# Understanding the idea behind.

##### Junior Member
What you are confused about is the difference between a "specific time" and a "time interval". We can do something only during a time interval, no matter how short. A specific time can only be the start or end of a time interval. It makes sense to talk about doing something in the time interval from 2:00 to 2:30 or in the time interval from 2:30 to 3:00. It makes no sense to talk about doing something at the specific time, 2:30.
But why it's pointless to talk at specific time? That's what confusing me .. In real life analogy you can say at specific time I do something...
So what's pointless here?

#### mmm4444bot

##### Super Moderator
Staff member
… In real life analogy you can say at specific time I do something …
No, you can't. You can say at a specific time that you started doing something.

After you stop doing that thing, then you can talk about the interval which describes how long the thing took to do.

Points in time are like points on a number line. They don't have any dimension; any specific point in time is not an interval of time. An interval of time always has a beginning point and an ending point.

#### Dr.Peterson

##### Elite Member
Hi guys!
I've a serious problem with understanding the given information of a question.

I've a question which is given like this way : there's a machine which from 2:00-2:30 is reading, and from 2:30 - 3:00 is writing, in other words half time is reading and half time is writing .. what's confusing me what about 2:30? what the machine does? reading or writing? how we determine? once again it's not given what the machine is doing at 2:30 , just given that half hour machine is reading , and in the second half the machine is writing .. so how should I understand at time 2:30 what the machine doing? it's really complex for me! are we assuming at 2:30 the machine isn't doing anything?!!

thanks in advance.
I would just answer that it doesn't matter what it is doing at exactly 2:30. In real life, you can't be sure what time is exactly 2:30, and machines can't instantaneously change from doing one thing or another; in a math solution, we imagine an ideal model in which it can, but our answer to whatever question is asked will not be exactly correct in the real world.

Within this idealized model, what happens for one instant will probably not affect the result. We can just suppose that it is in transition at that moment, and ignore it. But please state the entire problem exactly as asked, so that we can demonstrate that to you. What is it that you are asked to do with these facts?

#### topsquark

##### Full Member
If you assume "time" to be discrete - then smallest unit of time is:

Now you can stop reading tP seconds before 2:30 (AM ? PM? EST? GMT? ... whatever) and start writing at 2:30 or allocate the tP to reading and do less writing.
Actually no one has proven that this is the smallest possible interval of time. It just looks good, is all. (None of the "Planck" measurements have any known applicability.)

-Dan

#### Subhotosh Khan

##### Super Moderator
Staff member
Actually no one has proven that this is the smallest possible interval of time. It just looks good, is all. (None of the "Planck" measurements have any known applicability.)

-Dan
I know - just couldn't resist kicking up dust....