Light is a transverse wave that travels in empty space, but how can a wave do that? Sound is also a wave, but no sound travels in empty space because nothing can transmit it. Yet light from the sun and stars still reaches us across the emptiness of space, so how can a wave travel without a medium?
Consider a wave travelling across a pool surface. The wave moves because the water moves, but a cork floating on the pool just bobs up and down as waves pass it. The waves don’t push the cork along because the water doesn’t move in the wave direction, it moves up and down. What moves as a wave isn’t the water, but it’s up-down surface displacement, so when a pebble drops on a still pool, that displacement spreads as waves. Waves spread when a surface vibrates up and down, so shouldn’t light be the same?
A transverse wave vibrates at right angles to its movement direction, so water waves are transverse waves because the water moves up and down as they move on its surface. Light is also a transverse wave, although it moves in three dimensions, but it is said to have no medium because in physicalism, empty space is nothing. However if our space is a surface, then light could vibrate on space instead of in it.
In the theory of relativity, space curves so it is a surface, and complex number theory describes light as vibrating into a dimension outside space, which suggests the same. If these theories are correct, then light is a transverse wave on the surface of space. Light travels in a vacuum, so it either nothing vibrates at all, which denies how waves work, or our space vibrates. The simpler option is that light is a vibration on the surface of space itself.
Why then don’t we see light waves move up and down, as water waves do? We know that light vibrates, but a ray of light seen from the side doesn’t seem to move up or down. This is expected if the dimension into which light vibrates is sequestered from our space (Randall, 2005). Everything we see is based on light but a transverse wave can’t leave the surface it vibrates on, so we can’t see what happens outside space. It takes reverse engineering to deduce that light vibrates on space.
But what exactly moves when light travels in empty space? According to physicalism, nothing can, but the alternative now explored is that the quantum network does. Maxwell’s equations describe light as an electro-magnetic vibration orthogonal to space. If this vibration is the quantum network setting a transverse circle of positive and negative displacements, the result is a sine wave. If that network completes one cycle at a point, the result is null, or empty space, but the same process distributed over two or more points can be a wave of light (Figure 2.7). Chapter 3 gives more details, but essentially light is a positive-negative surface displacement just as water waves are. What moves when light travels is then the quantum network that defines our space.
Quantum waves spread on the quantum network, and light is their simplest form, but what actually are they? Schrödinger called them matter density waves, because they predict where matter exists, but quantum waves aren’t made of matter. Born called them probability waves, because their amplitude squared at a point is the probability that matter exists there, but a probability is just a number. We expected the ultimate reality to be made of matter, but instead we found only quantum waves. The quantum waves that predict physical events have no mass, momentum, velocity, or any other physical property, but they can manifest as space, light, or matter, as will be seen.