Real Lightsaber Theory

I’ve been thinking about this for a while, so in honor of the final Star Wars movie release, I decided to sit down and do the math on this. The concept I had if one were to attempt to make a real life lightsaber (potentially non-lethal) is basically this:

• Create a device which only outputs light or laser a specified distance.
• Rapidly pulse said light source to appear continuous to a human eye.

In order to accomplish this, one of 2 things (or both) would need to be done.

1. Activate light only long enough for it to travel the desired distance.
2. Slow down the light’s speed enough to restrict the distance traveled.

The basic concept behind slowing down light is by passing it through another material, such as water or glass, but that’s not the concept I’ll be digging into. I’ll be attempting to come up with a theory to accomplish task #1 using pulsating light. Some of the factors to consider here are:

• Speed of Light
• Speed of a computer processor
• What rate is visible by the human eye
• Thickness of the light/beam

First, in order to know how long the light must be activated, we must know the speed of light. Space.com says that the speed of light (in a vacuum) is 186,282 miles per second. First of all, that’s ridiculously fast, so shout out to God and Light. You both are amazing (and often referred to as one in the same).

Now that we know how fast light is, we need to figure out how “long” the lightsaber should be. Star Wars Fandom Wiki reports Obi Wan’s Lightsaber [blade] is 4 feet 9 inches. I would assume that if this was actually possible, a real lightsaber blade would have an adjustable length (like Luke’s) by simply adding a control to speed up or slow down the pulse.

All we have left to do is a little math. If we want something traveling 186,282 miles per second to only travel 57 inches, first we’ll convert MPS to inches. There are 63,360 inches in 1 mile, so 186,282 * 63,360 = 11,802,827,520 inches per second (that’s billion for those counting at home). So for each second, light will travel over 11.8 billion inches per second. So how many seconds will it take for light to go 57 inches? Time for some more math.

The formula here is to determine what fraction of 1 second equals 57 inches, where 1 second is represented by the distance light travels in one second (in inches), and the fraction will be represented by X:

X * 11,802,827,520 = 57
X = 57 / 11,802,827,520
X = 0.000000004829351 seconds

To make this number somewhat easier to read, that’s 4,829,351 preceded by 8 zeros, putting the 4 in the billionths decimal place. Now, accuracy is super critical here. We couldn’t exactly round up since the slightest change would result a drastic size difference of our lightsaber. So maybe a better calculation is find out the time it takes light to travel 1 inch. That would make calculating for a dynamic length lightsaber a little easier. This is also much easier math. We’ll start by converting to a smaller measure of time.

1 nanosecond = 1 billionth of 1 second
11,802,827,520/1,000,000,000 = 11.80282752 inches per nanosecond
1/11.80282752 = 0.08472546077 nanoseconds

Based on these calculations, light travels 1 inch in 0.08472546077 nanoseconds, or 84.72546077 picoseconds.

1 picosecond = 1 trillionth of 1 second

Now we’ve got some numbers that are a little easier to work with. For our final formula, we’ll take the time it takes light to travel 1 inch and multiply that by the desired length of our lightsaber, in this case, Obi Wan’s 4′ 9″ (57 inch) saber. Hopefully our number matches our original calculation.

0.08472546077ns * 57 = 4.8293512639ns
84.72546077ps * 57 = 4,829.35126389ps
or (our original calculation of) 0.000000004829351 seconds

It does! So in theory, if we were able to activate light for about 4.83 nanoseconds (or 4,829.35 picoseconds), it should only travel ~57 inches. That’s fantastic!

But what about the human eye? Will the eye even detect any light for 4.83ns? How fast would the light need to pulse? What about the blade diameter? Is there a laser thick enough to appear as thick as a lightsaber? So many questions that I don’t have time to answer right now. I hope to pick this topic up again sometime soon and answer all these. For now, I just wanted to get these thoughts and calculations jotted down. That’s all, thanks for reading!