- Physicists build a new model that suggests our universe may be sitting on a bubble expanded by dark energy.
- All particles in our universe are the endpoints of strings (as per string theory) extending out into another dimension.

In 1925, an American astronomer Edwin Hubble proved that our universe is expanding. This means, other galaxies are moving away from us, and the ones that are farthest away are moving the fastest.

This gave rise to another interesting phenomenon called dark energy. Albert Einstein was the first physicist to realize that empty space is not nothing. In fact, it has incredible properties, many of which are just beginning to be understood. Dark energy is one of those properties of space.

Then in the mid-1984, it was realized that string theory has the potential to describe all fundamental particles as well as the interactions between them. String theory says that all particles are one-dimensional strings whose vibration determine properties, for example, mass and charge.

Over the last couple of decades, hundreds of physicists have come up with their own versions of string theory and most of them require that reality consists of more than 10 dimensions.

On daily basis, we only experience 4 dimensions (3 of space and 1 of time). Rest of the dimensions are rolled up into an intensively tight point. The configuration of these extra dimensions determines the properties of the universe we perceive.

According to the string theory, there could be as many as 10^{500 }unique universes, in which our particular universe is just a small subsection. However, these theoretical universes lack dark energy. The mathematical equations governing string theory show that any universe containing dark energy (like ours) should rapidly decay away and vanish.

### The New Model Connects String Theory and Dark Energy

Recently, researchers at Uppsala University, Sweden, proposed a new model with dark energy in which our universe is riding on an inflating bubble in an extra dimension. According to this model, the entire universe is sitting on the edge of the expanding bubble.

*Reference: Phys. Rev. Lett. | doi:10.1103/PhysRevLett.121.261301 | Uppsala University*

All particles in the universe correspond to the ends of strings that extend out into another extra dimension. This sort of inflating bubbles can come into existence within the string theory framework. It’s possible that there are more bubbles that contain other universes.

Courtesy: Suvendu Giri

This is just a math fiction with zero experimental evidence. In fact, many string theorists have proposed large amounts of mathematical constructions that do not have any relationship with actual observations.

Read: Did ‘Anti-Universe’ Exist Before The Big Bang?

Overall, the model provides a different view of the formation and fate of the universe, while paving the way for techniques of testing string theory.