From the TV series The Universe:

The speed of light is the ultimate velocity in the universe. lt's Einstein's cop on the block. The speed of light is so fast that you could go around the Earth seven times in just one second. For you to jump to the Moon, at the speed of light you could reach the Moon in about one second.

I'm guessing block means area and the speed of light is similar to a policeman in that both don't allow law to be broken: Light doesn't allow anything to travel faster, and a policeman doesn't allow anyone to break the law.

  • 1
    You're right. On the block doesn't really mean anything in this simile: the writer is just using the phrase cop on the block (i.e. neighbourhood police officer), probably because of the sound or the friendly connotation.
    – Colin Fine
    Commented Jan 28, 2018 at 1:00

2 Answers 2


Aerial view of a neighborhood with lines showing a block

In AmE, "on the block" refers to the row of dwellings between two cross-streets, and the pedestrian walkway in front of those dwellings, if there is one. There is no sense of an "enclosure". That's why we wouldn't say "policeman in the block". However, we could say "The house is located in the 500 ("five-hundred") block of Main Street." When speaking of the block as a bounded section like a container, or as a set of dwellings, then it becomes in the block.

Last week there were three muggings on the 3900 ("thirty-nine-hundred") block of Chestnut Street.

In the past, a cop (a policeman) would be assigned to patrol, on foot, certain blocks which were his "beat".

The "cop on the block" keeps order on the block, and acts as a kind of limit on behavior.

As others have remarked, the analogy with light is very strained.

  • I looked up cross-street but I still can't visualize where the dwellings would be relative to the streets. Are these dwellings on both sides of the street?
    – Sara
    Commented Jan 28, 2018 at 19:20
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    I have added a map-view of a block with annotations. The dotted-line (-------------) runs the length of the block. The lines with arrows indicate the "cross-streets".
    – TimR
    Commented Jan 28, 2018 at 21:17

Yes, your guess is correct. The "cop on the block" is the local policeman who makes sure everyone is law-abiding. In a similar but tenuously metaphorical way, the speed of light is the ultimate "authority" in physics, since nothing can go faster.

It's an odd analogy, but it works for television.

  • 1
    Why not in the block?
    – dan
    Commented Jan 28, 2018 at 5:47
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    "The block" means "the neighborhood". See definition 6: a usually rectangular space (as in a city) enclosed by streets and occupied by or intended for buildings *. Because people walk around on the surface of the block, I guess "on" sounds better, much like *"on the street where you live".
    – Andrew
    Commented Jan 28, 2018 at 14:35
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    "Block" has many meanings, so using "in" implies something different, like a block of wood. "In the block" implies inside that object, The artwork featured a number of significant cultural objects embedded in a block of concrete (as a statement of how those cultures are inextricably grounded in the urban architecture from which they sprang).
    – Andrew
    Commented Jan 28, 2018 at 14:39

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