - I watch it on Hulu every week) while watching the most recent episode. I was really, truly pissed.

Let me explain. In the show, Shawn and company were tracking down evidence for a murder that was committed five years earlier to prove that the guy convicted for the killing is innocent. Shawn realizes that the scene, as it was told by the cops, couldn't be right - the dead guy had to have been shot from a different angle, meaning that the bullet would have flown out the window, explaining why the investigators never found it. They then set out to find the missing bullet which is likely lodged in one of the many trees just outside. Despite their best efforts, they can't seem to find the bullet hole, until Shawn's best friend reminds him that Shawn is looking at the wrong height - it's been five years since the shooting, after all. Low and behold, when they look a little higher, they find the bullet, but are chased off by gunfire before they can pull it out to find out who the real killer was.

Do you see it? Do you know what had me yelling at the screen?

No, it's not the odds that the bullet would be visible from 30 or so feet below five years later (though, really?). It's that the bullet somehow magically moved up a yard or two in five years. In fact, I'd be upset if it moved up in a hundred years. Let me explain.

Though it might seem intuitive that something placed at a certain height on a tree would move upward as the tree grows, that's simply not how trees do it. If it did, that would mean the tree is growing from the bottom, pushing the older tissues upward over time. Trees don't grow from the bottom, they grow from the top and outwards. What do I mean by that?

As a tree ages, it adds tissue to a limited number of places called meristems. These specialized areas of tissue occur at the tips of roots and branches as well as in the trunk of the tree, and are full of what you might call plant stem cells. They can differentiate to become any kind of plant tissue, which is exactly what you'd need to have wherever a plant needs to grow. The top of the tree, where a special meristem called the apical meristem occurs, is where height is added by these special cells dividing and differentiating.

While there are meristems in the trunk of the tree, they don't expand vertically, they expand horizontally. Once trunk tissue is laid down, it doesn't move upwards, only outwards, as new layers of secondary xylem and phloem (the vascular plant tissues that make up wood) are added. This is where tree growth rings come from - the yearly addition of layers of tissue to the trunk of the tree. It's why lovers can carve their names into a tree and come back and find the scars they created 50 years later in the exact same place, though the tree might be a little wider and taller than they recalled. It also means that no amount of tree growth would make a bullet lodged at a given height in the trunk move upwards.

What would actually happen to an object stuck in a tree over time? Something like this:

The tree trunk can actually grow around an object, so if anything, Shawn's missing bullet would have been deeper embedded and harder to see, not 5 feet higher up.

Am I strange to be so upset by this? Eh, maybe. But it bothered me that they could get something so small and simple wrong. I know, I know, it's just a TV show, but it's a pretty big biological mistake on the writers' part. If trees everywhere could yell at them, I'm sure they would.

6 comments:

Tim said...

I'm right with you - when I read the words "wrong height", I slapped my forehead and let out an "aagghh!"

Stephanie B said...

Now you know why I can hardly watch most "science fiction". My head would be flat on top from the slapping if I didn't just stop watching most of the time.

Armageddon, for instance,where we're dodging asteroids/cometary (which at head-on would be 28-78 km/s - good luck dodging material coming at 20 times faster than a high speed rifle bullet) and had an asteroid rover equipped with a MACHINE GUN - perfect for your pressurized environment. Not that it would have survived going through a cometary field.

Don't even get me started on Mir.

*sigh*

Spartezda said...

YES. Thank you! I gibbered for at least five minutes after seeing that part, complete with arm-waving and hopping up and down. Such an elementary fact, and yet...

Oh, Psych.

Anonymous said...

This was also the riddle at the center of an Encyclopedia Brown book, but I can't remember which one...

Looks like another blogger was annoyed too!
http://talkofsummertime.blogspot.com/2010/02/jonah-day.html

Mason Posner said...

I love Psych as well, and when I saw the title of your post I had to move my viewing of this episode up in my DVR queue. I kept waiting for something that would drive you to FAIL the episode, which was fun.

Is it OK to bend biology for a great plot twist? They needed a tall tree for Spencer to climb, and slide down, and the sap clue was good. Probably still a bad idea to spread arboreal misinformation. Or are we just to sciency?

Penguin collector: still keep the wounded... said...

LOL! Great rant. You must see Myth Busters (might be one word)! Great show.

I wonder if all of the writers of that show were that stupid about how trees grow or if they thought viewers are?

To be honest thought, I think most Americans would get it wrong.

Also, curious about possible altitude loss and how far before that becomes a factor for a bullet. Moreover, after passing through a person, could it travel 30 feet and embed itself into a tree?