I really need to poop...

putabagonit · 4 months

ha ha ha. i love the bag.

iamlouisck · 5 months

You are my favorite comic. I just bought your $5 act and it was awesome. Keep being awesome. That is all.

wisdomtooth · 5 months

pretty hilarious

JapaneseKitten · 6 months

"Love to laugh"

webbam · 6 months

Isn't that the case for the case I described, where the matrix would be:

1 0 0

0 1 0

0 0 1

And you multiply that by the independent scaling in each direction:

LambdaX

LambdaY

LambdaZ

to establish your position relative to the origin, which doesn't rotate?

(sorry for the formatting of this post, I'm trying to represent a 3x3 matrix multiplied by a 3x1 scaling)

webbam · 6 months

I use the terms "eigenvector" and "characteristic (basis) vector" interchangeably pretty regularly. I've yet to be corrected at work. I'd love to understand the difference, if you'd care to share.

webbam · 6 months

Yep. Thats why its not relevant to the discussion here. The polarization (with the glasses) just make sure each eye only sees one of the images to get that 3D effect. I just didn't want to convey that you can take 2 cameras eye-distance apart and see a 3D image simply by looking at their outputs. That's all.

webbam · 6 months

I agree that this is the only answer. I assumed the OP wanted to know how we arrive at that answer, so I illustrated 2 different ways of looking at position, both of which boil down to 3 dimensions.

There are a lot of yes or no questions in /r/askscience. In my opinion, it'd be nice to provide backing for your answer so that something is actually learned by reading your post.

webbam · 6 months

If I'm picking up what you're putting down, what you've described is the heart of Einstein's arguments for physics. Everything is relative. Even Tachyons, the hypothetical particle that is said "to be able to move backward in time" can be looked at as a particle always moving backwards in space but forward in time.

webbam · 6 months

Hmm... I feel like my posts answer your initial question about the universe (I assumed you meant the one we're in) by explaining how we get to 3 spatial dimensions. I'll make sure to be more direct with my answers.

According to the laws we (humanity) have established for motion and physics, we've broken the space dimensions of our universe down to 3 independent dimensions. Could another universe exist with 4 spatial dimensions? Sure. We even have loose models of how some objects would physically work in 4 dimensions (see the hypercube as an example).

So to answer your direct questions here:

There's no reason a different universe with a different set of physical rules CAN'T exist. There're debates whether or not it DOES exist (e.g. "are there multiple concurrent universes in time?"). The way we understand the universe to have played out so far doesn't acknowledge multiple universes but doesn't disprove them.
THIS universe is not fully understood yet. We've come up with a convenient way(s) to measure physical dimensions depending on what we're looking at. 3 dimensions is the norm because it's enough to describe the way we see things. Nothing more, nothing less. "Dimensions" don't exist to the universe, only to its observers.

Your question is "why 3?"

My answer is "because 4 is unnecessary (shown in my post above) and 2 is too few to the observer to clearly identify location." Any question about orbits is a subset of your initial question, in my opinion.

webbam · 6 months

Another awesome question. Let's see if I can tackle this one in a heuristic way.

Solving a system of equations for cases where only 1 variable changes helps you decide how they relate to each other. That's why eigenvectors are sometimes called "characteristic vectors". They characterize the system being observed. In a nice, simple system, we can change boundary conditions to solve for a partial answer to the question. Let's use this "real dimensions" question as an example:

Distance is in 3 dimensions. Check. But, at least notionally, I can walk on only a subset of those 3. Even moreso, I bet you that I can walk along only 1. It turns out that I can do this because my motion in 1 dimension does not alter my displacement in the other 2.

Let's use my favorite coordinate system to again - heuristically - drive the point home. ECEF (earth centered, earth fixed) has it's origin in the core of the earth, with one axis pointing in each independent direction. When you're on the north pole, you're standing at [0 0 1]. When you're on the intersection of the equator and the prime meridian, you're on [1 0 0]. When you're perpendicular to the plane of those 2 and standing at the origin, you're at [0 1 0].

These are the eigenvalues you can use to solve for position relative to the origin in this coordinate system. Any position you have relative to the core of the earth can be broken down into these 3 values with some coefficient attached.

silvare · 6 months

ha ha. good catch!

webbam · 6 months

I don't mean to be harsh and use you as an example, but please don't answer questions in /r/askscience like that. This isn't a philosophical sub-reddit, and there are obviously mathematical reasons that scientists pick the conventions that the use. His question is scientifically valid because it can evoke a scientific answer.

Science absolutely deals with the "why". We voraciously prove our work among panels of our peers on a very regular basis. "Why?" is the most common question asked.

webbam · 6 months

It's cool. It's morning so I'm a little groggy too (hence why I'm on the science section of reddit :P).

We travel in more than 3 dimensions all the time. In fact, based on what system you use, you could be travelling in omg, like, 10 dimensions. I'm not sure I agree with the video in that link, but it's a fun notional example. According to that, you're travelling along at least 1 path in all 10 dimensions, even if you can only observe the 3.

A clarification of time: Time is not a dimension of distance. We use time to reference change, among other things. When we want to know how far something has moved, time has no place in the equation. When we want to know how fast it moved, we need to take that difference and relate it to the time it took (in this case, distance/time). This is why learning derivatives and integrals are vital to math. It allows you to establish relationships between things with different units.

I hope that answers your question!

webbam · 6 months

This is an awesome question, and one easily explained.

There are many times in science, as in life, where you don't get what you want. Most sensors are a really good pair of eyes that can only see what's in front of them. To get a good idea of what's going on, maybe you'll move the sensor to take pictures from different angles and piece together what you're looking at as a whole. This is how 3D movies get made! *additional note at the end.

Anyway, so how do those sensors know where their target is if they can only identify "forward"? Well, we can realign the sensor and we should know how we aligned it. So now we can tell how far away our object is from the sensor, as well as use the alignment of the sensor to tell where he is in terms of elevation and azimuth along that sphere.

A note about 3D movies:

3D movies are made using 2 cameras with different polarization [polarization is not relevant to this answer] that are about a human-pair-of-eyes apart to mimic how we look at things. 2 cent explanation: cameras can only see in 2D, but you can take the difference between 2 pictures of the same thing to understand that third dimension pretty clearly. Other kinds of sensors that work in 1D work the same way, and you take differences in measurement by understanding their position in a similar way.

webbam · 6 months

Actually, we have no idea how many dimensions there are. From what we can prove and what math suggests, however, there are 3 when dealing with physical movement. Here are the basics of how physical dimensions get "made", and a worthy starting point to check out.

A LITTLE BACKGROUND:

In any type of multidimensional measurement (that is, a measurement of something that's dependent on more than one variable), it's useful to find the eigenvectors (N number of orthogonal (statistically perpendicular) vectors which notionally tell you that you have N independent variables with functions of their own). When you solve for those, you have an idea of how your system (of equations) acts and you can plot one versus another. [This is why in a cartesian coordinate system, height width and depth can be shown perpendicular to each other.] So, let's look at these "real" dimensions and see if we can come up with more than one answer to your question (we can!).

LENGTH, WIDTH, HEIGHT (or relative east, north, up):

I see you reading, all impressed over there. I want to walk toward you, but you're pretty far away. How far away? Well, by line of sight (LOS) you're probably, let's say... 100 miles away. But I can't travel by line of sight. In fact, I have to walk left, forward, and sometimes up and down (steps, hills, etc.) to get to you. I can break down any movement I make to get to you into these 3 independent "directions", which I chose arbitrarily. Can I break those 3 down further? No. And any direction I go is a combination of 1 or more of those independent ones. Bam! My 100 miles is really 90 forward, 4 (or whatever) left, and maybe 1-2 miles up. These are usually referred to as cartesian coordinates. I guess you're on a mountain and I'm on the beach. Sucker!

BONUS!

Let's see if we can pick 3 other dimensions that are also "real" but aren't length, width, and height (or north, east, and up as we like to call them for movement):

You're 100 miles away from me again. But I can't tell how far left or right from me you are... wait, sure I can. I'm looking at you (line of sight), and I know how far my head is tilted up (elevation) and to the left/right (azimuth) to see you. Lookin' good!

Now I can describe your movement (or my movement toward you) in 3 NEW coordinates that are very real: distance, elevation (in degrees) and azimuth (in degrees). These are often referred to as polar coordinates. What I'm describing is a sphere with me at the center, some radius (that line of sight distance) to you, and your position on the surface of that sphere. The first angle is how far above the equator of that sphere you are, and the second is how far to the left or right you are from it's prime meridian. If I chose my initial conditions wisely, then when I'm looking straight ahead both of those numbers are 0.

Hope this helps!

Sorry, I'm not sure if we're supposed to mention our credentials when answering these questions now. I'm a Radar Analyst (electrical engineer) for MIT, so I deal with distance problems in all their fancy dimensions all the time. :)

cheesecakegirl · 6 months

Did anyone else notice their 5th product feature on amazon.com? Made me lol.

For those too lazy, here's the spoiler:

0% of the proceeds will be donated to the Make-A-Wish Foundation

ANyTimEfOu · 6 months

I agree. I'm not a huge fan of the way MLG runs their shit (I guess neither is Idra or Naniwa), but this line up is incredible. Props to the players!

MIIAIIRIIK · 6 months

Sweet. Baby. Jesus.

robot voice PLEASE SIT ON MY FACE

Sawgon · 6 months

YEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEES

MGS4 was awesome fuck the guy below me.

PaperFlower8 · 6 months

I feed rabbits. a lot.

Olliebird · 6 months

I was just thinking that. Dude got the Skyrim Hummer achievement way earlier than anyone else.

Diachy · 6 months

this is why photoshop was invented. upvotes for you, sir

benfay · 6 months

Electrical Engineering. Electrical Engineer.

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