# Can you do science? Maybe you could help me out

Perhaps you’re familiar with lenticular images - you know, those pictures that animate when you tilt them from side to side. They show up on little cards you get in cereal boxes and Hello Kitty rulers and stuff. I saw one recently on a Spiderman drinking cup.

Anyway, what I would like to know is - would it be possible to create a lenticular image that would animate if you tilt it both horizontally and vertically? Like, if you had a grid of little prism ‘pixels’, would it work on the same principle?

Also, could I build an electromagnet powerful enough to open a fridge door ten kilometers away?

You probably could, but it’d look all shitty if you didn’t tilt it at exactly horizontal or vertical axis.

Also, second question - Yes.

I just recently saw a baseball card that was one of those, but it had like 8 different frames of animation. I was kinda amazed, as I was used to the standard 2 frames. One picture, tilt, another picture. This card basically animated a guy hitting a pitch in fairly fluid motion when you tilted it.

It’s not that hard to do them when they’re all leaning in the same direction. As nutsak pointed out however, if you add a second axis you pretty much screw it up. It’d be difficult to control which of the two horizontal images appeared when you tilted the vertical.

I Am Not A Physicist, so this post will earn me a kick in the head from those who know better.

The strength of a dipole magnet is inversely proportional to the cube of the distance. That’s why when you pull two strong magnets apart, it’s difficult at first. But once the magnets are separated you can feel that the attraction between them drops off quickly as you move them apart.

So, that fridge door. Let’s say when you pull the door by hand you exert as much effort as you would if you lifted a 1kg weight. We can use that as the basis for some shoddy napkin math.

At 10km, your magnet will pull 1kg. At 5km it is 8kg. At 2.5km, 64kg. Each time we halve the distance, we multiply the strength by 8.

100m from the magnet, you’re pulling over 250000kg. Don’t park your car near this thing.

So yes, I suppose if you conquered the engineering challenges of making your Doomsday Fridge Opener, you could build such a magnet. But you probably shouldn’t.

That’s had me laughing all morning. :lol:

Stupid question: Is there any sort of way to shield a magnet? Like something to put between two magnets and have them not effect each other?

Sure. Magnets work through magnetic fields, which are just a form of electro-magnetic energy. Therefore, you can put things that interfere with electric/magnetic fields between two field sources to muck with the interactions. The degree to which they muck with such things is a property of the material.

The difficulty is that air is one of the better dielectrics out there, because most air is made up of regularly unpolarizable molecules. It’s hard to find a whole lot that’s as inert as air. So if your magnets are already too strong in air, there’s not a ton else you can do (aside from perhaps very, very expensive high performance inert materials; this isn’t particularly my field).

There’s also something dealing with the strength of EM field necessary to break down the intervening material. Basically, if a field gets strong enough the pull is such that you begin stripping electrons off the atoms, allowing for charge carrying. (This is how lightning works to a drastic simplification.) I think the magnet of doom could well have problems with such issues.

Some physicist who actually works in E&M can probably correct all the stupid oversimplifications and half-remembered information from intro college physics here, but I think the principles are more or less correct.

Most magnetic “shields” are simply metals which are extremely sensitive to magnetism. It doesn’t “block” the magnetic force lines like a linebacker, it “shunts” them into itself, so they don’t continue through to the shielded device.

This is how a lightning rod works with electricity (closely related to magnetism). A metallic rod which really really likes electricity is placed over the protected house. Whenever a charge builds up and zaps, it is drawn to the “easier” target which then grounds the charge directly, preventing it from hitting the target.

I just recently saw a baseball card that was one of those, but it had like 8 different frames of animation. I was kinda amazed, as I was used to the standard 2 frames. One picture, tilt, another picture. This card basically animated a guy hitting a pitch in fairly fluid motion when you tilted it.

Apparently you can get them with 30+ frames without any degradation. Pretty cool.

Anyway, thanks again for your help people. I tracked down the website of the company that made the Spiderman cup and I’m going to send an email asking about some specifics, but it looks like what I had in mind isn’t going to be feasible. Disappointing, but hopefully it won’t matter too much - it should be okay just on the one axis.

Regarding the doom magnet:

I don’t know if it’s the most powerful man-made magnet, but this is the most powerful one Google gave me:

60 Tesla pulse magnet. That’s pretty magnetic. I’d like to know the range of the magnetic field and how they prevent it from pulling planes out of the sky. I bet the engineers would have to park a long way from work.

Probably the fact that it only works for 1/10th of a second at a time makes it a bit safer.

Is that sufficient time to open a refrigerator door?

The Los Alamos magnet concentrates the magnetic field into its central core. The core is a relatively tiny space, only a few inches across. Maybe a very tiny fridge could fit in there.

The magnetic field probably extends outside of the magnet a bit. Probably not anywhere near the 60 Teslas at the core.

Thanks a lot. Now more questions!

• If I wanted to make an electromagnet capable of attracting a metal object the size and weight of, say, a baseball from twenty feet away - how big/heavy would my magnet have to be?

• Is it possible to make curved plasma or LCD screens? Really what I mean is - is it possible to make or get curved screens that are also flat? Google is no help.

Is it possible to make curved plasma or LCD screens? Really what I mean is - is it possible to make or get curved screens that are also flat?

Seeing that the industry is working on foldable screens (like here , here, here or here) it might be something you want to look into.

-Julian