4 ms·
Remember that a light-year is a measure of distance, not time.
by lutusp 11y ago
Remember that a light-year is a measure of distance, not time.
- Cyph0n 11y agoI know. If we receive light that traveled a distance of X light years, then the event is occurring X years in the past.
- thaumasiotes 11y agoGiven that we already know that originating at point A and traveling to point B, such that the distance from A to B at the time you arrive is X, does not involve traveling a distance of X... I have trouble seeing your point.
- trentlott 11y agoRemember that space is expanding, so a photon which has traveled one billion light years originated less than one billion years ago.
- lutusp 11y ago> If we receive light that traveled a distance of X light years, then the event is occurring X years in the past. Not necessarily. By the time the light arrives here, its point of departure (and parts of its path through space) may have receded because of cosmological expansion, so its total travel distance, and its velocity, are no longer synchronized as they would be in Newtonian physics. Your remark would have been true for the static universe that Einstein believed to exist when he proposed the first version of the cosmological constant (before 1929).