Reading a Stephen Hawking book which brought up a question on what is our universe expanding into. But, my co worker brought up the question of what is it expanding into? Would it be another universe or nothing (which has to be something)?
There need not be any edge, nor anything for it to be expanding into, and in fact it’s generally believed that there isn’t.
Here’s a good explanation:
Right. For our terms, the universe defines existence, in both time and space. There is no “before” the universe, and there is no “outside.”
You and your friend are envisaging a universe that is finite and bounded. This implies that there is an edge, and a region that is outside the universe.
As I understand it, there are two other possibilities for an expanding universe:
- Infinite. In this case, the term “expansion” does not mean “becoming larger” but “becoming less dense”.
- Finite but unbounded. This describes a region of space-time of finite size, whose positive curvature means that it is “closed”. It is analogous to the 2-dimensional surface of a sphere (such as the earth) which is also finite but unbounded. In this case, “expansion” has the normal sense of getting bigger in extent.
My understanding (mainly gained from this board) is that observation shows that the universe is flat over very large scales, suggesting that 1) is likely to be the correct description of our universe.
Although I can’t say I understand it, I think a holographic universe would be similar to the second option.
Following Hubble’s law, all masses at a certain distance will approach the speed of light and hence will not be observable or have any impact on the observable universe. This distance as I understand is the edge of the Universe.
The Universe is falling “In”. There are seven other cardinal points to the four dimensions. The eighth cardinal point In is in a direction we can not see. We can not measure anything in that direction. That direction is an event horizon we can’t cross. This event horizon is the edge of the Universe. And we’re right up against it and falling toward it.The other seven cardinal points are Back and Forth, Up and Down, Left and Right and Out. In colaspase’d into a singularity. Leaving Out to Fall away anything that doesn’t quiet make it past the event horizon. And Out dragging the other six directions with it. Out is the Past. Any direction we look Out into the Universe, we see the Past.All the way back to just after the Big Bang. In is a Singularity, In is the Future. Mass, velocity or energy expended in the three Dimensions ninety degrees to Time, reduce the energy available for falling In the Future. As this Drag favors one direction more than the others. Just like drag with Electromagnetism distinguishes between Spacial Dimensions. So can drag with other energy fields, like the Higgs. Drag with the Higgs Field causes the Spacial Dimension Down to align with In. Thus Up is Out, back to the very beginning. The empty low energy places between the energetic massive areas have less Drag thus fall In more energetically This bends the Space between slower massive areas and lighter empty areas. The appearance of which is identical with expansion.
Glazer’s explanation is nonsense.
In a more subtle way, so is am77494’s.
Actually objects that recede faster than light due to the expansion of the universe are still visible; see
Expanding Confusion: common misconceptions of cosmological horizons and the superluminal expansion of the Universe