How big is earth in moon sky...?

I assume it would appear 4 times bigger than the moon does in our sky...?

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

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

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

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

"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.

"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.

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

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

"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...?