*“I checked it very thoroughly,” said the computer, “and that quite definitely is the answer. I think the problem, to be quite honest with you, is that you’ve never actually known what the question is.”*

*“But it was the Great Question! The Ultimate Question of Life, the Universe and Everything,” howled Loonquawl.*

*“Yes,” said Deep Thought with the air of one who suffers fools gladly, “but what actually is it?”*

*really* need is an answer to the question of what the Question was to get that Answer.

Any questions?

**Life**

There are so many things that 42 could be the answer to. In math alone, it’s the number of partitions of 10 – that is, the number of ways you can write 10 as a sum of positive integers; it’s the first number equal to the sum of its own nonprime proper divisors; the number of triangulations of a heptagon; and it was the last natural number below 100 to reveal a representation as a sum of three cubes – that last one

It turns up in the FIFA World Cup: it’s the number of all possible outcomes of each group stage, counting up all wins, losses, and draws. It’s the

Unfortunately, when it comes to human lives, 42 has a much less fun claim to fame: it’s pretty much the worst age to be.

At least, that’s the result of a

“The change-in-life-satisfaction function crosses the zero x-axis at ages 42.3 in the [British Household Panel Survey], 40.1 in the [Household Income and Labour Dynamics in Australia study], 41.4 in the [German Socio-Economic Panel] and 46.9 in the [Medicine in Australia Balancing Employment and Life study],” noted the authors. “By implication, these are the ages at which well-being reaches a minimum.”

And yes, if you were wondering, the average of those figures… is 42.

It makes sense, actually, because 42 is also the average age of a midlife crisis. That’s

The change in music taste at that age can’t be attributed to parenthood, and it only lasts for a couple years or so – but it’s definitely there, and, perhaps unexpectedly, it’s more pronounced in women. Don’t worry, though: by about 45, you’ll be back listening to painfully outdated golden oldies once again.

After all, apparently once you hit 42 years old,

**The universe**

We live on a rotating rock named Earth, orbiting a sun named, um, The Sun, which, in turn, orbits the center of the Milky Way, which itself orbits a supermassive black hole named Sagittarius A*.

It won’t always be this way. One day (whatever that may mean in this situation), our Sun

That won’t be the end of the Sun: when the temperature in the core gets high enough, nuclear fusion will start again – but this time, it will be turning helium into carbon, and fast. Eventually, it will blast out a planetary nebula and collapse into a white dwarf roughly the size of the Earth, and from there, a black dwarf – a type of star so old that none are currently known. But for the Earth, there’s a

And the really sad part? Technically, we won’t even have reached middle age.

“Throughout all of these changes, the Sun and our Solar System will continue to orbit around the Milky Way’s center, completing a full orbit every ~250 million years or so,” wrote astrophysicist and author Ethan Siegel in

With this information, we can figure out – more or less – how many galactic years the Earth-Sun system gets to enjoy before one cosmic dance partner finally destroys the other. And the result? You guessed it.

“42 is an answer that’s extremely consistent with the best data we have,” Siegel wrote. “It may yet turn out to be the exact answer to this question, although superior data will be required to know for certain.”

**Everything**

When it comes to “ultimate questions”, you could do worse than one concerning the fundamental nature of existence itself. And while we’ll leave the

“It’s a measure of how fast the universe is expanding at the current time,” Wendy Freedman, an astrophysicist at the University of Chicago who has spent her career measuring the constant, told

And it really does fulfill the remit of “everything”, too: “The Hubble Constant sets the scale of the Universe, both its size and its age,” she explained.

How’s that, you ask? Well, let’s start by thinking about how *big* the universe is. We know the observable universe is about *un*observable universe?

“We can only make inferences based on the laws of physics as we know them, and the things we can measure within our observable Universe,” Siegel wrote *least* 250 times bigger than the observable part.

“This means the unobservable Universe, assuming there’s no topological weirdness, must be at least 23 trillion light-years in diameter, and contain a volume of space that’s over 15 million times as large as the volume we can observe,” Siegel explained. “If we’re willing to speculate, however, we can argue quite compellingly that the unobservable Universe should be significantly even bigger than that.”

And it’s for this nigh-impossible question that the

See, the universe may be unfathomably huge, but it’s still expanding – and if we want to know how big it is, we need to know precisely how fast that’s happening. There are two main ways to measure this speed: we can either look at the nearest galaxies to our own and figure out how quickly they’re moving away from us, which is known as “late universe” measurement; or, we can extrapolate it from lumps and bumps in the cosmic background radiation, or “early universe” measurement.

While estimates of the Hubble Constant go back all the way to

And according to the most current of those estimates, the Hubble Constant is… 42.

“We have taken two measurements for the constant,” Richard Saunders, a senior lecturer at Cambridge University’s Cavendish Astrophysics Laboratory, told

Saunders had just headed up

The most up-to-date estimates of the Hubble Constant these days, which use data from the Planck mission, put the value a little higher. “There are multiple possible cosmologies that can reproduce the patterns we see [in the cosmic background radiation],” explained Siegel in a

Let’s take the middle of that interval, then, for balance – call it 67.5 km/s/Mpc. Well, what is that in imperial? That is, in miles/s/Mpc?

Oh. It just so happens to be 42.