

How To Imagine the Tenth Dimension - kwamenum86
http://video.google.com/videoplay?docid=-6626464599825291409#docid=4490129704776663304

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roundsquare
I really hate this video. It makes things more complicated than needed.

You can't "visualize" the fourth dimension (or I haven't met anyone who
could... and the kind of math/physics where this comes up was a common topic
for me for a while).

However, you can understand it pretty easily. Its really just another
coordinate. You can do algebra with it. If I say someone is at (3, 2, 5, 6)
and moves (1, 2, 3, 4) they are now at (4, 4, 8, 10)...

Want a 5th dimension? Add another comma/number.

People who "visualize" the higher dimensions actually visualize 2 or 3
dimensions and know how to generalize (from practice/experience/theorems).

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bad_user
I think the question that most often comes up is how many dimensions are we
living in? And, are all of them equal?

Sure, on paper you can have as many dimensions as you like, just add
coordinates, but that won't help us come up with the grand unified theory, or
find other new laws of our universe, which might have pretty useful practical
applications.

Unfortunately we are limited in seeing beyond our primary senses.

~~~
roundsquare
Its a fair point... sadly I don't know the answer in any great details. What
little I know says there are 26 dimensions and they are not all equal. 3 of
space, 1 of time, and 22... others...

Actually, I wonder, when people usually ask this question, are they just using
the word dimension as a buzz word or do they know what it means?

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Synthetase
I hate to be a spoil sort but the guy that made this doesn't know what he's
talking about. He' a musician, not a physicist or mathematician. His
proposition fails past the fourth dimension.

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ErrantX
This is what a physicist friend sent to me a while ago:

"there is really little point in trying to graphically represent anything
beyond spacetime. Possibly 3D space with a time vector is useful (i.e. an
object representing 3D space moving along a vector) because it is still
helpful to explain the concepts. Beyond that just stick with the numbers or
you risk confusing yourself on what is being talked about"

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herdrick
<http://news.ycombinator.com/item?id=1385736>

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herdrick
And: <http://news.ycombinator.com/item?id=1385745>

~~~
cianestro
I have to disagree. Just because "results where in 5-space and up you can see
and exist in all time simultaneously" appears to be "wacky" doesn't mean it's
not possible. It's simply not part of your definition or interpretation of
your current existence, which makes the 4th dimension seem out of place.

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henrikschroder
Again, there's a huge difference between 4D space and 3D spacetime. Both are
4-dimensional mathematical spaces, but the visualization is completely
different.

"Time is the fourth dimension" is the single most damaging sentence for your
understanding of time and space.

To have an n-dimensional spacetime where time is not the nth dimension makes
no sense.

~~~
bad_user
> _"Time is the fourth dimension" is the single most damaging sentence for
> your understanding of time and space._

The video didn't expand on the person living in a 2D space example ... if such
of thing would be possible, he would be able to explain the presence of a
third dimension using time (going so far as to consider time as being the
third dimension).

~~~
henrikschroder
_he would be able to explain the presence of a third dimension using time_

NO! Absolutely not! 2D spacetime does not look like 3D space at all!

In 3D space, I can take a 2D angle bracket, flip it in the third dimension,
and get its mirror image. This will seem like magic to 2D creatures. In 2D
spacetime, I can do no such thing. No matter how long I wait (i.e. move in the
third time dimension), the angle bracket won't transform into its mirror
image.

In 4D space, I can take a 3D right-hand glove, flip it in the fourth
dimension, and get a left-hand glove. This will seem like magic to 3D
creatures. In 3D spacetime I can do no such thing. No matter how long I wait,
a right-hand glove will never transform into a left-hand glove.

Do you understand?

Do you see how adding time to n-dimensional space does absolutely _nothing_ to
explain n+1 space?

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rbanffy
That's because dimensions are not ordered. There is no first dimension, or
second, or third. For a flatlander, time is what he perceives as a third
dimension. Depth may be a fourth dimension. If you wanted to do the same trick
to you, you would have to flip yourself in a non-time higher dimensional
space. I think any dimensional space would do.

But it's early in the morning and I haven't had breakfast. Talk to you when my
brain joins me.

To perceive time as a dimension is useful because it helps you realize you
actually perceive four dimensions the same way a flatlander perceives three.

~~~
henrikschroder
_To perceive time as a dimension is useful_

If you want to do space-time calculations, yes.

 _because it helps you realize you actually perceive four dimensions the same
way a flatlander perceives three_

Absolutely not. We perceive time as time and space as space. The concept of
spacetime does not help us understand or visualize higher dimensional spaces
at all. It only confuses the issue, which is exactly the original complaint
against the video this whole discussion is about.

Edit: One more example: Can you visualize the difference between a 3D cube
moving in time, and a 4D cube moving in the 4th dimension? If you project the
4D cube down to 3D, it will look like a double cube that twists itself inside
and out, but the 3D cube moving in time will just look like a 3D cube.
Spacetime _does not help you_ understanding 4D space.

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cianestro
I'm glad my 4th-dimensional-former-undulating-self-blob observed this point on
the 3rd dimensional plane.

Obligatory link: <http://news.ycombinator.com/item?id=1385543>

