Our universe may be multiply connected, meaning that space is closed in on itself in all three dimensions like a three-dimensional donut. If our universe were a finite donut, then such movements would be possible and physicists could potentially measure its size. Now we know the size of the universe.
A tasty problem
Physics uses Einstein’s general relativity to explain the universe.
- In a cosmological context, that language connects the contents of the entire universe to its overall geometric shape – dark matter, dark energy, regular matter, radiation and all the rest
- For decades, astronomers debated the nature of the shape
- Flat and open universes would continue to expand forever, while a closed universe would eventually collapse in on itself
- Multiple observations, especially from the cosmic microwave background, have firmly established that we live in a flat universe
Look to the light
If we could somehow determine whether one or more dimensions are wrapped in on themselves, then we would know that the universe is finite in that dimension.
- We could then use those observations to measure the total volume of the universe.
- Observations of the cosmic microwave background (CMB) give us our best chance to see the imprints of a multiply connected universe.
Making the Connection
The team found that a multiply-connected universe about three to four times larger than our observable bubble best matched the CMB data.
- While this result technically means that you could travel in one direction and end up back where you started, you wouldn’t be able to actually accomplish that in reality.
