Make a drain hole at the bottom of a lake, that comes out above it. Put in a water wheel, free energy.
Never thought about it before, but I guess this makes portal guns impossible, since scenarios like this break conservation of energy.
Maybe entering the portal takes as much energy as it would take to climb the long way? If the other end is on the moon you have to enter at 10km/s or something else you fall right back out. Warning: I am not responsible for damage caused by extreme tidal forces.
But you know it’s possible from firsthand experience. Whomsth’n’t reached terminal velocity by shooting the ceiling & floor and jumping in?
Maybe conservation of energy is wrong.
Well, the videogame kind are definitely impossible, but if the gravitational field could travel through the portal then it would probably still conserve energy. The gravitational interactions around vertical portals would be exceptionally weird. If they were close enough, you’d probably experience weightlessness while in between them, but I can’t wrap my head around what would happen as they move further apart. That makes me hope someone tries to make a mod that models that in Portal…
My first instinct would be that it would equivalent to putting another celestial body the mass of the earth at the distance from the earth is from each portal. Since gravity is a wave, it, in theory, would affect a region beyond what would considered “around” the portals.
So if you put one portal on the ground, and another 100 meters up, it would be similar to there being a second earth 100 meters from the surface of the earth, experienced by the entire earth (once the gravitational wave propagated.) How that would evolve over time is too complex for my basic understanding of physics, but a simulation of it would be a neat experiment.
Hm, I don’t think the “gravitational force” (as in the thing that pulls you towards the Earth) is a result of a gravitational wave; rather it is a result of you being in a static vector field. Gravitational waves are waves that travel through that field, e.g. the stuff that LIGO is measuring.
I’ve tried thinking about how it would work with portals. The problem is that the definition for gravitational field is g = -∇Φ where gravitational potential Φ(x) = ∑i(-G·mi)/||x - xi||, which depends on there being a single unambiguous “distance between two points” (x and xi in this case). But think about two points on the opposite sides of one “portal entrance” (e.g. imagine a portal entrance on a wall in front of you, with your friend on the other side of that wall). What is the distance between you and your friend now? If we’re to say it’s the same as it was without a portal, then (1) we get straight back to our problems with energy conservation, (2) there is no physical path between you and your friend that matches this distance as there’s a rift in space on that path. It would also be weird to conclude that it’s infinity - you can just go around the wall in our example and be right next to your friend. So we almost have to conclude that the shortest path would have to go around the portal somehow. Let’s just say that it would be the length of the shortest path around the portal. By the formulae for the gravitational field, this means that the gravity will pull you towards the shortest path to Earth’s center. If you placed one portal on the surface of Earth (let’s assume that the center of Earth is sufficiently far away that the gravitational field can be approximated as uniform in direction and magnitude) and another one somewhere far-far away in deep space (where let’s say that gravitational field is 0 for simplicity) it would look something like this:
Note how while the gravitational potential (Φ) is defined along the red line, the gravitational field would be undefined as there would be no gradient in the gravitational potential.
Now let’s try thinking what would happen on the other side. I’ll assume that our portals are just flattened wormholes with short throats. Thus we’ll just assume that portal entrances are actually “two-sided” (e.g. if they are just floating in your room, you can walk around them and see whatever is around the other portal at all times), and that the distance between them is 0 (let’s not think about how that works for now). Now the distance between an object on “one side” of first portal entrance and “the other side” of another portal entrance is even more messed up - I think the shortest path would technically be one that travels from first object to one of the “edges” of the first portal entrance and then from the corresponding edge of the second portal entrance to the second object. Thus the gravitational field around the other portal would look like this (I’ve added eyes to clarify how I’ve linked up portal sides):
The red line once again means that the gravitational field there is undefined.
Whew, it’s complicated, right?
Now, let’s put the second portal close to the first one. Note that I’m assuming here that only the shortest distance to the center of the earth matters.
The two red lines from before now overlap, and there’s another one - there’s no gradient when the distance to the blue portal and to the earth is the same. It’d actually be longer than what I’ve drawn, and some sort of parabola in those areas, but I’m too lazy to do that. Hanging in the middle of that red cross would be a weird feeling - your top half would feel as though you’re hanging upside down, while your bottom half would feel normal, and your arms and legs would be pulled in slightly different directions.
Although, I think that Newtonian definitions of gravity are playing tricks on us here. We should probably try using general relativity instead, but I am too tired to even attempt that right now, and I’d probably fail given that the fields involved there are a lot more complicated.
The trick would be finding the tallest vertical line of sight you can. Just making portable plates and flying one would be hard to beat, but failing that maybe a mineshaft.
Does it fire through water in the game?
There are no bodies of water but you can shoot through a falling stream of it.
No. The only water in the game is toxic (i.e. you die if you fall in) and you can’t fire the gun through it.
Open a portal to the moon at the bottom of the ocean
Assuming there is only one, sell my single use for ludicrous amounts of money to some Corp that has merchandise to move.
Save it. I don’t have anything currently that I would want to use a portal gun on given that I can only use it once. I might use it to get myself out of a sticky situation, or wait to see if I ever move into a relatively permanent home and I could make a portal from my house to another location for convenience.
So it’ll be just like the bag full of Maximum Heal potions when the credits roll, except I imagine you could pass it on to someone with a message not to wait for the perfect moment.
Maybe, but I don’t particularly feel the need to use a portal gun. If I never end up using it I don’t think I’d have particular regrets, but if I used it to save my ass during a high-stakes situation then I’d be quite glad.
I’ve always wanted to fuck my own ass.
Won’t work, as you thrust your ass will pull away. Only way I could think of is having the portals on platforms that would move with you.
I appreciate your in depth analysis of this situation.
Uhh huh huh… you said depth.
Maybe it would just double the friction.
Or potentially, you could just move one of the portals relative to the other.
Take a portal to a black hole, keep the portal open for funsies.
Upon receiving it I would spend the first god knows how many hours trying to convince myself not to use it for sex things.
Beyond that, I think I’d definitely have to consider permanently renting a storage room in a country I want to visit often, and storing a portal in there.
that looks just like me lol
Part of me is thinking: “But doesn’t the water slow down each time it comes into contact with the cog?”
And the answer is the yes, but the answer is also, “it begins to accelerate again right after it falls off the cog.”
And yet it’s still fucking with me, and somehow I’m imagining water getting slower and slower and less energetic each time, as if gravity itself is being weakened
See, I don’t think water is the way to do it. I think you do it with a massive lead pole with teeth to lock into a gear.
Fully contained, no spillage
I mean, genuinely, this would be infinite energy. I was thinking of somehow using magnets and induction to generate power, but it would be excessively high frequency and would be antithetical to multi-phase power.
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Put portals on two boards. See what happens if I put one board through the other portal.
Minute Physics did a video on it: https://www.youtube.com/watch?v=jSMZoLjB9JE
It would be a bad use of it, but probably pick a random road online and pick a random volcano. Whoever gets unlucky and doesn’t notice the nightmare portal in the ground gets a free trip to the base of a volcano at no cost. Would obviously need the portal to be in a location where you cannot just easily return from, though. Gonna turn a random volcano and random street into quite the tourist attraction for no reason.
I would put one portal on a pneumatically actuated plate above a dais that holds an object, and the other portal on a plate placed at a 45 degree angle. I would then see if an object on the dais would fly or fall out of the 45 degree portal, if the other portal actuated and closed the distance between its starting point and the dais.
How would you fix evaporation I’m dumb at this stuff
Anti-evaperation field, or just let rain do it’s thing
Moon.
How fast would this suck up all of our atmosphere? Hours? Days?
Pretty sure the game theorists channel on youtube did that one several years back. It’s been a minute since I watched it but a search should pull it for you.
This one? https://youtu.be/0Hwjmek0Uvw It more addresses survivability in space, but unfortunately not the „drain earth of its atmosphere“ thing. Then again, in game the portal was closed quickly again.
Unless the pressure differential causes it to escape the moons gravity well it would probably stabilize at some point before dumping the whole atmosphere, right?
Easy solution for that, you fire the earth portal on a wall inside some sort of specially constructed airlock.
That hard part would be getting the moon portal in a useful place, you’d probably need to go up there and find a good solid cliff face or something. On the plus side having done that you could be home again in a few seconds.
As long as I’m the first one through, the rest is set dressing.
Probably years, if not more. XKCD’s “What If?” has a nice explanation on a similar question, but in that case it was a portal at the bottom of the mariana trench and the question was about draining the oceans. The answer is that you probably wouldn’t notice in all your lifetime.
I remember that video, but I‘m not sure it is comparable — air might flow faster than water [citation needed] and there might be less of it [citation needed].
there’s more water than air (mass-wise).
Above you, atmosphere scale height is 8 km, with a density of 1.25 kg / m³.
That makes 10^4 kg of air above your head per m² surface area.
To get the same mass of water per surface area, it would only have to be about 10 m deep. But the ocean is kilometers deep in most places.
I’m pretty sure there is much more air. At least volume wise. Sphere volume goes up by radius cubed.
Nobody went with sending trump and musk to mars?
Create infinite energy machine
This is the correct answer given time and thought, but nah, would rather pee from my bed
