You can't do operations on infinity

[g.lemaitre]

I'm trying to get my words right. They say you can't do operations on infinity. Sorry I don't have an exact quote. But on the other hand you can do calculations involving infinite series. What is the proper way to describe what math can't do with infinity?

I want to say something along the lines of you can't use math to determine how the singularity (Big Bang) existed forever because the singularity was infinite and you cannot use math to understand infinity.

 

[micromass]

Of course you can do operations on infinity. This is done in math all the time. It's true that infinity won't be a real number though. And it's true that not all operations will be well defined. But we can perform some operations.

Furthermore, there are many different kind of infinities in mathematics, some notions are better suited in some situations than in others.

you cannot use math to understand infinity.

We most certainly can.

 

[phinds]

I want to say something along the lines of you can't use math to determine how the singularity (Big Bang) existed forever because the singularity was infinite and you cannot use math to understand infinity.

1) The big bang did NOT "exist forever" --- where did you get that notion?
2) The singularity is not known to have been infinite and you should not make that as a definite statement. It MAY have been infinite, but that is not known.

 

[1MileCrash]

We have operations on infinity that are defined and some that are undefined. Some of the ones that are deflined don't adhere to normal algebra, which is why you sometimes can get a contradiction when using standard algebra when infinity is involved.

So I think it is better to say that "we can't apply operations in the usual way" to infinity.

 

[g.lemaitre]

ok, looks like I didn't know what I was talking about. Thanks for clearing things up.