h2g2 The Hitchhiker's Guide to the Galaxy: Earth Edition

Who's to say we're *not* surrounded by people from out future?

One of my favourite explainations for UFOs which appear to be under intelligent control isn't small furry creatures from Alpha Centauri, but rather voyeurs ("researchers") from our own future! This fits in with the observed phenomena somewhat better - these "craft" are often seen over sites of "historic" significance, such as the first airbase to be issued with nuclear weaponry, or great religous moments. They generally go out of their way to avoid direct interaction with people, or if they do interact they try to erase all memory of the interactions. They appear to be able to hover stationary for prolonged periods, then suddenly accellerate to incredible speeds - it's assumed that this is against the laws of physics, but surely a craft able to manipulate the flow of time could make such manoeuvers seem like slow, smooth accelleration to its occupants...?

What if, for example, cattle mutliations involving the surgical removal of genitalia were simply an attempt by a future generation to restore a long-lost breeding line? Harvesting sperm and eggs would be an awful lot easier than fitting several cows and bulls into a small craft...

On a sci-fi line of thought, what about "abductions" where people claim to have had biological procedures performed upon them. Could a future version of ourselves have lost some genetic material which might prove invaluable in, say, a period of climatic change?

Abductees who have "close encounters" with such craft regularly report "missing time", where a 5 to 10 minute encounter leads to several hours missing from their day. Perhaps the devices' ability to distort time leads to this effect, and there really isn't any "missing time" to account for, but rather the victim was just passing through time at a different rate from everyone else for that ten minutes (or two hours, depending on your point of view... )

I saw a made-for-tv-movie like that on the Sci-Fi channel (U.S.)
The little gray men in the spaceship turned out to be a later stage in our evolution, from a bleak and desolate future. My memory of it isn't that good, but I believe that they (or rather, some representatives) had returned to the past in order to somehow find out or acquire a means to save their world (our world in the future). It was a good show.

What if they're from the future but going the opposite way in time? So they know our future, because it's their past but don't know their own future because it's our past. As if they're on a motorway going the wrong way. (Although it may be us going the wrong way...)

This sounds interesting. What was the name of the movie, if you recall?

I thought it was an original idea. Daft, granted, but original.

Maybe it is impossible to get massive particles to travel through time but light might be able to. Maybe future beings have a ....chronoscope? through which they can view past history and, I guess, their future. After all, somewhere out in space is the light reflected from Jesus Christ at the crucifixion, the pyramids under construction, murders as they are being committed..... Monica with her cigar!

"Flying saucers" might just be the image we receive from this end of the chronoscope and, like the beam from a laser that is a long way away, the image is capable of impossible speed and changes in direction with small changes in position at the source. In fact, taken as an object itself, I guess the end of the beam is capable of faster than light speed. For two targets that are two light years apart, the end of the beam that originates in the centre of the two could travel from one to the other in only one year - twice the speed of light!

Well, if you only want to *see* the past, then theoretically all you need to do is get a reeeeeeeeeely powerful telescope and look in the right direction. After all, the light which bounced off of various past events didn't disappear, it just went somewhere else. If you could collect a little bit of it, you could see the past.

Also, about the end of a laser beam moving faster than the speed of light... This would work if light traveled at an infinite speed, but because it doesn't, the point at the end of the beam doesn't move as fast as the end in your hand. The end will never move faster than the speed of light.

I thought about this a bit more after writing it. Of course in one sense our normal telescopes are seeing the past anyway but this wans't really the point. I was assuming that if all it takes to send a particle through time is energy and it takes too much energy to send massive particles through time, then perhaps it is possible to send massless particles. The trick with the "chronoscope" would be to send photons through time with a targeted focus. They could then be reflected from whatever you focussed on.

As for the end of the laser beam, it's a long time since I did any physics but I think it is the angular momentum that is constant. The end of the beam with a radius of a light year would travel through the same angle in the same time as the source but this would represent a much greater km per hour. Indeed, from the perspective of an external all seeing being, turning the beam around at the source would mean that the last of the beam would disappear from the first target after one year and reappear almost instantaneously at the new target - appearing to travel two light years in the time it takes to turn the source 180 degrees. But again, this wasn't the main point - I am not saying that a photon moves at more than the speed of light but that there is an effect that seems to travel at faster than light.

As for the laser beam thing, no laws are being violated as the "spots" on either planet are created by different photons, not the same photons travelling from one planet to the other.

Just a thought I had last week, but has anyone thought of starting up a virtual victim support group for laws of physics which have been violated?

OK, about the angular momentum thing: If I have a large stick, and I turn one end in my hand, the other end of the stick will move with the same angular momentum (rotations per minute) as the end in my hand. This is because the stick is a solid object. However, this is not true for beams, like laser beams. Imagine that you are holding a hose in your hand, and that the hose is forming a "water beam." Now, turn the end of the water beam which is in your hand. Does the other end of the water beam turn at the same rate? No. This is because once each water molecule has left the hose, its motion is no longer affected by the hose's motion. It will continue in a straight line in whatever direction the hose was facing *when the molecule left the hose* (discounting gravity, of course). A laser beam is like this. If you saw a side view of the laser beam which you just swung over your head, you would see a large arc, not a rapidly moving pole. No part of the beam, not even the end, would be moving faster than the speed of light.

Actually, the "spot" at the far end may appear to be travelling faster than the speed of light, but this isn't breaking any laws of physics... The "spot" is illusory, being composed of different reflected photons at any given instant. No single photon is travelling faster than light.

Precisely!

The suggestion that I was making is that those who claim to have seen flying saucers or things that appear to be breaking the laws of physics might just be seeing some sort of projected image. My further guess, on the theme of this thread, was that while one might not be able to make massive particles travel through time, it might be possible to make massless particles to do so. This then led to the idea of the chronoscope and the idea that our descendents might be spying on us through a machine that some might perceive, in our time, as a flying saucer. Of course, the spying might also be aliens searching the universe with a sophisticated searchlight

All this is, of course, pure speculation.

Massive particles are always travelling through time; the challenge is to make them travel at a detectably different rate from those around them...

The point I am trying to make is that the "spot" *would not appear to travel faster than the speed of light!* I don't care whether this would break relativity or not, I'm pretty sure it would not happen at all! Because of the water-hose effect (as I'm now calling it), the spot would never travel faster than the speed of light. Yes, it is made out of different photons, but it would still never travel faster than the speed of light.

Actually, there is one exception to this. It could be in one place, and then appear in another place without traveling the intervening distance (like this: I'm shining the laser at a really distant card. I then stick a card directly in front of the laser. Also, with this method, the spot would be in two places at once for a short time.) Nonetheless, the spot would never be seen traveling faster than the speed of light.

I'm sorry, but "the water hose effect" is specious and irrelevant to this argument. Imagine, if you will, two objects a light-year apart, both a long way from the source of the spot. You rotate the source to point from one to the other in less than a second. The light takes a long time to reach both objects, but, assuming they're the same distance from the source, once the spot has reached the first object it can appear to travel the light-year to the next in under a second!

Actually, that was the point I was making in my second paragraph. You see, the spot isn't, strictly speaking, traveling faster than the speed of light. It is just in on place at on instant, and another in the next instant. Though I don't know what level maths you have taken, this is easiest to think of in terms of calculas. Imagine we have a two-dimentional graph; the x axis is time and the y axis is position. At the point you're talking about, we have a jump discontinuity. If I tried to find the derivitive at that point, I would find that it doesn't exist. At that point, the spot has *no* speed. If the spot merely move from place to place faster than the speed of light, I could differentiate, and would find the speed to be greater than the speed of light. But because the spot is not traveling the distance between the points, it does not, strictly speaking, travel faster than the speed of light.

PhysycsMan

OK, then, instead imagine an object which is a light-year across in place of the two discrete objects. If you turned the light source from pointing at one end to pointing at the other end over the period of a second, the spot would *appear* to travel a distance of one light year in one second; moving at a defined speed greater than the speed of light, with no discontinuity - the spot would be visible on the surface continually through that second. The "hosepipe effect" isn't relevant, as once the movement has propogated along the beam to the object it still takes one second from beginning to end...

Thus, if you consider the spot as an entity in itself, it can alearly appear to travel faster than light in a measurable fashion. This still doesn't break any laws of physics, though, as we both clearly agree...

The thing is, I don't think that it would go from one end of this object to the other in the period of one second. *Just because your end of the beam moves that quickly doesn't mean that the other end will*; because of the hose-pipe effect, the spot would move slower (if you need, I'll explain the hose-pipe effect again). Though I have no particular reason to believe that this slowdown would reduce the speed to under c, I think it would.

PhysicsMan

I will have to get a hose and check it out. However, I suspect that I will get wet if I rotate the hose over my head in the vertical plane - although there may be some relationship to take into account regarding the nozzle velocity of the water relative to the angular momentum of the rotation, along with gravity, inertia and fluid dynamics.

Thinking about the beam of light from a torch/flashlight, this seems to provide a continous squiggle as I rotate it in my hand. If the stream of photons from the light source is truly continuous, then I suspect that the observer will see a stream of photons and the spot will appear to traverse from point A to point B in an impossibly short period of time. It will be as good an approximation to a continuous line as underlies the principles of calculus.

Hokay, think of it this way... Say the object is ten light years from the light source. At T=0 seconds, a photon leaves the source and hits one end of the object at T=ten years. At T=1 second a photon leaves the source and hits the other end of the object at T=ten years and one second. You're saying that your "hosepipe effect" will somehow cause this second photon to arrive late?