Stellar Corpses

the universe is balanced every action has an equal and opposite reaction this is newton's third law and has been a defining principle of physics since the late 1600s it's simple intuitive and very attractive for this reason einstein notoriously refused to accept the existence of black holes despite them being proven mathematically in its own field equations the existence of black holes would mean a breakdown in this balance and the crumbling of the beauty and symmetry at the backbone of physics before observing this breakdown in reality from collapsing stars we should understand the balance formed beforehand stars spend their whole life in balance over billions of years individual atoms and molecules of gas and dust slowly start accumulating due to some strange product of space-time called to gravity for some reason the universe likes to keep matter stuck together and the more that does the more intense that driving force becomes each particle in our forming protostar is trying to get to the core while those between them are pushing right back this outward force is from electrostatic repulsion think of it how the like sides of magnets push each other away initially the majority of electrostatic repulsion is from electrons but these electrons pushing against each other provide one another with energy and eventually it's too much to stay bound to individual atoms thus at the cores of most planets we find a plasma-like substance of free nuclei and free electrons earth's core is an iron-like plasma these nuclei contain protons which are positively charged but their internal magnetic moment is much weaker than electrons so they don't repulse other protons at the distances electrons repulse other electrons but now that our nuclei have lost their electrons they are able to get really close to one another and now their electrostatic repulsion starts pushing back against gravity as the matter of our protostar continues to build up over millions of years the amount of force squeezing our nuclei our protons together increases and they get closer and closer together until something truly strange happens inside each proton and neutron are three quarks these quarks are held together through a fundamental force we call the strong force similar to how a proton's electrostatic repulsion acts over shorter distances than electrons the strong force acts over an even shorter distance still about the width of a nucleon but there's one final force at play here and that is the weak force the weak force acts over an extremely short distance between a hundredth to a tenth the distance of the strong force generally the quarks inside of nucleons as close together as they are are usually too far from one another to interact via the weak force and even when they are close they have no reason to do so as the amount of matter and more crucially density increases the insane temperatures and kinetic motion of the protons in our core will force two protons so close that they are able to interact via the strong force the strong force is as the name implies stronger than electrostatic repulsion and thus pulls the two protons together in this briefest of quantum instances smooshed by the gravity of a star the quarks of the two protons are so close that they can interact via the weak force and the universe uses this opportunity to lower the internal energy of our core the strong force also mediates the attraction of protons to neutrons and believe it or not protons to protons but protons are still electrostatically repulsed by one another therefore a proton bound to a neutron is a lower energy state this is the cause of fusion when our two protons overlap the weak force causes one of the up quarks in a proton to flip into a down quark this causes the proton to convert into a neutron a positron and a neutrino the positron carries away the positive charge of the proton and immediately annihilates with the first electron it bumps into the neutrino carries off an unimaginably small amount of matter the proton and neutron then bind together forming deuterium deuterium then rapidly forms helium-3 which releases intense heat and energy after a long time two helium-3 nuclei can then fuse to form good old-fashioned helium the kinetic energy from these reactions allow particles to slam into the particles pushing towards the core balancing gravity regardless of the size of the star this balance is not forever helium is heavier than hydrogen so it sinks closer to the core over billions of years more and more helium collects at the core moving hydrogen fusion to a shell around the now helium core inquisitive minds may ask how can hydrogen fuse further from the core i thought that was the only place where the properties were extreme enough for fusion unfortunately that's a topic for another day as stellar fusion is a lot more intricate than one would think and this video is about the corpses left behind afterwards but eventually the products of fusion sink into the core of our sun when the outer shells run out of fusionable material the star will begin collapsing now the core is hotter than ever before but instead of fusing new materials this insane heat serves to act as a super fan and blows away the lighter outer layers the heavier matter that isn't blown away sticks around in a new balanced state electrons cannot by no means overlap exactly with another electron it simply cannot happen by any means of quantum mechanics as our dead sun collapses the pressure forces more and more electrons closer and closer together thus limiting the volume they can occupy eventually they are so insanely absolutely smooshed together they go just stop honestly i literally cannot be squished anymore where else do you expect me to go and thus our star shrinks no further this is called degeneracy pressure and it will be what creates balance at the end of our son's life the resulting object is a white dwarf this object will exist for the rest of time slowly cooling until it reaches the same temperature as the universe after a trillion or so years a brilliant physicist named subramanian chandrasekhar calculated that this would be the case for all stars up to a mass of 1.4 suns for stars larger than this the degeneracy pressure of electrons actually decreases due to the intense gravity and kinetic motion of the electrons it would not be enough to hold back the immense crushing force of the star's collapse but einstein's wishes would prevail yet again because another balance can still be struck for much larger stars as they collapse the electrons are forced right up into protons and just like with fusion the electron and the quarks inside the proton can interact via the weak force one of the protons quarks flips into a down quark and the electron flips into a positron again this occurs because the resulting products are in a more stable energy state neutrons can still interact via the strong force thus by converting our protons into neutrons we alleviate the electron degeneracy pressure however this drop in electron degeneracy pressure means our star continues collapsing in fact it collapses so much our neutrons begin to experience their very own degeneracy pressure they break their bonds between each other and suddenly just like electrons and white dwarfs they tell all the particles pushing on them that they physically cannot be shrunk any further and to stop and with this halt our neutron star is formed what einstein and many physicists of the mid 20th century continued to discover was that nature found ways to prevent the formation of a black hole since large stars always seemed to be accompanied with a supernova when they died many scientists were convinced that the environment from the star's collapse would force more and more matter to be ejected from the stars into the cosmos this would cause the mass to drop until reaching the limit to form a neutron star or perhaps like how protons were converted into neutrons perhaps in the unimaginable pressures at the limits of a black hole fundamental particles would be compelled to quantum teleport away at this time quantum mechanics was relatively fresh and this seemed like a very real possibility it wasn't until computers were able to start running rudimentary models that physicists began to realize just how crazy the birth of a black hole was and the unfortunate reality that the breaking of this balance in nature was quite real in the final video we will look at the death of truly immense stars and the strange events that go into forming a black hole [Music] you

Channel: But Why?

Views: 157,014

Keywords: black holes, fusion, neutron star, neutron, white dwarf, strong force, weak force, solar, quarks, star death

Id: n1FhudqXgvI

Length: 9min 27sec (567 seconds)

Published: Sun Sep 12 2021