In episode 7 of The Secret of Skinwalker Ranch, an unfortunate cow dies of natural causes. The team of scientists on cast study security camera footage for clues. As the cow is laying there dying small black object whizzes by.
It's only visible for two frames on the footage, meaning it travels between the two positions in 1/30th of a second. Possible more, as security camera footage is often a low framerate. But let's assume 1/30th.
How fast is it going? That depends on how big it is, or to put it another way, is it small, or far away?
The cast members choose to interpret the object as being at the same distance as the cow is - mysteriously flying over it as it dies, presumably with some intent. I think it's actually much closer to the camera.
The image quality is quite good. Unfortunately the bit we are interested in is the two smaller trees on the right. You can just make out the cow laying underneath them
The best look we have of the object is when they zoom in. Here I've overlaid two frames. Frame 1 is on the left, and frame 2 on the right.
You can see that in frame 1 (right) it's a bit longer and flatter than frame 2. This possibly indicates it's slowing down or changing direction. With only two frames we can't tell if it is traveling in a straight line.
How fast? We can calculate this as a multiple of its length. It's hard to say exactly how wide it is, as it is so blurry and there's a little bit of motion blur, but we can make a reasonable crop, and then stack them end-to-end between the two positions:
The result is about 33 lengths.
So we know that it travels about 33 lengths in 1/30th of a second. so in one second that's 30*33 = 990 lengths per second. Let's round that up to 1000 lengths per second.
From this we can insert a guess at the size, and see what speed it gives us.
Speed = 1000 * (size in inches), giving you inches per second. To convert to mph we divide by 17.6. It's always best to verify conversion with Google.
So speed in mph = size in inches * 1000 / 17.6
If the size is 1/4 inch, roughly the size of fly, then the speed is about 14 mph
If it's a large bird-sized object at cow distance, then that's more like 12 inches, and the speed is 681mph
So it would seem the far more plausible interpretation is that it's a fly, close to the camera.
This interpretation is confirmed 100% simply by viewing footage of actual flies, like in this video
We can take two frames of this (about 28 seconds in), overlay them to get two fly positions - again 1/30th of a second apart.
Counting the lengths between them, using a similarly cropped version of the fly on the right.
33 again! A minor coincidence, given the resolution, but demonstrates that we are certainly in the correct ballpark.
It looks like a fly. It flies like a fly. It's probably a fly.