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sundaju
2006-Aug-22, 01:52 PM
Why does the Sun appear bigger when it is on the horizon compared to when it is overhead?

jlhredshift
2006-Aug-22, 02:02 PM
For two reasons:

!) The atmosphere acts as a lense and by refraction magnifies the suns appearance; also at that angle the light has to pass through more atmosphere.

2) For some psycological reason when the human brain has a reference for size at the horizon it perceives it as being bigger.

Welcome to the forum.

sundaju
2006-Aug-22, 02:09 PM
Thanks for the pleasant welcome to the forum.

Hope to get more enlightenment ( the rational way, of course ) in the coming days,months, years and if possible, centuries ( height of optimism )..;)

pghnative
2006-Aug-22, 02:14 PM
For two reasons:

!) The atmosphere acts as a lense and by refraction magnifies the suns appearance; also at that angle the light has to pass through more atmosphere.
That actually is not true -- refraction bends the sun's rays (so it'll appear to be above the horizon, when actually it is below), but refraction does not magnify. See the various threads on the "Moon Illusion" for more details.

jlhredshift
2006-Aug-22, 02:22 PM
That actually is not true -- refraction bends the sun's rays (so it'll appear to be above the horizon, when actually it is below), but refraction does not magnify. See the various threads on the "Moon Illusion" for more details.

1) Thank you
2) Rats....
3):wall:

sundaju
2006-Aug-22, 02:24 PM
Wow.. It's getting interesting from the day one here...

With so many minds brainstorming so many ideas, I couldn't have asked for a better place to hangout...

Pals, I am excited a lot..

jlhredshift
2006-Aug-22, 02:38 PM
Wow.. It's getting interesting from the day one here...

With so many minds brainstorming so many ideas, I couldn't have asked for a better place to hangout...

Pals, I am excited a lot..

And some remember better than others, I knew in the back of my head that their was something wrong with what I was saying, sorry. However, the local TV news weather guy shows a video of each days sunset and on TV I do not notice any "apparent" size change. But, When the wife and I go to the lake to watch it "live" it has an "appearance" of angular size change, though extremely slight. The "mind" thing again I guess.;)

sundaju
2006-Aug-22, 02:45 PM
The "mind" thing again ...


I too had an inkling of this idea.. but was not really convinced... but now I am.

On the same lines, Will I appear less fatter than I am actually, if I am standing alone with no background objects or people nearby to compare me?

Or is it an illusion that applies only to distant objects that are of a reasonably big size? :think:

jlhredshift
2006-Aug-22, 02:58 PM
I think that it is along the lines of the TV commercials where the before actor is frowning and the after actor is smilling; therefore the product worked.
"Perception is reality, reality is perception." The minds eye....

Or, Spock's answer to a test question in "Voyage Home": "Nothing un-real exists":D

Jakenorrish
2006-Aug-23, 03:41 PM
The thing is that when the Sun (or Moon) is near the horizon, you may have something to compare it to, like a House or a Tree or whatever else. When they are overhead then they are against the (3d as you see it) sky. Then they look smaller as there is no easy reference to compare them to.

nb. Don't look directly at the Sun either when its overhead or near the horizon. You could damage your eyesight or at worse blind yourself.

hhEb09'1
2006-Aug-23, 04:00 PM
However, the local TV news weather guy shows a video of each days sunset and on TV I do not notice any "apparent" size change.Yep. If you take photographs, and compare them, there is no appreciable difference. The only difference seems to be in the personal perception.

OTOH, it's easy to take photos where objects do appear to be larger. But if you're careful about using the same equipment and settings each time, there will be no real difference.

AGN Fuel
2006-Aug-23, 11:46 PM
Yep. If you take photographs, and compare them, there is no appreciable difference. The only difference seems to be in the personal perception.

OTOH, it's easy to take photos where objects do appear to be larger. But if you're careful about using the same equipment and settings each time, there will be no real difference.


A simple test that I once did with my kids was to have them hold a ruler out at arms length as the full moon was rising and measure how "wide" it was. Then, 4 hours later in the evening, they did the same (with the aid of a red-light torch!).

No change, despite it appearing to be much 'smaller'.