In this course we will seek to “understand Einstein,” especially focusing on the special theory of relativity that Albert Einstein, as a twenty-six year old patent clerk, introduced in his “miracle year” of 1905. Our goal will be to go behind the myth-making and beyond the popularized presentations of relativity in order to gain a deeper understanding of both Einstein the person and the concepts, predictions, and strange paradoxes of his theory. Some of the questions we will address include: How did Einstein come up with his ideas? What was the nature of his genius? What is the meaning of relativity? What’s “special” about the special theory of relativity? Why did the theory initially seem to be dead on arrival? What does it mean to say that time is the “fourth dimension”? Can time actually run more slowly for one person than another, and the size of things change depending on their velocity? Is time travel possible, and if so, how? Why can’t things travel faster than the speed of light? Is it possible to travel to the center of the galaxy and return in one lifetime? Is there any evidence that definitively confirms the theory, or is it mainly speculation? Why didn’t Einstein win the Nobel Prize for the theory of relativity? About the instructor: Dr. Larry Lagerstrom is the Director of Academic Programs at Stanford University’s Center for Professional Development, which offers graduate certificates in subjects such as artificial intelligence, cyber security, data mining, nanotechnology, innovation, and management science. He holds degrees in physics, mathematics, and the history of science, has published a book and a TED Ed video on "Young Einstein: From the Doxerl Affair to the Miracle Year," and has had over 30,000 students worldwide enroll in his online course on the special theory of relativity (this course!).
Week 3 introduction
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来自 Stanford University 的课程
Understanding Einstein: The Special Theory of Relativity
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与讲师见面
Larry Randles LagerstromAcademic Director
So welcome to week three now of our course and the theme for
the week is Etherial Problems and Solutions.
We'll get to the quotes of the week in just a second or two, but
here are the main topics we'll be looking at.
We'll be starting off with Einstein's starting point, the two postulates
that he enunciated in his special theory of relativity, the June 1905 paper.
And essentially, what he said is we're going to just take these two things for
granted.
They actually were two principles that were well-established in a physics, but
that seemed to be somewhat in contradiction with each other.
And what Einstein did is sort of had the intellectual breakthrough, because he saw
that actually, even they seem to be in contradiction with each other.
If you took both of them to be true and then worked out some of the implications,
it gave you some very interesting results.
So he was just basing this on these two postulates, so
we'll figure out what those postulates actually are.
I just want to just give you a heads up, one is the so-called principal of
relativity and the second one is what he called the principal of light constancy.
And because that second principal deals with light and whatever light
constancy means, we need to figure out more this week about how light waves work.
How waves in general work, some of the key principles of light waves and
the phenomenon of light waves, so
that we can understand the background to what Einstein is working with here.
So, we'll spend a little bit of time exploring some light waves more or
less in a qualitative sense not a quantitative sense.
We won't do a full physical review say of how you describe
light waves mathematically and so on, and so forth.
And then well, we're talking about something called the ether.
You see etherial, problems and solution.
That's where it comes from and there's a little problem with the ether.
It was a cutting edge physics of the time, a number of very good and
great physicists had been working on it.
Whenever it happens to be is really the idea of the medium for light waves or
something has called the luminiferous ether, a light bearing ether.
We assume that waves must travel through something.
Water waves travel through waves.
Sound waves travel through air or whatever gas is involved.
And therefore, light waves must travel, have a medium,
which they travel through that the light vibrations.
The electromagnetic vibrations that make up light,
there must be some medium involved.
And so, that was known as the ether.
And yet, there's some key problems with it that Einstein was really
worried about and bothered him greatly.
And not only that, there were certain experiments that bothered everybody,
greatly actually and the classic one is known as the Michelson-Morley experiment.
So we're actually going to spend a fair amount of time looking at this in
a mathematical sense not deep mathematics.
It'll mainly be algebra that we're using here, but
this will be our first foray where we get a little bit more quantity than
we have been up to this point, but don't worry.
We'll take our principle make haste slowly.
So we won't try to rush through it, but make sure we're laying that solid
foundation as we construct our mental models of what this special theory
of relativity is all about and the implications thereof.
So the Michelson-Morley experiment will directly relate to what
the ether is like and give a certain result and then another well-known
experiment result called stellar aberration, also relates to the ether and
we'll find out that these two are actually in contradiction to each other.
So we had two very well-known experimental results and as it related to the ether,
one said one thing, the other said the other thing and
it really puzzled the physicists of the day.
So we're talking about this was in the 1880s, essentially.
Stellar aberration actually went all the way back into the early 1700s around
1725 or so, it was first observed.
So the question was what do you do with something like that,
how do you solve a problem like the ether?
It seemed like they needed the ether.
Otherwise, what is waving in terms of a light wave and the properties
of the ether, the Michelson-Morley experiment was saying one thing and
stellar aberration was saying another thing.
And there are other experiments too sort of on one side or the other and
it was a real problem in the 1890s, and up to 1905.
And so then, we'll look at some of the solutions to this.
How do you solve a problem like the ether?
For those of you who maybe remember the musical,
the sound of music, a sort of comes from how you do you solve a problem like Maria?
So now that I've said that you can probably, for
those of you who remember the musical can't get that out of your head.
So, I apologize for that.
But in this case, it's how do you solve a problem like the ether?
Well, there were certain solutions.
Somewhat ad hoc solutions just sort of pasted in there and
see if we can get our theory to work with it.
Einstein's solution was much more elegant and simple.
And so, we'll certainly want to find out more about that.
So that's where we are going this week and
let's go back to the quotes of the week, have them on your handout.
First one is there is no doubt that the special theory of relativity,
if we look at it's development in retrospect.
Again, this is by Einstein was ripe for discovery in 1905.
And so we will see some of that as we talk about some of these things that
other people working in this area that definitely was a well-known problem.
They had somewhat solved it, but not in a very satisfactory way.
And so Einstein came along and took a very different approach and
came up with a similar solution actually to what others were getting, but
in a more satisfying way.
But even have said that, it still took several years, a number of years before
people really accepted Einstein's approach to the problem versus some of the other
approaches there and the fact Einstein's approach was almost too simple.
It seemed too simplistic that he was just assuming these two postulates and
then taking off from there when some of the other theories that were getting
similar results were much deeper, much more more sophisticated in terms
of their physical and mathematical methods and so on and so forth with that.
But certainly, he said that if he hadn't done what he did in 1905,
somebody else probably would have done it in the next few years.
It was in the air, as it were.
As an aside, actually for his general theory of relativity not the topic of this
course, but ten years later that probably would not have been done as early as it
was if it hadn't been for Einstein working on that.
Second quote, I live in solitude in the country and
noticed how the monotony of a quiet life stimulates the creative mind.
I put that in here just not that we should all go live in the country in monotony or
live wherever in monotony, but
in our technologically oriented society where we're always hooked in and
connected and so on and so forth is sometimes we need to unplug as it were.
Turn off the email.
Turn off the Internet.
Turn off the texting.
Turn off the phone, the iPod, whatever it happens to be.
And use that time to do some thinking,
because that's what topics like this really require.
They require some deep reflection on various matters and that's what Einstein,
in particular was very good at terms of powers of concentration.
And stimulate that creativity and innovative thinking,
and deeper understanding of things.
So if you can use that as inspiration, Einstein's quote there inspiration for
doing that.
Sometimes, you'll probably be better off at least in terms of understanding
whatever you're trying to understand.
Then he also said, when I'm judging a theory,
I asked myself whether if I were God, I would arrange the world that way.
And then a second quote, very famous quote.
Subtle is the Lord, but malicious he is not.
I ask you just to consider what that might mean, even without understanding
Einstein's own context of how he came up with that, what that might mean.
Clearly, the whole topic of Einstein and religion is a huge one.
There been books written on his ideas in this area, quotes all over the internet
again on these topics of a famous one besides the subtle is the Lord one.
Another famous one is that science without religion is lame.
Well, religion without science is blind.
And sometimes when you pull these quotes out of context,
you get a misunderstanding of what Einstein's beliefs in the area were.
He really believed in more of a you could almost say, a cosmic God or
a cosmic religion.
Certainly not a personal God and you have to say also in this respect,
Einstein was definitely not a theologian.
It's not that his ideas were naive in this sense, but
that he hadn't the sophistication of his ideas was not necessarily as
deep as it might've been if he'd spent the same amount of time thinking
about these matters as he did with his physics and his science.
So whether it's Einstein or anybody else, you have to take those things
into consideration when they're sort of pronouncing on fields outside their own.
They might have very great wisdom in that area and very great insight,
but we can't just assume, because they're an expert and sort of.
A person everybody looks up to in one area even a genius doesn't
mean that goes over into another area.
So when he talks about when I'm judging a theory,
I asked myself whether if I were God, I would arrange the world that way.
He really believed in the beauty and grandeur of physical reality and
his religious belief in a sense if you could call it that was that we,
humans could actually gain insight into that through our reason and
through our rationality and through mathematics as well.
And that's what he is referring to when he also says things like subtle is the Lord,
but malicious he is Is not that the way that the universe is constructed.
The marvelous structure of reality.
We actually can penetrate into the insights of that and
the grandeur and beauty, as he put it in other places as well.
So just some quotes of the week to ponder there, if you want.
And then again, this week will be look at Einstein's starting points.
The two postulates and then especially light waves, and the problem of the ether.
Spend some with the Michelson-Morley experiment and stellar aberration, and
then sort of see the Einstein's solutions as well as some of the other solutions to
this problem.
And then next week after that where we start to get into the weird and
strange results that come out of Einstein's two postulates when you
accept both of them to be true.
