The begining of time

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Hi all! I have read a Stephen hawking lecture about the begining of time, and he says that time did have a definite begining. In Brian Greene's book the fabric of the cosmos, he makes some comments that t=0 may not have ever occurred. I'm wondering what you guys think.
 

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  • #2
Nugatory
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Hi all! I have read a Stephen hawking lecture about the begining of time, and he says that time did have a definite begining. In Brian Greene's book the fabric of the cosmos, he makes some comments that t=0 may not have ever occurred. I'm wondering what you guys think.
Both of those are written by well-regarded scientists who have spent more than a decade just learning the math that's required to begin to seriously work on the "beginning of time" problem. Neither of these are serious descriptions of the subject. They're Greene's and Hawking's best efforts to kinda sorta explain things to people who haven't put in the years of serious work that is required to understand the real thing.
It's useful, it's important, it's fun to read about, it's as close to real physics as most of the population will ever choose to go - but it is not the real thing.

If you google for "lies to children" you'll get a pretty good sense of what they're doing. And when the grownups are telling lies to children... You can listen, but at some point you're going to want to learn the real thing.
 
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Both of those are written by well-regarded scientists who have spent more than a decade just learning the math that's required to begin to seriously work on the "beginning of time" problem. Neither of these are serious descriptions of the subject. They're Greene's and Hawking's best efforts to kinda sorta explain things to people who haven't put in the years of serious work that is required to understand the real thing.
It's useful, it's important, it's fun to read about, it's as close to real physics as most of the population will ever choose to go - but it is not the real thing.

If you google for "lies to children" you'll get a pretty good sense of what they're doing. And when the grownups are telling lies to children... You can listen, but at some point you're going to want to learn the real thing.
My bad, those are just summarizing what they said. I'm hoping to get more into it, and I would love to know where to start.
 
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I would love to know where to start.
Do you know Newton's laws? That is the first place to start. Then you would want to learn Lagrangian mechanics. Then four vectors and special relativity. Then general relativity.
 
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anorlunda
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Professor Leonard Susskind has a number of great courses on physícs available on YouTube. He starts with classical physics (not elementary physícs), then special relativity, general relativity, cosmology, quantum mechanics, and more. The cosmology course gets close to your question.

In theory, you need elementary physics (Newton's Laws as DaleSpam said) and a bit of calculus before starting. Below is the first lecture of the classical mechanics course.


But contrary to theory, my wife has been viewing Susskind's Cosmology course. She has no education in algebra, calculus or physics. Nevertheless, she is able to pick up some of the more interesting concepts that Susskind discusses. Below is lecture 1 of Susskind's cosmology course.

 
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Professor Leonard Susskind has a number of great courses on physícs available on YouTube. He starts with classical physics (not elementary physícs), then special relativity, general relativity, cosmology, quantum mechanics, and more. The cosmology course gets close to your question.

In theory, you need elementary physics (Newton's Laws as DaleSpam said) and a bit of calculus before starting. Below is the first lecture of the classical mechanics course.


But contrary to theory, my wife has been viewing Susskind's Cosmology course. She has no education in algebra, calculus or physics. Nevertheless, she is able to pick up some of the more interesting concepts that Susskind discusses. Below is lecture 1 of Susskind's cosmology course.

Thank you. In fact, I have seen many of his videos but not those ones. He is a great professor.
 
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Do you know Newton's laws? That is the first place to start. Then you would want to learn Lagrangian mechanics. Then four vectors and special relativity. Then general relativity.
I am very familiar with newton's laws. What's the best source to learn Lagrangian mechanics?
 
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I am very familiar with newton's laws. What's the best source to learn Lagrangian mechanics?
I learned it from Goldstein, but many people are recommending Landau and Lifshitz. If you want to start out with stuff that's free and online instead, Google will find some pretty decent lecture notes - fortunately, this is a topic that mostly appeals to people who are serious about understanding physics, so more of the online stuff is real instead of the pop-sci oversimplifications that have been leading you astray.

You will want to be somewhat comfortable with differential equations and multi-variable calculus.
 
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I learned it from Goldstein, but many people are recommending Landau and Lifshitz. If you want to start out with stuff that's free and online instead, Google will find some pretty decent lecture notes - fortunately, this is a topic that mostly appeals to people who are serious about understanding physics, so more of the online stuff is real instead of the pop-sci oversimplifications that have been leading you astray.

You will want to be somewhat comfortable with differential equations and multi-variable calculus.
Thank you. This is very helpful.
 
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I learned it from Goldstein, but many people are recommending Landau and Lifshitz. If you want to start out with stuff that's free and online instead, Google will find some pretty decent lecture notes - fortunately, this is a topic that mostly appeals to people who are serious about understanding physics, so more of the online stuff is real instead of the pop-sci oversimplifications that have been leading you astray.

You will want to be somewhat comfortable with differential equations and multi-variable calculus.
Is this their statistical mechanics book? That is freely available online if I remember correctly.
 
  • #11
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Is this their statistical mechanics book? That is freely available online if I remember correctly.
Nope, the first volume. There are copies available online, but I don't know if they're legit or pirated - and I'm not going to recommend one until I do know.
 
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What's the best source to learn Lagrangian mechanics?
Nugatory mentioned Goldstein and Landau/Lifshitz. Those are usually considered graduate-school level textbooks, unless you're a real whiz. Some intermediate undergraduate textbooks that include Lagrangian and Hamiltonian mechanics are Fowles/Cassiday, Symon, and Marion. Pop over to our textbooks forum and search for "mechanics" and you'll probably find more. Most anything above freshman university level should include Lagrangian and Hamiltonian mechanics.
 
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anorlunda
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I am very familiar with newton's laws. What's the best source to learn Lagrangian mechanics?
That Susskind video on "Classical Mechanics" from post #5.

I too had to learn that Lagrangian mechanics is Classical, but Newtonian mechanics is Elementary. It is further confused by those who say that Quantum mechanics is most fundamental, so that we should really be taught in quantum-classical-elementary mechanics order.
 
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That Susskind video on "Classical Mechanics" from post #5.

I too had to learn that Lagrangian mechanics is Classical, but Newtonian mechanics is Elementary. It is further confused by those who say that Quantum mechanics is most fundamental, so that we should really be taught in quantum-classical-elementary mechanics order.
Doesn't that go against the concept of elementary? I can't imagine some of the kids in my science class even trying to understand QM.
 

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