Talking about true and false

[KerimF]

Hi All,

I don't think we will disagree on the right definition of parallelism (though it may differ a little bit when applied to different situations).

On the other hand, it seems since we are now mature persons, we like to forget that we were once upon the time... just little kids. So on purpose or not all here try to miss the main idea of the first question which reminds us that a baby is not a kid and a kid is not a teenager... etc.

I doubt someone here is/was able teaching his baby about when two lines become parallel, by presenting him any definition said so far on this thread.
Why it is impossible to do it?
Isn’t he a real human creature?!
The answer is that our brain needs time to perceive the details of reality as they are, and the process of learning should be made progressively.
Imagine we are talking to a 8-9 year kid about the notion of infinity. He may listen to us and even pretend to fully understand it, but surely it won’t be the way we (mature people) perceive it.

So while the definition on the post #1 is (should be) given deliberately as incomplete (hence wrong scientifically) to our little kids, it is a ‘great’ step for them toward the acquisition of the complete knowledge. Many here may not fully understand what I am referring to because it is very hard for a mature person to imagine how he/she really was when kid ;-)

When I was a teenager (perhaps a bit earlier), there was a need to go deeper in analysing our universe. The spatial geometry was introduced. So it was time to update the first incomplete definition:

Two straight lines are said parallel if they don’t intersect... and are on the same plane.

And it was the next great step toward perfection in knowledge

I thought it was the most complete definition about parallelism but its weakness didn’t show up till I grew up and needed to draw perspective pictures to present real views on a piece of paper (perspective geometry)..........

Kerim

 

[KerimF]

yes,it is true up from Logic

Which is true, from all what were already said? ;-)

Please don't tell you meant the false statement: :sad:

Two straight lines are said parallel if they don’t intersect.

Kerim

 

[thinkindia]

its true indeed!

it is true~

 

[KerimF]

Is the following definition true or false?
Two straight lines are said parallel if they don’t intersect.

its true indeed!

I am sure you are just joking
You already know that there are millions of straight lines that don't intersect in space and are not parallel ;-)

Kerim

 

[LvW]

I am sure you are just joking
You already know that there are millions of straight lines that don't intersect in space and are not parallel ;-)

Kerim

Up to now, I have never seen such lines. Beams (correct?) from the sun - after passing through a cloud - intersect always anywhere inside the cloud. Or not?

 

[KerimF]

Is the following definition true or false?
Two straight lines are said parallel if they don’t intersect.

I think all of us can imagine two parallel planes.
Let us draw one straight line on one of them.
I guess all straight lines on the second plane are supposed not to intersect with the straight line on the first parallel one.
But from the set formed by these zillion lines there is just a subset of them that can be said parallel to the first line.
So the above statement is false (as it is).

Kerim

 

[Mahammad]

The definition is incompletete it needed to be defined form -∞ to +∞

 

[KerimF]

The definition is incompletete it needed to be defined form -∞ to +∞

Thank you for your reply.
Although is is not the purpose of this thread, I am just curious now to hear your opinion about a complete good (true) definition of two straight lines said parallel. Could you please?

Kerim

 

[LvW]

You already know that there are millions of straight lines that don't intersect in space .................

Kerim, what do you think would be the answer from A. Einstein regarding a "straight line in space"?

 

[KerimF]

Kerim, what do you think would be the answer from A. Einstein regarding a "straight line in space"?

I got your point and you are kind to give a further proof to my end point here which is:

The humankind along history is like a growing person. It (human generations) has to learn the truth about anything in gradual steps. But during the early steps, the knowledge about any subject may likely be incomplete (hence wrong relative to the perfect science). This is exactly the way we (as persons) did follow while we were growing from the little kids we were up to what we are now.

Imagine you ask me this last question and I am 10 years old only :grin: Even if you try your best to let me perceive that straight lines in space had to be curved ones, it would be very hard for me to get the complete picture. But now, at my age, I may discover new theories based on it :twisted:

Conclusion:
The expression "They don't intersect and are on the same plane" became later "They DO intersect at infinity".
The next step:
The expression "The two straight lines..." has to be defined in a very limited space. Otherwise, "A straight line won't be the direction of the shortest line between two spatial points" ;-)

Kerim

 

[LvW]

Lovely meditation....thank you kerim.

 

[Mahammad]

To straight lines are said to be parallel if they do not intersect each other on extending both the ends of the two straight lines towards ∞ in space

 

[KerimF]

To straight lines are said to be parallel if they do not intersect each other on extending both the ends of the two straight lines towards ∞ in space

Thank you for your reply though I wished you had the time to read the previous posts. :smile:

The idea of this thread is to show that even a simple definition as of parallelism had to be taught gradually according to age.

I guess yours is much like the first one given at preliminary schools.
Later at high school, the expression “and are on the same plane” is added, because in space (I mean in the three dimensional space) we can always draw two straight lines which can never intersect but are not parallel (if they are not on the same plane).

Then at the university, in order to draw perspective images (representing three dimensional objects on a two dimensional surface) a more useful definition is given which says:

Two parallel straight lines DO intersect at infinity.

But this last definition cannot be given to a kid unless we like to confuse him by the “DO INTERSECT” and the notion of “infinity”.

The lesson of this thread is that while we are growing up (the same applies for the human generations along history), the learning process starts with incomplete forms of truth then goes on gradually toward its best form that a person (or a generation) can perceive.

Kerim

(So personally I don’t expect to find the best answers of my important questions about my existence from any ancient book or reference, because naturally our ancestors, the kids of the humanity, were not able to perceive what I do now :wink: ).

 

[xaccto]

....

(So personally I don’t expect to find the best answers of my important questions about my existence from any ancient book or reference, because naturally our ancestors, the kids of the humanity, were not able to perceive what I do now :wink: ).

Thanks Kerim,

a very good lesson.I'll try to commit this tactic to memory
But it doesn't help those who refuse to learn of new information and grow-up.

 

[KerimF]

Thanks Kerim,

a very good lesson.I'll try to commit this tactic to memory
But it doesn't help those who refuse to learn of new information and grow-up.

You are right because naturally I don't think there are many human beings on earth who have time to think... about their existence :grin:

 

[Mahammad]

Thans,
it was a good one .i liked your comment very much