# Conveying left/right to alien by description **URL:** \ **Category:** Factual Questions\ **Created:** [February 14, 2016, 3:17pm UTC](https://boards.straightdope.com/t/conveying-left-right-to-alien-by-description/746120 "2016-02-14T15:17:34Z")\ **Posts on this page:** 19\ **Page:** 5
**Author:** ![naita](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/naita/32/5862_2.png) [@naita](https://boards.straightdope.com/u/naita)\ **Post date:** [February 16, 2016, 7:38am UTC](https://boards.straightdope.com/t/conveying-left-right-to-alien-by-description/746120/81 "2016-02-16T07:38:19Z")
> [@Blake](#): > > Maybe I’m overcomplicating this by referring to the planetary poles, which I thought was the simple option. Let’s start from basics and see if you can point out the flaw in my reasoning. > > 1. Construct a Faraday cage with no external magnetic field. > 2. In that cage, construct a simple circuit. Basically, give instructions to lay out the circuit on the floor in a rectangular configuration. Place the power source closest to a wall and the anode furthest from the observer. My apologies if you’ve already grasped the flaw, but I’d like to point out that you’ve included it clearly in your choice of diagrams. You’ve made two, they are mirror images, and there is no way to indicate which is which without the concept of left and right. You could talk about inside and outside, and above and below, but not left and right. So which one are the aliens using? That matters, as in one case the magnet pole you want to tell the aliens about is pointing right, and in the other it is pointing left. You could use inside and outside, but the two mirror images you’ve created don’t consistently create the same pole inside the loop. ---
**Author:** ![Blake](https://avatars.discourse-cdn.com/v4/letter/b/a9a28c/32.png) [@Blake](https://boards.straightdope.com/u/Blake)\ **Post date:** [February 16, 2016, 8:03am UTC](https://boards.straightdope.com/t/conveying-left-right-to-alien-by-description/746120/82 "2016-02-16T08:03:03Z")
> [@naita](#): > > My apologies if you’ve already grasped the flaw, but I’d like to point out that you’ve included it clearly in your choice of diagrams. You’ve made two, they are mirror images, and there is no way to indicate which is which without the concept of left and right. You could talk about inside and outside, and above and below, but not left and right… That is not a flaw. I very specifcally and deliberately included both diagrams to illustrate my point. Why is everyone avoiding simply answering my question? ---
**Author:** ![Peter\_Morris](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/peter_morris/32/359_2.png) [@Peter\_Morris](https://boards.straightdope.com/u/Peter_Morris)\ **Post date:** [February 16, 2016, 9:35am UTC](https://boards.straightdope.com/t/conveying-left-right-to-alien-by-description/746120/83 "2016-02-16T09:35:09Z")
> [@mikecurtis](#): > > hey y’all, > i’m a longtime lurker here and while I enjoy a good in depth discussion about molecular polarity as much as the next guy/gal, I think youre making this too hard. they are humanoid, and have an understanding of our anatomy and can read our words, the fact that the back of the left hand resembles the first letter of the left word should be enough of a coorelation to start with Sorry, Mike, you’re not getting it. The problem is that the aliens are distant, we can send each other signals at the speed of light, but can’t actually meet. You tell them that the left hand looks like a letter L. Now describe to them what a letter L looks like: a vertical line, and a horizontal line that meet at the bottom left… Or you could send them a picture encoded as a series of pixels. Then tell them that they should scan the picture starting at the top left … See the problem? ---
**Author:** ![Francis\_Vaughan](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/francis_vaughan/32/3093_2.png) [@Francis\_Vaughan](https://boards.straightdope.com/u/Francis_Vaughan)\ **Post date:** [February 16, 2016, 9:39am UTC](https://boards.straightdope.com/t/conveying-left-right-to-alien-by-description/746120/84 "2016-02-16T09:39:30Z")
> [@Blake](#): > > Maybe I’m overcomplicating this by referring to the planetary poles, which I thought was the simple option. Let’s start from basics and see if you can point out the flaw in my reasoning. > > 1. Construct a Faraday cage with no external magnetic field. Nitpick. Faraday cages do not exclude static magnetic fields. Somehow this has become a deeply rooted misconception that pervades everywhere. Excluding static magnetic fields (or really any magnetic field short of RF) is actually really difficult. However this doesn’t materially affect the rest of your experiment. (What you need is a room surrounded by mu-metal. Such things exist.) > [@](#): > > the left hand side would point towards what we humans call the south magnetic pole. If done on the Earth this is true, and all is fine. However, given the OP has posited another planet, it would be good if you were more explicit about the terminology here.What is it about humans calling it the “south pole” that is important here. Humans can only call it that on the Earth. They can call the direction it points on another planet the magnetic South Pole for that planet. But calling it generically “the south pole” is ill defined. What I will again point out is that, even on the Earth, this experiment only works now, and would not give that answer 800,000 years ago, and won’t again sometime in the future. What your experiment does is provide way of creating an intermediate proxy that allows us to compare the direction of current in the wire versus the direction of current in the geo-dynamo. THis does allow you to tell the direction of the geo-dynamo in another planet - but only with reference to the > [@](#): > > If this is all correct we can move on to the next step. OK, it works on the Earth, and the magnet will point to what humans call the Earth’s magnetic south pole. What is the next step? ---
**Author:** ![Peter\_Morris](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/peter_morris/32/359_2.png) [@Peter\_Morris](https://boards.straightdope.com/u/Peter_Morris)\ **Post date:** [February 16, 2016, 9:48am UTC](https://boards.straightdope.com/t/conveying-left-right-to-alien-by-description/746120/85 "2016-02-16T09:48:54Z")
It seems to me that the solution is to point to some distant astronomical objects. If the aliens are on Mars, we could use the [Southern Cross](https://astronavigationdemystifieddotcom.files.wordpress.com/2012/08/cross.jpg?w=512&h=557). Tell them to take a 2D diagram, draw a line between Gacrux and Acrux, and another between Mimosa and Palida. Gacrux is “up”, Acrux is “down”. That should be enough to orient the diagram correctly. Then you can say that Mimosa is left and Palida is right. If they are from a more distant star, we could do the same thing with distant galaxies. Can anyone see anything wrong with that? ---
**Author:** ![Blake](https://avatars.discourse-cdn.com/v4/letter/b/a9a28c/32.png) [@Blake](https://boards.straightdope.com/u/Blake)\ **Post date:** [February 16, 2016, 9:56am UTC](https://boards.straightdope.com/t/conveying-left-right-to-alien-by-description/746120/86 "2016-02-16T09:56:49Z")
> [@Peter\_Morris](#): > > It seems to me that the solution is to point to some distant astronomical objects. If the aliens are on Mars, we could use the [Southern Cross](https://astronavigationdemystifieddotcom.files.wordpress.com/2012/08/cross.jpg?w=512&h=557). > > Tell them to take a 2D diagram, draw a line between Gacrux and Acrux, and another between Mimosa and Palida. Gacrux is “up”, Acrux is “down”. That should be enough to orient the diagram correctly. Then you can > > Can anyone see anything wrong with that? If you can see \*any \*common object, then the solution becomes trivially easy. No need to use the southern cross and complex relative descriptions, you can just tell them Venus is to the left Aldebaran when they look up (assuming they are low in the sky). ---
**Author:** ![Peter\_Morris](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/peter_morris/32/359_2.png) [@Peter\_Morris](https://boards.straightdope.com/u/Peter_Morris)\ **Post date:** [February 16, 2016, 10:07am UTC](https://boards.straightdope.com/t/conveying-left-right-to-alien-by-description/746120/87 "2016-02-16T10:07:34Z")
> [@Blake](#): > > If you can see \*any \*common object, then the solution becomes trivially easy. No need to use the southern cross and complex relative descriptions, you can just tell them Venus is to the left Aldebaran when they look up (assuming they are low in the sky). I don’t think so. A line of stars might appear to run left to right in the North, vertically at the Equator, and right to left in the South. With a cross, you can state which is the top. ---
**Author:** ![Blake](https://avatars.discourse-cdn.com/v4/letter/b/a9a28c/32.png) [@Blake](https://boards.straightdope.com/u/Blake)\ **Post date:** [February 16, 2016, 10:16am UTC](https://boards.straightdope.com/t/conveying-left-right-to-alien-by-description/746120/88 "2016-02-16T10:16:26Z")
> [@Peter\_Morris](#): > > I don’t think so. A line of stars might appear to run left to right in the North, vertically at the Equator, and right to left in the South. With a cross, you can state which is the top. Not really. The angle of difference across even a large planet wouldn’t make a measurable difference to the relative positions of stars. If Aldebaraan and Venus are both low in the sky, then you can only see them if you are facing that portion of the sky. Hence one always appears to the left of the other. Try it for yourself. Go out at night when Venus rises and mark a bright star to the left of it. Ask any doper anywhere else on Earth to go out and have a look when Venus rises. They will also say the star is to the left. ---
**Author:** ![naita](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/naita/32/5862_2.png) [@naita](https://boards.straightdope.com/u/naita)\ **Post date:** [February 16, 2016, 12:38pm UTC](https://boards.straightdope.com/t/conveying-left-right-to-alien-by-description/746120/89 "2016-02-16T12:38:53Z")
> [@Blake](#): > > That is not a flaw. I very specifcally and deliberately included both diagrams to illustrate my point. > > Why is everyone avoiding simply answering my question? As a result of your set up being flawed your description is wrong on a few points, and we’re not entirely sure which point indicates the faults in your understanding. Let me try to play the alien and see if that works. I create your set up, to the best of my understanding. Let’s say I create a current loop going counter clockwise and place my molten iron underneath the wire on the right hand side. Of course we don’t have common language about ccw and right hand, so you can’t know that’s what I did or tell me to do so, but so everyone “observing” knows what’s going on, that’s what I did. Know by Earth definitions the magnetic field lines go clockwise if you look in the direction of the current so my solidifying iron underneath the wire on the right hand side will form with a north pole to the left, pointing to the inside of the loop of wire. We do not however have common language about the direction of magnetic field lines or north and south poles, since these are arbitrary directions. We could easily have picked the other direction and have had a left hand rule, which would be more convenient since I could look at that hand _while_ writing and not have to switch back and forth between writing and checking the rule, but I digress. So now I have a ccw current loop and a magnet on the right hand side with a north pole pointing inwards. But I could as easily have had a cw loop with a magnet on the left hand side and the north pole pointing outwards. Without using outside references there is no way for you to indicate left/right, cw/ccw, or magnetic north/south. ---
**Author:** ![naita](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/naita/32/5862_2.png) [@naita](https://boards.straightdope.com/u/naita)\ **Post date:** [February 16, 2016, 1:09pm UTC](https://boards.straightdope.com/t/conveying-left-right-to-alien-by-description/746120/90 "2016-02-16T13:09:48Z")
I’m going to try another examination of your diagram while I’m at it: [quote=“Blake, post:78, topic:746120”] 1. Melt some iron, place it in a rectangular mould. Lay it at right angles to the circuit wire: ```auto _________________ | |^ | |^ -_ |^ _ |^ +| |^ | |^ | |^ | ______|_________ | | Molten iron | | | ________________ | | |^ | |^ | |^ | |^ | |^ _________________ _________________ ^| | ^| | ^| | ^| _- ^| _+ ^| | ^| | ^| | ________|______________ | | Molten iron || | _______________________ || ^| | ^| | ^| | _________________ ``` 1. Close the circuit and let it run while the iron cools. As a result of this, we will have created a magnet, possibly a weak one, but with no external fields we will have a magnet. And because of the left hand rule, the right hand side of this magnet will be the south pole. [QUOTE] This is true. But north/south are arbitrary descriptions of the magnetic field. > [@](#): > > We don’t need to actually use the word right hand at this stage. We just need to agree that if we allowed this iron bar to pivot on its long axis inside a magnetic field, the left hand side would point towards what we humans call the south magnetic pole. > > Or to say the same thing without using left or right, if we painted the anode side of the magnet blue, the blue side would face east. > > Do you see a problem with this? > > If this is all correct we can move on to the next step. Ah, now I see the problem in our communications. Some of us are pointing out the flaws in your next step before you’ve had the time to describe it. You are absolutely correct. You’ve managed to create a magnet with the north pole to the right. ---
**Author:** ![naita](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/naita/32/5862_2.png) [@naita](https://boards.straightdope.com/u/naita)\ **Post date:** [February 16, 2016, 1:12pm UTC](https://boards.straightdope.com/t/conveying-left-right-to-alien-by-description/746120/91 "2016-02-16T13:12:19Z")
> [@Blake](#): > > Not really. The angle of difference across even a large planet wouldn’t make a measurable difference to the relative positions of stars. > > If Aldebaraan and Venus are both low in the sky, then you can only see them if you are facing that portion of the sky. Hence one always appears to the left of the other. > > Try it for yourself. Go out at night when Venus rises and mark a bright star to the left of it. Ask any doper anywhere else on Earth to go out and have a look when Venus rises. They will also say the star is to the left. Now swap the rotation of the Earth and try that again. ---
**Author:** ![Nava](https://avatars.discourse-cdn.com/v4/letter/n/da6949/32.png) [@Nava](https://boards.straightdope.com/u/Nava)\ **Post date:** [February 16, 2016, 1:14pm UTC](https://boards.straightdope.com/t/conveying-left-right-to-alien-by-description/746120/92 "2016-02-16T13:14:27Z")
> [@scr4](#): > > No, I meant historically, we arbitrarily picked which direction we define as the direction of the magnetic field. It’s defined as the direction of field lines from the N pole to the S pole of a magnet, but that’s defined by the direction of earth’s magnetic field; it could just as easily have been the other way. But that’s exactly as arbitrary as the + and - of an electrical potential (which we got wrong). Will we get a different field if we create an electromagnet turning the coils clockwise or anticlockwise? Because if we get the same field, then we can use that to define N and S and that in turn to define left and right. ---
**Author:** ![scr4](https://avatars.discourse-cdn.com/v4/letter/s/59ef9b/32.png) [@scr4](https://boards.straightdope.com/u/scr4)\ **Post date:** [February 16, 2016, 1:18pm UTC](https://boards.straightdope.com/t/conveying-left-right-to-alien-by-description/746120/93 "2016-02-16T13:18:19Z")
Blake: “…left hand side would point towards what we humans call the south magnetic pole.” Alien: “Er, we call the 2 poles of a magnet A and B. Which one is the one that you call the ‘south’ pole?” ---
**Author:** ![scr4](https://avatars.discourse-cdn.com/v4/letter/s/59ef9b/32.png) [@scr4](https://boards.straightdope.com/u/scr4)\ **Post date:** [February 16, 2016, 1:23pm UTC](https://boards.straightdope.com/t/conveying-left-right-to-alien-by-description/746120/94 "2016-02-16T13:23:54Z")
> [@Nava](#): > > But that’s exactly as arbitrary as the + and - of an electrical potential (which we got wrong). The sign convention is arbitrary, but the quantity is not. You can send messages to the alien describing what electrons and protons are, and unambiguously communicate what we mean by a negative electrical charge. You can’t do the same for magnetic fields. > [@](#): > > Will we get a different field if we create an electromagnet turning the coils clockwise or anticlockwise? Yes, we get fields in opposite directions. ---
**Author:** ![scr4](https://avatars.discourse-cdn.com/v4/letter/s/59ef9b/32.png) [@scr4](https://boards.straightdope.com/u/scr4)\ **Post date:** [February 16, 2016, 1:33pm UTC](https://boards.straightdope.com/t/conveying-left-right-to-alien-by-description/746120/95 "2016-02-16T13:33:03Z")
> [@Blake](#): > > Go out at night when Venus rises and mark a bright star to the left of it. Ask any doper anywhere else on Earth to go out and have a look when Venus rises. They will also say the star is to the left. This isn’t even true on the same planet. An observer in London may see a star directly to the left of Venus; someone in Canberra will see that star below and slightly to the right of Venus. ---
**Author:** ![naita](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/naita/32/5862_2.png) [@naita](https://boards.straightdope.com/u/naita)\ **Post date:** [February 16, 2016, 1:49pm UTC](https://boards.straightdope.com/t/conveying-left-right-to-alien-by-description/746120/96 "2016-02-16T13:49:18Z")
> [@Blake](#): > > Go out at night when Venus rises and mark a bright star to the left of it. Ask any doper anywhere else on Earth to go out and have a look when Venus rises. They will also say the star is to the left. > [@scr4](#): > > This isn’t even true on the same planet. An observer in London may see a star directly to the left of Venus; someone in Canberra will see that star below and slightly to the right of Venus. Practical example. > **[Stellarium Web Online Star Map](https://stellarium-web.org/)** > > Stellarium Web is a planetarium running in your web browser. It shows a realistic star map, just like what you see with the naked eye, binoculars or a telescope. Venus setting in the southwest just after two UTC in Oslo, Mercury trailing it, i.e. to the left. Venus setting in the southwest just after seven UTC in Sydney, Mercury trailing it, i.e. to the right. I picked the setting Venus since that’s happening just about now here. ---
**Author:** ![gnoitall](https://avatars.discourse-cdn.com/v4/letter/g/bb73d2/32.png) [@gnoitall](https://boards.straightdope.com/u/gnoitall)\ **Post date:** [February 16, 2016, 3:13pm UTC](https://boards.straightdope.com/t/conveying-left-right-to-alien-by-description/746120/97 "2016-02-16T15:13:17Z")
> [@Blake](#): > > Interesting. This seems achievable. > > We can define an anode and a cathode easily enough. That means we can construct a circuit wire with a known anode and cathode. We can also therefore build a magnet with a known north and south pole, and from that define a north and south pole of the planet. We can then align a compass along a circuit wire with a known orientation. > > Then we just repeat the Orsted experiment. [If the north pole of your compass is facing the cathode, then it will deflect to the right. If it’s facing the anode, it will deflect to the left.](http://www.ekshiksha.org.in/image_magnetic_effect_of_electric_10/Figure_5.JPG) > > Thus left is the direction that the north pole of a north-facing a compass needle will deflect when current is run under it from a cathode in the south. > > Can anyone see why this wouldn’t work? Now, reverse the labels “north” and “south”, because they’re both as arbitrary as “left” and “right”. Does your Gedankenexperiment still work? ---
**Author:** ![ftg](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/ftg/32/2801_2.png) [@ftg](https://boards.straightdope.com/u/ftg)\ **Post date:** [February 16, 2016, 5:51pm UTC](https://boards.straightdope.com/t/conveying-left-right-to-alien-by-description/746120/98 "2016-02-16T17:51:05Z")
Another (quite minor) hitch in the “magnetic field induced by a current argument” is ensuring that the alien is not in an anti-matter chunk of the Universe.😉 [They aren’t if you’re communicating with them in a reasonable way.] ---
**Author:** ![newme](https://avatars.discourse-cdn.com/v4/letter/n/e0b2c6/32.png) [@newme](https://boards.straightdope.com/u/newme)\ **Post date:** [February 16, 2016, 7:11pm UTC](https://boards.straightdope.com/t/conveying-left-right-to-alien-by-description/746120/99 "2016-02-16T19:11:48Z")
> [@Blake](#): > > ```auto > > 5) Close the circuit and let it run while the iron cools. > > As a result of this, we will have created a magnet, possibly a weak one, but with no external fields we will have a magnet. > > And because of the left hand rule, the right hand side of this magnet will be the **south pole**. > > ``` The right hand side of the magnet will be a south **magnetic** pole; on a compass this would be a north **seeking** pole. For my own piece of mind, I just ran the experiment with a 9v battery, some wire, and a compass. With the anode at the top and the compass on top of the wire, the north seeking end of the compass deflected to face right. > [@](#): > > We don’t need to actually use the word right hand at this stage. We just need to agree that if we allowed this iron bar to pivot on its long axis inside a magnetic field, the left hand side would point towards what we humans call the south magnetic pole. Agreed. > [@](#): > > Or to say the same thing without using left or right, if we painted the anode side of the magnet blue, the blue side would face east. No, the anode side would face west. Agreed? [Previous page](https://boards.straightdope.com/t/conveying-left-right-to-alien-by-description/746120.md?page=4)