I love these special days. May the 4^th (Star Wars day) is cool, but still not as cool as ? day. But at least there is not a difference between U.S.Aians and others in this day. So a happy Star Wars Day to you. Now on to the physics.

First, I am going to talk about Star Wars and I claim that I don’t need to give a spoiler alert. If you haven’t seen the movie by now, do you think you are going to get around to it sometime soon? Anyway, giving away a plot element in Star Wars is similar to saying that Romeo and Juliet both die at the end. Oh! Did I just spoil that for you too?

Han Shot First

Let me start by looking at the original clip. Of course I am talking about the encounter between Han Solo and the bounty hunter Greedo. This is how it first played out in theaters during its 1977 release.

What is there to say? There isn’t really anything to analyze unless I wanted to try and explain why Greedo exploded — what is up with that? Maybe Greedo was carrying some super-awesome weapon that was unstable. Maybe his race has explosive skin. Perhaps Han shot some super-explosive projectile. Who knows?

However, this scene does say something about Han. It says he is a survivor. He will do what it takes to get through the day. It also shows that he has experience. He knows this isn’t going to turn out favorably unless he takes action. So, action he takes. Does it make him a bad person? How about bad-ass? For traditional viewers of Star Wars, this is a key character development. Han isn’t Lawful Good, that is for sure.

Poor Greedo. He never had a chance.

Han Shot Second

Here is the current vision of the Han-Greedo encounter as George Lucas would like it.

Note: this second video is not trivial to find. There are too many parody versions of the Han Greedo interaction.

The plan: look at the time between shots for both Han and Greedo. Oh, the first thing everyone should notice is what a poor shot Greedo is. He is just like 2 meters away and he missed? OK, so this video doesn’t really work too well for a full video analysis, but at least I can use Tracker Video to get the times of the different shots. Here is what I get:

A note about scale: not that it really matters, but I estimated 2 meters between Greedo and Han’s head. I used the x-direction as the line between them. Now, this line does not take into account perspective, so the velocity of the projectiles (or whatever they are) aren’t quite true.

The first thing I saw was that Han shot twice. Once just wasn’t good enough. If you go through the scene frame by frame, you will see two projectiles (they aren’t lasers) and two flashes from his gun. So, according to the above data, I have the following timeline:

• At t = 0.04 seconds, Greedo shoots.
• At t = 0.36 seconds, Han shoots his first shot.
• At t = 0.56 seconds, Han shoots his second shot.
• Greedo explodes.
• Han leaves a nice tip to cover the mess he made.

So, here is the real question: did Han have enough time to react to Greedo’s shot or was he going to shoot him anyway? How much time did he have? Well, there was 0.32 seconds from Greedo’s shot to Han’s first. Oh, but maybe Han reacted to Greedo’s pre-shot motions. However, Han would also need to move his finger to shoot. Let me just say that Han was a bit quicker, I will estimate this time to react at about 0.3 seconds. Is this reasonable? Maybe, it took 0.2 seconds for his second shot to come, so maybe he only had like 0.14 seconds to react.

What is a reasonable reaction time?

According to the Wikipedia article on Fast Draw, the best fast draw shooters can draw and shoot in 0.145 seconds. Zoom. Well, Han already had his gun out and didn’t need to draw it. I guess even 0.14 seconds is a possible reaction time.

Drat. I was hoping to show that there was no way Han could shoot a retaliation shot at Greedo unless he was some kind of Jedi. But maybe he is. Maybe he used his hidden and unknown Jedi powers to make Greedo miss. Maybe Han doesn’t even know he has these powers. Or perhaps that is just the kind of guy Han is. Perhaps this is what he was thinking:

“Oh, here is that Greedo guy again. I know what he is going through, pressure from Jabba the Hut to bring in someone and someone soon. Well, he is probably a good guy deep down. He won’t shoot me, I know he won’t. But you know what, I will keep my gun out just in case….
What?! Did he just try to kill me? And he MISSED? That is it Greedo, I am going shoot you. Shooting once isn’t enough for scum like you, so I am going to shoot you again. BOOM. You exploded. That’s odd.”

No one knows what really happened. Except of course, Chewbacca knows. He knows everything.

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