The science of…ghosts?

by Simon Jones

G-G-Ghosts?

Wait, what, science?! Well, there have been some explanations put forward for why certain places feel haunted, and why people are more likely to witness paranormal sightings in such areas.

The underground vaults at Edinburgh Castle are a good place to start. In these long rooms, sound echoes from one end to another. This causes the vaults to act as a resonance tunnel, and this makes the volume of the sound and the energy in the wave increasingly loud.

edinburgh castle

Photo: Kim Traynor CC-BY-SA

This creates a very low frequency soundwave, infrasound. In fact, your ears can still sense it even though you don’t consciously hear it. It is this which causes confusion in the brain and creates the feeling of dread and panic.

But infrasound also affects other body parts.One reported instance of this was by an engineering designer at Coventry University (he was inspired to do this job by one of our engineering shows, rumour has it). This person, Vic Tandy, also noticed the aforementioned depressing and ‘cold chill’ feeling that comes with infrasound, as well as a shortness of breath and even ghostly visions; the feeling that somebody was watching him out of the corner of their eye.

It transpires that the infrasound frequency, at around 18.9Hz (or 18.9 vibrations in a second – the lowest human ears can hear is 20Hz or 20 vibrations in a second), affects us much more than we may think. We’ve looked into extreme sounds before for our show research, but even this is new to us. NASA also noted this frequency has an affect on the eyeball, which causes it it vibrate and effectively ‘smear’ the incoming signals sent to the brain. The result is usually seen as bright orbs in the corner of the eye, or as shimmering. Our eyes are more sensitive to movement than they are to colour, so the latter is more likely.

To test this phenomenon, Tandy set up metal sheets in clamp stands, which vibrated of their own accord. This led him to realise that there was some ultra low vibration occurring, and once the source was tracked down (to ventilation fans), they were able to lighten the mood a little in their research lab. We’ve actually worked with Vic Tandy when designing our Sound at the Extremes show; he told us about his experiences first hand and gave us some fantastic angles on talking about sub-human sound!

Try it yourself…

Although using a very low frequency speaker could re-create this body bending effect, we don’t recommend it! However, resonance can be used in various other experiments. One of the our science made simple favourites is the straw oboe, also known as the musical straw.

musical_straw

Images: science made simple © all rights reserved

It’s incredibly straightforward to make; simply get the non-bendy part of a drinking straw and cut two V shapes into one end. Then blow through the straw with your lips pursed, and this will create a vibrating feeling and some noise.

In our sound shows we take this once step further and use really long straws so people can really see the effect of resonance. Here is a photo of Zoë and myself performing this at a European physics conference in Germany.

musical_straws

Photo: science made simple © all rights reserved

Here we are cutting away the end of the straw and making it shorter, which makes the pitch go higher and higher. It’s a very simple demonstration to show resonance. And just look how much fun we’re having.

So, how long does a straw need to be to make an infrasound vibration of around 18Hz? Well, the frequency of a wave is directly proportional to its wavelength, and in this case the wavelength is determined by the length of the straw. So, text books out:

halloween blackboard

To achieve the bitter and deadly panic of resonance from a straw oboe, we’d need one which is 9 meters long! That’s a lot of straw and a lot of blowing! If you do try give this a go, let us know how you get on.

So here’s just one example of something spooky that can be explained with science! Although we can’t claim to be able to explain all ghostly and ghouly sightings with science, that’s where we like to start looking for a possible explanation! Happy Halloween!

 

Posted in Exploring Science, Physics