# Negative Metric Signature

1. Jul 18, 2011

### jfy4

Hi,

Is a metric signature of $(-,-,-,-)$ unphysical?

Thanks,

2. Jul 18, 2011

### bcrowell

Staff Emeritus
You can flip all four signs in the signature, and it doesn't mean anything in terms of connection with observation. For example, my favorite signature is +---, but much of the literature uses -+++. They don't mean anything physically different.

So ---- would be physically identical to ++++, describing Euclidean four-space. Such a space has no time dimension, just space.

3. Jul 18, 2011

### jfy4

Thank you very much.