Can somebody explain me the concept of 4th dimension?
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A dimension is a geometric notion. Given a volume of space, you can specify a point in that space by saying how far you need to go along each of a given bunch of directions. The number of directions you need to be able to identify all possible points in the space is how many dimensions it has.
This is an abstract idea, but we can connect it to many kinds of spaces in the real world. For example, you can specify a point on the surface on the earth using two directions: north and east. "Go x to the north and y to the east" can identify any position on the surface of the earth, so that surface is two-dimensional (unless you worry about caves and tunnels and such, but let's forget about those).
The entirety of space in the universe is three dimensional: you can identify any point by saying "go x to the north, and y to the east; then the point is at an elevation of z".
So the idea of dimensions is abstract: you can apply it to the real world in several ways. Let's do one you are probably not familiar with. Consider a tennis ball flying through the air. Now suppose we want to specify not just its position, but also the direction and speed of its flight. Disregarding all decency, we now imagine a space such that a point in that space gives information not just about the position of the tennis ball, but also its velocity! Can we do that? The answer is yes: we simply include a couple more directions. The tennis ball can be pinpointed in our imaginary space by giving its position along the directions: north, east, elevation, northern speed, eastern speed, vertical speed.
This space is completely imaginary; in fact it is clearly not the same as the real "space" we see around us, but mathematically it works pretty much the same way: we used a bunch of distances along a bunch of directions to identify the state of an object we're interested in. The space we just came up with has six dimensions, and it is used by physicists who call it "phase space".
So, how many dimensions does our real space have? Well, we can identify any point with distances along three directions, but we can use the same trick as above and include the time of an event in its position in some imaginary space. So then we get a four dimensional space-time, that does not have anything to do with Einstein yet. A point in spacetime describes both the location and the time of some event in the universe.
So in this way, one can come up with a useful abstraction of the real universe that has four dimensions. It is not clear that the real universe somehow inherently is four dimensional: who knows how the world really works deep down in the uncharted laws of physics? Who says that we should only talk about the positions and times of events in the universe and not other properties of it, like speed or charge? But you need at least four dimensions to pinpoint an event, so in that sense we could claim that we live in a four dimensional space-time.
The reason that this whole story reminds you of Einstein is because he showed that objects move through the three spatial dimensions and the one temporal dimension in stranger ways than people had previously imagined, and that the spatial and temporal dimensions are intertwined in terms of their behaviour. That means that we really do need to include the temporal dimension in our description of events in space.
But in the end, the fourth dimension is just the fourth out of a bunch of directions we like to use to be able to pinpoint an event.
This is an abstract idea, but we can connect it to many kinds of spaces in the real world. For example, you can specify a point on the surface on the earth using two directions: north and east. "Go x to the north and y to the east" can identify any position on the surface of the earth, so that surface is two-dimensional (unless you worry about caves and tunnels and such, but let's forget about those).
The entirety of space in the universe is three dimensional: you can identify any point by saying "go x to the north, and y to the east; then the point is at an elevation of z".
So the idea of dimensions is abstract: you can apply it to the real world in several ways. Let's do one you are probably not familiar with. Consider a tennis ball flying through the air. Now suppose we want to specify not just its position, but also the direction and speed of its flight. Disregarding all decency, we now imagine a space such that a point in that space gives information not just about the position of the tennis ball, but also its velocity! Can we do that? The answer is yes: we simply include a couple more directions. The tennis ball can be pinpointed in our imaginary space by giving its position along the directions: north, east, elevation, northern speed, eastern speed, vertical speed.
This space is completely imaginary; in fact it is clearly not the same as the real "space" we see around us, but mathematically it works pretty much the same way: we used a bunch of distances along a bunch of directions to identify the state of an object we're interested in. The space we just came up with has six dimensions, and it is used by physicists who call it "phase space".
So, how many dimensions does our real space have? Well, we can identify any point with distances along three directions, but we can use the same trick as above and include the time of an event in its position in some imaginary space. So then we get a four dimensional space-time, that does not have anything to do with Einstein yet. A point in spacetime describes both the location and the time of some event in the universe.
So in this way, one can come up with a useful abstraction of the real universe that has four dimensions. It is not clear that the real universe somehow inherently is four dimensional: who knows how the world really works deep down in the uncharted laws of physics? Who says that we should only talk about the positions and times of events in the universe and not other properties of it, like speed or charge? But you need at least four dimensions to pinpoint an event, so in that sense we could claim that we live in a four dimensional space-time.
The reason that this whole story reminds you of Einstein is because he showed that objects move through the three spatial dimensions and the one temporal dimension in stranger ways than people had previously imagined, and that the spatial and temporal dimensions are intertwined in terms of their behaviour. That means that we really do need to include the temporal dimension in our description of events in space.
But in the end, the fourth dimension is just the fourth out of a bunch of directions we like to use to be able to pinpoint an event.
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the concept of 4 th dimensonal tell us that our earth has more than 3 dimensons these theury calles the string theury which tells us that our universe have 11 dimansons at all
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