Scientists develop a test for the theory, which if proved, would solve some major problems in particle physics.
Did the early universe have only one spatial dimension?
A new theory, proposed in 2010 by physicist Dejan Stojkovic and colleagues, says that the early universe — which exploded from a infinitely small point — was one dimensional (similar to a straight line) before expanding into two dimensions (like a plane) and then into three (the world in which we live).
If the theory turns out to be valid, it would address many important and unsolved problems in particle physics.
In their paper, published in the Physical Review Letters, Stojkovic and Marymount University physicist Jonas Mureika outline a test that could prove or disprove the “vanishing dimensions” hypothesis.
Because light and other waves take time to reach Earth, telescopes peering out into deep space can essentially look back into time. The more distant the object, the younger the universe was when you look at it.
Gravitational waves cannot exist in a one or two dimensional universe. Mureika and Stojkovic reasoned that the Laser Interferometer Space Antenna, a planned gravitational observatory, wouldn’t detect any gravitational waves propagating from the lower-dimensional period of the early universe.
Stojkovic says his theory represents a radical shift from the way we think about the cosmos and about how our universe came to be.
Four Spatial Dimensions?
The root of his idea is that the dimensionality of space varies based on the size of the space we’re attempting to observe, with smaller spaces being associated with less dimensions. This also means that a fourth dimension will be created — if it hasn’t already — as the universe continues its expansion.
The theory also suggests that space has fewer dimensions at very high energies — the kind present in the early, post-big bang universe.
If they’re right, they will be addressing fundamental problems present in the standard model of particle physics.
Problems With The Standard Model
- The incompatibility that exists when attempting to unify quantum mechanics and general relativity. Quantum mechanics and relativity are frameworks that describe the physics of the universe. Quantum mechanics describes the universe at very tiny scales (subatomic), while general relativity is good at describing the universe at large scales (celestial orbits and gravity). Currently, the two theories are incompatible. If the universe, at its smallest levels, had fewer dimensions, discrepancies between uniting the two frameworks would disappear.
- The unsolved mystery of the universe’s accelerating expansion. Physicists have observed that the universe isn’t just expanding, it’s also speeding up. Adding new dimensions as the universe continues to expand would explain this acceleration. (Stojkovic says a fourth spatial dimension could have already opened at the huge, cosmological level.)
- The need to alter the mass of the Higgs boson (often called ‘the God particle). The standard model of particle physics predicts the existence of an undiscovered elementary particle called the Higgs boson. For the standard model to describe the physics of the real world, researchers must artificially tweak the mass of the Higgs boson for interactions between particles that take place at higher energies. If space has fewer dimensions at high energies, the need for this kind of “adjusting” vanishes.
The Need For Radically New Thinking?
“Physicists have struggled with these problems for 10, 20, 30 years, and straight-forward extensions of the existing ideas are not likely to solve them.” Stojkovic says. “What we’re proposing here is a shift in that paradigm”
“We have to consider the possibility that something is systematically wrong with our current ideas,” he continued. “We need something new and radical, and this is that something.”
Since the planned deployment of LISA is years away, it will be a long time before Stojkovic and his colleagues are able to test their hypothesis.
Though, some experimental evidence already points to the possible existence of lower-dimensional space.
Scientists have observed that the energy flux of cosmic ray particles with energies that exceed 1 teraelectron volt — the kind of energy in abundance in the very early universe — are aligned along a two-dimensional plane.
If high energies are related to lower-dimensional space as the theory predicts, the researchers at the Large Hadron Collider particle accelerator (LHC) should see planar scattering at those energies.
Stojkovic says observing those events would be “a very exciting, independent test of our proposed hypothesis.”