I’m no scientist but I thought this would be a good topic.

The only immeasurable thing I can think of would be “now.” Is it an instant? How long is that?

Please, try to keep this within the realm of science, faith is off topic.

I think it's important to point out that your premise contains a rather large assumption. Some could equally argue that the present moment, the "now" is the only thing being measured. Unfortunately, these discussions are almost entirely metaphysical, and often have little (if any) bearing on or input from science.

"Our clocks do not measure time. No, time is defined to be what our clocks measure."

 

-- Seth Lloyd

For Chris Johnson, "now" is about two minutes long.

 

And since we have the ability to predict the future by envisioning desired outcomes, and the ability to affect the future by working hard to increase the probable occurrence of those outcomes, our own "now" doesn't seem as instantaneous anymore.