# eli5 – What is meant by single point in space and time?

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I have never understood what is meant when scientists say a “single point” is it something physical like an atom or or a size like the plank length?

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If you took all of time and made a timeline out of it, then you take all of space or all locations that would be relative to the context. You take one spot on each of those things and that would be your particular “random moment” you would reference. It’s basically like saying, “anytime, anywhere”. Of course, it’s taking into account that the point in space and time would be relative to the subject matter. For instance, let’s say you’re talking about human interaction, and the saying comes up, they’re clearly not talking about the planet Jupiter in 5,000 B.C.E., in this case they likely mean a single point in time and space where two humans have interacted, typically in the past as well, but not always. The point in time and space is inferred based upon what other information is being talked about. Sometimes, they will be literally talking about all space and all time, other times, they will mean a time in the past, or a space on or near Earth where s human being would exist or something else relative to the topic. It could mean a random place and time or one chosen by the dictator of the explanation, as well.

Its usage dependent. But I get the feeling you mean a mathematical point in space time. Its a dimensionless point. Exactly 0 meters in every dimension. It doesn’t have a size. So if you pick a point in space of 1, 1, 1 it has 0 volume. There is no radius because the location is 1.00000….. on each axis. Its not spread over an area. It’s not even a plank length size point, because a plank length still covers an area.

If you don’t mean the mathematical point, its generally determined by the scope of the measurement and precision required. A point in space for a satellite could be a cubic meter or a cubic kilometer. Depends on how accurate they want to be.

I’m not entirely sure what context you’re referring to but I understand the answer to your question to be: it’s a theoretical exactly precise coordinate in spacial dimensions and some framework of time coordinates