Is there any difference between "be able to" and "can"?

[miniwave]

Hi everyone!
Can anyone tell me if there is any difference in meaning between the use of "be able to" and the use of "can" ?
For example:
In the following pair of sentences it seems that they are similar in meaning:
Scientists are able to explore new planets.
Scientists can explore new planets.
But what about the following pair:
Are you able to help me with my homework? (seems to me that this sentence should be used in a situation in which I am not sure that the person I'm addressing has the knowledge to help me )
Can you help me with my homework? (and this one is more likely to be used in a situation in which I know that the person I'm addressing has the knowledge to help me but I'm not sure he is free right now to do so.)

Waiting for your enlightening answers

[djoulai04]

if i can help you, as far as i'm concerned i know that to be able to is a capacity (etre de capable de faire quelque chose)
and CAN (pouvoir).

[Coffa]

Originally Posted by miniwave

Hi everyone!
Can anyone tell me if there is any difference in meaning between the use of "be able to" and the use of "can" ?
For example:
In the following pair of sentences it seems that they are similar in meaning:
Scientists are able to explore new planets.
Scientists can explore new planets.
But what about the following pair:
Are you able to help me with my homework? (seems to me that this sentence should be used in a situation in which I am not sure that the person I'm addressing has the knowledge to help me )
Can you help me with my homework? (and this one is more likely to be used in a situation in which I know that the person I'm addressing has the knowledge to help me but I'm not sure he is free right now to do so.)
Waiting for your enlightening answers

My opinion is that there is no difference in Modern English between 'I can' and 'I am able to', but I am willing to be convinced...

I think the confusion in the questioner's mind is between 'are you able to ...' and 'do you have the ability to ...'.

[miniwave]

djoulai04 and coffa thank you for your answers and here's another one for everybody
Is there any difference in meaning between "ought to" and "should"?
I've read somewhere that "ought to" is more common to be used when we talk about a moral obligation. For example: "Children ought to respect their parents" but "It's cold outside, you should take a sweater".
In all the other sources I've checked it isn’t mentioned and actually they say that "ought to" can be used instead of should (and add that it is less common than should and more likely to be used in British English)
What do you think?

[Tdol]

I don't see much if any difference- there may be a few sentences where one is more likely to be used, but most of the differences in BrE, to me, are the fact that the negative and interrogative of ought to are used less because they're harder to say.