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# Solstice

Sat 21 Jun, 2014 04:55 pm
I have read that the summer solstice occurs when the sun reaches its furthest point north of the equator.

How could that be? The sun is a huge body more than one-hundred times the size of the earth. Does a scientist draw an imaginary line from the center of the sun to the earth "below"?
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Type: Question • Score: 12 • Views: 3,828 • Replies: 24

maxdancona

1
Sat 21 Jun, 2014 05:04 pm
@gollum,
Go outside tomorrow.

Point at the sun.

There is your "imaginary" line. Where you are pointing on the Solstice is farther north than were you are pointing any other day of the year.

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Setanta

3
Sat 21 Jun, 2014 05:08 pm
Either what you read was ineptly expressed, or you failed to understand what you were reading. The earth has an axial tilt of 23 1/2 degrees. That's why we have seasons. On the day which is called the summer solstice in the northern hemisphere, the earth's northern hemisphere is tilted 23 1/2 degrees toward the sun. Therefore, it appears to be "higher" in the sky than on any other day in our year. On the day which is called the winter solstice in the northern hemisphere, the earth's northern hemisphere is tilted 23 1/2 degrees away from the sun, so the sun appears to be "lower" in the sky than on any other day in our year. These conditions are, of course, reversed in the earth's southern hemisphere. These are optical effects--the sun does not actually move relative to the earth.
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Setanta

1
Sat 21 Jun, 2014 05:12 pm
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Setanta

1
Sat 21 Jun, 2014 05:48 pm
Here, let's complicate this even more. The orbit of the earth around the sun is not a regular circle with the sun at the center.

That is an exaggerated diagram of the earth's orbit around the sun. At perihelion (it means "near the sun"), we are about 91 million miles from the sun. At aphelion (it means "far from the sun") we are about 95 million miles from the sun. The earth is at perihelion in January, during winter in the northern hemisphere, and we are moving around the sun faster than at any other time of the year. The earth is at aphelion is in July. This means that the seasons in the northern hemisphere are moderated. In northern winter we are tilted away from the sun, but we are closer to the sun, we are moving fast, so northern winter is shorter than southern winter. In northern summer we are tilted toward the sun, but we are farther from the sun than at any other time of the year, and we are moving more slowly. Therefore, northern summers are longer than southern summers. I believe i am correct in stating that this condition applies to all of the sun's satellites.

Planetary satellites move in relation to the planets they orbit. When the moon is closest to the earth, that is known as perigee. When the moon is farthest from the earth, that is known as apogee. However, don't assume any symmetry in these relative relationships. For example, Mars has two satellites: Phobos ("fear") and Deimos ("terror"). Those "moons" rise in the west and set in the east relative to Mars, and they are not tidally locked to Mars--they move on their own. So, for example, Phobos takes less than five hours to cross the Martian sky. Their motion from west to east is considered to be evidence that they are either "asteroids" which were trapped by Martian gravity when passing Mars' orbit path, or that they are the ejecta from Mars when it was struck by a very large "meteor" or a planetesimal between three and two billions years ago--or that they are ejecta of the object which struck Mars.

Uranus is even more strange in its relationship to the sun. It's axial tile is more than 97 degrees (or one could say, just less than eight degrees). That means that rather than moving like a spinning top with regard to the sun, it moves like a billiard ball rolling around a round table. Uranus' orbital period is 84 years. That means that each pole of Uranus gets 42 years of light, and then 42 years of darkness. It is thought that Uranus was, three billions years ago or more, struck by a planetesimal about the size of the Earth.

The solar system is a very strange and wonderful place.
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rosborne979

1
Sat 21 Jun, 2014 08:04 pm
@gollum,
gollum wrote:
How could that be? The sun is a huge body more than one-hundred times the size of the earth. Does a scientist draw an imaginary line from the center of the sun to the earth "below"?

If the sun were much closer to the earth to the point where it filled the majority of the sky, then the sizes you mentioned would be more relevant to the effect. The axial tilt would still be there but its effect would be overwhelmed by the fact that the sun filled the sky (also the earth couldn't exist at that distance, but putting that aside for the moment...). When you think about the sun being over a million times the size of the earth, you also have to consider that is is 93million miles away.
farmerman

2
Sun 22 Jun, 2014 05:20 am
@rosborne979,
Down at the U of Delaware campus there is a representative "solar system" in the green. The sun is a huge patio with a representative orb of about 20 feet. Mercury is a bout a block away and by the time one hits Neptune, the kids who are "hiking the solar system trail' are about 6 miles away at the University Dairy farms. The rotational period and ecliptic characteristics (as well as more geeky typ data) for each planet are scannable by phone on a big bronze plaque and write-ups at each planet.
Princeton is planning to do one also xcept theres will be actual metal globes I understand. That oughta be good once you ecide on a sun size, how miniscule the inner 4 planets wil be.
contrex

3
Sun 22 Jun, 2014 05:58 am
Galileo would weep.
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gollum

1
Sun 22 Jun, 2014 11:23 am
@rosborne979,
rosborne979-
Thank you.

I think you are right. However, wikidedia says "It [the sun] has a diameter of about 1,392,684 km (865,374 mi),[5] around 109 times that of Earth....
contrex

1
Sun 22 Jun, 2014 11:30 am
@gollum,
gollum wrote:
However, wikidedia says "It [the sun] has a diameter of about 1,392,684 km (865,374 mi),[5] around 109 times that of Earth....

What has that got to do with the solstices?

gollum

1
Sun 22 Jun, 2014 11:45 am
@contrex,
contrex-
Nothing.

rosborne979 posted, “When you think about the sun being over a million times the size of the earth….”

Wikipedia reports, “The Sun is the star at the center of the Solar System. It is almost perfectly spherical and consists of hot plasma interwoven with magnetic fields.[12][13] It has a diameter of about 1,392,684 km (865,374 mi),[5] around 109 times that of Earth,”

So, I posted to rosborne979 (and anyone else interested) that I think he is right but wikipedia reports otherwise.
roger

1
Sun 22 Jun, 2014 01:35 pm
@gollum,
Are you comparing diameter, area of disc, volume, or mass?
farmerman

1
Sun 22 Jun, 2014 01:41 pm
@roger,
ros was talking volume cause the sun has about 1.3 million times the volume. pi r cubed would confirm it
roger

1
Sun 22 Jun, 2014 01:59 pm
@farmerman,
That's what I suspected. Ros would never be that far off.
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rosborne979

1
Sun 22 Jun, 2014 04:43 pm
@farmerman,
There's a display like that at the Museum of Science in Boston as well.
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rosborne979

2
Sun 22 Jun, 2014 04:44 pm
@gollum,
gollum wrote:

rosborne979-
Thank you.

I think you are right. However, wikidedia says "It [the sun] has a diameter of about 1,392,684 km (865,374 mi),[5] around 109 times that of Earth....

The diameter is only around a hundred times the Earth's, but the volume is over a million.
gollum

1
Sun 22 Jun, 2014 07:22 pm
@rosborne979,
rosborne979-
Thank you.

With a diameter 100 times the earth's.

The circumference of a sphere of a sphere equals 3.1416 times the diameter.

The volume equals 4/3 times pi times the radius cubed.

So, why would the volume be one-million times the earth's?
InfraBlue

1
Sun 22 Jun, 2014 07:55 pm
This is an animated gif of the sun in the arctic around the summer solstice.
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rosborne979

1
Sun 22 Jun, 2014 08:10 pm
@gollum,
gollum wrote:

rosborne979-
Thank you.

With a diameter 100 times the earth's.

The circumference of a sphere of a sphere equals 3.1416 times the diameter.

The volume equals 4/3 times pi times the radius cubed.

So, why would the volume be one-million times the earth's?

I didn't do the math. I just got the reference from several sites I found on Google. Most of them said approximately 1 million times the volume of Earth, so I went with that. Why? Are they inaccurate?
Romeo Fabulini

1
Sun 22 Jun, 2014 08:17 pm
Quote:
Gollum said: I have read that the summer solstice occurs when the sun reaches its furthest point north of the equator.
How could that be? The sun is a huge body more than one-hundred times the size of the earth. Does a scientist draw an imaginary line from the center of the sun to the earth "below"?

The sun is so far away that we don't notice its huge size.
This vid explains solstice stuff, but angles on spinning balls goes mostly over my head-

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