I came across this piece:

The old saying “step on a crack, break your mother’s back” may not apply to sidewalks for much longer now that MIT researchers have figured out why concrete breaks down. As a result of the discovery, structures like buildings, bridges, and yes, sidewalks, could last for hundreds of years longer than they currently do. A nuclear waste container built to last 100 years could, for example, last 16,000 years.

According to MIT professor Franz-Josef Ulm, creep (the process that create cracks) is created when calcium-silicate-hydrates (CSH) rearrange at the nano scale. When mixed with water, CSH particles change in density from 64% to 74%. By adding silica fumes–a waste product from aluminum production–to concrete, overall density can increase to 87%. That’s a change that could eventually lead to longer-lasting, lighter structures.

If Ulm’s theories are put it into practice, the concrete industry and the planet could benefit immensely. 5 to 8% of all manmade CO2 comes from manmade concrete construction, so any reduction in the need to produce more of the stuff would slow global warming. And with twenty billion tons of concrete churned out annually, there’s plenty of room to cut down on production.

Anybody know what does “step on a crack, break your mother’s back” mean in the context above? If it is an idiom, as I think, what are the origin and contexts wherein we could use it?

  • en.wikipedia.org/wiki/Old_wives'_tale
    – MetaEd
    Jun 22, 2012 at 13:49
  • 2
    It's not an idiom, it's a cultural thing, it is simply from a children's rhyme. It means what it says. The article is just saying there won't be as many cracks anymore.
    – Mitch
    Jun 22, 2012 at 13:52
  • 2
    When a problem comes along, you must whip it... Jun 22, 2012 at 14:24
  • When I was a schoolgirl I used to read a magazine called "Mad". I remember (and perhaps still have) an issue in which the main character, being particularly angry with his mother, stepped purposefully on the cracks between the stones which made up the pavement (or sidewalk, if you prefer), hoping to obtain exactly that result.
    – Paola
    Jun 27, 2012 at 0:14

2 Answers 2


It is from an old children's game: if you trod on the cracks between paving stones you were out.

I seem to recall we used to also have the line "step on a line, break your father's spine" in there.

  • 4
    ... when I was particularly mad at my mother, I'd sometimes intentionally step on cracks... Not thinking anything would happen of course, but just to amuse myself.
    – Charles
    Jun 22, 2012 at 14:37
  • The version I remember is “step on a nick, you’ll marry a brick – and a beetle will come to your wedding.” (Or was it a spider?) Jun 22, 2012 at 16:07
  • 4
    Of course, any sensible child knows that if you step on cracks your mother's back won't break. Bears will come and eat you.
    – Jon Hanna
    Jan 28, 2013 at 2:41
  • Unless you step on a plumber's crack, but then we don't want to go there! Mar 9, 2013 at 16:54

The meaning is clear in the very first sentence of the article. MIT researchers have found out why concrete breaks down. So, now, cracks in concrete can be avoided. As a result, the sidewalks - made of concrete - would no longer have cracks. And, thus, this saying would no longer be valid for sidewalks.

  • 2
    We included the sidewalk joints (intentionally made when a sidewalk is poured) when we jumped over cracks playing this game. I would think concrete workers would continue to use sidewalk joints, even with the improved concrete.
    – JLG
    Jun 22, 2012 at 20:51
  • 1
    @JLG, some concrete composites eliminate numerous joints. For example: "The Michigan Department of Transportation will use the ECC to replace part of a bridge that crosses Interstate 94. The slab will eliminate the need for expansion joints, which are moveable steel teeth that separate sections of regular concrete. With the ECC, a longer continuous slab will be possible." Jun 22, 2012 at 23:38

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