Dear Math People, Learn Me Gravity and Dark Energy

If I understand dark energy correctly, the idea is that it will keep getting stronger and accelerating galaxies farther and farther apart until the heat death of the universe. In many trillion years, this force will be so strong it tears apart even elementary particles like protons. So, here's my question. What happens to the mathematics of gravity as dark energy gets stronger? Does the inverse square law become invalid? Would the earth's gravity become something like 4 m/s^2? How would a scientist represent far future gravity?

Math people would not know that. Physics people would.

And as an engineer- the question isn't that important- by the time it happens, we will be all gone, and the earth wont exist.

I kid- it's a good question.

"dark" energy and "dark" matter are just constants that need to be in place to make our current models work.

Bear in mind that all models are flawed. All models we use (Quantum , Newtonian, etc) work very well in their own realms, but obviously none of them are correct since they don't work everywhere.

Basically, what I am saying is that focusing on the long-term effects of a dark matter is folly. It isn't really a thing, at least as much as we understand right now. Continue to use the models which work the best for what you're working on, and leave the rest as a fuzzy question mark near the edges of that realm when stuff is too big/small or too fast/slow.

"Dark ______" is just a place holder for stuff we know is there, but don't yet understand.

Grassroots Astrophysicssports?

Haha, thanks.

I'm writing a philosophical novel about, well, lots of things. So far it mostly seems to be about sexual mores, realpolitik vs. Christian ethics vs nihilism, and then the Nietzschean will to power. I don't need any math help on this stuff, at least not yet.

I'm also trying my hand at metaphysics, which is why I need math help. The idea started as an attempt to solve some of the classical problems that crop up between theists and atheists. The two classical atheist arguments seem to be the problem of evil (why does my goldfish die if God is so good?) and the unnecessary hypothesis argument (we don't need God/gods/the divine in our theory of the universe because science knows everything). The two classical theist arguments seem to be the cosmological argument (science doesn't work without cause and effect, what was the first cause, and there must be one because entropy precludes the possibility of infinite time) and the finely tuned universe argument (all the fundamental physical laws of the universe are perfect for us!).

In the book, I'm trying to solve these problems by proposing an amoral prime mover - basically "god" but only in the sense of something that is outside space, time and causality - that built, or kickstarted our universe as a simulation for whatever purpose. Being amoral or at least differently moral solves the problem of evil, being outside space, time and causality solves the cosmological problem and it also solves the finely tuned universe problem since any conceivable "god" would discard or modify simulations that collapse into nothing. The unnecessary hypothesis argument is, in my opinion, kind of dumb since nobody can explain away the cosmological argument, so I'm not going to deal with it.

There's also what I consider the most convincing atheist argument, Nietzsche's aesthetic atheism, but that's wild enough I can't boil it down well enough to fit in the book.

Anyway, so I decided to set my book in a universe near its own heat death. The people of this universe are understandably freaking out a bit about their impending annihilation and so decide to build millions of simulated universes with the hope one or more will contain civilizations smart enough to bail them out. One of those simulations will be us. The plot of the book is mostly the characters struggling to build, control and understand those simulations.

So, right now I'm working on a scene where the characters discover that gravity is failing. I realize this is probably completely pulled out of my ass, but the story is going to assume that near the heat death of the universe dark energy forms filaments. One of the filaments is going to touch one of our character's planet's moons and basically cancel gravity for a couple minutes.

I'd like to make this scene as realistic as possible.

GameboyRMH wrote: Grassroots Astrophysicssports?

My degree is just "physics". If you need a PhD in astrophysics, you need to see this guy:

Brian wrote: "Dark ______" is just a place holder for stuff we know is there, but don't yet understand.

Yeah, I get that. Even if the conception is wrong, though, it seems like you could mathematically describe gravity getting weaker over time. I'm just not sure what that math would look like.

tuna55 wrote: "dark" energy and "dark" matter are just constants that need to be in place to make our current models work. Bear in mind that all models are flawed. All models we use (Quantum , Newtonian, etc) work very well in their own realms, but obviously none of them are correct since they don't work everywhere. Basically, what I am saying is that focusing on the long-term effects of a dark matter is folly. It isn't really a thing, at least as much as we understand right now. Continue to use the models which work the best for what you're working on, and leave the rest as a fuzzy question mark near the edges of that realm when stuff is too big/small or too fast/slow.

If I understand Godel correctly, all models might be necessarily and eternally flawed.

https://bengarrido.com/2016/03/04/kurt-godel-and-the-limits-of-ai/

DaewooOfDeath wrote:

tuna55 wrote: "dark" energy and "dark" matter are just constants that need to be in place to make our current models work. Bear in mind that all models are flawed. All models we use (Quantum , Newtonian, etc) work very well in their own realms, but obviously none of them are correct since they don't work everywhere. Basically, what I am saying is that focusing on the long-term effects of a dark matter is folly. It isn't really a thing, at least as much as we understand right now. Continue to use the models which work the best for what you're working on, and leave the rest as a fuzzy question mark near the edges of that realm when stuff is too big/small or too fast/slow.

If I understand Godel correctly, all models might be necessarily and eternally flawed. https://bengarrido.com/2016/03/04/kurt-godel-and-the-limits-of-ai/

There is no need to be philosophical.

We are human. We have but five senses by which to observe the world. Imagine that we're all stuck in submarine like capsules. We have these five sensors and that's it. We can't actually just observe the world, we only observe what our senses tell us. There is no "heat" out there, or "blue" out there. These are just things our minds created to process the stimuli.

Hence, we make models to try and figure out what's happening. We run tests and collect data and revise and revisit. It's tremendously iterative. If you throw rocks all day, Newton will appear 100% correct. If that rock goes half the speed of light, all the sudden Newton's stuff is all wrong and you need some relativity to explain what happens. If stuff gets small enough, neither of those two do a good job at explaining what seems to be happening.

I mean we can't even explain what light is or how it works yet.

Every science ever made/written/discovered is an approximation that fits a specific set of circumstances. Nothing more. We probably won't get there, but it's important to recognize that we expect the universe to be logical, meaning it always follows the same rules, we just don't know what the rules are.

Imagine you're a blindfolded toddler thrown out onto a soccer field during a match. It's going to take quite a while before you figure out what is going on, and even then, you're only going to have some decent guesses.

I agree about the fundamental ignorance stuff and the way that we're really just thrown into reality with no rule book, though I'd posit that what you just wrote looks an awful lot like skepticism in the Socratic tradition mixed with some Kantian objectivity.

Godel was a mathematician, btw.

DaewooOfDeath wrote: I agree about the fundamental ignorance stuff and the way that we're really just thrown into reality with no rule book, though I'd posit that what you just wrote looks an awful lot like skepticism in the Socratic tradition mixed with some Kantian objectivity. Godel was a mathematician, btw.

Yes, I know he was, but that article was a philosophical argument.

The acceleration of an object in a vacuume due to the force of gravity is 9.6 meter/second/second. That's what I know.

If Daewoo and Tuna were to co-author a Sci-Fi book on this subject there's a 100% chance I would read it. Or just publish their dialog as they discuss the op subject and any related theories/subjects that come up, I'd read that too.

As it is, Daewoo, your book idea sounds very interesting to me and I want to read it.

Keep us posted!

I've been working on a work of historical fiction for a while but it's... not as interesting as this and stalled at the moment.

Brian wrote: "Dark ______" is just a place holder for stuff we know is there, but don't yet understand.

Yep... what we have now is a very fine approximation, except for that one little bit that doesn't quite make sense, until someone has an epiphany that either solves that problem or completely redesigns the approximation that we used to have.

I personally think it's the turtles pulling on the cosmic aether.

reading this thread makes me feel like i walked in on the wrong class in college... i'll see myself out...

I will ask my FIL... He is a PhD in Physics and Head of Sciences at Embry Riddle.

Yeah, you need a physicist to make the model and a mathematician to solve it.

Essentially you are asking what happens when the limit of the equation goes to infinity.

Fun things happen at the limit.

I'd suggest at least flipping through the Xeelee Saga by Stephen Baxter. It's 3 or 4 books, with at least one based as atomic scale beings living around a star near the universe heat death, building up to building a ring from hyperstrings to escape the universe(that book, conveniently called The Ring). For science fiction, even for ideas, I really appreciate him as an author, but it's tough. Some chapters tend to read like textbooks, but the man has done his diligence in research through the years.

AIUI, the question of whether the universe will end in an infinite expansion ('heat death') or being ripped apart by dark energy ('big rip') depends on some constants we haven't measured to that level of precision yet. The big rip is possible, but not likely.

Wikipedia has a reasonably good writeup if you're like me and want a layman's version that isn't full of equations:

https://en.wikipedia.org/wiki/Ultimate_fate_of_the_universe

BTW, If you're interested in philosophy, it would be very interesting to read Zen and the Art of Motorcycle Maintenance and GK Chesterton's Orthodoxy in succession. I would think those might be helpful in your overall subject arc.

Thanks guys, lots of good stuff here. I appreciate it very much.

Also, don't neglect khanacademy.com they have a pretty in depth lecture series on this topic, as well as tons of other things.