Limit Theory Forums

Dinosawer wrote:

Flatfingers wrote:....
Another question about gravity in LT as a relatively short-range effect: what if the ranges of gravity and electromagnetism were swapped in the LTverse compared to our own?

Well... [this is your last chance to run away]
They have the same range. Both potentials are 1/r. (A short range potential is e^(-r)/r )
The reason we don't notice electromagnetic forces is the fact that there are 2 opposite charges that stick together so there is no net charge on larger scales, whereas there is only positive mass.
The electromagnetic force is way stronger than gravity, actually.
If you would swap the strengths, my educated guess would be that stable atoms wouldn't form anymore, everything would be plasma and the universe would be full of black holes. Not very nice

...putting this gently, are you perhaps trying to impose our real-world physics in the LT universe?

My question wasn't so much "how would our rules work in LT" as "what if [these rules] existed? how would that universe work?"

It's a gedankenexperiment. Roll with the crazy and see what emerges!

Another question about gravity in LT as a relatively short-range effect: what if the ranges of gravity and electromagnetism were swapped in the LTverse compared to our own?

I was typing an answer here, but it looks like Dinosawer already covered everything I wanted to say ...

although I'm not sure about everything plasma, if you made gravity stronger, I suspect that black-hole formation would be much more common than we see now (also bigger black holes).

Edit: assuming you just meant swap out EM and Gravity without gravity being short ranged.

Flatfingers wrote:

Dinosawer wrote:

Flatfingers wrote:....
Another question about gravity in LT as a relatively short-range effect: what if the ranges of gravity and electromagnetism were swapped in the LTverse compared to our own?

Well... [this is your last chance to run away]
They have the same range. Both potentials are 1/r. (A short range potential is e^(-r)/r )
The reason we don't notice electromagnetic forces is the fact that there are 2 opposite charges that stick together so there is no net charge on larger scales, whereas there is only positive mass.
The electromagnetic force is way stronger than gravity, actually.
If you would swap the strengths, my educated guess would be that stable atoms wouldn't form anymore, everything would be plasma and the universe would be full of black holes. Not very nice

...putting this gently, are you perhaps trying to impose our real-world physics in the LT universe?

My question wasn't so much "how would our rules work in LT" as "what if [these rules] existed? how would that universe work?"

It's a gedankenexperiment. Roll with the crazy and see what emerges!

I'm not sure what you mean anymore.
Do you mean "a universe like ours but with EM and gravity "swapped"", that's what I did. The first part was about the fact that your question itself in that case doesn't really make sense (EM and gravity have the same range)
If you mean "swap those forces in the LT universe", no idea how it would look cause LT has neither.
I'm confused

Edit: Also, I know what a thought experiment is, 80% of physics is derived that way

Also kinda hard to know what would happen when you swap forces in LT without first knowing how the forces act/ behave in LT (or if they even exist).

Late by a few pages here, but my personal view is that the measure of "realism" in LT isn't if we can describe it in terms of physics in our universe, but whether whatever system we come up is consistent.

If we even want to care, then consistency is the most important factor. I'm perfectly happy with Tal's mechanisms if they're consistent. I'm not happy with the short-range gravity mechanism because it *isn't* consistent; I think if we want to think of LT's physics as using similar concepts from our own universe then we have to make sure we apply them consistently.

Dinosawer wrote:I'm not sure what you mean anymore.
Do you mean "a universe like ours but with EM and gravity "swapped"", that's what I did. The first part was about the fact that your question itself in that case doesn't really make sense (EM and gravity have the same range)
If you mean "swap those forces in the LT universe", no idea how it would look cause LT has neither.
I'm confused

Now I'm confused, too. I'll get you for this, Physics!

What I was trying (poorly) to describe was a universe in which gravity is strong but only operates locally (say within a few million kilometers at most), while the EM force is the weakest of the four but operates universally -- what might such a universe look like?

The notion was that we might get something like the LT universe, where there are still stars and planets but they exist only in wormhole-connected bubbles, and space has drag. There'd probably be other odd effects as well, which could be entertaining to explore.

"A universe consisting of a soup of particles and black holes" might be the correct answer based on physics as we know it.

But it's not a very useful answer relative to making a game that's fun to play, which was the emphasis I was looking for.

My apologies for failing to be more clear about the context I had in mind.

Random thought: what if
A) Gravity didn't follow our 1/r law in such a way that there are no stable orbits
B) there were 2 tours of mass (mass charges, in a way) but unlike electromagnetism, like attracts like and opposites don't influence each other. So if you get a mass2 planet around a mass sun they just stand still, if they're both mass or mass2 the planet either gets flung away our spirals toward the sun and is eaten.

And asteroids don't exist. Nope, doesn't work. Nevermind.

One other thing with short-ranged gravity that bothers me is the possibility of star formation;

If stars (and planets) in LT are still formed out of a giant dust cloud like happens in our universe, I doubt that stars would be common, due to the inability to collect enough mass to start a fusion reaction.

That's indeed a problem, you could tweak the range such a way that star formation was possible, but then asteroid fields wouldn't be stable.

Also

Flatfingers wrote: Now I'm confused, too. I'll get you for this, Physics!

Well, the problem is that you seem to misunderstand how the electromagnetic force works.
I'm tempted to interpret this as an invitation to explain further, but I have been wrong on that count many, many times before.

Flatfingers wrote: Now I'm confused, too. I'll get you for this, Physics!

Dinosawer wrote: Well, the problem is that you seem to misunderstand how the electromagnetic force works.
I'm tempted to interpret this as an invitation to explain further, but I have been wrong on that count many, many times before.

Please explain further, Dinosawer.
I'd like to know more, which button do I press?
(You won't be wrong in this instance, to explain further... my mind is a sponge.. or a wet mop!)

Alright then.
The electrostatic force and the gravitational one are very alike. Both are of the form
C*q1*q2/distance ²
In the electrostatic one q1 and q2 are the charges, in gravity they are the masses.
Furthermore, C is some constant, which isn't the same for the two.

The key difference is thus:
In electromagnetism, there are 2 types of charge, and likes repel each other while opposites attract.
In gravity, there is only 1 "charge" (mass) and likes attract.

This means that masses will attract each other, they will clump together, weigh more, attract more mass, etc until you have huge masses with large gravitational forces.

However, say you've got a positive charge. It will attract a negative charged friend and stick close to it.
Now if you look at those two from a distance and squint a bit you don't see any charge at all, because the two cancel each other out.

So the electrostatic force doesn't have a shorter range than gravity, there are just a lot of equally strong but opposite forces that cancel each other out.
So it's like the difference between a rope that doesn't move because it's lying around and a rope that doesn't move because someone is pulling on each end.

(In fact, when you look purely at the strength of the forces by comparing the constant in the formula, the electrostatic one is way stronger, which is why gauss guns exist but "gravity" guns don't)

Also, you do notice electrostatic forces in daily life. The fact that your body doesn't fall apart and you're able to sit on a chair instead of moving right through it are because of it.

Dinosawer wrote: Also, you do notice electrostatic forces in daily life. The fact that your body doesn't fall apart and you're able to sit on a chair instead of moving right through it are because of it.

This is my favorite part of physics - the fact that there's so much space in an atom's structure that you almost ought to quite easily go through everything without any fear of ever coming in contact. So few people understand that, though, that I've met. I'm very pleased to be among people who do.

In a certain quantum mechanical sense it's completely filled with "maybe electron", but that probably doesn't count.

Dinosawer wrote:In a certain quantum mechanical sense it's completely filled with "maybe electron", but that probably doesn't count.

It counts as much as space is filled with "maybe planet".

Talvieno wrote: This is my favorite part of physics - the fact that there's so much space in an atom's structure that you almost ought to quite easily go through everything without any fear of ever coming in contact. So few people understand that, though, that I've met. I'm very pleased to be among people who do.

Well, if you accept the notion that leptons (like quarks and electrons) are true point particles, an atom is 100% empty space by volume.