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kurious
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How does dark energy exert pressure - what does it push against.It must push against something solid if it has pressure units like Nm^-2?
Dark energy has negative pressure. And I don't think that dark energy exerts pressure in the classical sense of the term. It is a form of matter which, for example, may make itself know by a non-zero cosmological constant.. This means that Einstein's field equations, even in a vacuum, behave as if there is a non-vanishing stress-energy-momentum tensor which has non-zero pressure terms. Or it may make itself know by having negative values of its effective gravitational mass density, i.e.kurious said:How does dark energy exert pressure - what does it push against.It must push against something solid if it has pressure units like Nm^-2?
Nope. That is not the case. You're still thinking of the pressure associated with dark energy as being of the same kind of animal as the pressure of a gas. It is not that way. Dark energy is not what is responsible for galaxies moving apart. That happens in the absence of dark energy too. Dark energy is what is causing the rate of expansion to increase. There is nothing pushing on galaxies in the normal sense of the term. Think of it as antigravity or as a repulsive gravitational force.kurious said:pmb phy:
there is nothing in the middle of the room for the air to push on.
Kurious:
Air molecules can move objects by flowing in one direction.
Dark energy seems to move galaxies by exerting pressure equally in all directions.
No.Could an extra dimension of space make dark energy behave more like air so it could be said to be flowing in a particular direction - and the galaxies too? Or would an extra dimension upset the equations which describe dark energy's presence in the universe too much?
That seems to be a vauge question. I'm not sure what it means. But it seems that the best answer is that the units of dark energy are identical to that of energy, e.g. Joules etc.kurious said:Does dark energy have units of Nm^-2?
You can do that for the components of the effective energy-momentum tensor. This tensor has components which are mass-enegy density, momentum density and stress.The energy density of dark energy is the same as its pressure in magnitude:
can I write force/area = energy/ volume for dark energy?
Dark energy is a theoretical form of energy that is believed to make up about 70% of the total energy in the universe. It is thought to be responsible for the observed accelerated expansion of the universe.
Dark energy and dark matter are two separate and distinct components of the universe. While dark energy is thought to be a form of energy that permeates all of space, dark matter is believed to be a type of matter that does not interact with light and can only be detected through its gravitational effects on visible matter.
Dark energy cannot be directly measured, as it does not interact with light. Instead, it is inferred through observations of the universe's expansion rate and the distribution of matter within it. Scientists use various methods, such as measuring the brightness of distant supernovae and studying the cosmic microwave background, to estimate the amount of dark energy in the universe.
The exact role of dark energy in the universe is still not fully understood. It is believed to be the dominant force driving the accelerated expansion of the universe, but its ultimate purpose or function is still a topic of ongoing research and debate.
As dark energy is still not fully understood and cannot be directly measured or observed, it is currently not possible to harness or use it for energy purposes. Further research and advancements in understanding dark energy may lead to potential applications in the future, but it remains a theoretical concept at this time.