Past continuous or simple?

A Introduction

A reporter is interviewing Mike and Harriet.

Reporter: Mike and Harriet, tell me what you saw.

Harriet: Well, when we were driving home last night, we saw a strange object in the sky.

Mike: As we were coming down the hill into town, it just suddenly appeared in front of us. We stopped the car and got out.

Harriet: It was a very clear night. The stars were twinkling.

Mike: It was a spaceship. It seemed quite big. It had some strange writing on the side. And a light was flashing on the top.

Harriet: As we were watching it, it suddenly flew away and disappeared.

PAST CONTINUOUS

We use the past continuous for an action that we were in the middle of.

We were driving home. (in the middle of a journey)

A light was flashing.

We do not normally use the past continuous for state verbs.

NOT The spaceship was seeming...

NOT It was having some...

NOT It wasn't knowing...

PAST SIMPLE

We use the past simple for a complete action in the past.

We drove home. (finished journey)

The spaceship flew away.

Instead of past continuous we normally use past simple for states.

The spaceship seemed quite big.

It had some strange writing

I didn't know what it was.

B It happened as I was driving

We often use the past continuous and simple together when one (shorter) action comes in the middle of another (longer) one.

As we were driving down the hill, a strange object appeared in the sky.

While Laura was sitting in the garden, it suddenly began to rain.

You drove right past me when I was waiting for the bus.

The appearance of the strange object comes in the middle of the longer action, the drive down the hill. Shorter action; an object appeared.

In the three sentences above, the past continuous comes after as, while or when (As we were driving ...). We can also use when before the past simple.

We were driving down the hill when a strange object appeared in the sky.

David was making lunch when the phone rang.

But we use two past simple verbs for one action after another.

When we saw the spaceship, we stopped the car. (We saw it and then we stopped.)

C The sun was shining

PAST CONTINUOUS

We often use the past continuous to describe the background.

The sun was shining.

The stars were twinkling.

PAST SIMPLE

We use the past simple for actions in a story.

We arrived at the beach.

The aliens landed quietly.

TOGETHER

The sun was shining when we arrived at the beach. So we rented a bed and ran to swim into the sea.