Go under water, and you're experiencing a greater amount of pressure... hike up a mountain and you're under less pressure. Go to space, and you're in a vacuum (and probably dead if you could feel it).
Is there such a phenomenon where there is "negative" amounts of pressure (not negative pressure)...?
(think "is there another dimension other than the 3 we see, before we discovered there were more")
Posted Jul 9, 2016, 7:18 AM UTC
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When talking about pressures it makes sense to talk about pressure differences rather than absolute pressure. The reason is the same one that birds sitting on electric lines don't have a problem; a pressure difference exerts a net force while a voltage difference drives a current. So it's certainly possible to have negative pressure differences, but the negative sign just denotes direction of the applied force.
If we get a bit more philosophical, then when referring to a vacuum you really need to make clear what you mean. For example, the "vacuum state", as predicted by quantum mechanics, isn't actually "empty". But maybe you meant a vacuum that is macroscopically free of any particles. So you can see why formulating the questions in a more precise way is important.
To the notion of "extra" dimensions and their predicted effects--to my knowledge there are no easily measurable consequences of extra spatial dimensions predicted by exotic models. Buy it could be that something can escape into them (if they exist). For example, one proposed solution to the Hierarchy Problem is that gravity "bleeds" into these dimensions leaving us ordinary folk with a drastically weak gravitational force.
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