Thanks to a very interesting Q by TTT in a CAFE thread, I started wondering just what a sixth physical sense would be.
Some other range of EM?
A galactic awareness of time/space?
My imagination falters after that. Help us!
Being able to sense when people are thinking of you.
Being able to tell when somebody is attracted to you.
Gaydar.
Being able to tell which way is north.
Metal detector.
Being able to see peoples’ auras.
Precognition.
Echolocation (like dolphins).
Sense electrical currents (like sharks can).
IR sensors/vision (like pit vipers).
Ability to locate opening cans of food from miles away (like my cat).
Spider-Sense?
Well, looking to the animal kingdom, there’s the magnetic directional sense that some birds supposedly have. I’ve heard it claimed that humans might have some vestige of this as well, involving traces of iron in our noses or forebrains.
Sharks and some related sea creatures apparently have a sense of electromagnetic fields that allows them to detect living creatures in murky water. On the down side, it sometimes induces them to gnaw on electrical cables…
Elephants and whales, and possibly other animals, can communicate via “infrasound” – sound at such a low frequency that it’s more felt than heard. Humans can sense some such sounds in a limited fashion, but it’s arguably a still a different sense in the same way that plants and microorganisms can sense light without really being able to see.
Along that same line, one might argue that the highly acute olfactory sense of dogs and some other mammals is so highly attuned that it’s a sense above and beyond what we comprehend as “smell”.
tele-kinesis.
How about the lateral line system, like the one that fish have?
We could have an expanded sense of vision, allowing us to see wavelengths of light in the UV range. Lots of insects pull this one off without a problem.
Well I think there are lots more than 5 senses anyway… I think tactile touch is different than sensing temperature for example. I am sure that if we were to realyl think about it there would be 25 senses we could think of that differ enough to be considered as distinct.
Interesting take…
Perhaps some sort of sense of touch (the electric field sensing from Bosda and Umbriel ) is what makes us so sure at times that someone is watching us or is in the room with us.
And is motion sensing somewhat separated from normal vision?
You guys are doing a swell job for my imagination.
I see dead people…
I don’t think an electromagnetic “life sense” has ever been experimentally demonstrated in humans, but I suppose it’s a possible contributing factor to the proverbial “hairs on the back of the neck standing up”. I think there are a lot of possible inputs to that though, including subconscious recognition of faint sounds or air currents or heat (ala’ the pit viper sense that Bosda mentioned).
In fact, I’d go along with CC that what we think of as “senses” can have a lot of componants. Moreover, they can have as much to do with our brain’s processing and contextualizing of stimulae as with simple data input. I’m sure there are many books on the subject. One of the most vivid examples that comes to mine is in Oliver Sachs’ An Anthropologist On Mars, specifically the chapter “To See and Not See” about a man blind since near-infancy who has his sight restored, physically, but who has to literally learn how to see (the story was later Hollywood cheese-ified into the movie “At First Sight” with Val Kilmer and Mira Sorvino), but is frustrated to find that his brain is too old to truly master such a complex new trick. The story is quite fascinating, and drives home the point that seeing isn’t just a matter of images flowing into the eye and down the optic nerve and into our heads. There is arguably as much subjective as objective about vision, and perhaps any sense.
I think balance is sense; you are perceiving the direction of gravity, which is a way of sensing your environment.
But on the OP: We see objects that are farther away as being smaller. What if you could somehow directly sense the presence of an object? Would distant galaxies actually be perceived as being bigger than, say, a person standing next to you? Fun late night thoughts. 
The sense of balance that we have is classified under touch, because it’s performed by touch nerves in our inner ear. However, it wouldn’t have to be. It would be cool if we had dedicated, internal balance nerves, not just for our heads, but for every part of our body.
Just Imagine how useful the innate ability to know how much milk, how many coffee filters or how much toothpaste we have at any given moment would be?
Actually, I think that balance usually is classified as another sense. There are really 7 major senses - A sense of balance and the kinesthetic sense (awareness of your own body basically), plus the five traditional ones.
No, I don’t have a cite for this at the moment. I could in fact be completely wrong, but this is what I seem to remember.
Advanced Empathy that allows people to feel exactly what others are feeling. In the same way seeing someone sad makes some people sad.
After a while people with start to be able to figure out what is causing the emotions in people and maybe some clue to what they are thinking. From there you get Telepathy.
According to Wikipedia the general agreement is that there are at least nine.
How about absolute location; the ability to know exactly where you are (even down to being able to feel the Earth rotating.
Welll… Yes. I looked at Wikipedia, and I then rejected it. It’s a good source in that all it’s information is usually correct in some sense of the word, but often not phrased or defined in quite the traditional way.
I agree their definitions look plausible, but I’ve never seen that anywhere else so I remain mildly unconvinced, and will continue to refuse to use Wikipedia for cites.