It was the Easter holidays when I was eight, and Mum and Dad and I were in a tiny rented cottage just outside of Seahouses, which is on the Northumberland coast near Scotland.

Dad was a brilliant engineer, but I don’t think he earned all that much money because we never went abroad for holidays and we had an ancient old car.

So the three of us were walking back along the road that leads out of Seahouses to where our cottage was, and it was late, like ten o’clock, and really, really dark. We’d had dinner in the Seahouses Magna Tandoori, and Dad had spoken some Bengali to the waiter who hadn’t understood him, because Dad’s Bengali is pretty rubbish actually. Anyway, we were all chattering away, me and Mum and Dad, and then Dad stopped and gasped and said, “Look, guys!”

He was staring up at what must have been the starriest sky I had ever seen. There were no streetlights, and Seahouses was a mile behind us and round a curve in the road. The sky wasn’t even black, it was a sort of dark navy, and there were so many stars that some of them merged into one another and formed smudges across the sky.

It was a chilly night and Mum said that she wanted to hurry back to the cottage, so it was just me and Dad. “Come on,” he said, “I’ll show you something.” He hopped over a gate into a field and turned back to help me follow him over. We walked together over the black-green grass, the only light coming from the stars, and then we laid down on our backs, gazing upwards. I felt Dad’s hand reach over and grip mine.

“Do you want to see something that happened nine years ago?” he asked.

“Um … yeah?”

“It’s not a YouTube clip or anything, it’s real life.”

“OK.”

“Can you see that star there, the brightest one?” He was pointing not straight up, but more towards the horizon where a bright, bluish star was flickering. “That’s Sirius,” he said, “nicknamed the Dog Star. It’s a huge sun, bigger than our sun, and it’s 81 trillion kilometres away.”

Now, I don’t know about you but when someone starts talking about numbers like trillions, I kind of glaze over. I can’t even imagine what 81 trillion kilometres is like. As if reading my mind, Dad went on: “That’s eighty-one thousand billion.”

I wasn’t any wiser.

“Or in other words – nearly a million times greater than the distance between our earth and our sun.”

OK – that’s a little bit easier to imagine. Just a bit. I gave Dad’s hand a squeeze to let him know I was sort of following him.

“So, Al: the light from Sirius has taken nearly nine years to travel to earth. Nine years from leaving Sirius to hitting your eyeballs. In other words, you are looking at something that happened nine years ago.”

I gave this time to sink in. I think I understood, but I was only eight. I understand it better now.

Dad leapt to his feet and stood, hands on hips, head thrown back.

“So how many are there?” I asked. “Stars, I mean.”

There was a long pause, and I wasn’t sure Dad had heard me.

“Dad?”

“Yeah, yeah … I’m just thinking how to answer, because no one really knows for certain. You see up here, the ones we can see without a telescope? That’s probably only a few thousand. But you see that whiteish blur there?” He pointed to one of the smudges. “That’s the Milky Way …”

“Named after the chocolate bar?”

“Well, the other way round, but yeah. Our star, our sun, is part of the Milky Way. We sort of live on the outskirts of it, that’s why we can see the centre. And the whole Milky Way has about one hundred billion stars in it. Probably.

“They’re nearly all further away than Sirius – and some of them have already exploded –” he turned to me, his dark eyes shining in the starlight – “but the light from the explosion hasn’t even reached us yet! We’re still seeing what happened hundreds of years ago!”

He helped me up. By now we were both shivering.

“To look at the night sky, Al – that’s travelling in time!”

We walked back to the gate, and Dad was still talking about the stars and the galaxies, and how there’s billions more galaxies like the Milky Way, but I wasn’t listening any more. Not because I was bored, but because I was remembering what he said: that looking up at a night sky is travelling in time. I gazed upwards all the way back to our cottage, looking into the past.