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How do atoms come into existence? – Joshua, 7 years old, Shoreview, Minnesota
Richard Feynman, a renowned Nobel laureate in theoretical physics, noted that if he were to pass on just one piece of scientific knowledge to posterity, it would be about the atom.
Grasping how atoms form is crucial since they are the building blocks of all mass in the universe.
Many physicists seek to unravel the origins of atoms. Experts have only formed hypotheses regarding the formation of certain atoms.
What is an atom?
An atom consists of particles known as nuclei, which contain heavy centers termed neutrons. Surrounding the nucleus are lighter particles known as electrons that orbit the nucleus.
Each electron carries a single unit of negative charge, while protons carry a unit of positive charge, and neutrons carry no charge. Atoms are electrically neutral, possessing equal numbers of protons and electrons.
Currently, the simplest two types of atoms in the universe are hydrogen, which contains one proton, zero neutrons, and one electron, and helium, comprising two protons, two neutrons, and two electrons. Naturally, more complex atoms like carbon and oxygen exist on Earth, which will be discussed later.
Elements denote a collection of identical atoms, all possessing the same number of protons.
When did the first atoms form?
The majority of hydrogen and helium atoms in the universe formed roughly 400,000 years after the Big Bang, the event considered the inception of our universe, which occurred around 14 billion years ago.
Why did they form during that time? Astronomers have observed explosions of distant stars that illustrate how the universe has continued to expand since the Big Bang. Initially, when hydrogen and helium atoms formed, the universe was 1,000 times smaller than it is today.
Based on physical principles, scientists propose that the early universe was much hotter.
Prior to this cooling phase, electrons possessed too much energy to settle into orbits around the nuclei of hydrogen and helium. Consequently, these atoms could only form once the universe cooled to around 5,000 degrees Fahrenheit (2,760 degrees Celsius). For historical reasons, this process is inaccurately termed recombination – a more accurate term would be combination.
Helium and deuterium, a heavier form of hydrogen, formed even earlier just minutes after the Big Bang, during which temperatures soared past 1 billion degrees Fahrenheit (556 million degrees Celsius). Protons and neutrons collide only at such extreme temperatures to form nuclei.
Scientists estimate that nearly all ordinary matter in the universe consists of about 90% hydrogen atoms and 8% helium atoms.
How do larger atoms form?
Thus, during the recombination process, hydrogen and helium atoms emerged, allowing electrons to orbit due to cooler temperatures. However, you, I, and nearly everything on Earth is composed of elements beyond just hydrogen and helium. How do these other atoms come into existence?
The surprising answer: most heavier atoms are formed in stars. To create atoms that contain multiple protons and neutrons in the nucleus, high-energy collisions are requisite, which occur in extremely hot environments. The energy necessary for forming a heavy nucleus must be substantial enough to overcome the repelling forces between positive charges, such as those felt by two protons.
Protons and neutrons also exhibit differing characteristics, and when they are sufficiently close, they can bind together. This property is known as the strong force. The process by which these particles are joined is called fusion.
Scientists assert that most elements from carbon to iron are formed through stellar fusion, occurring in stars more massive than the sun, where temperatures can exceed 1 billion degrees Fahrenheit (556 million degrees Celsius), similar to conditions shortly after the Big Bang.
However, even the hottest stars cannot produce heavier elements than iron or nickel. The formation of these heavier elements is less straightforward, requiring additional energy input.
During a dramatic phenomenon known as a supernova, the inner core of a massive star collapses after exhausting its fuel. This collapse triggers a powerful explosion capable of forming elements heavier than iron and ejecting them into space.
Astronomers are still exploring other captivating events that contribute to the formation of larger atoms. For instance, collisions between neutron stars can release vast amounts of energy, leading to the formation of elements like gold amidst the birth of black holes.
To fully grasp how atoms are formed, it’s essential to delve into nuclei, particles, atomic physics, and even the broader theory of relativity. Complicating matters, certain aspects of the universe appear not to be composed of ordinary atoms, like dark matter. Scientists are investigating the nature of dark matter and its formation.
This revised article has been adapted from the conversation under a Creative Commons license. For the original piece, please refer to the original article.
Source: www.livescience.com