# How can one be invisible?

1. Jan 1, 2006

### nomorevishnu

How can one be invisible??

I am working on a science fiction.I am sorry to open such a thread in the general physics section but i thought I could get the maximum possible logic from this section.Its about making someone invisible.What are the faintest possible ways to do that??Please give me some suggestions.
Thank you!!!!!

2. Jan 1, 2006

### arildno

By stealing Harry Potter's invisibility cloak.

3. Jan 1, 2006

4. Jan 1, 2006

### Vixus

A science fiction story? Go wild! We don't read SF novels to see how plausible something would be.

5. Jan 1, 2006

### Pengwuino

At least most of us....

6. Jan 1, 2006

### -Job-

You could use a special suit where, for each photon that hits it on one area it emits a similar photon in the opposite area according to the angle of incidence. So suppose that a photon hits your shoulder at a 45 degree angle, then it would calculate where that photon would come out if it continued in a straight path and generate a similar photon in that very area. This would give the impression that light was going through the person wearing the suit. If you work it well you can make it quite believable unlike the classic novel "The Invisible Man" where the main character becomes invisible by noting that most cells in the human body are invisible, or transparent and then "bleaching" the features of the body that are not, like the blood, the hair, the nails, etc. Not a very good argument , not a bad read though.

7. Jan 1, 2006

### arildno

I like fantasy better than sci-fi; I'll stick to magical solutions to this problem.

8. Jan 1, 2006

### -Job-

Even though i'm not a huge fan of sci-fi, it tends to be a little over the top, i'm not at all a fan of fantasy. My favorite genre is general fiction. If it's something that's too unbelievable then i can't enjoy it, i can't lie to myself.

9. Jan 1, 2006

### Renge Ishyo

To make something truly invisible you would need the light approaching the something from behind to exit the something in the front in exactly the same way (no obvious absorption, no deflection). At present there is no way to accomplish this, but for the hell of it imagine a full body suit with it's own oxygen supply that had a super computer, and its own power supply in it. The incident light at one angle is ideally fully absorbed in the suit and the suit takes ALL (360 degrees) of the incident light in, and without any delay, can translate the light signals and reemit light from the suit on the opposite side in real time in all possible directions.

The problem (among many, but I see this as the main road block) is that light travels at the fastest speed known. It might be possible, for example, to design such a suit that transmitted sound waves "through" the body without percievably deflecting them (because sound moves at 340 m/s at typical temperatures), but light moving at 3x10^8 m/s? No super computer in the world at present could process light signals and reemit them at a speed comparable to the speed of light with no significant delay (maybe you wouldn't need to go that fast in order to trick the human senses, but at the same time any flaw in the suit would reveal your presence and so you probably wouldn't appear completely invisible).

Last edited: Jan 1, 2006
10. Jan 1, 2006

### Danger

There's one thing about it that has always bothered me. I mentioned it several months ago in a similar thread, but there was no response. Some feedback would be appreciated. I seem to be the only person on the planet who thinks that an invisible person would be blind. If your retinae are invisible, light can't interact with them, and therefore there would be no visual stimuli.

11. Jan 1, 2006

### -Job-

A truly invisble person wouldn't be able to see. However a visible person wearing an invisibility device (sounds pretty outrageous) could be able to see. There's a number of ways i can think so that this would be "possible". Of all the challenges that's not the hardest one to overcome.

12. Jan 1, 2006

### Danger

Yeah, I agree that a device of some sort would allow vision. It's the mutated, or chemically altered, or whatever type of SF character that I'm referring to. eg: Sue Storm from Fantatstic 4, DC Comics' The Invisible Kid, etc..

13. Jan 2, 2006

### nomorevishnu

Well.Danger,I know that an invisible person cant see.Because his retina wouldnt be able to reflect the rays.But is it possible in a way that some sort of genitical implantation is done and in such a way that the person can actually see everything.I am not talking about any kinda wonder drug.But something that can be implanted inside the human body rather than outside(just like the invisibility cloaks u all have been talking about.I dont want those).
Any ideas on these lines??It would be really great if some of you could still contribute to this thread!!!!

14. Jan 2, 2006

### starfield

Switch Of The Light! Ha!ha!

15. Jan 2, 2006

### zoobyshoe

I think the best way to become invisible is to affect the mind of anyone in the vicinity such that they cannot focus their attention on you. In a sci-fi novel this could be accomplished by having the "invisible" person wearing some device that affects the "attention" circuits of the brains of anyone looking in his direction. You might propose that device to be ultrasonic or electromagnetic. It might be a kind of helmet with omnidirectional sensors that are specifically dedicated to recognise when two eyes are focused in it's direction, whereupon it sends the jamming signal back to this target.

I've often had the experience of not being able to see something that is pretty much in plain sight, and I think this is due to some temporary inability to process a "recognition" of it. It's occured to me once or twice that there might be a way to induce this in other people. I've read claims it can be done with hypnosis, but that wouldn't be practical for someone who wanted to walk around invisible to any and all he encountered. It probably can't be done with any device, either, but that's not a problem in science fiction.

16. Jan 2, 2006

### nazgjunk

Could it be that you have read "The Hitch Hiker's Guide To The Galaxy" a bit too often? This reminds me very strongly of a SEP, a "somebody else's problem". It sounds sort of impossible to me though, especially when hidng something as big as a human being. After all, humans are "large stupid folk like you and me [who] come blustering along, making a noise like elephants which [hobbits] can hear a mile off", as J.R.R. Tolkien put it so nicely. We affect everything near, such as sand an the table you just bumped into. It would be very hard to hide that too.

17. Jan 2, 2006

### zoobyshoe

If you're unable to focus your attention on something it's size is irrelevant. The basic notion is as firmly grounded in neurology as the other ideas are in physics. There are dedicated circuits in the brain for recognition and they do break down in specific kinds of brain damage such that people can no longer recognise faces or words or sounds. This is called agnosia. There is a very famous book called The Man Who Mistook His Wife For A Hat which is a collection of case studies of people with various neurological disorders. The title story is about a man who has become unable to recognise the physical appearance of anything despite the fact there is nothing the matter with the physical apparatus of his eyes. The problem is in his brain where the visual information is processed.
I'm not sure why you pick my suggestion out to mention this because all the suggestions have the very same limitation. An invisibility suit isn't going to cover the sounds you make.

18. Jan 2, 2006

### arildno

Great idea, zoobyshoe, however that's just what the spirit magic spell "Invisibility" (3p, active) does in RuneQuest, 3rd edition.

19. Jan 2, 2006

### Danger

Zoob's idea was the basis for 'The Shadow' back in the 30's (or thereabouts)... 'the ability to cloud men's minds'. Unfortunately, that was before the advent of security cameras.
Sound will always be a problem, as will infrared signatures. Since those are radiated phenomena rather than reflected, your 'suit' or whatever would have to retain heat. I have no idea how you can mask the sounds that you make, unless you just move very carefully.

20. Jan 2, 2006

### ukmicky

This may be a bit futuristic but is this feasible

How about if the skin/surface of the thing that you wish to cloak is made from millions of microscopic optical fibres that are feed the light/image of the opposite side.

In the end all they have to do is reproduce colour. so if there were two types of fibres all mixed together and half of the fibres were sending the surrounding image of their side to the opposite side, and the other half were receiving the surrounding image from the other side it would be like a chameleon

would it work

Last edited: Jan 2, 2006