The phrase "a long expanse" is correct and usable in written English.
It can be used to describe a vast area or stretch of something, often in a physical or metaphorical sense.
Example: "As we stood on the cliff, we gazed out at the long expanse of the ocean, stretching endlessly to the horizon."
Alternatives: "a vast stretch" or "a wide area".
Measuring the history of expansion ultimately depends on comparing distance and redshift for enough Type Ia's over a long expanse of time; this is how accelerating expansion, propelled by dark energy, was independently found by two competing teams and announced in 1998.
To the left was a long expanse of black marble floor and six white marble basins on nickel pedestals.
The Jobsite Supply wall was a long expanse of gray concrete blocks covered with graffiti tags, and rust stains the metal roof.
A short walk away we found a solitary windbreak on a long expanse of warm fine sand that whistled gently when walked upon.
Between her short cutoff top and the absurdly low waistband of her trousers was a long expanse of flawless goosefleshed golden skin, curving into a sweet round rump.
There's a kids' playground, bathrooms and showers, and a long expanse of beach with low surf, access for watersports and a grassy area if you want to barbecue or set up a tent away from the sand.
Scientists count just five mass extinctions in an unimaginably long expanse of 450 million years, but they warn we may well be entering a sixth.
Down the center of its long expanse lies a fork lift highway.
They were at the edge of a long, rolling expanse of grass.
out of the marina, it was with a huge sigh of relief that I saw before us a long, glassy expanse of calm water.
This section of the journey was ridiculously scenic, first offering nonstop views of Lake Zurich, and then the even more breathtaking Walensee, a long, shimmering expanse of clear, blue water backed by silvery limestone mountains.
