|MadSci Network: Physics|
Corey, you are right to be skeptical. Every scientist should be careful to make sure that observations do indeed make good sense. In this particular case, you are correct that we can not see atomic or sub-atomic particles with our own built-in senses. However, we can design tools that will sense the effects of such small particles in ways that can be amplified or modified to make them evident to our own eyes and ears. Let me give two examples. Sub-atomic particles (neutrons among them) moving at very high speeds collide with the gas that is contained in that chamber. If we make the chamber conditions right, then the energy dissipated in these collisions can cause a trail of droplets to form. This is called a cloud chamber, and the tracks of the particles are visible in such. Or, I can bang such fast-moving particles into a semiconductor diode, or a low-pressure gas tube, with a voltage across it. The incident particle will create a swarm of electrons, etc, all knocked loose by the collisions of its passage. This will make a low-resistance path and a pulse of current will flow. This can be amplified and routed to a speaker. We hear a *pop!* each time an energetic particle flies through the detector, which is essentially a Geiger counter type device. Many classic experiments use such methods. A famous one is Millikan figured out the charge on the electron. He had tiny oil drops go through an electric field and pick up a small charge. By then using a field to suspend the oil drop against gravity in a vacuum, he could balance the electromagnetic force against the force of gravity. By observing (through the equivalent of an optical microscope) how much field was required to balance gravity for quite a number of charged oil drops, he figured out what the charge on the electron had to be, as his electromagnetic force was quantized (so many electrons on one oil drop). Such indirect methods are not limited to small things. The recent detection of planets around nearby stars, for instance, is done by extremely careful measurements of the spectrum of that star, looking for a Doppler effect caused by the wobble of the star around the common center of gravity of the planet and star. Note that we can not, now, directly image the planet. It is as invisible to us as the neutron, but by using classical gravitation and Doppler effects (and a very sophisticated spectral analysis system) we can detect its effects. The general answer to your question, therefore, is that we use a variety of indirect methods of measurement when working with atomic and sub-atomic scale events. The specific method used, of course, depends on what one is trying to detect or evaluate. There is, in fact, a whole branch of science called metrology (the study of measurement) that worries about some very, very fundamental things (how you measure how much time a second is, for example) to extremely high levels of precision.
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