The physicists used magnetic fields to manipulate and measure the neutrons' spin, and conducted a series of measurements where they systematically changed the parameters of the measuring device. These quantities are related, just as position and momentum are, so that the more precise a measurement is made of one, the less precise a measurement can be made of the other. To test how much this fundamental property contributes to the overall uncertainty, the researchers devised an experimental setup to measure the spin of a neutron in two perpendicular directions. "In order to describe the basic uncertainty together with measurement errors and disturbances, both particle and measurement device in a successive measurement have to be treated in the framework of quantum theory." "This has nothing to do with error or disturbances due to a measurement process, but is a basic fundamental property that every quantum mechanical particle has," Sulyok told LiveScience. This probabilistic nature of particles means there will always be imprecision in any quantum measurement, no matter how little that measurement disturbs the system it is measuring. This is also true of a particle's other properties, such as its momentum, energy and spin. Instead, particles can behave like waves, and can only be described in terms of the probability that they are at point A or point B or somewhere in between. In quantum mechanics, particles can't be thought of as marbles or billiard balls - tiny, physically distinct objects that travel along a straight course from point A to point B. Sulyok worked with a research team, led by physicists Masanao Ozawa of Japan's Nagoya University and Yuji Hasegawa of Vienna University of Technology in Austria, to calculate and experimentally demonstrate how much of the uncertainty principle is due to the effects of measurement, and how much is simply due to the basic quantum uncertainty of all particles. "But this explanation is not 100 percent correct." "In the early days of quantum mechanics, people interpreted the uncertainty relation in terms of such back-reactions of the measurement process," said physicist Georg Sulyok of the Institute of Atomic and Subatomic Physics in Austria. Though not imparting as much disruption to the electron's momentum, a longer wavelength of light wouldn't allow as precise a measurement. The smallest wavelength of light, called gamma-ray light, can make the most precise measurements, but it also carries the most energy, so an impacting gamma-ray photon will deliver a stronger kick to the electron, thereby disturbing its momentum the most. The wavelength of the light determines how precisely the measurement can be made. When a photon, or particle of light, hits the electron, it will bounce back and record its position, yet in the process of doing so, it has given the electron a kick, thereby changing its speed. Imagine shining light at a moving electron. Heisenberg originally explained the limitation using a thought experiment. Or you might choose to determine an electron's momentum fairly precisely, but then you will have only a vague idea of its location. Its logic is perplexing to the human mind, which is acclimated to the macroscopic world, where measurements are only limited by the quality of our instruments.īut in the microscopic world, there truly is a limit to how much information we can ever glean about an object.įor example, if you make a measurement to find out exactly where an electron is, you will only be able to get a hazy idea of how fast it's moving. The uncertainty principle only applies in the quantum mechanical realm of the very small, on scales of subatomic particles.
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