As we kick back to celebrate the Fourth of July, we are also sitting farther from the Sun than any other day during the year. Earth's orbit around the Sun is not a perfect circle...sometimes we are farther from the Sun and sometimes we are closer. It comes as a surprise to most people that we are closest to the Sun in July!
We call this aphelion and are 152.6 million kilometers away from the Sun today. Six months from now in January, we will make our closest approach at 147.5 million kilometers away from the Sun. So the Sun is a little less intense now (averaged over the Earth) than it is in January. Of course, the seasons are due to the fact that Earth's rotational axis is tilted 23.5 degrees. The Sun is high in the sky and more intense in the northern hemisphere during our summer months and the days are longer giving us a nice warm summer.
It may also surprise you to know that the average global temperature is highest in July when Earth is farthest from the Sun! Its almost 4 degrees Fahrenheit warmer than in January when we are close to the Sun! What the heck is going on here?
The answer can be found by taking a look at a globe. Notice that the northern hemisphere has a lot more land while the southern hemisphere has a lot more water. Land heats up and cools down very quickly compared to water (water has a very high heat capacity which means it heast up and cools down very slowly compared to land...living next to a large lake in Racine, I was very aware of that fact!) Therefore, the northern hemisphere heats up very quickly in June and July when the intense summer Sun beats down. In January, the southern hemisphere's summer, the energy from the Sun is larger, but the water heats up VERY slowly resulting in a lower average global temperature when we are closer to the Sun!
You can do a simple experiement to observ this effect. Take a digital camera. Get some solar film to cover the lens (you can raid eclipse shades available for a couple of dollars at American Science and Surplus in Milwaukee). Cover your lens with the solar filter and take a picture of the Sun sometime in the next few weeks. Wait until December or January and get your camera and filters our and take the picture again (be sure to use the same zoom setting!) Put the pictures side by side on your comptuer screen and measure the diameter of the Sun in pixels on your computer. You will find the Sun is smaller in July than in January. The Sun appears slightly smaller when it is farther away!
As I go out to watch fireworks after the improv show tongiht, I will be grateful that we are slighlty farther away from the Sun right now as the temperature will probably still be in the upper 90s here!
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8 comments:
Happy 4th, hale-bopp! The weather has been perfect here, at least for me - sunny, low 70's.
I don't care if it's farther away, I much prefer the summer sun to the winter sun (when we see it). One of the many reasons I dislike winter driving is the low sun in the sky, often blinding me.
This is my 2nd summer in this apartment. It has a west-facing exterior brick wall and windows. Towards the end of the day, the sun makes it feel like a kiln in here. I'm grateful for a/c.
Happy 4th!
If I could even see the sky or even across the street from all the smoke of the illegal fireworks that have been going off for the last 5 hours...
I prefer the summer sun too.. but any sun is good for me!
But how about those legal fireworks that went off tonight over the beach - WOW WOW & WOW again! I think it just may have been the best works show I've ever seen... WOW.
The sun may be far far away but holy smokies what a close & brilliant bunch of stars!
Thanks, orbs. Hope everyone here had a great 4th.
Got a nice storm through here last night. Saw a transformer get hit by lightning as I was driving to the show last night and the street light I was approaching go out. Fireworks here were delayed about 40 minutes but did happen.
My townhome has windows on the north and south sides. Sunrise and sunset are far enough north at this time of year that I do get morning and evening sun in the northern windows. The sun is low in the sky and not very intense at that time of day, but I still notice it.
So how did the show go, hale? Did you knock 'em out?
Sylvia, my neighbor went NUTS last night too. He must have set off $500. worth of fireworks over the course of the evening. Most of them were close to professional. Made me nervous as some debris landed on my roof. The smoke in the street looked like dense fog!
kk - and I wonder if there actually WAS a dense fog all over last night... When I got home from the works I thought my house was on fire - even the air smelled like fire - I ended up thinking it was the neighbors' new fire pit (and perhaps a few illegal works too) but it certainly seemed foggy!
Decent show, but a small audience last night. Tried out some new stuff that went well.
I didn't notice nearly as many fireworks in the neighborhoods here as in years past...think the rain kept it down...wonder if they will be out tonight instead.
Happy 4th Hale Bopp and everybody!
Hale-Bopp, you make me think more than my brain can handle sometimes, but I will read it again a few times and see if it makes more sense tomorrow after some sleep :)
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