There room a the majority of soft points out there: cats, infants, expertly-laundered sweaters. If there to be some sort of omniscient softness guide, ranking every item in the world in stimulate of softness, these 3 items would for sure land in the direction of the top. That course, together a guide would it is in very challenging to assemble: together softness is at least partly subjective, you’d require teams that volunteer softness-assessors to handle each item, and also some fair/statistically sound means of averaging all your reactions. And at some point, among these softness-assessors would surely asking why exactly they’re doing any of this in the an initial place, lowering morale and also jeopardizing the totality project. I m sorry is why, because that this week’s Giz Asks, we’re maintaining things simple: 4 materials scientists, representing no one however themselves, weighing in ~ above their an option for the pure softest thing.

You are watching: What is the softest thing in the world


Charles Dhong

Assistant Professor, products Science and also Biomedical Engineering, college of Delaware

At first, the seems choose finding the “softest point ” would be straightforward. You could go to the hardware store and buy an assortment that “soft” materials. Perhaps you would begin with rubber, relocate onto marshmallows and foams. The difficulty with this strategy is the it cannot tease personally what world are law to recognize the soft of an object. In fact, you have the right to make 2 objects do from the same product feel more difficult or softer depending upon its shape. Together an example, human being hair is often taken into consideration soft, yet it is made from keratin, the same product as in our fingernails and also the horns that a rhinoceros. Creating something that feels soft is related to what the thing is made from, however there space some subtleties.

Recently, rather of perceiving a solitary material residential or commercial property (most civilization might guess “elastic modulus”), we showed that people use a mix of 2 physical cues to recognize the perceived softness of an object. These cues are figured out in component by material properties and in part by the form of the object. As soon as you touch an object, 2 things occur to your finger. First, her finger pushes, or indents, into the object and the object likewise pushes into your finger. Second, the object spreads throughout your finger through a certain contact area. This mix of indentation and contact area on her finger develops the physics basis for perception of softness. So, any type of object which generates a large indentation depth or call area will feel “soft.” The tardy of soft is also not solely identified by the physics the materials. That is likewise informed by just how our brains procedure information. Also though our fingers are soft, we uncovered that people currently account for the soft of their own fingers. In various other words, ours models were much more accurate as soon as we pretended that the finger was as rigid as a rock.

We room excited in ~ the possibilities and feasible illusions that these straightforward studies in soft revealed. We additionally think the there space careful and methodical ways to uncover our tactile limits, such together what is the softest and hardest object we deserve to feel. These proved that there room multiple paths to managing the perceived softness of an object, which can be beneficial in future virtual fact applications. It likewise reveals exactly how our mind is processing and also synthesizing tactile information.


“When you touch one object, two things take place to your finger. First, her finger pushes, or indents, into the object and also the object likewise pushes right into your finger. Second, the thing spreads across your finger v a details contact area. This mix of indentation and also contact area on her finger creates the physical basis for perception of softness. So, any type of object which generates a huge indentation depth or call area will certainly feel ‘soft.’”

Anthony Rollett

Professor, products Science and Engineering, Carnegie Mellon University


When us talk about softness, we usually begin with the term ‘compliant’—which is once you push on a piece of material and also it offers easily. In other words, girlfriend can change its shape without needing lot force. That’s the engineer’s an interpretation of soft. But there’s more to it 보다 that, due to the fact that ‘soft’ is as much a sensation together it is an design concept—what’s also important is just how the material, the substance, feels to you. Yes a method in which something have the right to feel soft it is not fully independent the how easily it gives, or how conveniently it changes shape. An additional dimension of softness is how the material encounters heat, or how an excellent an insulator the is. And that can take different civilization different ways. However for the most part, soft is usually linked with substances that space relatively good insulators—blankets, because that instance, have tendency to feeling soft, partly because of the method they answers mechanically, but also partly due to the fact that they nothing transmit or conduct heat very easily. Whereas many gels feeling a little bit clammy, which we don’t exactly associate with softness, also though they have actually a the majority of ‘give.’

So ns think something choose an eiderdown duvet would certainly be among the softer things around, and that’s partly since it has structure in ~ multiple scales, and this is, i suspect, a multi-scale problem—meaning that the softest materials, or the products that provide you the impression of gift soft, frequently have multiple scales to them. You have the right to make a carpet out of other that’s fairly compliant, but unless you’ve obtained a product like soft structure on peak which can likewise give way easily, then it’s no going come feel an especially soft. Yet the multi-scale framework of one eiderdown duvet allows it come impart part sensation to your skin while in ~ the exact same time giving way extremely easily, and also as it doesn’t conduct heat very easily yes a particular element of warmth in it that us associate with softness.


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“I think something choose an eiderdown duvet would certainly be among the softer things around, and that’s partly because it has actually structure at multiple scales, and also this is, i suspect, a multi-scale problem—meaning the the softest materials, or the products that offer you the impression of gift soft, often have multiple scale to them.”

Jana Grcevich

Jana Grcevich is an astronomer and astronomy outreach coordinator at Columbia University and also co-author of Vacation overview to the Solar System.

I was asked what the softest product in the people is, however that is also limiting. I’d favor to answer, taking part liberties, a different question: what is the softest planet? us now recognize of end 4,000 planets orbiting approximately other stars. This “exoplanets” represent just the small portion that we have been able come observe. Many more, perhaps thousands of billions simply in our own Milky way galaxy, await ours discovery. What we have learned from finding them is over there is a staggering diversity that worlds. We have found worlds made that rock choose the Earth, human beings with two suns, and worlds likely entirely covered in lava. We’ve likewise found a grasp of bizarre, “soft” worlds, a form of exoplanet called a “super-puff.”

The light any exoplanet reflects or offers off is usually also feeble for united state to see contrasted to the blinding irradiate of the star it orbits. Instead, we “see” it when it orbits in front of the star indigenous our suggest of view, blocking several of the star’s irradiate in what is called a “transit”. By looking at exactly how much the the star’s irradiate is blocked, we find out that over there is a planet there and likewise how large across that is. With a various method, we can find their mass. Together it orbits, it gravitationally tugs the star towards it, i m sorry we see as motion in the star toward Earth, and also then away, in a regular pattern caused by the planet’s orbit and also revealed in slight transforms in the color of the star’s light due to the doppler shift. The strength of the tug gives us the massive of the planet. The mass combined with the size provides us density, and those planets with exceptionally low densities, close to one tenth that of water, are called super puffs. They appear to be nearly the dimension of Jupiter, yet these planets only weigh 1% what Jupiter does.

The earth’s mossy hills and sandy beaches have the right to be soft in your way, but the weird barely-there softness of super-puff planets come native their exceptionally low densities. A straightforward experiment the a child can do speak you something around the thickness of everyday objects—does the sink, or does that float? absent is lot denser than water so it would certainly sink, ice floats. In our very own solar device Saturn has actually a density less 보다 water, so you could imagine the in the “floats in water” category of things. This odd planets have actually densities also less 보다 that the ice, much more like the density of styrofoam or cotton candy!

Just together gas bubbles climb in water, a planet made of largely hydrogen and helium gas has a much lower density than a rocky world. Saturn’s density is a little higher than the gas that makes it up because the crushing heaviness of the top layers of gas compress the persons deeper down. So finding a planet with a density close to cotton candy? Astronomers to be shocked: that’s simply unimaginably weird. Exactly how does it not get compressed to greater densities under its very own weight?

The mystery of this planets is however to be solved, however there are plenty of theories. Maybe the planet’s environment is heated by the star, i m sorry fluffs it up, and gas deserve to escape indigenous the planet’s gravity into room over time. Possibly dust flowing out of the upper layers of the planet’s environment inflates our estimates for the size. Or maybe our assumptions around the densities room wrong, and also what we’re yes, really seeing are planets v opaque rings at an angle which blocks extra light from the hold star, inflating our estimate of the size. Luckily, astronomers have actually plans to search for much more super puffs, check theories for how they form and evolve, and also learn just how soft super-puffs yes, really are.


“We’ve additionally found a handful of bizarre, ‘soft’ worlds, a kind of exoplanet dubbed a ‘super-puff.’”

John E. Hayes

Associate Professor, and also Director, Sensory evaluation Center, The Pennsylvania State University

Softness is basically a tardy (a percept). This implies it occurs in the brain, which in turn method that it can only be measured through a human assessor. With any type of human sensory system, there are borders of detection, both in ~ the high end and also low end, and outside this limits, we cannot call (perceive) a difference, also if a maker or tool might. Consider the hardness of cut glass and also a cut diamond—when we touch them v our fingertip, they each depress our skin (and the mechanoreceptors in our skin) by approximately the same amount, so we cannot tell castle apart, also if a lab tool could.

Of course, measuring things with world can be quite tricky, due to the fact that when civilization use a word prefer soft, its definition can vary considerably in the context of use—this ice cream cream is softer 보다 that ice cream cream method something very different than this t-shirt is softer than that t-shirt. In the an initial case, soft is some mix of meltability and force required to scoop if in the second, it might refer to friction knowledgeable by the hand as we traction it end the fabric. In yet an additional context, softness may be some role of compression force and also bending force. One branch of experimental psychology (psychophysics) has actually been working for 150+ years on how ideal to measure sensations quantitatively.

These kinds of nuances can also be hugely prestige for customer perception and product acceptability. Because that example, once I watch a brand-new hoodie in the store, the an initial thing I perform is stick my hand ~ above the inside to see how soft the sweatshirt is. If the isn’t very soft and cozy, I keep looking, no matter how good it might look. Accordingly, understanding and also measuring complicated sensations have the right to have important financial consequences. Numerous of the foods and also consumer products you use each day have been optimized by sensory and consumer scientists using classical and also applied psychophysics come quantify the emotion they provide.

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“Of course, measuring things with civilization can be fairly tricky, because when people use a word choose soft, its meaning can vary considerably in the context of use—this ice cream is softer 보다 that ice cream cream way something very different than this t-shirt is softer than that t-shirt.”

David Needham

Professor, mechanically Engineering and Materials Science, duke University

First, what is softness? Watson, that Crick and Watson fame, to be reported to have actually once said: “if you desire to recognize depression, research happiness.” So, i say: “if you want to understand softness study hardness.”

So: is softness just a reduced level of hardness? indigenous an engineering perspective, hardness is measure up by how a product responds to an used force or stress. There are number of standard hardness scales, favor the Mohs hardness scale, i beg your pardon consists, follow to this definition, “of ten mineral arranged in boosting order that hardness such the each mineral will scrape the one on the scale listed below it, but will not scrape the one above it.”

Could you execute the very same for softness, whereby one product moves or bends an additional material?

Could girlfriend take, say, a feather, and also see if that will relocate a wool fiber?

There room a lot of of really soft material in every-day life, choose a wool fiber, cotton balls, jello, feathers, or flimsy magnetic tape. However what around a functional material that in reality supports life ~ above the planet?

One the the softest functional materials known is the membrane that surrounds every cabinet on the planet. In my research study of the past 40 years, we attend to phospholipid membranes. These are, in fact, the membranes the surround every cell on the planet. They space made that lipid bilayers and also are only two-molecules thick (thin). Using special methods that rental a glass micropipette that can be manipulated in a microscope chamber containing aqueous solution, and also to which we can apply very gentle optimistic (blow) and aspiration (suction) pressures, we have actually actually measured your softness. Softness, in this case, is what it takes come stretch and bend the membrane.

This softness has actually values in between that of a liquid and also a gas. How soft is a liquid? exactly how soft is a gas?

Dip your finger right into a glass the tepid-warm water and gently stir; what execute you feel? Now, push your hands the end in prior of you; what perform you feel?

So this two-molecule-thin lipid bilayer product is softer than a liquid and also a tiny bit harder than a gas! Right… it’s that soft!


“One the the softest sensible materials known is the membrane that surrounds every cell on the planet.”