Isaac0427 said:Hi all! I have read a Stephen hawking lecture about the beginning 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.
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.Nugatory said: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 sort of 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.
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.Isaac0427 said:I would love to know where to start.
anorlunda said: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.
I am very familiar with Newton's laws. What's the best source to learn Lagrangian mechanics?DaleSpam said: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.
Isaac0427 said:I am very familiar with Newton's laws. What's the best source to learn Lagrangian mechanics?
Thank you. This is very helpful.Nugatory said: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.
Nugatory said: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.
djpailo said:Is this their statistical mechanics book? That is freely available online if I remember correctly.
Isaac0427 said:What's the best source to learn Lagrangian mechanics?
Isaac0427 said:I am very familiar with Newton's laws. What's the best source to learn Lagrangian mechanics?
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.anorlunda said: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.
The debate between Stephen Hawking and Brian Greene centers around the concept of the beginning of time and the origins of the universe. Hawking argues that the universe has no beginning and that time is infinite, while Greene believes that the universe had a definite beginning and that time had a starting point.
Hawking's theory is supported by the concept of "imaginary time" in his quantum theory of gravity, which suggests that time behaves differently at the subatomic level. He also points to the absence of a "singularity" (a point of infinite density) in his model of the Big Bang, which suggests that the universe did not have a definite beginning.
Greene's theory is based on the concept of inflation, which suggests that the universe expanded rapidly in the first moments after the Big Bang. This supports the idea that the universe had a beginning, as it would have started from a single point and expanded outward. Greene also argues that the singularity at the beginning of the universe is still a valid concept, despite Hawking's arguments against it.
The debate between Hawking and Greene highlights the ongoing search for a definitive understanding of the origins of the universe. It challenges scientists to continue exploring and questioning our current theories, and to push the boundaries of our knowledge about the universe.
While Hawking and Greene may have differing opinions on the beginning of time, both theories are based on scientific evidence and are constantly evolving as new discoveries are made. It is possible that a future scientific breakthrough could provide a resolution to this debate, but for now, it remains an ongoing discussion in the scientific community.