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OK…so the problem is… Immense gravitational forces act inward c ausing the star to

You know about Newton’s law of universal gravitation…the law states that all masses everywhere attract each other with a force proportional to the product of their masses and inversely proportional to the square of their distance.

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OK…so the problem is… Immense gravitational forces act inward c ausing the star to

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  1. You know about Newton’s law of universal gravitation…the law states that all masses everywhere attract each other with a force proportional to the product of their masses and inversely proportional to the square of their distance.

  2. Well then…why don’t truly massive objects like stars, including our Sun, just IMPLODE owing to the huge gravitational forces inward toward the center? Would you believe it… Conservation of Momentum comes to our rescue?! Read on to see how…

  3. OK…so the problem is… Immense gravitational forces act inward causing the star to tend to implode. Something must be counteracting this huge force of attraction! But……what?

  4. To find the answer …look closer… look at one atom inside the star… Atom

  5. All the atoms in the starare continually absorbing energy (heat, light, whatever) and emitting energy (usually as light). Thus each atom is either in an excited state (higher Bohr level) just after absorbing energy, or in a ground state (lowest Bohr energy level) just after emitting energy. Atom

  6. Consider an atom sitting at a particular instant in an excited state (higher Bohr level) just after absorbing energy. The atom now emits this energy in the form of a photon of light….that’s the little red guy below… Photon is Emitted Atom But…hang on…Conservation of Momentum demands that the atom, after shooting a photon to the right with some momentum, MUST recoil to the left with an equal and opposite momentum! Like so… Photon is Emitted Atom Atomic Recoil

  7. The fun begins when this emitted photon happens to collide with a neighboring atom which happens at that particular instant to be sitting in the ground state. The second atom absorbs this photon, like so... Photon emitted by first atom is absorbed by the second atom Atom Atom Atomic Recoil But…hang on…Conservation of Momentum demands that the second atom, after absorbing the photon, MUST recoil to the right! As shown below… Second Atom Recoils Also Photon emitted by first atom is absorbed by the second atom Atom Atom Atomic Recoil

  8. So we have a process where both atoms end up recoiling away from each other, i.e., repel each other!! This interatomic repulsive force, generated by conserving momentum during the process of photon emission and absorption, is what counteracts the colossal imploding force of gravity!!! BTW, the process by which the photon emitted by one atom is absorbed by a neighboring atom is called RADIATION TRAPPING. Photon is Emitted Photon is Absorbed Atom Atom Atomic Recoil Second Atom Recoils Also

  9. Once a star dies, i.e., stops producing light, the huge gravitational forces win and the star implodes, forming either a dense white dwarf (a 110 lb person on this object would weigh 400,000 tons!), or a neutron star ( a 110 lb person on a neutron star would weigh 340,000,000,000 tons!), or – the ultimate – a black hole.

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