# An invisible traveller

Maybe not a typical riddle, but here it is:

I can travel from there to here by disappearing, but I can also travel from here to there by appearing.

What am I?

The letter 't'

Because

The words here and there differ by the letter 't' which either appears or disappears depending on which direction you go.

• Because of the lateral-thinking tag, this seems off. If we ignore that tag, this might be the right answer, congrats. Jul 10 '18 at 16:31
• @Orphevs do you mean that it would be tagged wordplay, rather? Well, I think it almost fits: we expect disappearing and appearing at “here” and “there” to describe places, not something parallel — okay, so maybe parallel-thinking more than lateral-thinking Jul 11 '18 at 17:26
• @can-ned_food wordplay:"A form of wit in which the used words become the main subject of the work, primarily for the purpose of intended effect or amusement.". lateral-thinking:"A puzzle solved through an indirect and creative approach, using reasoning that is not immediately obvious and involving ideas that may not be obtainable only using logic.". Compare this question to the lateral-thinking Q with the most votes, and you will see what I mean. Jul 11 '18 at 20:34
• @Orphevs Yes, I know wordplay — that's what my (admittedly only) puzzle posted was. :-) Also, I read the tag summary of lateral-thinking prior to posting my comment, and I think I have a decent enough experience with it from Mindtrap and such, so I'm not sure what your point is; you need to explain it a bit more thoroughly, I'm afraid. Maybe in chat? Jul 12 '18 at 1:27

Maybe it's

the Sun?

What is that which can travel from there to here by disappearing

From our point of view, it goes from West to East by disappearing

but it has that special ability to travel from here to there appearing.

From our point of view, it goes from East to West in plain sight

• Can it also apply for zbba(rot13)?
– m4n0
Jul 9 '18 at 19:44
• Actually I started my answer with it. It probably applies to nal fngryyvgr, angheny be abg Jul 9 '18 at 19:49

Maybe it is

Because

It travels from there to here shortening its length and eventually disappearing.

And

It travels from here to there appearing and subsequently increasing its length.

My initial thought is

Time

Because

Time always seems to disappear when you need it

and

There often seems to be a extra Time appearing when you are waiting around for something

Overall this makes:

A Time traveler

• Welcome to Puzzling.SE! This is a decent answer, congrats on your first points. I see you have your 1st badge. you can get another by filling out your profile and taking the tour. Jul 9 '18 at 21:15

I guess it's

the Moon

because

At one time it appears in a place and then due to its rotation it disappears and re-appears the next night.

Maybe it is

Rain

Disappears

Evaporates

Appears

In the form of rain

It sounds like a

Photon

I can travel from there to here by disappearing, but I can also travel from there to here by appearing.

It sounds like this is describing quantum entanglement, where a particle will exist simultaneously in both locations until observed. When you observe one particle, the other paired particle's spin will be determined based on that observation. The reverse is also true.

This is my second approach. My previous answer pointed at something about we cannot say is invisible at all (as title suggests).

The better match is:

Lower air pressure or low tide.

It is invisible because:

Air is almost transparent. Although you can observe low tide living seaside but obviously you cannot see it, when you travel by ship.

It travels from there to here by disappearing:

When air/water flows towards us, the lower pressure/tide disappears.

It travels from here to there by appearing:

Opposite by analogy. :)

• Damn, my answer is perhaps a bit more general version of this and I was writing it while you posted this answer. Oh well :/. I'll leave it there anyway, but if one of us is correct, you were first :P. Jul 10 '18 at 11:53
• @Netzia Thanks, but I would perceive it as separate answer anyway, because stepping up into abstraction you might loose some properties. For instance: optical invisibility of the change or direction of flow of the medium :) Jul 10 '18 at 15:02

Is it

remoteness/distance itself?

I can travel from there to here by disappearing

what was "there" would be "here" if the distance separating them vanishes

I can also travel from here to there by appearing.

and vice versa

airplane, because it disappears form the source airport after it takes off and appears on the destination airport after landing.

• [ :-( ] I don't think so: per this answer, it first disappears then appears regardless of whether it goes from here–to–there or from there–to–here. Jul 11 '18 at 17:19

I highly doubt this is what you had in mind, but something that behaves like this is

A local change of a variable or a quantity in a system that tends to a global equilibrium.
In a physical system this could be e.g. pressure or temperature. If for some reason there appears a local change in, say, pressure (positive or negative), the change "travels" from here to there, i.e. the magnitude of the local difference in pressure decreases where it appeared and the magnitude of the pressure difference increases everywhere else, as the system tends to a new equilibrium.

Thinking about it the other way around,

if the "original" change suddenly disappeared (i.e. the reverse happens) the change would "travel" from there to here as the system again tends to the "original" equilibrium.

As an example:

For some reason a local pocket of overpressure appears: the system tends to a new equilibrium by distributing the pressure evenly, thus introducing overpressure (relative to the "original" state) everywhere else. Then at the same location a pocket of underpressure of equal magnitude to the earlier change is formed (meaning the overpressure "disappears" locally): the system tends to the original equilibrium by redistributing the pressure and thus the overpressure travels from everywhere else to "here".