We are running out of stars.

As you look deeper into space, you see the universe as it was when it was much younger than it is now. Light from distant galaxies takes time to reach the Earth, so as you look further into the sky, you’re looking at light that has taken longer to reach us and hence started its journey much earlier. Using this fact, it’s possible to probe how the universe used to be billions of years ago, long before humans even existed.

It’s because of this fact that we know the universe used to be very different. Over the past 11 billion years, the rate of formation of stars in the galaxies that surround us has been declining. At best, the universe might produce 5% more stars than we currently see, but star formation is only a tiny fraction of its peak 11 billion years ago.

The amazing, and perhaps sad truth is that we’re living in a universe full of old stars. The prime stellar period of the universe occurred billions of years ago before any trace of human life existed. We’re now in the final days of the universe’s Stelliferous Era. Though, admittedly, those ‘days’ might outnumber those for which our species will continue to exist on Earth. One day the final star will form in the sky, after that the universe will slowly, but surely, succumb to darkness.

It’s easy to forget that everything we see is temporary. We like to think of the universe as fixed and…