109 votes
Accepted

My time machine needs to know when it is

If you can deploy a good quality, wide-angle telescope and take photos of the night sky over a period of more than a few days, you can determine the time down to seconds over a wide range of history. ...
Mark Olson's user avatar
  • 14.3k
100 votes

Would a 4-dimensional being be able to see inside other people?

Can you as a three-dimensional being see inside a two-dimensional circle? That depends on your position relative to it. When you are looking right at its edge, you can't. But if you are above or below ...
Philipp's user avatar
  • 48.7k
84 votes

How can it be bigger on the inside

In such matters, it's always helpful to scale things down to the familiar. So, imagine for a moment that you are a 2-dimensional being. You can move freely left or right, back or forward, but you have ...
Werrf's user avatar
  • 15k
70 votes

My time machine needs to know when it is

Instead of having the device determine the time it is sent to, have it leave something in place, that you can find in the present to determine exactly when in the past it traveled. This is best if ...
Josh King's user avatar
  • 24.9k
63 votes
Accepted

Could you have more than one building in the same spot by "stacking" them in 4th dimensional space?

Yes It isn't any different to occupants of a 2D world asking whether - if there were 3 dimensions - could we stack objects on top of each other in a third dimension? One thing to note, however, is ...
Lio Elbammalf's user avatar
57 votes
Accepted

How would a higher-dimensional being enter a lower dimension?

In short, a higher-dimensional entity does not "enter" a lower dimension, it passes through it. Consider a planar (two-dimensional) universe. If you or I were to interact with it, we could stick our ...
Dave Sherohman's user avatar
57 votes

How can I make the rules of my Faerie Portal free from contradiction?

How to make internally consistent magic Magic lets you do pretty much whatever you want, especially when talking about the kind of spells that completely side-step the known laws of nature... so ...
Nosajimiki's user avatar
  • 92.6k
48 votes
Accepted

What does it actually mean to have two time dimensions?

First people need to understand how relativity works. There's a thing called proper time which we regard as an interval between two events or points in spacetime. In "ordinary common sense" space ...
StephenG - Help Ukraine's user avatar
44 votes
Accepted

What happens to the space created due to wormholes?

No new space is created (outside of the wormhole) by the wormhole. The curvature depicted in the image is just to portray the idea that a traveler going from one side of the wormhole to the other ...
Theraot's user avatar
  • 6,380
37 votes
Accepted

Aritifical Gravity through Rotating wheel generalisation in a spatial 4th dimension

This setup wouldn't work, not even in a mathematical sense, at least as you described it. In four dimensions, you can't actually rotate with respect to an axis. Instead, a 4D rotation leaves either ...
pregunton's user avatar
  • 1,526
36 votes

Could you have more than one building in the same spot by "stacking" them in 4th dimensional space?

You are the master of your world, so yes. Some practical concerns: Your guests are only three-dimensional and would like to stay that way. How do you get them from one "hyperfloor" to the next? ...
Stig Hemmer's user avatar
36 votes

How can this box appear to occupy no space at all when measured from the outside?

Extra Dimensions In two dimensions your box works like this: Spacetime bulges near the box to put more space between the walls. The two red lines are 5m even though they do not reach the middle of ...
Daron's user avatar
  • 66.2k
34 votes
Accepted

How is it possible that some extra-dimensional pouches can store living things while others can't?

Why can you carry an alive kitten in a cardboard box with some holes in it, while you cannot do the same if the box is filled with water? Simply said, because the internal conditions of the box in one ...
L.Dutch's user avatar
  • 287k
31 votes
Accepted

How would a radar work while inside a FTL dimension?

Lit buoys. Your dimension is kind of like boating at night. You can't see anything. It is easy to get lost. It is easy to hit shallow water. So there are lit buoys. These mark the path. Your ...
Willk's user avatar
  • 305k
28 votes

Would a 4-dimensional being be able to see inside other people?

If the 4th dimension is spatial, it really depends on how you want normal people to be 3 dimensional: You could imagine that every visible thing is from a 4-dimensional POV flat and glued to the 3-...
don-joe's user avatar
  • 1,033
28 votes
Accepted

Why would a five dimensional creature need memories?

To know what is happening at the other end of its body, This creature passes through time the same way a fence passes through a field. The fence has a start and an end and everything in between, but ...
Daron's user avatar
  • 66.2k
27 votes
Accepted

How to test a time machine?

What do you need is a series of experiments. Sending small, unconsequential things are best. For the fourth point (multiverse or not), I have two experiments (there can be more). Both require ...
jose_castro_arnaud's user avatar
25 votes

My time machine needs to know when it is

You need to know when you are sending stuff, not how much time they stayed in the past (from their perspective). So sending clocks is a no-no. One way you could do it is by collecting air samples ...
The Square-Cube Law's user avatar
25 votes

How would a higher-dimensional being enter a lower dimension?

By proxy It would be terrifying to enter a 2d world. But we do it all the time in video games and it is fun, because we have a tech interface that interprets a 2d world in a way that make sense to ...
Willk's user avatar
  • 305k
19 votes

Could you have more than one building in the same spot by "stacking" them in 4th dimensional space?

Initially consider it as time. There was a building before the one you're in and a building after it. All you need to be able to do is move between those buildings. Consider a co-ordinate system x,...
Separatrix's user avatar
  • 118k
18 votes

How can it be bigger on the inside

D&D's Bag of holding (and other spells & effects) describe the use of pocket dimensions to achieve this. Also see: Rope Trick. The bag does not compress or use a portal; the inside of the bag ...
Ross's user avatar
  • 2,266
18 votes

My time machine needs to know when it is

Assuming you can't take a star fix for whatever reason (during some of these time periods, Earth's surface could be pretty hazardous, and I'm not sure what precautions your time machine uses to avoid ...
Cadence's user avatar
  • 38.2k
18 votes

Is there a good geometric analogy for a 'trap' dimension that you can stumble into easily but is very hard to exit?

The Hyperbolic Plane/Space Hyperbolic geometry grows exponentially with respect to radius. This means that it's very easy to get lost. Anyone who has played HyperRogue is familiar with this: the final ...
Christopher King's user avatar
18 votes

How can I make the rules of my Faerie Portal free from contradiction?

Brace yourself for a surprise, you won't see the witches. This is actually a built-in safety mechanism in the Charm Walk, if you are observed by someone not following the path along with you it won't ...
Moghwyn's user avatar
  • 351
17 votes

Why are extra-dimensional monsters harmed by electricity but not physical blows?

Electromagnetism is Mirrored Across Dimensions This is at odds with how we understand actual additional dimensions to work, but so are extradimensional horrors, so we can roll with it. If you shoot a ...
jdunlop's user avatar
  • 32k
16 votes

How do Time Keepers log their diaries?

The diary itself is a timeline The entries happen one after another and as such are representative of the owner's personal timeline. They don't have to be dated, they merely have to be presented in ...
Separatrix's user avatar
  • 118k
16 votes

Is there a good geometric analogy for a 'trap' dimension that you can stumble into easily but is very hard to exit?

Spheres. A sphere is a 3 dimensonal object. We can walk on a sphere and we will eventually wind up where we started. That is how our Earth is. In your world, other 3d spaces intersect with ours ...
Willk's user avatar
  • 305k
16 votes

Teleportation without loss of consciousness

The more or less classic way to do this has been a portal, wormhole, etc. Think of the tunnels in Tunnel in the Sky or the Gate in Stargate et. al. These effectively amount to connecting two distant ...
Zeiss Ikon's user avatar
  • 45.9k
16 votes

This teleporter causes gravitational warping of the user’s body—how come it doesn’t kill them?

You can't do what you're suggesting to the degree you're hoping for in the way you want This is a frame challenge. In many ways the human body is remarkably resilient. Somebody smacks you on the arm ...
JBH's user avatar
  • 122k
15 votes
Accepted

How can it be bigger on the inside

I have done some thinking about making an “abcess” or “bleb” of folded spacetime on the far side of a throat that’s smaller than the room it contains. I’ll illustrate using flatland. Draw a small ...
JDługosz's user avatar
  • 69.4k

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