Can you explain to me how time is regarded as the 4th dimension? Does it mean that if we assume time as a dimension then an object traveling to different time period is possible?
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You’re travelling in time right now. In fact, you can change how fast you are travelling through time. Go near a massive object and time will run slower for you. Go really fast and time will run slower for you.
So we know how to get to the future faster but we don’t know of any ways to go backwards in time.
So, a “dimension” is (essentially) a measurable factor in determining an object’s general description in terms that are easy to understand, without having to necessarily go into the minute dots and lines of it.
That is why being able to describe an object’s width, height, and depth in 3 dimension is really useful: You are describing roughly how much space it takes on a desk, for instance.
Now, time still follows that, in determining whether the object is somewhere, was somewhere, will be somewhere, or is moving. Without time, we cannot know any of those factors, but they’re still a basic characteristic of the object itself. If you are looking at a car moving on a road, at all times, it is moving, it was somewhere, it is somewhere, and it will be somewhere, and we can use the other 3 coordinates (called respectively x, y and z) along with time to describe that car’s exact location in what is called the “spacetime”.
If time wasn’t a dimension in determining that, if you came to my house yesterday, I could say today “u/doflamingo13 is in my house”, despite you leaving after dinner, and it would be valid. Clearly, if you left, I would need to add time to describe this, and that is why it’s an important basic descriptor.
If you’ve ever drawn a distance-time graph then you’ve used time as a dimension. A dimension isn’t fundamental to the fabric of the universe, it’s just about describing movement. We can describe movement in three spacial dimensions normally, and also we can describe their movement through time. It mostly comes up in special relativity where one object might not be moving through time at the same rate as another. This isn’t about time travel, it’s about how someone travelling very close to the speed of light would perceive time as travelling slower.
And to be clear: time isn’t *the* 4th dimension, it’s *a* 4th dimension. When you see mathematicians talking about 4 dimensional shapes, the 4th dimension isn’t time. It’s a fourth dimension of space that we can’t really understand visually but can still describe mathematically. 3 dimensions of space just means there’s three directions you can move in, x y and z. Adding a fourth dimension means adding another possible direction. This can be time but doesn’t have to be.
Okay so picture the future as being down, the past being up. But you are a 2 dimensional being so up and down are not directions you can perceive, you can only perceive the cross section of that up and down axis that intersects with you. Now imagine falling as that 2 dimensional being, and as you are falling, completely oblivious that it is even happening at all, you pass a balloon. From the perspective of the 2D being a dot would appear, grow into a ring, expand, shrink back into a dot and phase out of existence over time.
In much the same way as that 2d being was moving through the 3rd dimension, and so experiencing something changing over time from it’s perspective, we are moving/falling through the 4th dimension. Instead of falling from up to down, we are falling from past to future and things appear, grow, shrink, and eventually seem to disappear in the same way as that balloon seemed to vanish for the 2D being even though it was still there just outside of it’s perception.
Could we travel through time? We already are. Could we control the rate and direction we are moving through time? Maybe, but it will be extremely difficult to get our bearings. For instance point in the direction of the past right now. See my point?
I hope this explained things this is a really difficult concept to simplify
When you have defined the location of an object. You then need to define the duration that it will be there.
We are meeting on the second floor of the restaraunt located on the corner of main st and 5th Avenue.
We have three axis x=main st, y=5th Ave, z= 2nd floor… but when do we meet?
Edit: it’s also helpful to remember that spacetime is one thing. Two objects can’t occupy the same spacetime… but two objects can occupy the same space… separated by time.
Disclaimer: I don’t come from a scientific background, this is just how I visualise things.
Imagine a 1D object as a horizontal line. It has no depth, no height, only width (our one dimension).
To get a 2D object, you have to add height (our second dimension). If you layer a bunch of these 1D horizontal lines one above the other, you get a 2D plane. Visualise it as a piece of paper with no thickness.
So we got from a 1D line to a 2D plane by laying the 1D shapes side-by-side.
Let’s do the same again to get a 3D shape. This time we’re adding depth (our third dimension). Imagine placing all of your 2D pieces of paper on top of each other to form a stack. Now you have a 3D cube!
Great! So every time we’ve layered our shapes side by side to add in another dimension. But how can we possibly do this with 3D shapes to get a 4D object? If you place lots of 3D cubes next to each other you just get one really long rectangular 3D shape!
The trick is, we need to break out of our current dimension. Adding more cubes to the 3D cube would be like adding more length on to the end of the 1D line to get a longer 1D line, or adding more height to the 2D plane to get a longer (but still flat) 2D plane.
Here’s where time comes in. It’s the next dimension. Imagine our cube passing through time; it exists at each second, one after another. Kind of like an old-fashioned movie where still images are played next to each other really fast to create the illusion of a single, moving object, when really it’s lots of individual images side-by-side. To get a 4D object we need to place these 3D cubes side-by-side through time, with one 3D cube at each point in time to create a single 4D object stretched through time. The cube can change over time; you could squish it and stretch it, and it would appear to be a single 4D object that’s getting pulled about, rather than a succession of 3D objects that are a slightly different shape to the one before and the one after.
Here’s how I think of it:
Think of an empty room with just one chair. You or I can sit in that chair (location in space) just not at the same time.
If you’re sat in it, I can’t. If I’m sat in it, you can’t. We can both occupy the same chair (space), just not at the same time.
A simple example.
Imagine someone riding a car. The car can go forward or backwards, turn left or right, it can go up or down a hill. It can move in 3D space.
But what was the position of the car 1hr ago? Or 5minutes ago?
So by considering time as a dimension we can consider how things change over time.
The car may be at the base of a hill, in 5 min it’s moved up the hill increasing its height and distance away. 10 min later it’s over the hill and the height is now back to the same it was before but it’s distance is further and more time has passed.
Side Note:
A “Dimension” is often thought of in terms of 3D space and time….
But it’s really anything that could be put into a table. For example if you have a recipe in a table with the ingredients across the top and the servings on the left. Each column can be considered a different dimension to the recipe.
So
1st Dimension may be number of servings
2nd Dimension may be amount of flour
3rd Dimension may be amount of water.
4th Dimension may be cooking time.
Etc.
Spacial dimensions are not the same thing as time dimensions.
If you are talking in maths/physics terms almost anything that can be represented as a continuous number could be called a dimension, but mostly that’s a question about the definition of the word dimension not about the nature of the universe
Dimensions are basically this : how many coordinates do you need to pinpoint the location of an object in that system?
2 dimensions, think of the classic coordinate cross. 2 coordinates, x and y (left/right and up/down) gives you a location.
In 3 dimensions, you need an additional z for “depth”. On our Earth, you could pinpoint for example the times square on a map by three coordinates. “Z” is needed so you don’t start searching for it in the stratosphere or at the center of the earth.
Now, you could say that our space is 3 dimensions, but actually it’s 4. If you want to find the times Square, you need to also know the time frame in which it exists at x, y, and z. So, you need 4 coordinates to pinpoint its location. Hence, time is the 4th dimension.
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