A couple of weeks ago, there was a question about Shields on the Dune subreddit, and I thought this would be the perfect time to share the article I’ve written on the topic.

Except - I had to realize - that said article did not exist. Yet.

So here we are, talking about yet another application of the Holtzman field.

Just like prana-bindu is the go-to explanation for any superhuman ability in Dune, the Holtzman effect is the thing that makes every piece of advanced Imperial technology possible.

Fold space for interstellar travel? Holtzman.

Float the Baron's rotund bulk around? Holtzman.

Stop a sword or a gun? Holtzman.

Need your spice coffee at the perfect temperature? Also Holtzman. Probably.

Herbert doesn’t just skip any kind of explanation; he’s explicit about how the Holtzman equations simply cannot be understood - even after thousands of years of research. All we know is that they work.

Of course, this is a recurring theme in Dune - the science bits only being there to enable the fiction.

But let’s see what crumbs of information we can gather from the six original books.

The most memorable application of shield technology is the personal shield.

When you activate one, you'll feel a "crinkled-skin tingling" at your forehead and down your back.

And if your shield comes in direct contact with another, prepare for crackling energy, electric tingles along your skin, a blue glow at the points of contact, and the sharp smell of ozone.

(If you’ve never smelled ozone in your life, it’s a very distinct smell. Personally, I’d liken it to burnt electronics but with the almost suffocating sense you get from chlorine.)

Maybe the most interesting “rule” of personal shields is that they’re only blocking fast-moving objects.

The shield is what makes swords relevant, and the selective permeability is what determines the style of swordfighting. Victory belongs to whoever can execute a slow, controlled thrust while their opponent is caught off-guard by feints and misdirection.

Or to those who bring specialised weapons, like the stunner.

And while fast strikes may be repelled, some kinetic energy still transfers to the wearer. A powerful enough impact could kill through blunt force trauma without ever breaching the field.

Extended combat presents its own dangers: the air inside a shield bubble can grow stale during intense fighting because oxygen consumption outpaces the slow molecular interchange at the field boundary.

As a sidenote: this is part of the reason the Baron Harkonnen survived Leto’s assassination attempt: the Duke blew the poison cloud too fast.

And this also explains why sounds take on a "shield-filtered flatness" - since air can’t move freely, sound cannot move freely either.