Light’s weird dual nature weathers trip to space and back

ScienceNews.com ^ | October 25, 2017 | Emily Conover

[ETL]

'Delayed-choice' test, a first with spacefaring photons, affirms light can behave like a wave or a particle.

Light is two-faced: Sometimes it behaves like a wave, sometimes like a particle. Now, scientists have shown that light’s shifty disposition persists even after trekking thousands of kilometers into space and back again, researchers report October 25 in Science Advances.

Depending on how light is measured, it can either be particle-like, lighting up a camera pixel, for example, or wavelike, interfering with other waves like ripples on the surface of water. It’s one of the many oddities of quantum mechanics. Before light is measured, quantum theory suggests, it is in a particle-wave limbo, neither purely one nor the other.

Physicists have tested this idea by performing “delayed-choice” experiments in the lab, in which researchers send light into a device and randomly choose whether or not to flip a switch that seems to retroactively change the light’s behavior (SN: 5/30/15, p. 9). In one configuration, the light travels down two paths at once and acts like a wave, interfering with itself. In the other, the light acts like a particle, taking a single path. That choice of configuration can be made even after the light has already traveled through the device but before being measured, revealing that light remains in quantum limbo until it is finally detected.

For the first time, physicist Paolo Villoresi of the University of Padua in Italy and colleagues took the technique into space. The researchers sent light through a lab apparatus and up to a satellite equipped with reflectors, which bounced the light back down to the device. While the light was in transit, the scientists used a random number generator to determine whether to configure their apparatus so that the light would behave like a particle or a wave. The light performed as expected, verifying that quantum mechanics holds even over the round trip into space and back.

[Getready]

What it means is that we cannot understand it...we can just throw imaginative maths at it and try to describe the behaviour...we may have hit the knowledge limit...maybe knowledge curve is asymptotic .....always learning but never coming to knowledge of the truth

[ETL]

we may have hit the knowledge limit...maybe knowledge curve is asymptotic

I seriously doubt that we're approaching any limits on knowledge of the physical world. The nature of knowledge is exponential if anything, in that one new discovery branches out into many. But then, can we ever, realistically, say that there is a single universal "meaning" or "understanding" of what reality is? It all depends on who or what is doing the observing, and at what scale or dimension.