Galu, the past may seem to show a agglomeration of countless random events, but surely once it becomes the past, it is no longer random. It is a fixed and absolute record of what transpired. The future is different. We can predict the probable course of events (I’m talking about physical events like atoms interacting, stars, planetary orbits, asteroids etc ie not human events) but there still remains a huge potential set of outcomes - the point at which the event moves into the past, there is only a single outcome. From infinite possibilities to only a single outcome.
That’s my take on it anyway! 🙂
That’s my take on it anyway! 🙂
I continue to plough through Carlo Ravelli's book "Reality is not what it seems - The Journey to Quantum Gravity".
It's quite enlightening. I'll crack it yet. I just need to combine Quantum Mechanics, General Relativity and maybe Information Theory.
The Past is as unknowable as much as the Future. Why? Relativity!
Mars (Barsoom) can be 15 light minutes from Earth at Times. What does this mean? It means that you Earthlings cannot agree with the Martians about Past, Future and Now. They are 15 minutes "Elsewhere"
You have to read the book!
Here's another Weird but True Relativity thing. What path does a cricket ball take when hit it for 6? You can ignore air resistance.
If your name was Galileo, you'd say a Parabola. 😎
YOU'D be WRONG! If your name was Einstein, you'd say a straight line. 🤣
See, we know that time passes more slowly near the ground than it does higher up. Well, Believe it or not, a ball hit upwards falls downwards for the same reason: it "gains time" moving higher up, because time passes at a different speed up there. The ball follows a straight trajectory. Very important to distinguish Space from Spacetime, and Straight lines in a Euclidian geometry from Geodesics on a curved surface.
I'd never thought about it that way, either. Hope it helps.
It's quite enlightening. I'll crack it yet. I just need to combine Quantum Mechanics, General Relativity and maybe Information Theory.
The Past is as unknowable as much as the Future. Why? Relativity!
Mars (Barsoom) can be 15 light minutes from Earth at Times. What does this mean? It means that you Earthlings cannot agree with the Martians about Past, Future and Now. They are 15 minutes "Elsewhere"
You have to read the book!
Here's another Weird but True Relativity thing. What path does a cricket ball take when hit it for 6? You can ignore air resistance.
If your name was Galileo, you'd say a Parabola. 😎
YOU'D be WRONG! If your name was Einstein, you'd say a straight line. 🤣
See, we know that time passes more slowly near the ground than it does higher up. Well, Believe it or not, a ball hit upwards falls downwards for the same reason: it "gains time" moving higher up, because time passes at a different speed up there. The ball follows a straight trajectory. Very important to distinguish Space from Spacetime, and Straight lines in a Euclidian geometry from Geodesics on a curved surface.
I'd never thought about it that way, either. Hope it helps.
I cannot resist to mention chaos theory.
In classical mechanics, the future cannot be predicted over extended periods.
Weather predictions do not go seriously beyond 4 days.
The solar system is way more stable with a very well know state, however over billions of years to come we do not know how it will be. Calculations diverge exponentially with time whatever accuracy in the initial data.
The future is blurred not only because of randomness, but the Heisenberg principle at quantum theory level and chaos theory at macro physics level.
In classical mechanics, the future cannot be predicted over extended periods.
Weather predictions do not go seriously beyond 4 days.
The solar system is way more stable with a very well know state, however over billions of years to come we do not know how it will be. Calculations diverge exponentially with time whatever accuracy in the initial data.
The future is blurred not only because of randomness, but the Heisenberg principle at quantum theory level and chaos theory at macro physics level.
Is this one of those Benoit B. Mandelbrot jokes? Chaos Theory is about non-linear systems IIRC. Tricky stuff. We don't like non-linear in Audio.
AFAIK, there are certain predictable and stable states even in the 3-body problem. Joseph-Louis Lagrange was the top man in classical Celestial Mechanics.
He identified L4 and L5 as stable. https://en.wikipedia.org/wiki/Lagrange_point
L1, L2 and L3 can tend to Chaos. Lagrange also stated that the Classical 3 body problem, in general, always tends to occupy an increasing volume with time and generalised that to the n-body problem.
Once the Earth and Moon system has settled down enough that they always face each other, so no Tidal forces to affect things, and orbits have become circular, a third body can be added at 60 degrees to the Moon in its orbit, the Trojan Point, and it sits there forever.
Think I have that right.
AFAIK, there are certain predictable and stable states even in the 3-body problem. Joseph-Louis Lagrange was the top man in classical Celestial Mechanics.
He identified L4 and L5 as stable. https://en.wikipedia.org/wiki/Lagrange_point
L1, L2 and L3 can tend to Chaos. Lagrange also stated that the Classical 3 body problem, in general, always tends to occupy an increasing volume with time and generalised that to the n-body problem.
Once the Earth and Moon system has settled down enough that they always face each other, so no Tidal forces to affect things, and orbits have become circular, a third body can be added at 60 degrees to the Moon in its orbit, the Trojan Point, and it sits there forever.
Think I have that right.
I've found a great illustration of that joke:
Attachments
Wishful thinking. Then again those with this problem apparently find it quite unpleasant.😳
Trust the French speakers to pollute our serious and pure Physics Thread with Filthy French Jokes! 🙄
Another Saturday Night at the Forums (or is it Fora?):
*** Ancient Greek Mathematician Zeno leads an Infinite Set of friends into the Bar of the Hilbert Hotel. Yes, it's a big bar.
"Barman, I'll have half a glass of wine. My friend Pythagoras will have a quarter glass. Euclid will have an eigth of a glass. Archimedes wants a sixteenth glass..."
"Let me stop you right there, Zeno. I know the answer to this. I am pouring exactly 1 glass, and you can pass it down the line! I am more worried about Georg Cantor who is coming in later." 😀
Another Saturday Night at the Forums (or is it Fora?):
*** Ancient Greek Mathematician Zeno leads an Infinite Set of friends into the Bar of the Hilbert Hotel. Yes, it's a big bar.
"Barman, I'll have half a glass of wine. My friend Pythagoras will have a quarter glass. Euclid will have an eigth of a glass. Archimedes wants a sixteenth glass..."
"Let me stop you right there, Zeno. I know the answer to this. I am pouring exactly 1 glass, and you can pass it down the line! I am more worried about Georg Cantor who is coming in later." 😀
A convoluted presentation that says nothing more about Lagrangian points.
The Moon and Earth system is just a case, it's settlement is out of topic as well.
What is Trojan about L4 ( or L5 ) point is from stability, the possibility of capturing a cruiser that could sit there forever.
Because there are many systems with L4 and L5 in our solar system, I wonder how many alien artifacts are sitting there.
On the subject - I hope ya all used the 3D button on the Webb page 🙂 to se the solar system model...
//
//
mchambin, you sound bored! 🙂
I too, dislike mathematical statements without references:
https://webb.nasa.gov/content/about/orbit.html
My advice to you is to join Plato's Academy. https://www.theguardian.com/commentisfree/belief/2009/sep/07/plato-dialogues-philosophy
Surprisingly Liberal entrance requirements: "Let no-one enter who is unversed in Geometry."
Just showing off really, but I know of solutions to the 3-body problem that put NASA's feeble efforts with James Webb to shame:
https://en.wikipedia.org/wiki/Three-body_problem
They could have put it to L4 or L5. Cheapskates!
I too, dislike mathematical statements without references:
https://webb.nasa.gov/content/about/orbit.html
My advice to you is to join Plato's Academy. https://www.theguardian.com/commentisfree/belief/2009/sep/07/plato-dialogues-philosophy
Surprisingly Liberal entrance requirements: "Let no-one enter who is unversed in Geometry."
Just showing off really, but I know of solutions to the 3-body problem that put NASA's feeble efforts with James Webb to shame:
https://en.wikipedia.org/wiki/Three-body_problem
They could have put it to L4 or L5. Cheapskates!
What! 😵
Webb is at L2 for a very good reason!
What is special about Webb's orbit is that it lets the telescope stay in line with the Earth as it moves around the Sun. This allows the satellite's large sunshield to protect the telescope from the light and heat of the Sun and Earth (and Moon).
Attachments
- Status
- Not open for further replies.