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How big is earth in moon sky...?
I assume it would appear 4 times bigger than the moon does in our sky...? |
#2
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Barry Schwarz wrote:
On Thu, 1 Jul 2004 18:02:58 +1000, "Whisper" wrote: I assume it would appear 4 times bigger than the moon does in our sky...? You know, or can find, the distance from the Earth to the Moon. Same for Earth's diameter. All you need is a spreadsheet or calculator with an arctan function. Just the multiply and divide keys should be sufficient for most purposes. Since the angle subtended by the moon is about 30 arcmin, which is pretty small, we can get away with small angle approximations. The moon's diameter is ~3476km, the earth's 12756km (equatorial). So the earth should appear ~30*12756/3476 arcmin or 1.8 degrees across in the sky to someone on the moon. That's about the same angle the width of your thumb subtends at the eye when held at arms length. DaveL |
#3
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Barry Schwarz wrote:
On Thu, 1 Jul 2004 18:02:58 +1000, "Whisper" wrote: I assume it would appear 4 times bigger than the moon does in our sky...? You know, or can find, the distance from the Earth to the Moon. Same for Earth's diameter. All you need is a spreadsheet or calculator with an arctan function. Just the multiply and divide keys should be sufficient for most purposes. Since the angle subtended by the moon is about 30 arcmin, which is pretty small, we can get away with small angle approximations. The moon's diameter is ~3476km, the earth's 12756km (equatorial). So the earth should appear ~30*12756/3476 arcmin or 1.8 degrees across in the sky to someone on the moon. That's about the same angle the width of your thumb subtends at the eye when held at arms length. DaveL |
#4
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Whisper wrote:
I assume it would appear 4 times bigger than the moon does in our sky...? Pretty much; the Earth's diameter is around 3.67 times the Moon's, and of course the viewing distance is about the same. Note from this, however, that the *area* of the Earth's visible disc as seen from the Moon will be something like 13.4 times the area of the Moon's as seen from here. -- Odysseus |
#5
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Whisper wrote:
I assume it would appear 4 times bigger than the moon does in our sky...? Pretty much; the Earth's diameter is around 3.67 times the Moon's, and of course the viewing distance is about the same. Note from this, however, that the *area* of the Earth's visible disc as seen from the Moon will be something like 13.4 times the area of the Moon's as seen from here. -- Odysseus |
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"Dave" wrote in message
... Barry Schwarz wrote: On Thu, 1 Jul 2004 18:02:58 +1000, "Whisper" wrote: I assume it would appear 4 times bigger than the moon does in our sky...? You know, or can find, the distance from the Earth to the Moon. Same for Earth's diameter. All you need is a spreadsheet or calculator with an arctan function. Just the multiply and divide keys should be sufficient for most purposes. Since the angle subtended by the moon is about 30 arcmin, which is pretty small, we can get away with small angle approximations. The moon's diameter is ~3476km, the earth's 12756km (equatorial). So the earth should appear ~30*12756/3476 arcmin or 1.8 degrees across in the sky to someone on the moon. That's about the same angle the width of your thumb subtends at the eye when held at arms length. And so to answer his original question, since the moon appears about 1/2 a degree across in our sky, yes, that's about 4 times bigger. |
#7
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"Dave" wrote in message
... Barry Schwarz wrote: On Thu, 1 Jul 2004 18:02:58 +1000, "Whisper" wrote: I assume it would appear 4 times bigger than the moon does in our sky...? You know, or can find, the distance from the Earth to the Moon. Same for Earth's diameter. All you need is a spreadsheet or calculator with an arctan function. Just the multiply and divide keys should be sufficient for most purposes. Since the angle subtended by the moon is about 30 arcmin, which is pretty small, we can get away with small angle approximations. The moon's diameter is ~3476km, the earth's 12756km (equatorial). So the earth should appear ~30*12756/3476 arcmin or 1.8 degrees across in the sky to someone on the moon. That's about the same angle the width of your thumb subtends at the eye when held at arms length. And so to answer his original question, since the moon appears about 1/2 a degree across in our sky, yes, that's about 4 times bigger. |
#8
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Paul Lawler wrote:
"Dave" wrote in message ... Barry Schwarz wrote: On Thu, 1 Jul 2004 18:02:58 +1000, "Whisper" wrote: I assume it would appear 4 times bigger than the moon does in our sky...? You know, or can find, the distance from the Earth to the Moon. Same for Earth's diameter. All you need is a spreadsheet or calculator with an arctan function. Just the multiply and divide keys should be sufficient for most purposes. Since the angle subtended by the moon is about 30 arcmin, which is pretty small, we can get away with small angle approximations. The moon's diameter is ~3476km, the earth's 12756km (equatorial). So the earth should appear ~30*12756/3476 arcmin or 1.8 degrees across in the sky to someone on the moon. That's about the same angle the width of your thumb subtends at the eye when held at arms length. And so to answer his original question, since the moon appears about 1/2 a degree across in our sky, yes, that's about 4 times bigger. A bit more succinct, but hmm, yes DaveL |
#9
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Paul Lawler wrote:
"Dave" wrote in message ... Barry Schwarz wrote: On Thu, 1 Jul 2004 18:02:58 +1000, "Whisper" wrote: I assume it would appear 4 times bigger than the moon does in our sky...? You know, or can find, the distance from the Earth to the Moon. Same for Earth's diameter. All you need is a spreadsheet or calculator with an arctan function. Just the multiply and divide keys should be sufficient for most purposes. Since the angle subtended by the moon is about 30 arcmin, which is pretty small, we can get away with small angle approximations. The moon's diameter is ~3476km, the earth's 12756km (equatorial). So the earth should appear ~30*12756/3476 arcmin or 1.8 degrees across in the sky to someone on the moon. That's about the same angle the width of your thumb subtends at the eye when held at arms length. And so to answer his original question, since the moon appears about 1/2 a degree across in our sky, yes, that's about 4 times bigger. A bit more succinct, but hmm, yes DaveL |
#10
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"Paul Lawler" wrote in message ... "Dave" wrote in message ... Barry Schwarz wrote: On Thu, 1 Jul 2004 18:02:58 +1000, "Whisper" wrote: I assume it would appear 4 times bigger than the moon does in our sky...? You know, or can find, the distance from the Earth to the Moon. Same for Earth's diameter. All you need is a spreadsheet or calculator with an arctan function. Just the multiply and divide keys should be sufficient for most purposes. Since the angle subtended by the moon is about 30 arcmin, which is pretty small, we can get away with small angle approximations. The moon's diameter is ~3476km, the earth's 12756km (equatorial). So the earth should appear ~30*12756/3476 arcmin or 1.8 degrees across in the sky to someone on the moon. That's about the same angle the width of your thumb subtends at the eye when held at arms length. And so to answer his original question, since the moon appears about 1/2 a degree across in our sky, yes, that's about 4 times bigger. Thank you. That's quite a big object isn't it.........? I guess you could discern certain landmarks? Maybe great wall of China with a telescope for eg...? |
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