It turns darker, faster.

[Anima Aeterna]

If I'm not mistaken, the seasons of the year exist due to Earth's translation around the Sun, and how close our planet is from it during this oval-shaped route the Earth "draws" during It's course. (therefore causing temperature and weather variations)

 

Now, I'm curious. Day and Night happen due to Earth's rotations around It's own axis, therefore causing certain locations of our planet to be "shadowed", while others receive the Sun's light. In certain seasons it becomes dark faster than in others, while the time at which the sun rises and the environment becomes bright again, seems to remain the same despite season.

 

I wake up more less about the time the sky becomes bright and light barges into my room. This is more less at 7am. As we headed towards Autumn, and into Winter, I noticed it became darker at about 6:30pm rather than at about 8pm. For a while now, though, it becomes dark at about 5:40pm or so. Maybe a bit latter. I haven't noticed it becoming brighter in the morning earlier though. It seems to become bright at the same hour, around 7am.

 

What causes this phenomena? Is earth's rotation not at a constant speed? Does the atmosphere cause some kind of effect unknown to me? Do I need to buy a new watch?

 

 

Thanks in advance for any corrections to anything inaccurate I may have said, too.

[michel123456]

If I'm not mistaken, the seasons of the year exist due to Earth's translation around the Sun, and how close our planet is from it during this oval-shaped route the Earth "draws" during It's course. (therefore causing temperature and weather variations)

 

No. Look at wiki article season

Seasons result from the yearly revolution of the Earth around the Sun and the tilt of the Earth's axis relative to the plane of revolution.[1]

 

emphasis mine.

The tilt makes the season.

IIRC the variation of distance to the Sun has no effect upon temperatures.

 

Fig. 1

This is a diagram of the seasons. Regardless of the time of day (i.e. the Earth's rotation on its axis), the North Pole will be dark, and the South Pole will be illuminated; see also arctic winter. In addition to the density of incident light, the dissipation of light in the atmosphere is greater when it falls at a shallow angle.

From Wiki.

 

 

Now, I'm curious. (...)

 

That's fantastic. Never stop to be curious.

And never stop to ask.

"He who asks is a fool for five minutes, but he who does not ask remains a fool forever" Chinese proverb.

Edited November 14, 2011 by michel123456

[swansont]

Is earth's rotation not at a constant speed?

No, it isn't, because the orbit is slightly eccentric. We are closest to the sun in early January and furthest in July. Orbital mechanics dictates that you move faster when you are closer (equal areas are swept out in equal times) so the length of day actually changes over the course of a year, and this also skews the noon, sunrise and sunset times — if you looked at the position of the sun at the same time very day, over the course of a year it would trace out a figure-8: an analemma

 

http://astroprofspage.com/archives/564

http://www.sciquill.com/analemma/page2.html

[michel123456]

No, it isn't, because the orbit is slightly eccentric. We are closest to the sun in early January and furthest in July. Orbital mechanics dictates that you move faster when you are closer (equal areas are swept out in equal times) so the length of day actually changes over the course of a year, and this also skews the noon, sunrise and sunset times — if you looked at the position of the sun at the same time very day, over the course of a year it would trace out a figure-8: an analemma

 

http://astroprofspage.com/archives/564

http://www.sciquill.com/analemma/page2.html

The lenght of the day depends from the speed of the Earth on its orbit?

[swansont]

The lenght of the day depends from the speed of the Earth on its orbit?

 

Yes. You measure a day by how long it takes for the sun to return to the same place on a vertical line. Because the earth is moving, it has to rotate more than 360º for this to happen (about 361º), and if it's moving faster the angle is slightly larger, so it takes a little longer.

[michel123456]

Thank you. I learned something today.

[michel123456]

Does summer coincide with the point of least distance onto the orbit?

[Anima Aeterna]

No. Look at wiki article season

 

 

emphasis mine.

The tilt makes the season.

IIRC the variation of distance to the Sun has no effect upon temperatures.

 

 

From Wiki.

 

 

 

That's fantastic. Never stop to be curious.

And never stop to ask.

"He who asks is a fool for five minutes, but he who does not ask remains a fool forever" Chinese proverb.

 

 

I agree! I love that chinese proverb, I've learned to always ask about everything and seek answers.

 

Thank you so much for your explanations, let me see if I got this straight. I used to imagine Earth's translation to only happen in a 2 dimensional manner. Basically, if we look at the Solar System "sideways", lol, only the X and Y coordinates of the Earth changed, while the Z coordinates (altitude?) remained "0". But after your explanation I realized this is untrue! Still looking at the Solar System sideways, the Earth translates around the Sun in a diagonal route, right? In a way that at times the North Pole will be "shadowed" while the South Pole will be illuminated (when the Earth finds itself "over" the sun) and other times the opposite will happen (when the Earth is "under" the Sun).

 

Did I get it right thus far?

 

So the temperatures and weather of our planet are not at all affected by our distance from the sun during translation? Is our distance from the Sun actually altered during translation at all?

 

EDIT: Oh wait, or is it that this phenomena is only related to Earth's inclination? Silly me.

Edited November 15, 2011 by Lil_Knowledge_Seeker

[michel123456]

I agree! I love that chinese proverb, I've learned to always ask about everything and seek answers.(...) Still looking at the Solar System sideways, the Earth translates around the Sun in a diagonal route, right? In a way that at times the North Pole will be "shadowed" while the South Pole will be illuminated (when the Earth finds itself "over" the sun) and other times the opposite will happen (when the Earth is "under" the Sun).

 

Did I get it right thus far?

(...)

 

Yes. When you look at the solar system sideways, as you said, you are in the ecliptic plane. The wiki article is a bit complicated IMHO. The important thing is:

As the rotational axis of the Earth is not perpendicular to its orbital plane, the equatorial plane is not parallel to the ecliptic plane, but makes an angle of about 23°26', which is known as the axial tilt (or obliquity of the ecliptic).

That is the angle you may notice on a terrestrial globe.

 

So the temperatures and weather of our planet are not at all affected by our distance from the sun during translation?

I am not sure. That is what i recall. Some other member may answer that.

 

Is our distance from the Sun actually altered during translation at all?

The orbit of the Earth is not circular. It is an ellipse. But it is an ellipse looking-like-circle, with small eccentricity. So the distance Earth Sun changes. Above that, the path of the Earth is altered by the Moon. Actually it is the center of gravity of the Earth-Moon system that follows an elliptical orbit. This center , the barycenter, is somewhere inside the Earth, but not at its center. And there must exist other alterations I am not aware of.

Edited November 15, 2011 by michel123456

[ewmon]

Just a couple suggestions ...

it becomes dark faster

This might seem picky, but science is like that sometimes.

 

The phrase "becomes dark faster" sounds as though the time is shorter between the bottom of the sun touching the horizon until it's completely out of sight. I heard about such a thing years ago, so I looked around the internet a bit, but I don't find much info on whether this varies (ie, faster or slower) throughout the year.

 

The phrase "becomes dark earlier" (or "becomes dark later") would more accurately indicate how the times of sunrise and sunset change throughout the year, as shown in the diagram below for London England. And yes, as shown in the diagram, the earliest sunrise and latest sunset (and vice versa) do not occur on the same day, which still puzzles me.

 

I also have found this cool real-time image of the earth showing where it's currently day and night (and so, where the sun is seen "rising" and "setting"), and you can click on it to zoom in to a particular location.

 

Day and night on the Earth

[Klaynos]

Just a couple suggestions ...

This might seem picky, but science is like that sometimes.

 

The phrase "becomes dark faster" sounds as though the time is shorter between the bottom of the sun touching the horizon until it's completely out of sight. I heard about such a thing years ago, so I looked around the internet a bit, but I don't find much info on whether this varies (ie, faster or slower) throughout the year.

 

That was my initial thought on reading the topic title.

 

On another note, this thread has prompted me to return to looking at a blog post I started writing over 2 years ago...

[Anima Aeterna]

No, it isn't, because the orbit is slightly eccentric. We are closest to the sun in early January and furthest in July. Orbital mechanics dictates that you move faster when you are closer (equal areas are swept out in equal times) so the length of day actually changes over the course of a year, and this also skews the noon, sunrise and sunset times — if you looked at the position of the sun at the same time very day, over the course of a year it would trace out a figure-8: an analemma

 

http://astroprofspage.com/archives/564

http://www.sciquill....emma/page2.html

 

How amazing. So the line the Earth draws as it translates around the Sun, can be compared to for example, a child with a whoola whoop, where the child is the Sun and the whoola whoop is the route drawn by the Earth during It's course around the Sun. (I'm referring to a frozen image of this example, by the way, not sure It's that much of a comparison) Except of course as you said, this route is only slightly eccentric, right?

 

What you mentioned about orbital mechanics dictating that an astro (An astro is any kind of celestial body? Correct me if I'm wrong, this includes stars, planets or "satellites", right?) moves faster when It's closer to the astro it translates around, is a phenomena which happens due to, obviously, gravity, correct?

 

Like having a round magnet tied to a string, and another magnet magically hovering in mid-air, and spinning one of these magnets around the other. As we are doing this with, of course, the aid of the string to spin one magnet around the other, and we approach the magnet a bit more to the one in the center, the magnet translating around the other is attracted more strongly to the center magnet, and therefore there's a (stronger) force pulling it in, yet, since the rotating magnet is already "carrying" movement (i.e. another force), rather than being pulled in towards the magnet, completely, the rotating magnet approaches the center magnet but carries on his circular route being launched out of the "hot zone" (the zone where we are spinning the magnet closer, hence drawing an eccentric route).

 

So, would this example be accurate? The magnet reaches the "hot zone", accelerates in this zone due to being more strongly attracted to the center magnet, is "shot out" of this zone, and while it completes It's route further away from the center, it slows down and continues the same cycle, accelerating again, etc. Is this a good comparison to Earth's translation? (except much slower of course)

 

Is this also why some years are "Leap Years", and others "Common Years"? I hope I'm not being obnoxious with all the questions! Thank you!

 

Yes. You measure a day by how long it takes for the sun to return to the same place on a vertical line. Because the earth is moving, it has to rotate more than 360º for this to happen (about 361º), and if it's moving faster the angle is slightly larger, so it takes a little longer.

 

 

It took me a while to understand this. It didn't make sense for the Earth to complete 361º around itself to be able to, well, complete a full rotation around itself. But I understand now, It's because, since the Earth is moving, the location where our planet is receiving the light of the sun is slowly changing, and therefore, by the time it completes a full rotation, in order to "catch up" with the Sun, lol, it has to rotate a little more.

 

Coming to these forums was the best decision in my life.

 

Yes. When you look at the solar system sideways, as you said, you are in the ecliptic plane. The wiki article is a bit complicated IMHO. The important thing is:

 

That is the angle you may notice on a terrestrial globe.

 

 

I am not sure. That is what i recall. Some other member may answer that.

 

 

The orbit of the Earth is not circular. It is an ellipse. But it is an ellipse looking-like-circle, with small eccentricity. So the distance Earth Sun changes. Above that, the path of the Earth is altered by the Moon. Actually it is the center of gravity of the Earth-Moon system that follows an elliptical orbit. This center , the barycenter, is somewhere inside the Earth, but not at its center. And there must exist other alterations I am not aware of.

 

That last part sounds pretty complex. It had me researching a bit more about gravity. I read a bit about it and, according to Wiki, gravitation causes dispersed matter to coalesce, and coalesced matter to remain intact, but it still leaves me wondering, if the Earth, being of a greater proportion than the Moon (and thus exorcising greater gravity force?), attracts it into it, why does the Moon not collide with the Earth?

 

What force is responsible for this, how does it work? If there's indeed a force not just attracting the Moon towards our planet, but another force also repelling it and thus keeping it at a certain distance, then perhaps from that point on I could conclude that (and there I go making silly comparisons again) the Earth-Moon gravitational relationship, can be compared to two children holding each other's hands, spinning and pulling each other towards each other, thus "sling-shooting" each other each time they complete a full spin, and since they won't let go of each other, the force of each "sling-shot", causes them to move around as they spin. This is what I imagine happens in the Earth Moon rotation, but I have the feeling I'm far from what actually happens!

 

Just a couple suggestions ...

This might seem picky, but science is like that sometimes.

 

The phrase "becomes dark faster" sounds as though the time is shorter between the bottom of the sun touching the horizon until it's completely out of sight. I heard about such a thing years ago, so I looked around the internet a bit, but I don't find much info on whether this varies (ie, faster or slower) throughout the year.

 

The phrase "becomes dark earlier" (or "becomes dark later") would more accurately indicate how the times of sunrise and sunset change throughout the year, as shown in the diagram below for London England. And yes, as shown in the diagram, the earliest sunrise and latest sunset (and vice versa) do not occur on the same day, which still puzzles me.

 

I also have found this cool real-time image of the earth showing where it's currently day and night (and so, where the sun is seen "rising" and "setting"), and you can click on it to zoom in to a particular location.

 

Day and night on the Earth

 

Well we can't say something is "half-accurate" or "half-wrong" can we? Haha. Either It's inaccurate or accurate, and if the words I used are unappropriated, I thank you for correcting me! Also thank you for that link, that's amusing! They make all kinds of awesome "tools" these days! It's pretty helpful to understand the concept better.

Edited November 15, 2011 by Lil_Knowledge_Seeker

[michel123456]

That last part sounds pretty complex. It had me researching a bit more about gravity. I read a bit about it and, according to Wiki, gravitation causes dispersed matter to coalesce, and coalesced matter to remain intact, but it still leaves me wondering, if the Earth, being of a greater proportion than the Moon (and thus exorcising greater gravity force?), attracts it into it, why does the Moon not collide with the Earth?

 

What force is responsible for this, how does it work? If there's indeed a force not just attracting the Moon towards our planet, but another force also repelling it and thus keeping it at a certain distance, (...)

 

Now you are entering science by the wrong door.

IMHO you should keep your enthusiasm to learn some basic physics. You may find it in your school books you weren't interested in, or in future courses, or over the Net (that's much more difficult because you'll need advice).

 

Your question was the same as Newton posed to himself: why does the Moon not collide with the Earth? Or "why does the Moon not fall upon the Earth?"

 

His answer was outstanding: the Moon indeed falls constantly upon the Earth. So, why do they not collide? That is because the Moon constantly miss the Earth. The path of the Moon missing the Earth is called its orbit.

See the wiki article about orbit.

 

Don't miss Newton's canon ball.

 

 

The phrase "becomes dark faster" sounds as though the time is shorter between the bottom of the sun touching the horizon until it's completely out of sight. I heard about such a thing years ago, so I looked around the internet a bit, but I don't find much info on whether this varies (ie, faster or slower) throughout the year.

 

The night falls faster when the angle at which the Sun touches the horizon is closed to the perpendicular. That happens at low latitudes (the tropics). (edit. I have to check that, not so sure if it is correct after all...)

I guess it varies throughout the year.

Edited November 16, 2011 by michel123456

[michel123456]

Found this from here

The fastest sunsets (and sunrises) occur at or near the equinoxes. What’s more, the slowest sunsets (and sunrises) occur at or near the solstices. This is true whether you live in the northern or southern hemisphere. And, by the way, when we say sunset here, we’re talking about the actual number of minutes it takes for the body of the sun to sink below the western horizon.

 

When the sun sets due west – as it does on the day of an equinox – the sun hits the horizon at the steepest possible angle, which hastens the duration of sunset. Although the sunset duration varies by latitude, the equinox sun sets in about 2 and 3/4 minutes at 40 degrees latitude (Denver, Philadelphia).

 

On the solstices, the sun sets farthest north or farthest south of due west. The farther the sun sets from due west, the shallower the angle of the setting sun. That means a longer duration for sunset. At 40 degrees latitude, the solstice sun sets in roughly 3 and 1/3 minutes.

 

Note: at sunset, the Sun does not hit the horizon. The horizon is getting up and hits the Sun. The next time you observe the sunset, put in your mind that the Sun is fixed and that you are a passenger on an immense spaceship: the Earth.

Edited November 16, 2011 by michel123456

[swansont]

Does summer coincide with the point of least distance onto the orbit?

 

Perihelion currently occurs in early January, aphelion in early July. So in the northern hemisphere it is winter right around earth's closest approach to the sun.

[michel123456]

Perihelion currently occurs in early January, aphelion in early July. So in the northern hemisphere it is winter right around earth's closest approach to the sun.

Can we conclude from this that distance to the Sun has no influence on temperatures?

[swansont]

Can we conclude from this that distance to the Sun has no influence on temperatures?

 

No. What we can conclude is that the effect of the tilt is greater than the effect of the distance, since both hemispheres see winter.

[Anima Aeterna]

Now you are entering science by the wrong door.

IMHO you should keep your enthusiasm to learn some basic physics. You may find it in your school books you weren't interested in, or in future courses, or over the Net (that's much more difficult because you'll need advice).

 

Your question was the same as Newton posed to himself: why does the Moon not collide with the Earth? Or "why does the Moon not fall upon the Earth?"

 

His answer was outstanding: the Moon indeed falls constantly upon the Earth. So, why do they not collide? That is because the Moon constantly miss the Earth. The path of the Moon missing the Earth is called its orbit.

See the wiki article about orbit.

 

Don't miss Newton's canon ball.

 

 

 

The night falls faster when the angle at which the Sun touches the horizon is closed to the perpendicular. That happens at low latitudes (the tropics). (edit. I have to check that, not so sure if it is correct after all...)

I guess it varies throughout the year.

 

Thank you very much! It keeps missing the Earth, it makes perfect sense! Then again, why does the Earth not hit the Sun? The Sun isn't moving fast enough for Earth to keep missing it, is it? It's moving, yes, but very slowly. Everything is moving iirc since the whole universe is expanding.

 

You're right! I should probably actually save this enthusiasm and eagerness to study and get good grades at my current course. I'm even considering the chance of becoming a chemistry or physics teacher. If I could teach with as much enthusiasm maybe I could actually make the students as interested as I am myself. You know, show them the magic there is in all of it! Be a little crazy!

 

I just have one final question for everyone. Do you know any good movies related to physics or chemistry? Could be a documentary, or a science fiction movie that gave emphasis to something related to chemistry or physics. You know, a movie which actually taught me something important. Thank you again! I'll study those links a bit and go back to focus on the things I'm suppose to be studying right now at my current course, haha.

Edited November 16, 2011 by Lil_Knowledge_Seeker

[michel123456]

You're welcome.

I learned also 2 things during this conversation.

Thanks to Swansont.

It was fun.

[swansont]

I didn't have time earlier, but we can take a stab at quantifying the effects. A 5 million km change in the distance at 150 million km is a 3.3% change in r, which means a 6.75% change in area. The variation in amount of daylight will be a little different because of the change in speed we already discussed. But the average change in time of sunlight due to the tilt is much larger — at 45º latitude, you almost double the number of daylight hours in summer vs winter, plus the sun is higher in the sky. The result of all of that can be seen in insolation maps; many solar power sites have such maps.

 

A larger eccentricity couple with a smaller tilt, from precession, would result in a larger relative effect from the distance.

[michel123456]

So if i understand correctly summer in the southern hemisphere is hotter than in the northern. And winter in southern is milder.

Edited November 17, 2011 by michel123456

[swansont]

So if i understand correctly summer in the southern hemisphere is hotter than in the northern. And winter in southern is milder.

 

There's a lot more that goes into local temperature; air masses are transported and geography comes into play, for how that air moves and the effects of the albedo. Also, the northern hemisphere may get less insolation from the distance change, but it gets it for slightly longer. Remember, climate is a tad complicated.

[TonyMcC]

i have learnt alot here.i dont have anything 2 contribute but i just want to ask a question.the question seem stupid,did apollo really travelled to the moon?

 

I am wondering why you ask the question. There are reasons why some people have their doubts. For some people there are religious teachings that deny the possibility - and those people are unlikely to respond to argument. There are always people who hold onto a conspiracy theory and they think those that can't see their point of view must be blind! I guess I must be one of the huge majority who will be thought of as "blind" by the small minority.

[Anima Aeterna]

Interesting topic you brought up there, TonyMcC. It reminded me of something important. You see, I too have been "blinded" by theories or religious beliefs in the past. It's important for one to form their own beliefs, yes, but while maintaining a certain skepticism. Keeping an open mind to possibilities. Otherwise, anyone who closes themselves to a single set of believes will be separating himself from other people psychologically, isn't that right? Closing oneself away in their own world and preventing growth even, I'd say. In a way.

 

I, for example, really like the quantum theories, while most knowledgeable people are very skeptical toward these quantum theories. Despite loving these inspiring ideas, I always keep my mind open to the possibility they're completely inaccurate, but also the opposite, and even if I am very skeptical towards many religious beliefs I will respect others' views and even then have a certain open-mindedness towards those subjects, while I might explain them to myself in a different way, though.

 

Remember that, iirc, Giordano Bruno was burned to death for supporting the idea the Earth was round. If the people responsible for his death weren't so skeptical and even insulted by the defense of this possibility, perhaps they'd have found the truth sooner. They didn't because it made zero sense for the Earth to be round, since if it was so, we'd fall off, according to their belief. So may that be a good reminder that, just because something is very unlikely to happen, or even seemingly impossible, doesn't really mean it is indeed impossible.

 

Just a small reminder I decided to share, anyway! Thought It'd be important.

[michel123456]

Lil_Knowledge_Seeker when did you grow up like that? Great post.