Here is an interesting thought, can us 3D people live in a 4D universe, if somehow a thousand earthlings got transported by 4D aliens to their universe and planet (a planet with similar to our climate, weather, etc.), could we live there?....would the laws of physics be different over there.

Again - real simple - Height, width and depth are 3 dimesions. the forth is motion in relation to anything else. Time is nothing more than motion from one spot to another and saying anything is only 3D means that it doesn't move in relationship to anything else - which is impossible because EVERYTHING in the known universe is moving.

So what do you mean by 4D? We are all in motion (we move from a quantum state on up to our podies moving, the Earth spinning and revolving around the sun, the sun moving through the galaxy, the galaxy revolving and headig away from all the other galaxies...) so we ARE 4D creatures!

The laws of physica are pretty much the same throughout the universe unless you can prove other dimensions... And if Hawkins can't, I'm pretty sure no one here can.

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And here is where the other stuff is.

yeah whatever, i still believe we are in a 3D universe

I think what Ikyoto is trying to tell you is that time is the 4th dimension. Although that may be simplyfying things a lot, the point is that there are clearly 4 dimensions in which we move. This is pretty basic science, and nothing new. If you're wondering if we could perceive additional dimensions, that's something different.

Ok PR - There needs to be clarification. Most of the people I know and the science books I've read and the few courses i took in mechanical drawing all use the following.

D's 1 & 2 (interchangable depending on who starts the drawing) are height and width.

D3 is depth. With these we have a way to show each and every object we can percieve.

D4 is motion through those first three in relative postion to observer.

Time (or motion through the three dimensions) in commonly refered to as the forth dimension.

Now - what do you mean? Clarification of terms is the first step to communication.

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What would Scoobie do?

And here is where the other stuff is.

A fourth spatial dimension is conceivable and may in fact exist according to string theory (just wrapped up so tightly that we can't see it).

If there were a fourth dimension and it weren't wrapped up, I think it would make the laws of physics different - in particular, you probably wouldn't have the usual inverse square law of gravity. Not sure what the implications would be, though.

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You could think about the analogy that in our 3(spatial)D-universe would live 2D-people. These people would be infinitely thin, so we wouldn't even see them. But would our 3D objects have some kind of disturbing effect to them, that I don't know. I mean that if you stick your finger through them, would they feel it? I assume that they would feel it, so to get back to your question, I quess that we could live in the 4D-universe, but it would be more dangerous place than our 3D-universe, because there would appear strange objects from that higher dimension without any warning to us.

You should read the book "Flatland". It explains the adventures of a 2D being (A. Square) who first visits a 1D universe and then a 3D universe. While it is written as a fantasy, the idea is to explain multi-dimensional geometery. There have been a lot of follow-ups to this. I remember reading an article about the chemistry of a 2D universe; since the atomic orbitals that require 3D dimensional symmetry are not allowed (like the F orbitals) the periodic table is much more limited. So I would suppose that a hypothetical univerese with four spatial dimensions would have very different physics and chemistry.

But that is just a thought experiment, I don't think we live in such a universe (not counting the closed dimensions of string theory).

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IIRC, in Flatland, Magnetism wasn't allowed either since it requieres 3D

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As others have pointed out, we essentially do live in a 4D universe. Humans perceive length, width, and height - so we have three spatial dimensions. The fourth dimension is temporal - time.

If one wants to hypothesize about other dimensions, one could look at the rate of change of those dimensions. Of course, I'm not sure that's a 100% valid way of looking at things.

... of course, then there's string theory which hypothesizes that the universe we live in actually has several more dimensions.

... as to "aliens transporting us" - I think you've been watching too much Sci Fi channel... ;-)

to the original post, i think PR is referring to a 4 spatial dimension. so combined with the temporal dimension, it makes a 5d world. imo, the physcis in such world would be much, much different than ours.

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fine if we do live in a 4D then my question is "could we live in a 5D universe"

We see color... data charts often use color as a way of denoting a specific aspect to a data group. Color is a dimension in this example. But we do see color in our real world, it is an aspect of real phenomena. If we state it more simply as the frequency of electromagnetism, then it may be necessary to describe it, therefore being a 5th dimension.

This should then allow for the very real possibility that we might eventually meet alien beings that are a hyper-intelligent shade of the color blue.

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J Pax

Here's a question: if the singularity of a blackhole has no volume, as I've been led to believe, would that make a singularity a 3d object, as it is missing a dimension?

And fingolfen, are you sure that length, width and height are the 3 dimensions? All three of them are interchangable depending on how you look at something right?

I was always under the impression that the 3 basic dimensions were volume, mass and velocity.

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I think a singularity has 0 dimensions, since it takes up no space and time doesn't pass there.

As for dimensions, for mathematical/analytical purposes you can consider anything measurable a dimension of sorts. But in terms of relativity and such, there are three spatial dimensions (length/width/height or whatever you want to call them), plus time.

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I see that many of you have beaten me to the answers. Let me still take a stab at this.

Imagine you are looking down on a world that is only 2D. Length and width - no height whatsoever. All creatures only have these two dimensions, no height. They don't even know what the third dimension is. Therefore, they cannot look "up". There is no "up" for them.

Rob and Bob are two such creatures in that 2D world. Now, imagine that they are having a good conversation about higher dimensions. Now you want to have some fun. You just lift Rob from his lawn chair. What will Bob see?

Bob will see that Rob simply vanished into thin air!! He can't even fathom what happened to Rob. He will go and tell all his friends that Rob simply vanished.

When you place Rob back in "front" of Bob, he will see that Rob reappeared from nowhere.

Similarly for us, the Earthlings, who live in 3D world, Time happens to be the fourth dimension. So, while you and I are talking, if a naughty time-traveling alien from another world lifts me out into another time (time travel?), then you would see that I vanish into thin air.

Like Ari Jokimaki pointed out, we probably could live in a higher D world, except that it could be more dangerous. You have to be aware of the objects that might suddenly appear from "nowhere". For instance, if Rob and Bob are aware of the fact that something can come from "above" for them, they will have to be careful. Similarly, for the Earthlings, if something else traveling in Time tries to occupy the same space that you do at a particular time instance, the results could be disastrous. You are driving and suddenly a vehicle appears in front of you from nowhere!!!

Hope this is clear.

(Edited for Typos)

Oh, us 3D creatures could be much meaner than that. Assume that the 2D creatures are little squares with a right-handed symmetry. You could take Rob and flip him over (turn-him through the unknown to them 3rd dimension) and when you put him back he'll be left-handed! It would like a 4D creature taking you, turning you through the 4th dimension, and now your liver is on the left side of your body (you've become your mirror image)

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Reminds me of an old Steven Wright joke - he isn't afraid of heights but he's afraid of widths. So when he wants to take is dog for a walk he does it on the ledge of his apartment house. :roll:

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And you wouldn't be able to digest anything because we can only get nourishment from "left-handed" organic molecules. It might be a good weight-loss program in the short term, but eventually you'd starve to death.

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A dimensional rotator would make a good diet aid. You step through it, eat all you want, and step through again later for your light meal.

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it was just a wild example

I've just gotta chime in here ...

I've met 'em, when you get them Drunk, they're not that smart, in fact they make Arthur the Teetolar, look like a Freakin' Binge Drinker!

As for staying on topic, Michio Kaku does an exelent job on this very thought experiment, in his book Hyperspace, mentions Flatland too, if i remember correctly.

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Here is the flatland for anyone interested.

Aren't we already?

Oh, you're talking about spatial dimensions. Yes, it would be possible. However, we would be extremely vunerable to any beings that naturally lived in a 4D (5D really) area. Picture a flat creature in a 3D (4D) world. Not only would the flat creature have an incomplete understanding of what was around them, since they view the world in only two dimensions, but we could manipulate them in their own dimensions.

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THIS IS IN RESPONSE TO THE FIRST POST(S):

We DO live in a 4-D universe. The FOURTH DIMENSION is TIME!

There are three kinds of four dimensions: Space-like, Time-like, and Light-like.

So, we DO live in a four-dimensional universe. However, in M-Theory (inherited from Superstring Theory which had ten dimensions), there are eleven dimensions. The other dimensions are all curled up. The other dimensions are supposedly so tiny that we will never be able to discern their existence. So, we must wait and see about that. Of course, I do not expect to live that long, so I will leave experiencing eleven dimensions up to the rest of you young folks.

ljbrs :wink:

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is the bood Hyperspace worth reading?? it seems quite interesting

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Very much so.

He does some simply amazing things when he starts describing Tesseracts.

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Hi Platinum Rhymer


If you have the patience to read a few pages , you might want to check out www.uniformexpansion.com

In that website you will see a theory which proposes that our 3 dimensions of space are actually moving in a 4th spatial dimension we are not directly aware of.

Kinetic energy is described by E = 1/2 mv^2; Einstein’s energy equation is E = mcc, If our universe were moving in an unobserved dimension, with a velocity of c/(square root of 2), then E= mcc, is simply the result of motion in an unobserved dimension and is the same kinematical expression of E = 1/2 mv^2.


snowflake

Its hilarious really.

You ask a "What if .." question about the possibility of a 4th dimension. This makes it seem like you are trying to explore new ideas and concepts.

Then someone tells you that our best model of the universe says there are 4 dimensions already (possibly more with string theory, only squeezed smaller than the planck length).

Now you say you don't believe in the 4th dimension (time).

I think it was Einstein who said "Time is what stops everything from happening at once." Then he went on to proove mathematically various relationships using this concept of 4d spacetime, between velocity and time and the speed of light, etc.

So are you saying that you don't believe in time? That time doesn't exist?

If you're saying you believe in time, but that it's not a dimension, please provide us with your math proofs/experimental evidence showing that Einstein was wrong.

Meanwhile, using your algorithm again, I postulate that the 4th dimension is Kirby the Giant Invisible Penguin.

(edited to fix quote)

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<3

Could we live in a 4d planet
(I think you mean on a 4d planet )


Yes.