# Is “now” the bounding edge of the universe in the time dimension? [duplicate]

The universe is expanding in the 3 spatial dimensions, could it not also be expanding in time dimension. In other words, are we stuck in 3 dimensions because we are riding the "bow wave" of the big bang in the time dimension, stuck on a 3d plane perpendicular to our world lines in spacetime? Think of a 3d-printer, are we on the upper surface of the printed object with new time being added continuously.

Would this mean that the quantum foam is the moment when the universe comes into existence, that the collapse of wave functions is when probability becomes reality? In that way there would be no need for the many worlds interpretation of quantum physics. Ahead of now is "outside" the universe i.e. there is nothing so the extra quantum states never "existed" in any sense, they were only ever mathematical probabilities. The act of observation is simply being in the now and that's why quantum systems are different depending on where you measure them - it's a different locus of the 3 spatial dimensions and "now".

Update

I don't believe that this is a duplicate question. After some discussion elsewhere it turns out that what I am describing is the Evolving Block Universe. It is well (and more formally) described by South African cosmologist George Ellis in this paper:

http://arxiv.org/abs/gr-qc/0605049

There is also a YouTube presentation, recorded in 2012, here:

## marked as duplicate by John Rennie, Brandon Enright, Emilio Pisanty, ACuriousMind♦, Kyle KanosAug 8 '14 at 13:39

• – John Rennie Aug 8 '14 at 7:25
• I mean expanding in the sense of growing and being created rather than in the sense of being stretched. For example, a point 100m from where I'm sitting now is currently outside the bounds of the room I'm sitting in but if the walls of the room were to move outwards then the after some time the point would be within the room. The distance (co-ordinates) would still be exactly the same. I'm asking if "now" is like the walls of the room and the point currently outside the room is in the future (but doesn't exist in any sense). The wall sweeping through space is the moment of "creation". – JohnnyD Aug 8 '14 at 8:31
• I'm not sure what it is you're asking. Are you asking about the flow of time? If so it's been asked before, and the answer is that there is no answer. – John Rennie Aug 8 '14 at 8:53
• Time is like building a railway, the age of the universe - the total length of track gets bigger (though the track itself doesn't - the distance between sleepers remains the same - thus creating new track (the past); the point at which new track is laid down is "now". Where the track is going to be is the future but there is nothing there - it is outside the universe of the track and inaccessible. If you are fixed to the leading edge of the track then time would appear to flow but really it's being constantly created. It's not that all the track exists and we're simply moving along it. – JohnnyD Aug 8 '14 at 9:08
• No, this is quite incorrect (sorry!). When you solve the equations of GR the result is a metric, and the metric gives us the time and space axes from $-\infty$ to $\infty$ (unless a singularity gets in the way). The flow of time is merely the advance of the observer's time coordinate along the time axis. The time axis is not constructed, like a railway, as the observer moves along it. The time axis already exists. This is an absolutely vital point to understand. The solution to Einstein's equation is a spacetime - the whole spacetime. – John Rennie Aug 8 '14 at 9:38