Do you have some Earth orbiting our star, the Sun, stories?
Do I ever!!!
Story #1 Kepler's 3rd Law of Planetary Motion story
First I have to paint the picture of how this whole idea came to me, as you again, will not find this very interesting fact anywhere on the internet or hear this story from anyone else, unless they had learned it from me.
One day, one of my Astronomy classes were very busy with our Neutral Buoyancy Lab day. This is a much longer story but suffice me to say that a retired pipe fitter neighbor had helped me build a space station the width of our high school pool, and a professional scuba person (who ran a scuba store in Stevens Point, WI) brought in enough scuba gear so every student who wanted to experience the neutral buoyancy of outer space could.
The scuba instructor would go through his first lesson while the students with the scuba gear on stood on the shallow end of the pool. Then the students would scuba underwater and pull themselves through the space station under water (as one cannot swim in space but astronauts pull themselves through the space station) in single file before standing up in the deeper water again and getting their finale directions before entering the deep end of the pool with even more neutral buoyant chores (astronaut training) in the deep end.
It was the end of January, in central Wisconsin (my family from SW Wisconsin and my wife's family from SE Wisconsin called where we lived, "far up in Northern Wisconsin" as it took a good 3 hours to drive to our home from their homes.) and was probably 10 below zero outside, that day. I was supervising the Neutral Buoyancy Lab activity and noticed one of my students surfacing with her scuba gear and asked if she was OK. She said, yes, that she was OK but just had to fix some little thing on her scuba gear before returning under the water. This set me to thinking...this young lady was from New Zealand in the Southern Hemisphere. It was cold out here now as we were in our winter season; and at her home in New Zealand it was summer and warm. Winter was my least favorite season and I knew that the Earth is actually closest to the Sun in January and I taught that Kepler's 3rd Law of planetary motion said that planets swept out equal areas, in their elliptical orbits, in equal increments of time.
Another way to state Kepler's 3rd law of Motion is; a planet moves faster when closer to the sun and slower when further away from the sun, in it's orbit. That set me to thinking that our winters (because the earth is closer to the sun) should be much shorter than our summers (because the earth is farther from the sun and moving slower) but in the southern hemisphere they had to put up with longer winters and shorter summers. That thought made me feel blessed to be living in the northern hemisphere as winter was my least favorite season.
So, I had to prove that our winters in the northern hemisphere was shorter than our summer months, how was I going to prove this? The thought came to me that I could search when exactly spring equinox and the following fall equinox was (though summer) and then the following spring equinox again (through winter) and the amount of days to go from spring through summer to fall, should be several days longer than from that fall through winter to the following spring.
Here, I search these facts off now again in 2022 and go through this exercise with you:
(note: this time, I easily picked up these facts from heavens-above.com choosing the Sun information and then changed the year to 2023 and updated to get the 2023 spring date.)
spring 2022 started exactly: March 20th, 10:33
fall 2022 will start exactly: September 22, 20:03
spring 2023 will start exactly: March 20, 16:24
Ok, the days, minutes and seconds from March 20th, 10:33 through summer to the start of fall 2022, Sep 22, 20:03 and (to the right below) Sep 22, 20:03 through winter to spring of 2023, Mar 20, 16:24 calculations below:
# of Days # of Days
Mar 20-31 11 Sep 22-30 8
Apr 1-30 30 Oct 1-31 31
May 1-31 31 Nov 1-30 30
Jun 1-30 30 Dec 1-31 31
Jul 1-31 31 Jan 1-31 31
Aug 1-31 31 Feb 1-28 28
Sep 1-22 22 Mar 1-20 19
from 10:33 to 20:03 is 9 hrs. & 30 min from 20:03 to 16:24 is 3 hrs. 57 min + 16 hrs. 24 min
Totals 186 days 9 hours 30 minutes and 178 days 20 hours 21 minutes
so, taking the difference by changing the 186 days to 185 days and 24 hours to make the math easier, you get:
185 days 24+9 = 33 hours and 30 minutes - 178 days 20 hours 21 minutes = 7 days 13 hours 9 minutes
So, the Northern Hemisphere Winter (or Southern Hemisphere Summer) is 7 days 13 hours 9 minutes shorter than the Northern Hemisphere Summer (or Southern Hemisphere Winter). Over one week longer from spring through summer to winter than fall through winter to spring; I'll take that any day as winter is my least favorite season.
One day, one of my Astronomy classes were very busy with our Neutral Buoyancy Lab day. This is a much longer story but suffice me to say that a retired pipe fitter neighbor had helped me build a space station the width of our high school pool, and a professional scuba person (who ran a scuba store in Stevens Point, WI) brought in enough scuba gear so every student who wanted to experience the neutral buoyancy of outer space could.
The scuba instructor would go through his first lesson while the students with the scuba gear on stood on the shallow end of the pool. Then the students would scuba underwater and pull themselves through the space station under water (as one cannot swim in space but astronauts pull themselves through the space station) in single file before standing up in the deeper water again and getting their finale directions before entering the deep end of the pool with even more neutral buoyant chores (astronaut training) in the deep end.
It was the end of January, in central Wisconsin (my family from SW Wisconsin and my wife's family from SE Wisconsin called where we lived, "far up in Northern Wisconsin" as it took a good 3 hours to drive to our home from their homes.) and was probably 10 below zero outside, that day. I was supervising the Neutral Buoyancy Lab activity and noticed one of my students surfacing with her scuba gear and asked if she was OK. She said, yes, that she was OK but just had to fix some little thing on her scuba gear before returning under the water. This set me to thinking...this young lady was from New Zealand in the Southern Hemisphere. It was cold out here now as we were in our winter season; and at her home in New Zealand it was summer and warm. Winter was my least favorite season and I knew that the Earth is actually closest to the Sun in January and I taught that Kepler's 3rd Law of planetary motion said that planets swept out equal areas, in their elliptical orbits, in equal increments of time.
Another way to state Kepler's 3rd law of Motion is; a planet moves faster when closer to the sun and slower when further away from the sun, in it's orbit. That set me to thinking that our winters (because the earth is closer to the sun) should be much shorter than our summers (because the earth is farther from the sun and moving slower) but in the southern hemisphere they had to put up with longer winters and shorter summers. That thought made me feel blessed to be living in the northern hemisphere as winter was my least favorite season.
So, I had to prove that our winters in the northern hemisphere was shorter than our summer months, how was I going to prove this? The thought came to me that I could search when exactly spring equinox and the following fall equinox was (though summer) and then the following spring equinox again (through winter) and the amount of days to go from spring through summer to fall, should be several days longer than from that fall through winter to the following spring.
Here, I search these facts off now again in 2022 and go through this exercise with you:
(note: this time, I easily picked up these facts from heavens-above.com choosing the Sun information and then changed the year to 2023 and updated to get the 2023 spring date.)
spring 2022 started exactly: March 20th, 10:33
fall 2022 will start exactly: September 22, 20:03
spring 2023 will start exactly: March 20, 16:24
Ok, the days, minutes and seconds from March 20th, 10:33 through summer to the start of fall 2022, Sep 22, 20:03 and (to the right below) Sep 22, 20:03 through winter to spring of 2023, Mar 20, 16:24 calculations below:
# of Days # of Days
Mar 20-31 11 Sep 22-30 8
Apr 1-30 30 Oct 1-31 31
May 1-31 31 Nov 1-30 30
Jun 1-30 30 Dec 1-31 31
Jul 1-31 31 Jan 1-31 31
Aug 1-31 31 Feb 1-28 28
Sep 1-22 22 Mar 1-20 19
from 10:33 to 20:03 is 9 hrs. & 30 min from 20:03 to 16:24 is 3 hrs. 57 min + 16 hrs. 24 min
Totals 186 days 9 hours 30 minutes and 178 days 20 hours 21 minutes
so, taking the difference by changing the 186 days to 185 days and 24 hours to make the math easier, you get:
185 days 24+9 = 33 hours and 30 minutes - 178 days 20 hours 21 minutes = 7 days 13 hours 9 minutes
So, the Northern Hemisphere Winter (or Southern Hemisphere Summer) is 7 days 13 hours 9 minutes shorter than the Northern Hemisphere Summer (or Southern Hemisphere Winter). Over one week longer from spring through summer to winter than fall through winter to spring; I'll take that any day as winter is my least favorite season.
Story #2 How can we in the Northern Hemisphere be so much closer to the sun because it is so much colder?
Story #2: Our seasons have everything to do with the angle to sun hits the earth, much more than how far we are from the sun. The more direct the sunlight is, the hotter it is.
So, the fact that the Earth is tilted 23 degrees on its axis (actually, 22.1 degrees to 24.5 degrees, it varies because the Earth wobbles like a top slowing down, around itself. But that's another story later.) is what causes the seasons.
Do you have a globe of the Earth in your home?
1). If you do have a globe of the Earth and it is tilted to its base (as it should be) hold the globe and walk around your dining room table or kitchen island or couch in living room, any one of these representing the Sun. Now the trick is, you have to no what direction is north and have the top of your Earth globe always point North as you walk around the object representing the sun.
As you orbit the sun with your earth globe, several times, while keeping the top of your globe facing north; notice there is one place that when you spin the globe so the United States (or whatever northern hemisphere country you are from) is tilted toward the Sun. This season is Summer when the globe tilting north is tilted toward the sun in the northern hemisphere (note Australia in the southern hemisphere if you spin the globe 180 degrees is tilted away from the Sun as it is winter in the southern hemisphere). Now, as you walk east around your object (representing the sun) a quarter of the way around, you'll encounter fall (12 hours of light and 12 hours of darkness for everyone) and as you orbit another quarter away around (keeping your Earth globe tilt pointing north the whole time) you'll see the United States is tilted away from the Sun in the winter and that is why we are colder as the rays of sunlight are not hitting the northern hemisphere as directly as when the Earth is in its summer position of its orbit. Finally, another quarter orbit around the sun gives you spring, where again, everyone on earth gets 12 hours of light and 12 hours of darkness.
Did walking your Earth globe around an object representing the sun, help? It did me also.
2). If you do not have an Earth globe; just use kinesthetics and you be the Earth and walk around an object representing the Sun.
This is not as easy as you think because of the tilt but a lot of people enjoy challenges.
OK, if the Earth is tilted about 23 degrees, bend at the waist so that the top of your head is about 23 degrees from vertical, leaning toward the north (if you start on the south side of the sun facing the sun, it is the easiest position to start as you just have to bow at the waist 23 degrees). How far is 23 degrees? Well if standing straight is 0 degrees and bending 90 degrees is with your head and back parallel to the floor looking down at the floor, then half way between is 45 degrees and if you come up half of the 45 degrees toward standing straight up again, you'll have 22.5 degrees which is close enough to 23 degree tilt for what we are doing.
OK, you are south of the object, bending at the waist so your head is about 23 degrees tilt from standing vertically, toward the object representing the sun. Look at your sun and note that you are kind of looking up at it with your eyeballs compared to where I'm having you go next.
Walk 180 degrees around the object representing the sun but now you'll have to bend backwards about 23 degrees so the top of your head is still facing north. Now look at the object representing the sun again and note that your eyeballs have to attempt to look down at the sun, as your top of your head is in the northern hemisphere and light from the sun is having a harder time hitting the top of your head and your eyes are closer to the top of your head than they are to your chin (which would be more like Australia on your head represent the earth.)
Now, if you wish to attempt this with your family and/or friends and/or a classroom of students; have everyone simultaneously stand around the object representing the Sun. (this is more fun and I've done this with classes for decades) Have everyone around the sun, tilt at the waist, so the top of their head is about a 23 degree tilt from the vertical north (tell everyone which way is north by picking an object in the room or outside that is north of everyone).
Have everyone look at everyone else now; can everyone tell who in the circle closest represents the earth where it is in it's orbit when its summer and who is in the position of winter and the two at the spring and fall positions? Answer: if the top of their head is bend toward the Sun they are in the summer position, if away from the Sun they are in the winter position and note if each person spins through one day (keeping the top of their head at about 23 degrees from the vertical pointing north the whole time they spin) making sure they spin toward their east (as the sun has to rise in the east and set in the west) so if everyone orbits the sun going east while keeping their 23 degree north tilt simultaneously (few people can physically do this so don't feel bad if you cannot do it) you'll see who represented spring and fall as you know that winter goes into spring than summer and then fall.
Did that help you understand why we in the northern hemisphere are colder in the winter than the summer as the sunlight is hitting us at a much more oblique angle than the direct sunlight in the summer due to the earths tilt? Yep, it helped me understand it also.
So, the fact that the Earth is tilted 23 degrees on its axis (actually, 22.1 degrees to 24.5 degrees, it varies because the Earth wobbles like a top slowing down, around itself. But that's another story later.) is what causes the seasons.
Do you have a globe of the Earth in your home?
1). If you do have a globe of the Earth and it is tilted to its base (as it should be) hold the globe and walk around your dining room table or kitchen island or couch in living room, any one of these representing the Sun. Now the trick is, you have to no what direction is north and have the top of your Earth globe always point North as you walk around the object representing the sun.
As you orbit the sun with your earth globe, several times, while keeping the top of your globe facing north; notice there is one place that when you spin the globe so the United States (or whatever northern hemisphere country you are from) is tilted toward the Sun. This season is Summer when the globe tilting north is tilted toward the sun in the northern hemisphere (note Australia in the southern hemisphere if you spin the globe 180 degrees is tilted away from the Sun as it is winter in the southern hemisphere). Now, as you walk east around your object (representing the sun) a quarter of the way around, you'll encounter fall (12 hours of light and 12 hours of darkness for everyone) and as you orbit another quarter away around (keeping your Earth globe tilt pointing north the whole time) you'll see the United States is tilted away from the Sun in the winter and that is why we are colder as the rays of sunlight are not hitting the northern hemisphere as directly as when the Earth is in its summer position of its orbit. Finally, another quarter orbit around the sun gives you spring, where again, everyone on earth gets 12 hours of light and 12 hours of darkness.
Did walking your Earth globe around an object representing the sun, help? It did me also.
2). If you do not have an Earth globe; just use kinesthetics and you be the Earth and walk around an object representing the Sun.
This is not as easy as you think because of the tilt but a lot of people enjoy challenges.
OK, if the Earth is tilted about 23 degrees, bend at the waist so that the top of your head is about 23 degrees from vertical, leaning toward the north (if you start on the south side of the sun facing the sun, it is the easiest position to start as you just have to bow at the waist 23 degrees). How far is 23 degrees? Well if standing straight is 0 degrees and bending 90 degrees is with your head and back parallel to the floor looking down at the floor, then half way between is 45 degrees and if you come up half of the 45 degrees toward standing straight up again, you'll have 22.5 degrees which is close enough to 23 degree tilt for what we are doing.
OK, you are south of the object, bending at the waist so your head is about 23 degrees tilt from standing vertically, toward the object representing the sun. Look at your sun and note that you are kind of looking up at it with your eyeballs compared to where I'm having you go next.
Walk 180 degrees around the object representing the sun but now you'll have to bend backwards about 23 degrees so the top of your head is still facing north. Now look at the object representing the sun again and note that your eyeballs have to attempt to look down at the sun, as your top of your head is in the northern hemisphere and light from the sun is having a harder time hitting the top of your head and your eyes are closer to the top of your head than they are to your chin (which would be more like Australia on your head represent the earth.)
Now, if you wish to attempt this with your family and/or friends and/or a classroom of students; have everyone simultaneously stand around the object representing the Sun. (this is more fun and I've done this with classes for decades) Have everyone around the sun, tilt at the waist, so the top of their head is about a 23 degree tilt from the vertical north (tell everyone which way is north by picking an object in the room or outside that is north of everyone).
Have everyone look at everyone else now; can everyone tell who in the circle closest represents the earth where it is in it's orbit when its summer and who is in the position of winter and the two at the spring and fall positions? Answer: if the top of their head is bend toward the Sun they are in the summer position, if away from the Sun they are in the winter position and note if each person spins through one day (keeping the top of their head at about 23 degrees from the vertical pointing north the whole time they spin) making sure they spin toward their east (as the sun has to rise in the east and set in the west) so if everyone orbits the sun going east while keeping their 23 degree north tilt simultaneously (few people can physically do this so don't feel bad if you cannot do it) you'll see who represented spring and fall as you know that winter goes into spring than summer and then fall.
Did that help you understand why we in the northern hemisphere are colder in the winter than the summer as the sunlight is hitting us at a much more oblique angle than the direct sunlight in the summer due to the earths tilt? Yep, it helped me understand it also.
Story #3 Why is the sun shining in different windows now in the spring than it did in the winter?
In the Figure Above: The noontime position of the Sun in the sky, plotted over a year, produces a figure eight-shaped curve known as the analemma. Earth’s elliptical orbit produces the curve of the analemma. Its lowest and highest points are, respectively, the winter and summer solstices. The vertical line running through the analemma is the meridian. This view shows the Sun at noon on 4 January 2007, the day of perihelion – Earth’s closest approach to the Sun.
Story #3: The Sun appearing to move further north in the summer and further south in the winter months (as seen from the northern hemisphere.)
This analemma shape of the sun's movement throughout a year has always intrigued me.
First, if you count the dots, they each represent the sun's position in the analemma shape for the same amount of time. I counted 36 dots so about 10 days elapsed from one dot at noon to the next dot at noon.
Now notice that the dots get closer together as you approach the top of the loop and the bottom of the loop and are spaced further apart near where they loop intersects itself.
When I use to do in the UWSP planetarium lectures, in Stevens Point, Wisconsin , I'd have my students note the suns position throughout the year on the planetarium domed ceiling and it was obvious that as the sun approached summer (the longest daylight of the year) at the top of the dome, it appeared to slow down and when the sun fell toward fall, the sun appeared to speed up (accelerate, as we lost daylight faster each day in the northern hemisphere) until it neared the bottom of the dome again and the sun obviously slowed down to make the turn back up again (just like you slow down, in your car, to take a curve in the road). What does this mean to us? Well, around the shortest day of the year (around Dec 21st each year) the amount of sunlight we get in a given day is about the same for a few weeks before and after Dec 21st BUT a few weeks before spring and after spring, we gain several minutes of day in the morning and evening. Around June 21st (the summer solstice, longest daylight of the year) the days are long a few weeks before and after that date, as the sunrise and sunset times do not vary much from day to day.
This analemma shape of the sun's movement throughout a year has always intrigued me.
First, if you count the dots, they each represent the sun's position in the analemma shape for the same amount of time. I counted 36 dots so about 10 days elapsed from one dot at noon to the next dot at noon.
Now notice that the dots get closer together as you approach the top of the loop and the bottom of the loop and are spaced further apart near where they loop intersects itself.
When I use to do in the UWSP planetarium lectures, in Stevens Point, Wisconsin , I'd have my students note the suns position throughout the year on the planetarium domed ceiling and it was obvious that as the sun approached summer (the longest daylight of the year) at the top of the dome, it appeared to slow down and when the sun fell toward fall, the sun appeared to speed up (accelerate, as we lost daylight faster each day in the northern hemisphere) until it neared the bottom of the dome again and the sun obviously slowed down to make the turn back up again (just like you slow down, in your car, to take a curve in the road). What does this mean to us? Well, around the shortest day of the year (around Dec 21st each year) the amount of sunlight we get in a given day is about the same for a few weeks before and after Dec 21st BUT a few weeks before spring and after spring, we gain several minutes of day in the morning and evening. Around June 21st (the summer solstice, longest daylight of the year) the days are long a few weeks before and after that date, as the sunrise and sunset times do not vary much from day to day.
Story #4: The Flooding of the Nile in Egypt story.
During the winter, into the spring, Orion's belt is high in the night sky, in the evening. That's when I point out two of the brightest stars, Sirius and Procyon. If you follow the three Orion belt stars east, they will point to the brightest star in the sky, as seen from anywhere on Earth, Sirius in Canis Major (Orion's big hunting dog), then head north to the next bright star, Procyon (which means, proceeds the bright one [referring to Sirius]). You see, Procyon is further north (closer to the North Star Polaris, at the end of the handle of the Little Dipper in Ursa Minor) and the closer to Polaris a star is (and our sun is a star) the longer that star will stay above the horizon as all heavenly objects circle Polaris each day due to the spin of the Earth on its axis as the axis always points toward Polaris, all day long, and all year long. You see, the Nile River in Egypt always flooded when the bright star Sirius was seen for the first time that year at sunset (called the stars helical rising and caused by the Earth orbiting the Sun) and since Procyon was closer to Polaris, Procyon had it's helical rising six weeks before Sirius did. So, when the Egyptians along the Nile noticed Procyon for the first time, they knew they had six weeks to prepare for the flooding of the Nile. The stars were humans calendars and clocks long before the invention of clocks and calendars as survival was important for you and I to be here on the planet currently.
So, just as Procyon is closer to Polaris because it is further north than Sirius; our sun when its further north in the summer spends a longer amount of time above the horizon than in the winter when the Sun if further south so spends less time around the horizon.
During the winter, into the spring, Orion's belt is high in the night sky, in the evening. That's when I point out two of the brightest stars, Sirius and Procyon. If you follow the three Orion belt stars east, they will point to the brightest star in the sky, as seen from anywhere on Earth, Sirius in Canis Major (Orion's big hunting dog), then head north to the next bright star, Procyon (which means, proceeds the bright one [referring to Sirius]). You see, Procyon is further north (closer to the North Star Polaris, at the end of the handle of the Little Dipper in Ursa Minor) and the closer to Polaris a star is (and our sun is a star) the longer that star will stay above the horizon as all heavenly objects circle Polaris each day due to the spin of the Earth on its axis as the axis always points toward Polaris, all day long, and all year long. You see, the Nile River in Egypt always flooded when the bright star Sirius was seen for the first time that year at sunset (called the stars helical rising and caused by the Earth orbiting the Sun) and since Procyon was closer to Polaris, Procyon had it's helical rising six weeks before Sirius did. So, when the Egyptians along the Nile noticed Procyon for the first time, they knew they had six weeks to prepare for the flooding of the Nile. The stars were humans calendars and clocks long before the invention of clocks and calendars as survival was important for you and I to be here on the planet currently.
So, just as Procyon is closer to Polaris because it is further north than Sirius; our sun when its further north in the summer spends a longer amount of time above the horizon than in the winter when the Sun if further south so spends less time around the horizon.
Story #5 Which stars to observe first during a night sky observation session?
The stars closest Polaris are up all night, because as they circle Polaris, as long as they are between the distance of the northern horizon up to Polaris, they will never set. Here in Dripping Springs, Tx our latitude is 30.2 degrees North so any star within 30.2 degrees of Polaris will never set year round (and Polaris is always your latitude above the northern horizon).
(Be careful if you try this) but if four people joined hands and the one end person became the center of a wheel as everyone else circled that person as they held each other hands; you'd note that the person furthest from the person being circled has to move the fastest by far because they have to cover much more distance (a bigger circle) in the same amount of time as that closest person to the center person they are all circling.
Another way to put it is; if you put a point in the middle of a piece of paper and draw concentric circles around that point and then draw a horizontal and vertical axis through the center point of your circles and then bisect each of those to get 45 degree angles all around. Notice, the length of the arcs on the outside are much longer arcs than the inside circle arcs.
Well, all the stars circle Polaris throughout the night so Polaris represents the center of all your concentric circles. That means the stars on the southern horizon are furthest from Polaris so have to really bug out (move fast) across the southern horizon to circle Polaris in a day.
And stars appear to rise in the east and set in the west (because the Earth is spinning east making the stars appear to rise in the east) so during an observation session we attempt to see anything furthest southwest first as it will disappear for the night the quickest so observe from the southwest along the west horizon toward the north west in an angle that is much longer (from the southwest point to the due south point) in the southern sky than as you approach Polaris. The southern horizon stars changes the fastest during any night observation session.
(Be careful if you try this) but if four people joined hands and the one end person became the center of a wheel as everyone else circled that person as they held each other hands; you'd note that the person furthest from the person being circled has to move the fastest by far because they have to cover much more distance (a bigger circle) in the same amount of time as that closest person to the center person they are all circling.
Another way to put it is; if you put a point in the middle of a piece of paper and draw concentric circles around that point and then draw a horizontal and vertical axis through the center point of your circles and then bisect each of those to get 45 degree angles all around. Notice, the length of the arcs on the outside are much longer arcs than the inside circle arcs.
Well, all the stars circle Polaris throughout the night so Polaris represents the center of all your concentric circles. That means the stars on the southern horizon are furthest from Polaris so have to really bug out (move fast) across the southern horizon to circle Polaris in a day.
And stars appear to rise in the east and set in the west (because the Earth is spinning east making the stars appear to rise in the east) so during an observation session we attempt to see anything furthest southwest first as it will disappear for the night the quickest so observe from the southwest along the west horizon toward the north west in an angle that is much longer (from the southwest point to the due south point) in the southern sky than as you approach Polaris. The southern horizon stars changes the fastest during any night observation session.