The Threshold of Human Sensation
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What is the smallest thing a human can actually feel?
Hello and welcome to the Rest is Science. I'm Michael Stevens. And I'm Hannah Fry. And I was just really shaking my camera by moving. Look at that. Whoa.
Michael.
Speaking of feeling things, We're going to be asking, what's the smallest thing you can feel? And whether or not we arrive at an answer, I don't know. I've got a bunch of notes here. I did a bunch of research, and this is gonna be a look into my mind just as much as it's a look into human sensation and perception.
Let's clarify it. Smallest thing you can feel. We're talking about physical sensation, not an emotion, right? We're talking about
Every sense of the word feel. Ooh because I can't just leave it at what I mean is of the classic five senses. It's like, no, we're gonna go all over. We're gonna really mold what this question might mean. What does it mean to feel? What does it mean to touch yourself? That is a huge question in phenomenology. I still don't understand their approach to it, but we'll get to what I mean by that later. Okay?
And look at that, look at that Michael, we've got the title already. This episode
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I think the first place I wanna start in is about me. I've been trying to Learn an answer to this question for at least six years. My daughter was a little newborn baby when I first started trying to write a script about this. And I found a whole lot of answers with like no source. Okay. If you go to the Wikipedia page for sense, they've got a human sensation section with the whole like chart that shows the absolute threshold of human sensation for different. Senses with absolutely no sourcing, except for one article about humans' ability to make decisions with probability. It doesn't mention sensation, perception, thresholds, anything. Like I don't even know where these numbers came from. But that's been copied all over the internet.
There are all these images that you can find that do this. I'll read to you what it says. And then we'll dive into what the actual science tells us. The absolute threshold of our sense of hearing. Is this just straight from Wikipedia or literally dozens of other websites that have turned this into their own little infographic? The quietest thing we can hear they say is the ticking of a watch twenty feet away in an otherwise silent environment. That's not like an amount of decibels or an amount of energy in the pressure wave. It's just like a very Intuitive physical object thing.
I'm there. I'm there.
A watch ticking twenty feet away. What kind of watch? They don't tell us.
Well, it's not w not your one that just says now on it.
The I'm not even wearing a watch today, but my the the one I've been wearing, it it is loud enough that if it gets really quiet here in my office, I hear it. I almost have to take it off 'cause I just can't stop hearing it. For vision, they say a candle, a single candle flame thirty miles away on a dark and clear night.
Thirty miles away.
Thirty miles away, on a clear dark night, a single candle flame can be seen. And that's like the threshold. That's the bottom.
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Chapters
8 chapters
1
What is the smallest thing a human can actually feel?
0:01–6:23
2
How low can our hearing threshold go – can we hear a single air molecule?
6:23–13:28
3
What is the minimum amount of molecules needed to taste something?
13:28–20:03
4
How sensitive is our sense of smell compared to taste?
20:03–26:29
5
What is the smallest physical stimulus our vestibular system can detect?
26:29–33:02
6
Can a single photon trigger a visual response in the eye?
33:02–39:54
7
How do emotions fit into the discussion of the smallest perceivable sensations?
39:54–46:48
8
What conclusions do the hosts draw about the limits of human perception?
46:48–52:13