Nice job making it all the way here. The Planck length is the distance light travels in a single unit of Planck time. A unit of Planck time is defined by the time it takes light to travel one Planck length. A bit circular logic by Planck. In any case, physicists say that anything smaller than a Planck length “makes no sense” with our existing models. In other words, until further notice, the Planck length is the Universe’s pixel size.
The rules of general relativity say that mass warps the canvas of space time. You can imagine that like a ball resting on a sheet of stretchy fabric. But general relativity likes things to be extra, so it also claims if we zoom in very closely to the fabric we would see that it isn’t smooth like woven cloth, but actually made of a bubbling foam of tiny new dimensions unfolding and folding back onto themselves, appearing and disappearing with incomprehensible rapidity. As usual, the quantum realm refuses to just be normal and intuitive.
A quantum string is a theoretical, one—dimensional wiggly little string that can exist in 11 dimensions, whatever that means. The string is the core idea of string theory, the most well—known crack at an overarching theory of physics that can explain both the quantum physics of the tiny world and the gravitational physics of the larger world.
A string is supposedly about 10^-34m long. That’s embarrassingly short. If the smallest neutrino were the size of the Sun, a string would be just 2 mm long.
But that doesn’t capture the intense smallness well enough. Let’s try this another way:
Imagine creating an Earth like ours, but the size of a marble. Now imagine that someone on that Earth does the same thing, making a mini-Earth the size of one of their marbles. And then someone living on that double-mini Earth does it again. And now, imagine that someone on that triple—mini Earth is playing the guitar. The guitar strings are the length of our world’s quantum strings.
The OMG particle needs to get a grip. It’s the highest energy particle ever detected, the equivalent of taking the kinetic energy of a thrown baseball and packing it into one single proton. We don’t know where exactly it comes from, but it’s somewhere in space where crazy things are happening. Because they’re traveling so close to the speed of light, these protons have their length contracted by a trillion times! Seen from Earth, they’ll whiz by like tiny little proton pancakes.
Neutrinos are the smallest and lightest fundamental particles, and the most energetic neutrinos are the tiniest. Take another particle, the proton, as a reference: A proton compares to a grain of sand like a grain of sand compares to the Sun. So how small is a neutrino? If the smallest neutrino were a basketball, a proton would be the size of the Moon. Some nerve to be that small.
The smallest and highest energy neutrino ever detected was found in a giant particle detector built into the Antarctic ice sheet, above the South Pole. We don’t know what makes neutrinos with this much energy, but it could be crazy things happening around the black holes at the centers of galaxies.
Atmospheric neutrinos are produced when cosmic rays — high-energy particles like protons and electrons — collide with our atmosphere.
Atoms are on package deal: they consist of protons, neutrons and electrons. Electrons are small but mighty, contributing very little to the atom’s mass but hugely influencing physical phenomena like electricity, magnetism, and chemistry. Most atomic illustrations, like ours, show electrons orbiting atomic nuclei like planets around the Sun. That’s an intuitive way to think about it, but it’s not actually what’s happening. An electron shell is actually a probability distribution for where you’re most likely to “find” the electron at any moment.
Electrons, like all fundamental particles, don’t actually have a true intrinsic size. This is one common approximation physicists use for working with them.
The runt of the quark litter, top quarks are very short—Iived phenomena: they are found in high energy particles which only exist for fractions of a second during collisions.
The weak nuclear force is one of the four known fundamental forces of nature, together with electromagnetism, gravity, and the strong nuclear force. The weak nuclear force is responsible for interactions of subatomic particles and radioactive decay, like the fusion happening in the Sun. If the weak force were any stronger the Sun would already have burned out. If it were weaker, the Sun wouldn’t have ignited at all. So let’s all be glad things worked out the way they did!
Quarks were discovered little by little. The existence of the bottom and top quark, for example, had been predicted for a long time before they were found. Physicists were so happy about them turning up eventually and confirming their ideas that the new quarks were briefly called “beauty quark“ and “truth quark.“ Once everyone got ahold of themselves, they were renamed “bottom quark” and “top quark”.
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