Big Bang Black Holes No Math ASTR PHYS 109 Dr David Toback Lecture 25 26 Big Bang BlackEarly Times Fate of the Universe Topic 1 Holes No Math Possibilities 1 Was due Today L25 Reading Unit 6 was due already Pre Lecture Reading Questions Unit 6 Stage 2 due Today End of Chapter Quizzes Chapter 17 Papers Paper 3 Revision if desired Stage 2 due Paper 4 Stage 1 due Monday Big2Bang Black Holes No Math Was due Today L26 Reading Unit 6 was due already Pre Lecture Reading Questions Unit 6 Revision if desired Stage 1 due Today End of Chapter Quizzes Chapter 17 Papers Paper 4 Stage 1 due today Big3Bang Black Holes No Math Honors Papers Due Monday April 28th at 11 55PM on eCampus in turnitin Stage 1 MUST be approved in order to get full credit for the assignment Early Times Fate of the Big Bang Black Holes No Math Universe Topic 1 Possibilities 4 Unit 6 Going back in time and going forward in time Before the first millionth of a second and the Fate of the Universe Early Times Fate of the Big Bang Black Holes No Math Universe Topic 1 Possibilities 5 Outline of Unit 6 1 Possible Fates of theToday Universe Dark Matter and Dark Energy 2 Particle Physics Dark Matter and the Very Early Universe 3 Inflation Early Times Fate of the Big Bang Black Holes No Math Universe Topic 1 Possibilities 6 Caveats While the data is VERY powerful some of the interpretations of the data are not fully proven or understood Still need data to tell us about the theory and theory to tell us about the data New data and theoretical advances have recently changed our understanding of the Universe Early Times Fate of the Big Bang Black Holes No Math Universe Topic 1 Possibilities 7 The Fate of our Universe Will the Universe continue expanding forever That depends mostly on a few things 1 How fast is it expanding now 2 How much STUFF there is in the Universe 3 How big it is now 4 Are the laws of physics Early Times Fate of the Big Bang Black 8 really understood Holes No Math Universe Topic 1 Possibilities Why the first three are so important Gravity is trying to pull space time back together again Attractive force Either it s strong enough to pull the universe back together again or it isn t Early Times Fate of the Big Bang Black Holes No Math Universe Topic 1 Possibilities 9 What about that last issue Dark Energy fits into this story but it is an effect that only impacts on the largest scales Takes 10 billion years and HUGE distance scales to have ANY effect Start by discussing gravity first then come back to it Kinda when we did the 10 Early Times Fate of the Big Bang Black like Holes No Math Universe Topic 1 Possibilities Gravity Three Possibilities There are basically three possibilities Use an analogy Shooting a bullet into the air at the surface of the Early Times Fate of the Big Bang Black Holes No Math Universe Topic 1 Possibilities Earth 11 Possibility 1 Small Speed Universe ends in a Big Crunch If the bullet is shot up with a small speed gravity will eventually stop it and it will fall back to the Earth Can think of the gun shooting the bullet as an explosion our big bang If the Bang is too small all the stuff in the Universe will Early Times Fate of the Big Bang Black 12 eventually all fall back Holes No Math Universe Topic 1 Possibilities Continue the analogy It s a balance between the speed of the bullet and the density of the object the bullet is trying to leave Does the bullet have a below the escape Early Times Fate of the Bigspeed Bang Black 13 Holes No Math Universe Topic 1 Possibilities A bullet has a speed smaller than the escape velocity Early Times Fate of the Big Bang Black Holes No Math Universe Topic 1 Possibilities 14 The Sun Big15Bang Black Holes No Math Possibility 2 Big Speed Universe expands forever If the bullet has a speed greater than the escape velocity gravity will not be strong enough to pull it back Will keep on going away from the Earth forever Like launching a rocket into outer space but using a slingshot not thrusters that Early Times Fate of the Big Bang Black firing 16 keep Holes No Math Universe Topic 1 Possibilities Early Times Fate of the Big Bang Black Holes No Math Universe Topic 1 Possibilities 17 The Moon has a small escape Velocity Big18Bang Black Holes No Math To infinity and beyond As the bullet gets further and further from the moon the gravitational attraction gets smaller and smaller It still slows the bullet down but less and less Eventually the attraction is so small since they are so far away from each other that the bullet effectively moves off into space at the same speed forever Early Times Fate of the Big Bang Black Holes No Math Universe Topic 1 Possibilities 19 Possibility 3 In between It will approach zero speed as it gets farther from the Earth It s true that it can orbit the Earth it has just the right speed but that s not what we are talking about here Early Times Fate of the Big Bang Black Holes No Math Universe Topic 1 Possibilities 20 Back to the Universe Since there is a lot of mass in the Universe if it were expanding slowly enough the force of gravity would cause it to eventually stop expanding and then start contracting again Even with a large speed today gravity might force it to stop expanding and then Early Times Fate of the Big Bang Black 21 contract Holes No Math Universe Topic 1 Possibilities Look at it the Other Way Since we can observe the speed of the expansion of the Universe we ask the question the other way Is the density of the universe big enough to make the Universe contract again Collapse back on itself Big Crunch Early Times Fate of the Big Bang Black A 22 Holes No Math Universe Topic 1 Possibilities Summary 3 Possibilities 1 Over the critical density Collapse an anti big bang or a Big Crunch Gnab Gib 2 Under the critical mass Expanding forever but slows down and eventually hits a constant speed 3 Exactly critical mass Eventually stops expanding just barely enough Speeds get smaller and smaller Early Times Fate of the Big Bang Black 23 although never reaches Topic 1 quite Possibilities Holes No Math Universe Look at all three together Early Times Fate of the Big Bang Black Holes No Math Universe Topic 1 Possibilities 24 Do an expanding grid Early Times Fate of the Big Bang Black Holes No Math Universe Topic 1 Possibilities 25 A Universe Ending in a Big Crunch Remember this is only an analogy There is no center or edge of the Universe Early Times Fate of the Big Bang Black Holes No Math Universe Topic 1 Possibilities 26 …
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