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  So from this law, he would confirm the idea that the force is toward the sun and from knowing how the periods of the different planets vary with the distance away from the sun, it's possible to determine how that force must weaken at different distances and he was able to determine that the force must vary inversely as the square of the distance. Now so far, he hasn't said anything because he only said the two things which Kepler said, in different language. one is exactly equivalent to the statement that the force is forward the sun,  the other exactly equivalent to the statement that the law is inversely as a square of the distance But people had seen in telescopes that Jupiter's satelites are going around Jupiter. It looked like a little solar system. So the satelites were attracted to Jupiter. And the moon is attraceted to the earth and goes around the earth. It's attracted in the same way. So it looks like everything's attracted to everything  else. The next ...

  This model (Supply and Demand) raises a very important distinction that we're gonna focus on this semester. It's gonna trip you up. I guarantee you a number of times. So, I want you very careful thinking about this, which is the distinction between positive economics and normative economics. Positive economics study the way things are.  Normative economics is a study of the way things should be.  Now to consider to understand this let's consider a great example of economics at work which is eBay. When eBay came along, I know it is older than all of you, but it's younger than me.  When eBay came along, economists were very excited because economists love auctions. Auctions are, if you will, the standard market that used to exist in, you know, 15th century England. It's literally people bidding against each other in a way that reveals who wants the good the most. And what's wonderful about that, and we'll come back to this throughout the semester, is it ha...

This fact hints at an important law that governs our void,  The law of stability . Unstable blobs fall apart and vanish. Stable ones endure.   Now, watch what happens if we speed this up dramatically, maybe a couple of years per second, maybe even a couple million . You can see our blobs keep getting random jolts of energy, so they combine with others to form more complex compounds. Most attempts fail and fall apart, but every so often, by pure chance, you get a compound that is more stable than the blobs it's made of.   This doesn't happen because the blobs want to build more complex structures. It's just because these new configurations happen to be more favorable in the environment. And now when these complicated compounds become abundant enough, they too get a chance to combine, making our void increasingly complex. And one day, by accident, this causes an extremely unique shape to form, one with a special property.  See, the blobs it's made of just happen ...

  Can anyone tell me what that means ?  Your marginal rate of substitution (MRS) is 2.5 That is a meaningful concept.  Utils are not, but that is . Yeah, say it loudly so we can hear.  AUDIENCE:  You're willing to trade two pizzas for one cookie.  JONATHAN GRUBER:  Exactly, you're willing to give up 2.5 slices of pizza for one cookie. That's what that number means. And that is a meaningful number.  That's not an ordinal. That's cardinal.  We can use that.  You are willing to give up 2.5 slices of pizza to get one cookie.  What is the market asking you to give up?  How much pizza do you have to give up to get one cookie?  Half a slice.  You are happy to give up 2 and 1/2 slices of pizza to get a cookie, but the market is saying we'll let you have a cookie for half a slice of pizza .  So what should you do?  JONATHAN GRUBER: Eat less pizza. Eat more cookies . That will unambiguously make you happier. And that'...

  And this is proportional to the mass, So that if we were to take two different objects, first swing one, and then swing another one at the same speed around the head and measure the force in the second one , that second one, the new force is bigger than the other force in the proportion that the masses are different.  This is a way of measuring the masses by how hard it is to change the speed.  Now then Newton saw from this, that for instance, to take a simple example, if a planet is going in a circle around the sun no force is needed to make it go sideways, tangentially if there were no force at all on it, it would have just keep coasting this way. But actually, the planet doesn't keep coasting this way, but finds itself later not out here, Where it would go if there were no force at all. But further down toward the sun. In other words, its velocity, its motion has been deflected toward the sun.  So what the angels have to do is to beat their wings in toward the s...

  There's got to be somepart of our mind that came out our nature. I know that because I'm in a twin, an identical twin. And so when it came to writing my PhD dissertation. I thought to myself if there's any part of human behavior that has a biological origin. It must be our patterns of love and marriage. Because as Darwin would have said, if you have four  children and I have no  children, You live on  and I die out.  The game of love matters.  And so you would think there would have been selection for all kinds of behaviors that would enable you to fall in love with somebody, form a partnership and raise your babies as a team. And so that's why I started to study love, And you know people will often think,  "Well she studied love because had a bad relationship in high school" Well, nobody gets out of love alive. We all have problems with love. But that did not stimulate me to study romantic love. It was simply because I was an identical twin. And I w...

  Basically we write down the functions are invertible. And we use them both ways, it's the bottom line. It doesn't we're really writing down equilibrium in Q and P. It doesn't really matter what X and Y is. We're really just writing down an equilibrium relationship.  It's just the convention is to put Q on the X- axis. Even though the convention will sometimes write demand curves with P on the left hand side the graphic convention will never change but  How I write the curves might change How I write the equations might change You use opportunity cost to justify why demand sloping? Great question. Okay, let's go through it. That's exactly the kind of question I want to hear this semester. Is does someone want to take a crack at it? Anyone want to explain? and speak up  If the price is higher to in order to get that rose, you had to give up more because the price represents sort of like your opportunity. Right, for the opportunity cost of any good in the...