Question

♥️✝️HOLA FRIENDS ...✝️♥️

I HVE A QUESTION...

Why is the universe expanding???

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SABRINA ♥️

Answer 1

The universe is not embedded in some higher dimensional space (at least there is no evidence to suggest so). When you use the phrase "expanding into", you assume that there is some space which gets occupied or displaced as the "universe" takes its place. This intuition works for everyday experiences like inflating a balloon, but this is not correct. The universe is all the "space" that is there and there is no such thing as "outside" it. 

To aid the intuition think about it this way. Imagine the universe to made up of small units of fixed volume. There may be infinite number of such 'units'. When scientists say that the universe is expanding, that does notmean we are adding more "space units" to some 3 dimensional boundary. Instead,  what it means is that each unit is getting bigger in size. Its something like a 2 dimensional analogue of stretching an infinite elastic graph paper. The paper is not taking up any more space than to start with, but the distance between the individual cells gets stretched apart. Technically, its called metric expansion of space. 

As a rule of thumb, one should always be careful of generalizing ordinary intuitions of space, time and causality to domains which are completely outside our experiences.