so: to summarize,In the proposed model, the Universe is expanding as membrane #3 though timespace #1. thought to be a featureless realm in which infinitely old energy and time exists. There were no 3 space dimensions for us , in the time before the "Big Bang". therefore
we live now in "spacetime", the time (marked as #2, the "past" , stretching from the central BB #4 to the present in #3. ). this is our section, out of total limitless timespace, a section marked by the existence of space, since and after after the "Big Bang".
For you it might also be "teatime", or "sleepytime" right now.
Before our Universe, there was energytime, then we came, now it is spacetime. Those that advocate other bubble/baby universes, would think that they have their own 3D space & time, their own "spacetime", so-called, if they spoke a german-like language, because
The term "spacetime" came from Einstein's mother tongue's feature to run words together to no end, to name unique new concepts, like a one-word summary of ideas.
the terms "timespace" and "energytime" are to be understood in the same way. " mathematical imaginations"
Time and energy are fundamental, uncreated. they exist in a realm dubbed timespace or energytime. We live in/during spacetime, our allotted section of it, but expanding into the future.[/QUOTE]
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Time has no physical dimension in and of its self .
Time is Totally dependent on physical things , the real dimension of physical things , and their movements .
Three dimensions is fundamental to all things .
To say that there is no three dimensional space dimensions misses the understanding that physical things , are fundamentally three dimensions . BB could never exist without real three dimensional thing existing .