“Light years ahead”? Not so much

I heard it on NPR today. I saw it in an editorial yesterday. Heck, I probably said it myself two days ago. “Light years ahead …”

Now, in retrospect, I’m not sure that phrase makes any sense. Let’s think this one through.

Some context: The NPR report was about democracy in Tunisia, which the reporter said is (according to some analysts) “light years ahead of most of the Middle East.”

Leaving aside the political discussion (I know, it’s hard, but you can do it …): Light years? Really? How long, exactly, is a light year?

Well, if you’re a human being watching light travel, a light year is … well, a year. 365 days, give or take. If you happen to be going a little faster than your average duck, according to Einstein, that light will take — wait for it — a year. If I understand my General Relativity, you can be going 99.9% the speed of light (with an unthinkable mass, but ignore that), and the light you’re watching will still take a year to travel a light year.

Strike one. For any sub-luminal sentient creature, a light year is just a year.

Let’s imagine that you’re the beam of light. Things get pretty tricky here. Brian Greene, in The Fabric of the Cosmos, says we can’t even imagine what that’s like. But people of my sort like to try, so here goes. Presumably, a beam of light, from its own perspective, exists entirely in three-dimensional space but not at all in the time dimension. Since light speed is the benchmark beneath which “time” as we understand it occurs, light must somehow exist alongside of time, or beneath it, or without it.

Or, put another way, if you’re a photon (a particle of light) looking out at the world, you are always at the entire trajectory of your flight from the source to the point at which you were absorbed. You experience yourself (pretend with me here) as a line stretched out in three-dimensional space.

Strike two. For a photon, a light year is … basically a zero. It falls outside your existence, like the fifth dimension falls outside of ours. (Oh trust me, there is a fifth dimension. Has to be.)

All right, metaphor, you’re down two strikes in the count. Any life yet?

Sure. An idiom doesn’t have to make sense. Of course, this was supposed to be a metaphor, not an idiom, so I’ll call that ball one.

Try again. My Apple dictionary tells me that the term “light years ahead …” is an “informal” use of the term. Great. This is an admission of inaccuracy; I’ll call it ball two.

So the count is two and two. Here comes the pitch, and … metaphor connects. Here’s my Apple dictionary again: “INFORMAL a long distance or great amount : the new range puts them light years ahead of the competition.” See it there? “Light year” is a metaphor, not for a lot of time, but for a huge distance. And here it works, because we’re talking about almost 6 trillion miles for every year the light is going. A truly mind-boggling distance.

Is it a home run? Is my NPR commentator at least on the base path? Well, not quite. Compare these two statements:

“Tunisia is decades ahead of the rest of the Middle East in developing democracy.”

“Tunisia is 100 miles ahead of the rest of the Middle East in developing democracy.”

Looks to me like she meant time, not distance. Pop fly. You’re out.

But hey, at least the metaphor survived to go to bat another day.


3 thoughts on ““Light years ahead”? Not so much

  1. Amusing, thanks for the post 🙂

    The thing that sticks out for me with that expression is the sheer distance involved. People do use the phrase “miles ahead” which implies minutes or hours ahead in time depending on the accepted mode of travel. Similarly, light years ahead implies vast distances but in this case, really more like unimaginable distances, which is almost always a gross exaggeration, akin with “a distance so great it can never be closed”, which is clearly not the case in the story you cite. Still, in the end, it’s just an expression.

    Regarding your astronauts at 99.9% the speed of light, in any frame of reference, the speed of light appears to be the same. What this means as a practical matter is that compared to an observer on earth, time on the spaceship is running 22.4 times slower but to the astronauts would be running at ‘normal’ speed. Even at 0.5c, time would be running 15% slower. This dilation also affects the energy required to achieve these speeds since the mass also is greater.

    • Thanks! Yes, I admit to a little tongue-in-cheek on this one.

      You’re right, time dilation is an important part of this. Makes for some interesting (and strange) possibilities.

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