Tim asked in Science & MathematicsPhysics · 5 months ago

# A simple way of explaining 4 dimensional?

What is it exactly?

Is it a real thing?

Are we actually 4D?

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• 5 months ago

Dimensions can be considered measurements, of different types.

One common "Four dimensional" coordinate system is location + time; where a person or thing was at a certain time.

A hypothetical or mathematical concept is four spatial dimensions.

In that concept, three dimensional shapes are projections or cross sections of four dimensional objects, like 2D shapes can be projections or cross sections of 3D objects.

A common example is a tesseract, the four dimensional version of a cube.

They cannot physically exist as objects, but the sections or projections can be represented by drawings and the shapes they could be if "unfolded" to three dimensions (like unfolding a folded paper cube) can be made.

https://en.wikipedia.org/wiki/Tesseract

Multiple dimensions are often used in computer programming, as data arrays.

eg. A one dimensional array could contain a single list of numbers.

2D gives you a grid of numbers,

3D gives you a multi-layer block of grids.

One way of thinking of more dimensions (the way I do it) for this use:

4D could be thought of as a line or list of blocks;

5D a grid of blocks,

6D a multi-layer block of blocks etc. etc.

• neb
Lv 7
5 months ago

A dimension is an independent degree of freedom of a geometric structure or the space it is embedded in (if any). It’s very important to think of it this way since ‘objects’ don’t have the dimensionality of the space they may be embedded in, but rather have a dimensionality based on the degrees of freedom inherent in the object.

For instance, it may be tempting to say that some curve embedded in 3-d space is three dimensional - but it is in fact 1-d. There is a single degree of freedom inherent in the line, and that degree of freedom is along the line itself.

Similarly, a perfect sphere in a three dimensional space has only two degrees of freedom on its surface (e.g.,longitude and latitude), so the sphere is a 2-d object embedded in a 3-d space.

People are clearly 3-d objects. We can certainly be embedded in a 4-d space, but by analogy with the above we are still 3-d objects. If we were embedded in a 4-d space we wouldn’t know it directly since we still only perceive 3 degrees of freedom, and we have no direct perception of motion in 4-d space.

In physics, we include time as an extra degree of freedom in addition to the three spatial dimensions, so we have the concept of being 3-d objects that are moving through a 4-d spacetime. This is certainly how we model it mathematically in relativity. So, when we think we are physically at rest in the 3-space dimensions, we are actually still moving in the time dimension. While this can certainly be a mathematical convenience, it leads to remarkable unifications in physics.

String theory has many extra dimensions. While we normally think of a dimensions as linear, stretching out to infinity, the dimensions in string theory are not linear nor are they infinite (again this why it’s a good idea to think in terms of degrees of freedom). Mathematical convenience or reality? No one knows.

• Anonymous
5 months ago

The 4th dimension is time.

Is it a real thing? Theoretical physicists are not sure time actually exists but the rest of us divide time up into measurable units that have NO weight or Physical size that can be measured with a ruler , thermometer or pressure gage ,your guess is as good as anyones.

Are we actually 4D? YES Because we move through time & change our physical appearance due to ENTROPY.

Your next question should be ,what is entropy? I dont know ,maybe its time tor you to look it up yourself?