# Two parallel lines meet?

1. Apr 27, 2005

### irony of truth

Hello.

I believe that there are proofs showing that two parallel lines meet at a certain point... but this cannot be proven through the concepts of a
simple geometry... some say that it can be proved by projective geometry.

Are there sites that show these proof?

2. Apr 27, 2005

### Data

Parallel lines never intersect... in a Euclidean geometry. This is actually one of Euclid's postulates. It is not a necessary postulate, though, and you can find other geometries where parallel lines do intersect.

Here's some information:

http://mathworld.wolfram.com/ParallelPostulate.html

3. Apr 27, 2005

### HallsofIvy

Staff Emeritus

I think that's misleading. It is not that there exist geometries in which "parallel lines do intersect". Parallel lines, by definition, do not intersect. What is true is that there exist geometries (elliptic geometry) in which there are no parallel lines.

4. Apr 27, 2005

### TD

When you work in projective geometry, isn't it so that 2 lines are said to intersect at a point at infinity?

5. Apr 27, 2005

### matt grime

Yes, but still there are no *parallel* lines in projective geometry since all lines interesect.

6. Apr 27, 2005

fair enough~