The tiniest is much lighter than an electron

The universe is vast, but it is made up of many minute pieces. The periodic table is made up of elements like oxygen, carbon, and other building blocks that make up things like stars, kittens, and coffee cups. Scientists have been thinking about and finding smaller and smaller basic particles — those tinier than atoms that make up the universe — since the turn of the twentieth century. So, which of these basic particles is the tiniest? Which, on the other hand, is the largest?

One of the scientists attempting to solve this topic is Don Lincoln, a senior researcher at Fermi National Accelerator Laboratory (Fermilab), in Chicago. Scientists at Fermilab use a particle accelerator to smash individual particles together and examine the debris — which could include new fundamental particles — that results. According to Lincoln, there are two methods for determining particle size: researching their mass and measuring their physical size, such as estimating a ball’s diameter.

These questions are pretty easy to answer in terms of mass. The neutrino is the smallest nonzero-mass particle known to science, according to Lincoln. However, because the detectors used to compute the mass of fundamental particles aren’t sensitive enough, we don’t have a precise measurement of a neutrino’s mass.

“A neutrino is a particle, a kind of subatomic ghost,” Lincoln explained. Neutrinos are the second most prevalent particle after photons and interact with matter extremely weakly (which behave more like waves than actual particles). In fact, millions of neutrinos are flowing through your body right now. Neutrinos have a mass of almost nothing and travel at almost the speed of light.

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Neutrons, protons, and electrons make up an atomic nucleus. According to Lincoln, protons and neutrons are around one-tenth the size of the nucleus as a whole. Although an electron has a mass of nearly zero, it weighs 500,000 times more than a neutrino (again, whose exact measurement is impossible to make at this point).

According to Lincoln, physicists use electron volts (eV) to quantify the mass of subatomic particles. The unit is eV/c2, where c stands for the speed of light. 1.6×10-19 joules is the equivalent of one electron volt. To make things easier, physicists adopt a set of units in which the speed of light is equal to one. You’d use Albert Einstein’s famous equation E=mc2 to calculate the mass (m) in kilograms to find out the mass of a subatomic particle.

According to Lincoln, an electron weighs 511,000 electron volts, which is 9.11 x 10-31 kg. According to him, a proton in the nucleus of an atom weighs 938 million electron volts, or 1.67 tens of kilograms.

According to Lincoln, the largest (in terms of mass) fundamental particle we know of is a particle called a top quark, which has a mass of 172.5 billion electron volts. Quarks are another fundamental particle that cannot be split down into more bits, as far as we know. Up, down, strange, charm, bottom, and top are the six types of quarks discovered by scientists. Protons and neutrons are made up of up and down quarks, which weigh 3 million and 5 million electron volts, respectively. The top quark, in comparison, is 57,500 times heavier than the up quark.

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Physical size is a more difficult question to answer. Some particles have physical sizes that we know about, but we don’t know about the tiniest ones. Some “insignificant” particles that individuals encounter on a regular basis, such as virus particles, are actually rather massive.

This is how Lincoln provided a feeling of scale: A normal virus particle measures between 250 and 400 nanometers in length (a nanometer is a billionth of a meter, or 10-9 m), while an atomic nucleus measures between 10-14 m. (0.00000000000001 m). That a virus’s atomic nucleus is the same size as a virus’s nucleus is to us.

Scientists can currently measure the smallest physical size with a particle accelerator that is 2,000 times smaller than a proton, or 5 x 10-20 m. Quarks are smaller than that, but scientists haven’t been able to figure out by how much.

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