ericgibbs said:
Is the space between atoms really empty?
Eric
According to quantum mechanics, the vacuum is not empty, but teeming with virtual particles that constantly wink in and out of existence.
The vacuum of empty space is a restless place. According to quantum mechanics, particles pop in and out of
existence, and those "virtual" particles give the vacuum energy and can affect tiny objects. For example, two parallel metal plates will feel a minute force, called the Casimir effect, pulling them together. That's because
virtual photons with certain wavelengths cannot exist between them. The vacuum outside the plates thus has more energy, so it squeezes the plates together.
Existence of vacuum, then an entity called “no thing,” physics has achieved great insights into its nature, especially after the discovery and the subsequent development of quantum mechanics. A perfect vacuum—a space
devoid of any particles and at zero temperature— cannot be achieved, neither in theory nor in practice. A vacuum cannot exist in the cosmos due to the presence of the CMB radiation and to the quantum mechanical phenomenon of vacuum fluctuations.
A vacuum cannot exist inside an atom either, due to the presence of the force carriers of the various forces existing in nature. Even if such a vacuum could exist, the laws of quantum mechanics tell us that we would destroy it trying to observe it, and also even if we suppose that we can locate a small region of space vacant of particle/ antiparticle pairs and force carriers, a vacuum should still not be observable. There is a key quantum-mechanical concept introduced in using the word ‘observable’.
Moreover, it is known that a perfect vacuum cannot be created experimentally due to the third law of thermodynamics. However, applications of techniques for creating conditions of near perfect vacuums span several
disciplines, from microprocessing to food storage to metallurgy and plasma studies.
Based on their importance within laboratory testing environments and within the disciplines listed above, scientists will continue to search for powerful techniques to reach higher and higher levels of vacuum in the hope
of eventually achieving a perfect vacuum.
An “empty” space is never truly empty, physicists believe, even if every atom and particle in it has been removed.
This is because particles will continue to appear out of nowhere, then vanish.
In the new research, physicists report having measured this activity using a cloud of atoms that merge to effectively become one giant atom. This bizarre substance, called a Bose-Einstein condensate, was invented a
decade ago but has found little practical use since then.
The new findings, researchers say, mark the first time a Bose-Einstein condensate has been used to study anything besides its own properties. It was employed to investigate something perhaps even stranger: the so-called virtual particles that appear and disappear in the void.
Engineers must take virtual particles into account as they design ever-tinier machines and robots, a growing industry. On small scales, virtual particles create unpredictable forces that can throw off these devices.
In studying virtual particles, the researchers probed a phenomenon that seems to violate a physical law recognized more than two centuries ago: the law of conservation of energy.
The law says energy can neither be created nor destroyed. It’s also true of any object, because objects have mass, and mass is convertible to energy. Einstein showed this.
Virtual particles get around this law thanks to a subatomic phenomenon called the uncertainty principle.
Understanding the principle, as well as Bose-Einstein condensates, requires some explanation of the nature of subatomic particles.
Scientists consider subatomic particles as things with two seemingly contradictory natures: they are both particles and waves. This is because they act like one or the other depending on the experiment one does.
One can shoot them into a target like tiny bullets, in which case they act like particles.
But they also move like waves: for instance, they create interference patterns. These are patterns similar to those that appear when one drops two pebbles in a pond. Complex ripple patterns will appear where the two sets of circles, each expanding outward, overlap.
Physicists have found that subatomic particles’ wave nature makes it impossible for the particles to have both a precisely defined location and speed. This ultimately lets them briefly appear out of nowhere.
The effect is due to certain oddities of particle-waves.
So not only does it have an imprecisely defined location, it also has an imprecisely defined speed. In fact, more precisely you define its location, the less precisely you define its speed—because you’re adding more waves. The
more precisely you define its speed, the less precisely you define its location—because you’re subtracting waves and increasing the spread.
The idea that there’s no such thing as empty space stems from this finding that a particle can’t have both an exact speed and location. A point of “empty” space is mathematically identical to a weightless particle with a
speed of zero and a perfectly defined location, that being the point itself. This isn’t allowed.
Therefore, physicists postulate that empty space is actually full of subatomic particles that flash in and out of existence.