Idea: Gravity wells

So all you have is an appeal to authority?

It's always like that isn't it? Ridicule and credentials but not actual arguments. All bark and no bite.

What I'd like to know is why one interpretation is more valid than another. Or why an interpretation should be taken as truth at all. Anything with gravity could create an accretion disc. Tons of things could be spewing jets of material. But it has to be a black hole? I don't buy it.

Wow, bmb. There's no need to get all hipster about this.

Astronomy, like most fields of science, is based on what we can see and what we have seen. It is more speculative than most fields simply because we have no way to go out and check first hand. So you get a lot of nerds covering napkins in huge formulas, taking bets on who can most accurately recreate what we see through our telescopes. It's always a cutting edge field because we're getting better instruments and cooler observations all the time.

If that sort of thing appeals to ya, then go nuts. But it is silly to decry all that we have so far, when it is our current best understanding of the universe. If you don't like what science has done, then prove something better. That's how science works.

Also, prepubescent teens are a poor authority on subjects they flunked out of.

So bmb, given that you don't believe in relativity, please explain the observed differences in the half-lives of muons at rest and muons moving at high fractions of the speed of light (Frisch and Smith, Measurement of the Relativistic Time Dulation Using mu-Mesons, American Journal of Physics Volume 31, Issue 5, 1963, for one). Please provide full citations and/or derivations from first principles to support your argument.

If you want evidence for black holes, all you need to do is look towards the center of our galaxy, towards the Sagittarius constellation. At the center of our galaxy is a massive source of radio waves, and around it we can see stars moving at extremely high velocities. The only thing we can use to explain this is a black hole. Also, other black holes we actually can 'see' because of the intense radiation they give off and because of the accretion disks that form around them, which glow and give off visible light. Some black holes even have jets which spew out matter and energy.

Relativity, too, is a well understood concept, and many of our hyper-accurate measurements with atomic clocks would not be possible without a clear understanding of how time dilation due to gravity works. Since you like YouTube videos, here's one for you. Don't worry, it's short:
http://www.youtube.com/watch?v=ky4RgRvVDoA

Now, as for what this kind of thing can be used for in-game, other than looking neat, I don't know; I'm not a game developer. Ultimately all of the decisions for the gameplay mechanics rest with the development team. I just thought that adding black holes and other interstellar phenomena would be interesting and fun.

And here come all the armchair physicists in defense of their precious theory.

Not what the thread is about.

So you're talking about all of modern physics and when people come in to show you how wrong you are you chicken out?

Btw. what's an armchair physicist? Does having studied that stuff for some years make me an armchair physicist or can I be upgraded to a couch pysicist?

*edited by Uber. Play nice, ya'll*


edit by small.cpu: Ups, kinda lost my cool here. Sorry bmp.

You're right, this is offtopic. On to the topic of destroying planets then.

Not willing to defend your position in public? Sounds like a concession to me.

Also: When people with credentials disprove you, you cry "argument from authority" and when people don't state their credentials you call them "armchair physicists"; if you'd actually made any arguments I'd accuse you of moving the goalposts, but that would imply that you'd actually set up any goalposts.

I'm not here to argue physics, I made that clear from the beginning. I entertained the inquiry as an aside but now you've dragged it off topic.

C'mon guys. I don't want to ignore half of the board.

Yeah, realistic trajectories for any spacebound object would be cool, but have them as an effect rather than a gameplay mechanic. Have the unit cannons calculate the right slingshots and stuff.

If the subject is physics and we're citing astrophysicists then appeal to authority is not a problem. If we were citing marine biologist or lawyers it would be. Appeal to authority is a fallacy when the authority is irrelevant or unconnected to the subject.

As for GPS, it would still work if it didn't use relativistic calculations. However it requires relativity for it's accuracy, otherwise from what I understand, it's accuracy would be measured in kilometres not metres.

As for game play, black holes wouldn't really off much that couldn't be mirrored via other methods. Decaying orbits, asteroid belts and what not. The problem with game play is you can't get too far off reality before it starts to break immersion. I guess for some giant planet sucking black holes are awesome, for others they're just ridiculous.

Gravity slingshot orbits are surprisingly hard to do and not exactly the amazing thing everyone thinks they are. Seems unlikely that true Newtonian flight has a place in an RTS.

How difficult is it to solve an orbit for a given destination and point of origin in a multibody system anyway? I'm not really into orbital mechanics. Seems like it could either be a super simple five minute implementation or something you'd need a super computer for.

:roll:

To answer the question, it's trivial to do a simplified model of multi-body systems. You just add up all the force vectors from the various bodies' gravitational forces for each point in time.

F = G(m1 * m2)/r

F is the force between the masses (a vector pointing towards the second mass),
G is the gravitational constant (6.674 x 10^-11),
m1 is the first mass,
m2 is the second mass, and
r is the distance between the centers of the masses.

http://en.wikipedia.org/wiki/Newton's_law_of_universal_gravitation

"Newton's law has since been superseded by Einstein's theory of general relativity, but it continues to be used as an excellent approximation of the effects of gravity. Relativity is required only when there is a need for extreme precision, or when dealing with gravitation for extremely massive and dense objects."

Calculating a slingshot path is much more complex than simply calculating the effect that gravity has on something though.

It is actually more difficult than that. In a multibody system, the way objects will act on each other is hard to calculate, as not only will your spaceship be affected by some planets' gravity, but the planets will be affected by each others' gravity. However, that doesn't really matter in this case. It would if we were trying to model planets orbiting each other.

Though really, I feel like it wouldn't be too difficult to do orbital calculations. You'd just have to calculate how fast an object would move the closer it was to a sun or planet, and base velocities off of that. I mean, there are plenty of games with orbital simulations, such as Kerbal Space Program and many simple physics simulators.

Actually, it's r^2, so it would be

F = G(m1*m2)/(r^2)

The problem wasn't to simulate an orbit, the problem was to solve an orbit that goes from point a to point b in a multibody system. Orbital pathfinding basically.

Correct, typo on my part.

The intention with that equation is for each object to calculate F between itself and each other object, then add up all the vectors to get a resulting acceleration vector. Unless the number of objects is especially large, the calculations are still trivial. It's only if you want to be precise, and start using Einstein's equations, or having to factor in the changes in force across the surface of a planet (can be important, as this can cause planets to rip each other apart if they get too close) that it becomes difficult to calculate.

Yes, pathfinding taking these forces into account is much harder. Probably not too taxing though, just complex to code. Not many objects would actually need this though, so a higher performance cost should be acceptable.

You guys are making this problem way more complicated than it needs to be. Unless you're planning on putting something into a halo orbit or the like, there should be no real need to solve an N-body problem (you don't need to account for the sun or Jupiter to get a reasonable approximation of the moon's orbit around the earth, for example).

Most of the time, one body accounts for almost all of the gravitational force exerted on an object, so you can just use the 2-body problem equations of motion to simulate the spacecraft/asteroid (requires no heavy computation, since they just follow conic trajectories). Computing trajectories between stars/planets then becomes fairly trivial.

Of course, the devs could just make up their own laws of physics for the game (it just has to look plausible, right?)