# Difference between revisions of "Talk:1276: Angular Size"

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: Not really. You see the stars and planets as points because their angular size is lower than your eyes' resolution. They have measurable (or, in case of really distant or small objects, computable) angular sizes. For stars etc. these angular sizes are really small - but Earth is quite big, so if you cut a portion of a sphere the radius of Earth corresponding to these small solid angles, you get sizable areas. I haven't checked Randall's math, but I'd rather believe his results. If it is non-intuitive for you consider the Sun and Moon example - when observed by naked eye, the Moon looks for you as being the size of a dime held up in your hand - and yet it's shadow during an eclipse covers quite an area of Earth's surface. It is true that sizes of some of these "footprints" are quite surprising compared to other ones. [[Special:Contributions/89.174.214.74|89.174.214.74]] 08:55, 11 October 2013 (UTC) | : Not really. You see the stars and planets as points because their angular size is lower than your eyes' resolution. They have measurable (or, in case of really distant or small objects, computable) angular sizes. For stars etc. these angular sizes are really small - but Earth is quite big, so if you cut a portion of a sphere the radius of Earth corresponding to these small solid angles, you get sizable areas. I haven't checked Randall's math, but I'd rather believe his results. If it is non-intuitive for you consider the Sun and Moon example - when observed by naked eye, the Moon looks for you as being the size of a dime held up in your hand - and yet it's shadow during an eclipse covers quite an area of Earth's surface. It is true that sizes of some of these "footprints" are quite surprising compared to other ones. [[Special:Contributions/89.174.214.74|89.174.214.74]] 08:55, 11 October 2013 (UTC) | ||

:: Definitely surprising. I'll put faith in Randall doing his math correctly, but still needed to check on a couple of these because they did elicit a "What? No. Really? Can't be." reaction. Using the formula described in the Explanation above, for Venus I get 12742 km (Earth radius) * 12104 km (Venus diameter) / 38000000 (shortest distance to Venus) = 2.03 km. | :: Definitely surprising. I'll put faith in Randall doing his math correctly, but still needed to check on a couple of these because they did elicit a "What? No. Really? Can't be." reaction. Using the formula described in the Explanation above, for Venus I get 12742 km (Earth radius) * 12104 km (Venus diameter) / 38000000 (shortest distance to Venus) = 2.03 km. | ||

− | :: Hard to picture that something such a small dot in the sky is actually directly over such a large patch of ground. But there you are. [[Special:Contributions/67.51.59.66|67.51.59.66]] 17:11, 11 October 2013 (UTC) | + | :: Hard to picture that something that is such a small dot in the sky is actually directly over such a large patch of ground. But there you are. [[Special:Contributions/67.51.59.66|67.51.59.66]] 17:11, 11 October 2013 (UTC) |

Does someone know how to use LaTeX formulas? And if so, can they translate my formula into something more pleasing to the eye? [[User:Irino.|Irino.]] ([[User talk:Irino.|talk]]) 05:49, 11 October 2013 (UTC) | Does someone know how to use LaTeX formulas? And if so, can they translate my formula into something more pleasing to the eye? [[User:Irino.|Irino.]] ([[User talk:Irino.|talk]]) 05:49, 11 October 2013 (UTC) |

## Revision as of 17:12, 11 October 2013

What is the meaning of "football field" in panel #2? --Kevang (talk) 04:50, 11 October 2013 (UTC)

- I was wondering the same thing. Probably misplaced text. Irino. (talk) 05:49, 11 October 2013 (UTC)
- It does seem to be misplaced, but if that's the only glitch, this is the only panel without a unique reference object. "20 football pitches long" isn't all that easy to grasp. jameslucas (" " / +) 09:09, 11 October 2013 (UTC)
- The image is fixed by Randall. I did an update here.--Dgbrt (talk) 11:28, 11 October 2013 (UTC)
- Well, that's a letdown. I'm surprised Randall didn't use Heathrow. jameslucas (" " / +) 13:42, 11 October 2013 (UTC)

- The image is fixed by Randall. I did an update here.--Dgbrt (talk) 11:28, 11 October 2013 (UTC)

- It does seem to be misplaced, but if that's the only glitch, this is the only panel without a unique reference object. "20 football pitches long" isn't all that easy to grasp. jameslucas (" " / +) 09:09, 11 October 2013 (UTC)

I haven't done any lookups or maths to check these, but give the size of these as "stars" in the sky, everything from panel 2 onwards seems to me to be an order of magnitude or two too large. Mark Hurd (talk) 05:17, 11 October 2013 (UTC)

- Not really. You see the stars and planets as points because their angular size is lower than your eyes' resolution. They have measurable (or, in case of really distant or small objects, computable) angular sizes. For stars etc. these angular sizes are really small - but Earth is quite big, so if you cut a portion of a sphere the radius of Earth corresponding to these small solid angles, you get sizable areas. I haven't checked Randall's math, but I'd rather believe his results. If it is non-intuitive for you consider the Sun and Moon example - when observed by naked eye, the Moon looks for you as being the size of a dime held up in your hand - and yet it's shadow during an eclipse covers quite an area of Earth's surface. It is true that sizes of some of these "footprints" are quite surprising compared to other ones. 89.174.214.74 08:55, 11 October 2013 (UTC)
- Definitely surprising. I'll put faith in Randall doing his math correctly, but still needed to check on a couple of these because they did elicit a "What? No. Really? Can't be." reaction. Using the formula described in the Explanation above, for Venus I get 12742 km (Earth radius) * 12104 km (Venus diameter) / 38000000 (shortest distance to Venus) = 2.03 km.
- Hard to picture that something that is such a small dot in the sky is actually directly over such a large patch of ground. But there you are. 67.51.59.66 17:11, 11 October 2013 (UTC)

Does someone know how to use LaTeX formulas? And if so, can they translate my formula into something more pleasing to the eye? Irino. (talk) 05:49, 11 October 2013 (UTC)

According to the wikipedia page, the M25 is 117 miles long. That sounds more like "37 miles across" to me. Kaa-ching (talk) 08:46, 11 October 2013 (UTC)

- it originally stated 15 miles, someone has fixed it now. Thanks! Kaa-ching (talk) 11:35, 11 October 2013 (UTC)

Neither the sun or moon, nor Messier 25 (declination -19°) can ever culminate in the zenith over London. :-( Admittedly, Townsville, Australia would be sort of overwhelmed by M25. --129.13.72.198 11:27, 11 October 2013 (UTC)

- M25 is a reference to the highway that surrounds London, not the Messier object, which is probably nowhere near the angular size of the moon. 65.129.214.100 15:17, 11 October 2013 (UTC)

Does anyone know why the exoplanet "HD 189733 b" is labled as "Permadeath" ? Same question for the other weird names in the same pannel (the "tilde on keyboard" one) ? Jahvascriptmaniac (talk) 11:32, 11 October 2013 (UTC)

- A reference to Exoplanet Names. Squornshellous Beta (talk) 12:08, 11 October 2013 (UTC)

If you were looking from the center of the earth, as the situation suggests, wouldn't the M25 be reversed, east-to-west, as you look at the sun and the moon?--76.105.133.220 16:09, 11 October 2013 (UTC)

- I visualize it as looking down on Earth, with the "shadow" of the celestial object on top of the M25/soccer field/laptop/etc. 67.51.59.66 17:02, 11 October 2013 (UTC)