WEEK #1 SEMESTER 2
-Energy produced by fusion heats the gas and builds up enough pressure to balance
-So the sun is ﬁghting gravity
•It is not winning, it is losing
•The stalemate is only temporary
-As sun was born from collapsing cloud of interstellar has the contraction of all gas
caused gravitational potential energy to be turned into kinetic energy which heated
the sun up.
-The strong force: acts like superglue, binding neutrons and protons together. At short
distances, there is a force that pulls protons together.
-At the center of this collapsing cloud, the density increased, the pressure increased
and the temp increases.
•The buildup of pressure is the ﬁrst attempt to stop gravity.
-Sun was born with enough hydro to shine steadily for a lifetime of 10 billion years/
•Halfway through life cycle presently.
•When all you have is helium, the pressure of gravity collapses star and it dies.
-On earth we need some upward pressure to counteract gravity.
-If there isn’t a balance of pressure and gravity, things change.
-Sun couldn’t survive just as a core. Shelves above it (layers) that provide outwards
-If temp of suns core increases just a lil, fusion rates would increase a lot. That would
increase temp further. Thus increasing pressure. This would cause the core to
expand, If it expands, it’ll cool down. And return fusion rate to normal.
-The sun is getting brighter because the core contracts slight due to total number of
particles slowly decreasing over a long time. Fusion rate increases and energy
production goes down.