Something to think about...

[alkatran]

Well, I was in physics yesterday when I thought "You know... technicly almost every answer I've given this year is wrong because it's in 2d."

A good example is gravity, you divide by r^2 (which has to do with the surface area of a sphere). If we're in 2d, we should only divide by r (perimeter of circle) and not divide at all in 1d...

Just struck me as kind of odd. Also means if we were in 4d gravity would be weaker. (divide by r^3)

[wossname]

That would suck.

What about time, isn't that the 4th dimension? So we are in 4d really.

[alkatran]

Personally, I don't consider time to be a dimension in the same sense as position... Time could just be the illusion created by speed and acceleration...

[ZaidGS]

Originally posted by alkatran
Personally, I don't consider time to be a dimension in the same sense as position... Time could just be the illusion created by speed and acceleration...

i think is wrong to say that time is time is an illusion.
if you want to define your position, u'd say: at 10:30 AM i was
at point 3,10,20.
but at time 11:00 AM you were at point 4,10,20,
so actually your position is determined by not
only by x,y,z but also with time.

how could we calculate speed and acceleration
if time was just an illusion.
its true that speed and acceleration are relative,
but this doesnot mean that time is an illusion.

[alkatran]

Yes, I just finished reading Eintein's book.. deep stuff.

[mendhak]

Originally posted by wossname
That would suck.

What about time, isn't that the 4th dimension? So we are in 4d really.

Geometrically, it is not. Time is just a reference, and we can call it our fourth dimension.

As for time being an illusion, let's not get philosophical here. We have chit chat for that.

[wossname]

Originally posted by mendhak
As for time being an illusion, let's not get philosophical here. We have chit chat for that.

Dude, check my sig if DA says so then it must be true.

[mendhak]

Originally posted by wossname
Dude, check my sig if DA says so then it must be true.

Btw, have you read any of his books, other than HHGG? Reccommended?

[NoteMe]

Originally posted by alkatran
Personally, I don't consider time to be a dimension in the same sense as position... Time could just be the illusion created by speed and acceleration...

Wouldn't then position also be an illusion, since it is created by a illusional axis? At least it is relative.

[wossname]

Originally posted by mendhak


Btw, have you read any of his books, other than HHGG? Reccommended?

Oh yeah highly recommended, I'll list the books of his that I have...

The HHGG trilogy of 5...
- Hitchhikers guide to the galaxy
- Restaurant at the End of the Universe
- Life the Universe and Everything
- So Long and Thanks for All the Fish
- Mostly Harmless

Others...
- The Long, Dark Teatime of the Soul
- The Salmon of Doubt (a compendium of his previously unpublished works, laden with pathos, excellent read)

I would recommend getting a copy of the BBC HHGG radio series (available on tape from WHSmith) and getting used to that first, then read the 5 books in order.

Probably the best and most knowledgeable scifi author ever. Ineffably good.

And when the villagers cried: "What does ineffable mean?" Old Thrashbarg said "Look it up!". Which was a problem, because Old Thrashbarg had the only dictionary in the village and he wouldn't let them borrow it.

If I were you I'd get the unabridged tape version of all of his HHGG series (read by DA himself, no less!) I keep meaning to grab a copy. Now where did I put that £140? (the cassette version is only £70!)

[mendhak]

Aargh!

I was getting a good deal on the set of 5 the other day, real cheap too. I have no idea why I didn't buy it.

I'm feeling like a duffer now.

[wossname]

Nah, its still worth paying proper money for.

Mostly Harmless is a most fitting conclusion to the series, but it only makes sense if you read it after the others. Its hard enough to get my head around it even then!

[RAEsquivelC]

Alkatran, you posted, in part:

A good example is gravity, you divide by r^2 (which has to do with the surface area of a sphere). If we're in 2d, we should only divide by r (perimeter of circle) and not divide at all in 1d...

Very good! Notice that, for the intensity of light that falls on an area perpendicular to the source, it diminishes, in terms of the distance to the source, in this manner:

For a point source, by 1/d^2

For an infinite line source (as in an infinitely long line of fluorescent tubes), by 1/d

And, for an infinite surface source (as in an infinitely extending ceiling covered all over with fluorescent tubes), by 1/(d^0), or 1/1, which is to say, the light intensity doesn't diminish at all, no matter how far away we go!!!

[da_silvy]

1) isn't r the radius of the circle, not the perimeter


2) and as squivel said, it's proportional to 1 / r^2.

that is it drops away more etc, according to distance from the center of the object, not the surface area

how is gravity a good example

the potential energy of an object is the one divided by r

U = GMm / r

[sql_lall]

I had always thought the r^2 was because there were two objects, so the distance was used twice (once from A to B, once from B to A)

same with magnetism

[alkatran]

the potential energy of an object is the one divided by r

Almost right! Potential gravity is actually like so:
U = GMm/r^2*d

d just happens to be the same as r. In 2 dimensions the formula wouldn't even have a division after it was simplified. Which is really blowing my mind right now because it means in 2d it doesn't matter how far from an object you are you will have same change in kinetic energy once you reach it... and it would take 0 work to lift things...
-Just remembered that it's average force over distance, not force at current location, which explains that...

I had always thought the r^2 was because there were two objects, so the distance was used twice (once from A to B, once from B to A)

same with magnetism

No it's because the force has to 'spread out' as it goes further away from the centerpoint.

1) isn't r the radius of the circle, not the perimeter

My fault, I meant "propotional to"