I watched a lecture that derived the robertson walker metric by creating a metric to describe a four dimensional sphere in three dimensions. Then from minkowski's equation-(adsbygoogle = window.adsbygoogle || []).push({});

https://lh3.googleusercontent.com/proxy/dWewIZYdx7aQRy2DtIjNF60tzgEdwxmrbyaqHl1QsAGyrENiErbEKLdBESnKijWbHk0UAnK4tRxkvi2Uiz-ZGUV7N3560lx8wdKofZY-YALhDORrks_t80D5gX38Y8Vtcf2lDg=w252-h22-nc

the time variable was added.

And this equation came by using pythagorus' theorem on the minkowskian plane. So my question is, why is there a minus sign after the time variable? I would have thought is to be a plus.

The final equation became-

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# How is time incorporated into the robertson walker metric?

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