The Question

It’s Saturday afternoon and it is raining.  I wanted to go rollerblading earlier today, but I looked outside, saw some dark clouds forming in the sky and said to myself, It’s going to rain.  So now I am writing instead.  But why didn’t I say It’ll rain?  Don’t we use will or be going to interchangeably to make predictions?  Well, not always.  Let’s look at it:

These pairs of predictions are fine:

Friday is Johnny’s birthday!  The whole family will be there!
Friday is Johnny’s birthday!  The whole family is going to be there!

She’s probably going to study tonight.
She’ll probably study tonight.

This is delicious!  They’re going to love it!
This is delicious!  They’ll love it!

These sentences express beliefs about the future.  And of course, you have reasons for your beliefs about the future.  But we know that our beliefs may turn out to be wrong.  In fact, knowing this, many people are able to express certainty or a lack of certainty in their predictions.
Consider:

Look at those dark clouds!  It’s going to rain!
Look at those dark clouds!  It’ll rain!

The sentence It’ll rain is unusual in this context.  When you have evidence now – when the present situation that you observe makes a future event seem certain, we use be going to.  The dark clouds in the sky tell you that it is going to rain soon.

Likewise,

That glass is going to fall! (The speaker sees the glass tipping on the edge of the table)
That tank is going to explode! (The speaker sees the fire immediately beside the tank)
She’s going to crash! (The speaker sees the car out of control on an icy street sliding toward a tree)
It’s going to overflow!  (The speaker sees the boiling soup rising to the top of the pot)
I’m going to slip! (The speaker is losing control on an icy sidewalk)
She’s going to make it! (The speaker sees the cyclist just before the top of the hill)

In each case, there is something you observe that compels you to make your prediction. 

Time for a Prediction

Maybe if the prediction were made earlier on, there would be less certainty:

She’ll make it. 

Here, she is at the bottom of the hill just starting to ride up, but I believe she will make it.  However, I won’t be in shock if she doesn’t make it.  I know I could be wrong. 

And, even if she is starting at the bottom of the hill I could say She’s going to make it, but then I am expressing certainty for reasons that might not be obvious.  In fact, the person standing next to me may wonder why I’m so certain.  A common response might be How do you know? or even Why are you so certain?  It could be that I know that this cyclist has made it up this hill several times in the past.  So I have good reason – I have evidence from past performance – to be certain she’ll make it up this time, and I would be surprised if she didn’t.

Let’s go back to our list above.  Would an earlier prediction be made with less certainty?

She’ll crash.  (She is a new driver.  The roads are icy.  I believe she’ll crash.  But I could be wrong)  
It’ll overflow.  (The person filling the pot often forgets to turn off the water.  Overflowing pots are common in this kitchen)

Here the speaker is making a prediction, but with less certainty.  Maybe she’ll drive 5km/hr and not crash. Maybe she has more driving skill than you would expect with her lack of experience.  Maybe the cook filling the pot has finally developed a better attention span.

Will and Certainty

I have tried to show that when you predict something for the future based on evidence, the more accurate phrase is be going to.  Evidence leads to certainty.  But I am not saying we don’t use will to express certainty.  Sometimes, will is the best word, actually.  In fact, expressing certainty is one of the main uses of will.  So, in a near future blog we will look at expressing certainty using will.  

(Featured image by MasterTux/ Pixabay)