It is space itself, and especially its dynamics, that gives rise to the force of gravity. Listen to the void: Why cosmic nothingness has so much to sayĮinstein took this one step further with general relativity, where space is promoted from a background stage to a starring actor - a dynamic, flexible entity that responds to the presence of matter and directs the motion of that matter. Giant voids of nothingness may be flinging the universe apart This is modern physics in a nutshell: Objects move and interact with each other on the background of space, which is assumed to exist. Isaac Newton elevated the concept of space to serve as an absolute background for the motion of objects and the physical laws that govern their behavior. If you've ever written down the x- and y-axes of a Cartesian grid, you have Descartes to thank for it. But the concept of space began to take on a more concrete character with the work of René Descartes, the 17th-century genius who invented a mathematical foundation to describe space. We like to think of space as just a mathematical abstraction, a way for us to measure location and extent. You'd still be an object in space, and some view space itself to have existence. So what if you concocted a device to nullify the vacuum energy (which is technically impossible, but let's keep going with the thought experiment)? Would you finally, truly be alone in the universe, surrounded by the perfect ideal of an all-encompassing nothingness? Even though you wouldn't have any particles around you, you'd still have this energy to be your sole companion. This energy is omnipresent throughout the universe. ![]() But when left to their lonesome, the quantum fields have an intrinsic energy, known as vacuum energy. Physicists have discovered that quantum fields soak all of space and time, and these quantum fields give rise to the particles of everyday life. Quantum physics provides a surprising answer: No. ![]() (Technically, the walls of the box would emit photons of their own, but let's leave that aside for this thought experiment.) Would you be alone then? So let's say you were to build a giant box thick enough to block out the neutrinos and the CMB, leaving you alone inside. (Image credit: © ESA and the Planck Collaboration) So, even in the darkest voids, you're not entirely lonely.Ī map of the sky shows the Cosmic Microwave Background (CMB), a remnant of the period of the early universe when this lost dark matter might have existed. This radiation, known as the cosmic microwave background (CMB), is responsible for over 99.99% of all the radiation in the universe, and it's impossible to escape. Suffusing the entire cosmos are lightweight, neutral particles called neutrinos as well as the radiation left over from the early days of the universe. The cores of the voids are so empty that not even dark matter - the mysterious, invisible form of matter that makes up the bulk of every galaxy - doesn't even have a presence.īut still, space wouldn't really be empty. In the depths of the largest voids, you can stand hundreds of millions of light-years from the nearest galaxy. To reach the emptiest places in the universe, you have to travel to the cosmic voids, the vast regions of nothingness that dominate the volume of the cosmos. Even though the density of interstellar space is billions of times lower than even our emptiest human-made vacuum chambers, it's not 100% percent empty. ![]() Still, even far from Earth, there's plenty of stuff floating around: charged particles zipping here and there, wandering hydrogen atoms, bits of fluff and dust minding their own business. No changes were detected - and soon, Einstein would demonstrate that the speed of light was always constant - so scientists eventually moved away from the concept of the ether, allowing for the possibility of a true vacuum. However, in the late 1800s, two physicists in Cleveland, Albert Michelson and Edward Morley, devised a clever experiment to measure changes in the speed of light as Earth moved through the ether.
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