For conversational purposes, yes. The phase of the moon is caused by the positions of the Sun, Moon and Eearth. If you hold your thumb up next to where you see the moon, you'll see the same 'phase" on your thumb- the same ratio of light and dark, caused by the angle between a line from your eye to the Moon/thumb and a line between the Sun and the Moon/thumb. If you call your friend anywhere on the Earth and ask them what it looks like to them, or looked like when they could see the Moon, you'll probably agree on the phase..
It depends on how finely you define the phases and "the same time". "New", "Quarter", "Full", "3/4" and "Old" are probably sufficiently broad that everyone, everywhere, would agree to them during the 12+ hours it would take for the Moon to be visible from every point on the Earth.
If you mean one instant, when the moon is visible to, at most, half the Earth, then for the seme, broad, phases, everyone who could see the moon would probably agree on its phase.
However, since the Earth is over 8000 miles (13000km?) in diameter, and the moon is 245,000 (on average) miles away, there is a slight (8/245 = 1/30.6 = 1.4 degrees) shift in angle between the place where the moon is just rising and the other side of the world where its just setting. You'd have to compare photographs or measure the proportion (percent or degrees or whatever) of the Moon that's illuminated for the 1.4 degree shft to make much difference.
Also, consider that the Moon's orbit around the Earth takes it 360 degrees (all the way around) in 29.5 days, relative to the Sun. (Its the Sun that causes the phases). So the Moon must appear to move 360 degrees / 29.5 days or 12.2 degrees per day. Therefore, during the 12 hours the moon is visbile from any given point on the Earth, the Moon moves 6.1 degrees across the sky, while the viewer's angle changes 1.4 degrees from Moon-rise to Moon-set.
So it is not precisely true that the Moon 'looks the same" to everyone at the same time, whether you define 'everyone at the same time' as all those who can see the Moon *now*, all those who will see the Moon at some point in the sky in an (approximatley) 12 hour period, or all those who will see the moon at a particular point in the sky over an (approximately) 24 hour period.
To cut it very finely:
There will be a particular area where, at a specific time, the first sliver of a new Moon will become visible. There will be a particular area where, at a specific time, the full moon will appear to be its largest. And there will be a particular area, at a specific time, where the moon will appear to change from very old to completely dark.
starchild.gsfc.nasa.gov
It depends on how finely you define the phases and "the same time". "New", "Quarter", "Full", "3/4" and "Old" are probably sufficiently broad that everyone, everywhere, would agree to them during the 12+ hours it would take for the Moon to be visible from every point on the Earth.
If you mean one instant, when the moon is visible to, at most, half the Earth, then for the seme, broad, phases, everyone who could see the moon would probably agree on its phase.
However, since the Earth is over 8000 miles (13000km?) in diameter, and the moon is 245,000 (on average) miles away, there is a slight (8/245 = 1/30.6 = 1.4 degrees) shift in angle between the place where the moon is just rising and the other side of the world where its just setting. You'd have to compare photographs or measure the proportion (percent or degrees or whatever) of the Moon that's illuminated for the 1.4 degree shft to make much difference.
Also, consider that the Moon's orbit around the Earth takes it 360 degrees (all the way around) in 29.5 days, relative to the Sun. (Its the Sun that causes the phases). So the Moon must appear to move 360 degrees / 29.5 days or 12.2 degrees per day. Therefore, during the 12 hours the moon is visbile from any given point on the Earth, the Moon moves 6.1 degrees across the sky, while the viewer's angle changes 1.4 degrees from Moon-rise to Moon-set.
So it is not precisely true that the Moon 'looks the same" to everyone at the same time, whether you define 'everyone at the same time' as all those who can see the Moon *now*, all those who will see the Moon at some point in the sky in an (approximatley) 12 hour period, or all those who will see the moon at a particular point in the sky over an (approximately) 24 hour period.
To cut it very finely:
There will be a particular area where, at a specific time, the first sliver of a new Moon will become visible. There will be a particular area where, at a specific time, the full moon will appear to be its largest. And there will be a particular area, at a specific time, where the moon will appear to change from very old to completely dark.
starchild.gsfc.nasa.gov
