Greenwich Mean Time (GMT) is defined as mean solar time measured with reference to which longitude?

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Multiple Choice

Greenwich Mean Time (GMT) is defined as mean solar time measured with reference to which longitude?

GMT is defined as mean solar time measured with reference to the Prime Meridian, the 0° longitude line that runs through Greenwich. This line is the standard reference longitude for time, so the time at 0° longitude is GMT. The other options aren’t relevant to GMT: 90° longitude is just another meridian, the International Date Line sits near 180° longitude and marks calendar date changes rather than the reference for GMT, and the Tropic of Cancer is a latitude line, not a longitude.

GMT is defined as mean solar time measured with reference to the Prime Meridian, the 0° longitude line that runs through Greenwich. This line is the standard reference longitude for time, so the time at 0° longitude is GMT. The other options aren’t relevant to GMT: 90° longitude is just another meridian, the International Date Line sits near 180° longitude and marks calendar date changes rather than the reference for GMT, and the Tropic of Cancer is a latitude line, not a longitude.

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