Gamov (as well as Ronald W. Gurney, around that same time) proposed that such "quantum tunneling" did exist, and was the main cause of radioactivity in heavy elements. There was one modification: the most likely transition, requiring the least energy, was not the escape of a single proton, but of a helium nucleus--two protons and two neutrons bound together by the nuclear force, a very strong bond. Such energetic nuclei are known as "alpha particles" (α particles), a name introduced in the early days of research on radioactivity, after physicists found that some positively charged particles were emitted, but could not yet tell what they were.
It may take millions and even billions of years before an α particle manages to "tunnel" its way out, and such radioactivity is the source of much of the internal heating of the Earth (radioactive potassium also contributes). Other types of radioactivity in heavy elements often represent the re-adjustment of nuclei left unstable by α-particle emission, sometimes leading to the emission of additional α-particles.
Sooner or later, the α particle captures two electrons from its environment and becomes an ordinary atom of helium (and meanwhile the nucleus, having undergone α-emission, has reduced its positive charge and therefore must give up two electrons, preserving the electrical neutrality of matter as a whole). Nearly all of the helium found trapped in rocks or extracted from natural gas is in fact contributed by this process (we can tell this because it is deficient in a lighter form of helium, observed on the Sun and elsewhere). Thus the gas used to fill airships and balloons is almost entirely the product of radioactivity!
The study of gamma rays from radioactive nuclei suggests that nuclei, too, have energy levels. However, using quantum mechanics to calculate such levels is much harder here, because nuclear particles are much more tightly bound, and nuclear forces are more complicated. Still, at least in some approximation, quantum theory can be applied to many nuclear processes (as it was to α-radioactivity, above), also to fast collisions of particles and to nuclear fission.
Space physics deals with big objects--stars, plasmas, planets etc.--far above the sub-microscopic scale of most quantum processes. However, it still needs quantum mechanics, to account for atomic-scale processes involved in the behavior of such large objects. The energy of stars such as the Sun is mostly due to reactions between atomic nuclei, and most elements we know (excluding only the lightest ones) are apparently rapidly "cooked" in the catastrophic collapse of big stars, creating what is known as a "supernova." Indeed the matter of the original "big bang" seems to have lacked all the familiar elements from carbon and up, on which life (among other things) depends.
Other quantum processes determine
and many other phenomena. The universe cannot be understood without quantum theory.
- the physics of the Sun's atmosphere
- the loss of trapped plasma produced in a magnetic storm (by "charge-exchange" collisions with the cloud of hydrogen atoms surrounding Earth)
- the chemistry of the upper atmosphere and ionosphere
- the colors produced by the polar aurora
Almost all the preceding describes work done between 1900 and 1960. Much more was added since then, in particular about the way elementary particles interact in high-energy collisions (with application to the early universe, after the Big Bang). "Elementary particles" here means protons, neutrons and electrons, as well as unstable products of energetic nuclear collisions. That however lies far beyond the level of this overview, also it is quite beyond the writer's own expertise, two good reasons to stop here.
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