The solution to the complex problem of light shows that time can only go forward

Light is something very familiar to our world, yet it can still create some amazing curves when you look at it in detail. One of these new discoveries comes from a well-established phenomenon: what happens when light passes through an interface? This could be glass, water, or something completely different. The solution to this has been worked out for a long time, but now scientists have found something strange going on in the middle.

When light passes through the interface, its speed changes. The solution to the behavior of light on one side of the interface or the other is the well-established standard wave equation. They can be linked without any problem (partitioned and persistent solution) but that doesn’t explain what’s happening in the interface itself. There, the wave must experience an acceleration that is not accounted for in the current solution.

Now an equation has been put forward in the case of a universe that has one space dimension and one time dimension.

“Basically, I found a very elegant way to derive the standard wave equation in 1+1 dimensions. The only assumption I needed was that the wave speed is constant. Then I said to myself: What if it isn’t always constant? Eastern Finland, in an article: “This turns out to be a really good question.” statement.

The team came up with an equation for an accelerating wave. At first, the solution didn’t make sense, but physicists realized they needed a reference speed: the speed of light in a vacuum. Solving the equation yielded the correct solution both on the interface and on both sides, but it had one crucial requirement. She just needs time to move on.

The arrow of time is a fairly important concept in science. In physics we often talk about the thermodynamic arrow of time. In all isolated systems, entropy increases with time. This clearly gives direction to time.

This equation, although only in one dimension, seems to indicate that the arrow of time does not simply come from thermodynamics, but may be an intrinsic property of nature that even diffuse light must obey.

For the field of optics, solving this equation means resolving a long-standing controversy that has puzzled physicists for years.

“There is this very famous debate in physics, called the Abraham-Minkowski debate. The debate is that when light enters a medium, what happens to its momentum? Minkowski said momentum increases, while Abraham insisted that it decreases,” explained study leader Professor Marco Ornigotti.

Experimental evidence supports both sides, and according to the new equation, momentum is conserved thanks to relativistic effects. its just It seems To increase or decrease depending on how you look at it.

“We found that we can attribute a ‘good time’ to the wave, which is exactly analogous to the good time in general relativity,” Ornigotti continued.

The work jumps from a specific visual puzzle to a possible fundamental truth of the universe. If the arrow of time always goes in one direction, we may have to say goodbye to dreams of time travel to the past.

The study is published in the journal optica.