universeThe universe is an amazing thing. While you are “sitting still” reading this post, you, me, and everyone else are hurdling through space at an unfathomable speed. This is almost as amazing as the fact that we, for the most part, don’t even notice that we’re doing it. The Earth rotates 1,600km/h at the equator, which goes down to 0 at the poles, for an average of 800km/h across the planet. Our orbit takes us around the sun at 107,000 km/h and our solar system’s orbit around the galaxy has us going about 792,000 km/h. On top of that our solar system kind of meanders about at 70,000km/h in our section of the Milky Way. On top of all of that, our galaxy’s movement in relation to the background cosmic radiation has us cruising at a cool 2.1 million km/h through the universe. All tolled, we are moving through space at about 3,000,000 km/h OR 853 km/s OR 0.3% the speed of light. That is damn fast.

What the hell does this have to do with ghosts?

Glad you asked.

Ghosts are ethereal entities, lost spirits, that are stuck in our realm of the physical plane. The myths surrounding ghosts vary considerably, but one thing that most stories agree on is that they are completely non-physical. Gravity does not affect them, they can fly, float, hover, and traverse over any terrain in any direction. Further, being non-physical, barriers cannot stop them. Ghosts can go through walls, floors, any type of matter whatsoever. It’s true that some myths talk of ways that we can restrict a ghost’s movement, but it’s always through a kind of magic or spiritual power. Strictly physical forces simply have no effect on a ghost. Which brings us to a bit of problem for spectre spotting.

All that movement I described at the beginning of this post are due to purely physical forces and would not affect ghosts. Just as the momentum of, say, a baseball bat being swung at the head of a ghost would pass through the spirit, so would our spinning planet. And just as a ghost can fly because gravity doesn’t pull it to the ground, the gravity of our sun will do nothing to keep the ghost in orbit. Thus, if a ghost appeared right in front of you, it would instantly disappear. Or rather, we would fly from the ghost at 3 million km/h while the ghost would be stuck in space, right were it appeared, wondering where everyone went. Meanwhile, our planet, solar system, and galaxy would be carrying us further and further from the bewildered phantom.

You might think that if a ghost was conjured directly in front of you, you might catch the merest glimpse of it before we rocketed away from it on our terrestrial space vessel, but let’s do some figuring. The fastest an eye can recognize any kind of visual stimulus is in 13 milliseconds. Any less, and we simply are not physically equipped to register anything at all. And using our earlier figure of 853km/s (853 m/millisecond) we can determine that ghost appearing right before you would be about 11km away in those 13 milliseconds it would take you to even notice that there was anything to look at.

Now, most ghosts are described as being mostly anthropomorphic, their form matches that of the mortal coil they used to be attached to. If we were to take, as an example, the ghost of a rather large person that is 2m tall (6’7”) and 0.5m wide (1’8” shoulder to shoulder), it would appear as such if it was standing a meter in front of you. However, in those first 13 milliseconds, it would be 11,000 meters away, meaning it would appear 1/11,000 the size.

That is to say, it would look 182 micrometres tall and 45 micrometers wide.

How small is that? I considered making a picture showing the exact size, but I ran into an issue. Screens typically display 72 ppi, that is it requires 72 pixels to display a one inch line. If I were to draw a line on your screen 1 pixel wide and 4 pixels high, it would be almost 8 times larger than the ghost. The image of the ghost is too small to render accurately on your screen.

So let’s try an example that might be a bit more accessible. The cruising altitude for large passenger aircraft is about 35,000 feet, which converts to 10.7km – pretty close to our 11km figure. And so, trying to see a ghost would be like trying to see person on the ground while flying overhead at max altitude in a 737. And you only get one instant to do it. Not gonna happen.

But wait! – I hear the most pedantic of you cry out- I might not register that I see the ghost, but it would STILL be in my visual field for that brief moment. That is, the information I receive from my retina would be ever so slightly different than if the ghost had not been there, even though I would be consciously unaware of this infinitesimal difference. So in an extraordinarily generous definition of “seeing”, it is still technically possible to see the ghost!

SFHNo no no, little Timmy. You see, up to this point in our thought experiment, we’ve been using a convenient, yet completely unfeasible best-case scenario. We’ve been talking as if the ghost would move away from us in a straight line. But if we recall how got the speed of which we would be travelling away from the ghost, we see that it involves spinning in an orbit within an orbit, each stage with it’s own version of wobble, tilt, and/or wandering. Our path follows a 3D spirograph from hell. Before the 13 milliseconds we physically require to see anything could elapse, not only would we be kilometres away, we would also be turned around and no longer facing the apparition. It is completely impossible to see a ghost.

Now I have a small confession to make. While it has been fun debunking any and all tales of spectre sightings, house hauntings, and apparition appearances in one fell swoop, the arguably more important consequence of this post is thus: it has provided a solid justification for sharing this wonderful song from Monty Python’s ‘The Meaning of Life’. You’re welcome.