This is extraordinary: Gravity can create light, all on its own

As far as we know, our universe kicked off a long time ago with the Big Bang. One giant explosion set everything into motion and scattered the first material out into space.Over time, the universe has changed and evolved in huge ways, forming generations of stars and planets, black holes, electromagnetic fields — you name it. But throughout all of this change, we can still see evidence of some of the earliest states of the universe. Video above: NASA says risk of danger 'low' as satellite falls to EarthSome of the most mysterious signatures from the beginning of time are gravitational waves. These waves, often referred to as ripples in spacetime, radiate through the universe and carry the effects of gravity out and away from the generating body. The strongest ones come from cataclysmic events like black hole mergers and supernovae — of the rapid expansion of the universe immediately following the Big Bang.According to a new paper, some of the waves from that last category are strong enough that they can spontaneously generate light.It all has to do with something called resonance, where a wave or motion that happens periodically can build and build and build on itself if it’s boosted at the right time. In the case of these gravitational waves, they were experiencing something called parametric resonance—the kind you get when you pump your legs on a swing to get higher. The researchers believe that, as expansion facilitated the rapid swelling of the universe and subsequently ended, the universe was left with many interfering gravitational waves. Some of those waves would have been able to build on each other until they were incredibly strong. A few of those waves could have built up and formed what are called standing wave patterns, where waves sort of freeze in place. The places in which the waves remained frozen would have been incredibly intense points of gravitational energy. In these gravitationally-intense regions, the researchers found that the gravitational energy may have been enough to excite any electromagnetic field it may have come into contact with, prompting the field to produce light from just the energy of gravity. No other source of energy is needed — just gravity.More research still needs to be done on the topic and, unfortunately, it’s probably not something we’ll be able to see in the modern universe. The strength of the gravitational waves needed to “turn on” an electric field is many times higher than the strength of the gravitational waves we’re able to detect today. Unless we somehow have a second Big Bang coming our way, gravity-produced light is probably a thing of the past. But that doesn’t mean it isn’t exciting. The very earliest moments of our universe are quite mysterious and difficult to probe, so collecting information about the way it could have been filled in a corner of a fairly empty picture. Any little piece helps in our efforts to understand the universe we live in.