## Tuesday, April 17, 2012

### Abolishing the Fourth Dimension

Seems like there's a lot of new discussion happening in the last few days about whether it's proper to call space-time the fourth dimension. With this project, I've often argued that time is not a dimension, it's a direction, and as with any of the other directional names (like up, forward, north, and so on) it's arbitrary what dimension we assign a particular label, as long as we recognize that there's an opposing direction (like down, backward, south, and so on) which we need to pair it up with if we're going to be thinking about a dimension rather than just a direction. But the following video, posted on the YouTube Minute Physics channel just a few days ago, takes the controversy to another level: it's titled "There is no 'Fourth' dimension".

(By the way, the lovely optical illusion at the top of this blog was posted in the comments area for a Gizmodo article about this MinutePhysics video. If this optical illusion works as well for you as it does for me then you may be surprised to learn that this is not an animation, it's just a still image. Any motion you might see is being imparted by your observation of the still image - what a wonderful visual metaphor for the quantum observer! I wish I could give credit to the creator but that information is too difficult to see in this copy of the image.)

Here's the comment I sent to the Minute Physics channel, if they ever respond I'll be sure to add what they say to this blog entry.
Dear Minute Physics,

Congratulations on the success of this channel! Scientific American published a blog last summer asking why there weren't more viral science channels on YouTube (and at that time identified my channel as one of the few). Clearly you have moved into that space, good for you. I have some comments about your latest video.

Larry and Moe. Who is the third stooge? Curly.
Moe and Curly. Who is the third stooge? Larry.
Length and width. What is the third dimension? Depth.
Depth and length. What is the third dimension? Width.

Saying there's no fourth dimension is the same as saying there's no third stooge or there's no third dimension. At best it's a semantics discussion: yes, you can't say who the third stooge is unless you also first identify who the other two stooges are. But at worst this video has the danger of leading people to conclusions such as this: wasn't Einstein wrong then when he agreed with Kaluza about our universe's field equations being resolved at the fifth dimension? Surely, some people will say, if this video's claim that "there's no fourth dimension" is correct, then there must also be no fifth dimension or no tenth dimension as well.

I agree that it's important for people to realize that you can't have a fifth dimension without acknowledging the other four dimensions that are included within. But saying there's no fourth dimension seems like a dangerous oversimplification to me. Your thoughts?

Sincerely,

Rob Bryanton
Then, as a further interesting coincidence, my friend Lee Price sent me a link to this new article written by Lisa Zyga and posted at phys.org. It's entitled "Physicists Continue Work to Abolish Time as Fourth Dimension of Space". Here's the opening paragraphs from that article:
Philosophers have debated the nature of time long before Einstein and modern physics. But in the 106 years since Einstein, the prevailing view in physics has been that time serves as the fourth dimension of space, an arena represented mathematically as 4D Minkowski spacetime. However, some scientists, including Amrit Sorli and Davide Fiscaletti, founders of the Space Life Institute in Slovenia, argue that time exists completely independent from space. In a new study, Sorli and Fiscaletti have shown that two phenomena of special relativity - time dilation and length contraction - can be better described within the framework of a 3D space with time as the quantity used to measure change (i.e., photon motion) in this space.

The scientists have published their article in a recent issue of Physics Essays. The work builds on their previous articles, in which they have investigated the definition of time as a “numerical order of material change.”
As Lee pointed out when he sent me this article, this is a viewpoint that would have interested Gevin Giorbran. Gevin's Everything Forever - Learning to See Timelessness encouraged us all to visualize the underlying structures of our reality from a perspective where we are "outside" time. But in his book Gevin also embraced my approach to visualizing the dimensions, because he saw how that same timeless viewpoint is reached by the time we've envisioned the ultimate ensemble of the tenth dimension.

So is it really possible to say "time is independent from space" (Sorli and Fiscaletti's viewpoint) while still acknowledging the existence of extra dimensions? As I've said in entries like Imagining the Third Dimension, visualizing the third dimension as timeless is the approach that physicists like Julian Barbour ask us to use, and accepting the need for some additional degree of freedom to change from state to state is how I describe the direction of time no matter what dimension we're discussing. It would be nice to say both of the above examples are just semantics, that a rose is a rose, and no matter what you call the additional degree of freedom the third dimension uses for change from state to state doesn't change the fact of its existence. But Sorli and Fiscaletti are talking about a change which is more fundamental than that, and ultimately may not require the existence of extra dimensions at all. As I said most recently in Connecting Zero to Ten,  "the idea that there are really no dimensions, that there are just infinite vectors within one underlying fabric which is dimensionless, actually resonates more strongly for me..." because that's another way of describing this timeless ultimate ensemble my approach reaches with the tenth dimension.

One final note: as long as both of the examples we've looked at here (from Minute Physics and the work of Sorli and Fiscaletti) are willing to acknowledge the existence of the multiple outcomes predicted by Everett's Many Worlds Interpretation of Quantum Mechanics, then I believe we really are talking about different ways of describing the same thing. On the other hand, if either of these are intended to encourage us all to believe that there is only one possible set of outcomes for our universe from its beginning to its end, then that's where my project would have to part ways.

Even if time is an illusion, free will is not. Enjoy the journey!

Rob Bryanton

P.S. - here's my video for Imagining the Fourth Dimension, which works very nicely as a response to the Minute Physics video.

Next: New Video - Timelessness and the Ultimate Ensemble

Anonymous said...

I think the Minute Physics video is equivocating the idea of dimensions as a property. A way I see it is thinking of the dimensions as blue: you have blue objects, but blue itself isn't really a discernible object, it's a property of an object. We can say "that thing is blue" in the way we say "that thing radiates light of a specific wavelength we call blue", but we can't say "that thing is blue" in the way we say "blue is that thing". It's not as if blue doesn't exist at all, merely that it only exists as a property, not something we can physically feel or locate with our bare hands. Similarly, there are x-dimensional objects (lines, cubes, universes, et cetera), but just like the colours, the dimensions are properties, not distinct physical objects. That's why he underlines the "the" in "the fourth dimension", as if to say it is definitively a single object. In a way, it is a semantic issue, but in another way, it's also likely important to visualizing and fundamentally understanding the dimensions. After all, even today, I see a lot of people treat a dimension as a universe (or some other type of concrete structure) rather than the property it is more like.

So essentially, dimensions aren't objects--there is no "the" fourth dimension--they're properties or descriptors of objects: my pillow is four dimensional. I think that's the message he's trying to get across in a very condensed way,considering the video is only several seconds over two minutes long.

Chris Pearson said...

I can resonate with this. After it's been shared, this is the type of knowledge that seems obvious, but only in retrospect.

However, how does this principle or analogy translate with 5th dimension "probability space?" I can vaguely or abstractly picture the concept, but I am woefully inadequate to express anything of the sort as concisely and succinctly as the previous comment.