Earth's orbit

[Mr. Blackwell]

I have just stumbled on information that says Earth does not orbit the sun and that our classical ways of thinking about physics is equivalent to believing the earth is flat.

Does that strike anyone as odd?

[Nick]

Reading the bible again?

[Gohavesomefun]

The orbit isn't a perfect circle if thats what you mean, it's actually elliptical, hence why it's cooler in the winter and warmer in the summer.

[Mr. Blackwell]

Well, first there is this



Which goes into greater detail about our rotation and tilt but it still leaves something out.

[Mr. Blackwell]

I'm not going into conspiracy mode here but why is this model of the galaxy not taught in schools?

[Cyberia]

They are correct, but they are also changing the POV.  For example, remember the way planets spiraled through space?  Imagine that from end-on, and you'd see the classic version.

This is basic orbital-mechanics, btw, and well understood.


And common-speach "year" is shorthand for a "tropical year" in the first video.

[kin hell]

bm

[Quesi]

Walking home with my 5 1/2 year old, she pointed towards the pink sky, and said:

"Mommy!  Look at the beautiful sunset!  Wouldn't it be cool to live over there?  Over by the sunset? Then you would have such a beautiful view outside of your window!"

She has a good point.  I'm thinking of investing in some real estate closer to the sunset. 

[wright]

The orbit isn't a perfect circle if thats what you mean, it's actually elliptical, hence why it's cooler in the winter and warmer in the summer.

Seasons are actually caused by the Earth's axial tilt:http://en.wikipedia.org/wiki/Axial_tilt

She has a good point.  I'm thinking of investing in some real estate closer to the sunset. 

Your daughter is wonderfully wise. Be sure the world doesn't beat that open-eyed wonder out of her.

[Anfauglir]

The orbit isn't a perfect circle if thats what you mean, it's actually elliptical, hence why it's cooler in the winter and warmer in the summer.

I really, really hope you don't actually believe this?  The Earth is actually far closer to the sun in January than it is in July - about 3 million miles closer, in fact, so if the "orbit causes seasons" argument is true, then we should expect the warmest weather to be in the winter months.

[Graybeard]

I really, really hope you don't actually believe this?  The Earth is actually far closer to the sun in January than it is in July - about 3 million miles closer, in fact, so if the "orbit causes seasons" argument is true, then we should expect the warmest weather to be in the winter months.

Whereas you are, of course, correct in dismissing the "orbit causes seasons" argument; it is the inverse square law that makes any Earth - Sun distance of minimal effect.

[3sigma]

The orbit isn't a perfect circle if thats what you mean, it's actually elliptical, hence why it's cooler in the winter and warmer in the summer.

I’ve never understood how anyone could say something like this. Doesn’t the fact that when it is winter in the northern hemisphere, it is summer in the southern hemisphere give you any pause at all?

[Hatter23]

The orbit isn't a perfect circle if thats what you mean, it's actually elliptical, hence why it's cooler in the winter and warmer in the summer.

I’ve never understood how anyone could say something like this. Doesn’t the fact that when it is winter in the northern hemisphere, it is summer in the southern hemisphere give you any pause at all?

I understand that was I was told as a child, but 5th grade Earth Science class corrected that false notion.

[jaimehlers]

The belief that the Earth's elliptical orbit causes the seasons is as good an example as any of how conventional thinking can lead one astray.

As others have stated, it's the axial tilt that causes the seasons, but it isn't because one hemisphere is closer than the other.  It's because the tilt changes the angle of deflection.  It's the same basic reason why sunlight is reddish at sunrise and sunset - because the light has to travel through more atmosphere and thus loses energy.  It just isn't as obvious because the sun gets far enough above the horizon most places where people live that the light doesn't actually change color.  It's also the same basic reason why the sun in a polar region never sets during summer or rises during winter.

You know, I'll bet that's why the moon (and sun) appear so much larger when they're near the horizon - because the light is being spread out by the atmosphere then.  I never could quite figure that out.

[screwtape]

You know, I'll bet that's why the moon (and sun) appear so much larger when they're near the horizon - because the light is being spread out by the atmosphere then.  I never could quite figure that out.

Optical illusion.
http://science.nasa.gov/science-news/science-at-nasa/2005/20jun_moonillusion/

[inveni0]

The orbit isn't a perfect circle if thats what you mean, it's actually elliptical, hence why it's cooler in the winter and warmer in the summer.

WRONG

What you've shared is a common misconception.  We have seasons because of the tilt of the Earth, not the "shifting" orbit.

[inveni0]

You know, I'll bet that's why the moon (and sun) appear so much larger when they're near the horizon - because the light is being spread out by the atmosphere then.  I never could quite figure that out.

Optical illusion.
http://science.nasa.gov/science-news/science-at-nasa/2005/20jun_moonillusion/

THIS

You can actually test this theory by looking at the difference between the moon rise where I live and where I work.  I live where the tree line is MAYBE a half mile from my point of view.  So the moon rise is AWESOME.  The moon looks so freak'n huge against the tree line.  But, when I watch the moon rise at work, I see a TINY little thing.  That's because I have a 50-mile view to the horizon at my office.  So the visual effect is different.

EDIT:  I should also add that the moon's phases aren't caused by the shadow of the Earth.  I was actually TAUGHT this in school, and never thought about it until I bought a telescope.  While setting up the scope for first use, I looked at the moon.  Then, I looked at the sun.  They were both in the west.  Interesting, then, that the moon was crescent shaped.  I feel foolish for never thinking about what I was told.  And even more foolish for never NOTICING that it was wrong.  And it just goes to show you that we, as thinking creatures, should spend more time observing the world around us.

[Gohavesomefun]

Haha, I deserved that.

I do stand corrected. 

[JeffPT]

Haha, I deserved that.

I do stand corrected. 

Don't sweat it.  Until she was 39 years old, my wife had no idea how the moon gave off light.  Plus, you learned something new, which always makes for a great day. 

Movement is all about perspective.  The orbit of the Earth is what we've always heard it is, but what is left out is the fact that the sun is also moving rapidly through the galaxy.  Thus, our actual movement relative to outer space is sort of like a cork screw.  Our movement relative to the sun is elliptical.  Funny thing is, the galaxy is also moving through space, which adds a whole new wrinkle to it as well. 

[Gohavesomefun]

Not only does it ease the sting of an ambarrasing post, it also educates. Thank you Jeff and thank you wwgha

[Gnu Ordure]

From Bertrand Russell's ABC of Relativity:

Before Copernicus, people thought that the earth stood still and the heavens revolved about it once a day. Copernicus taught that 'really' the earth rotates once a day, and the daily revolution of sun and stars is only 'apparent'. Galileo and Newton endorsed this view, and many things were thought to prove it - for example, the flattening of the earth at the poles, and the fact that bodies are heavier there than at the equator.

But in the modern theory the question between Copernicus and earlier astronomers is merely one of convenience; all motion is relative, and there is no difference between the two statements: 'the earth rotates once a day' and 'the heavens revolve about the earth once a day'. The two mean exactly the same thing, just as it means the same thing if I say that a certain length is six feet or two yards. Astronomy is easier if we take the sun as fixed than if we take the earth, just as accounts are easier in decimal coinage. But to say more for Copernicus is to assume absolute motion, which is a fiction. All motion is relative, and it is a mere convention to take one body as at rest. All such conventions are equally legitimate, though not all are equally convenient.

A contemporary explanation here, which concludes:

the Earth revolves around the Sun or the Sun revolves around the Earth, depending on where you place the origin of your three-dimensional coordinate system.

[Cyberia]

@Gnu - That is true for any two-body system, but when you start adding more celestial bodies a justification arises for choosing one reference point over another.  For example:

You second quote is true, but now add in the other planets.  If you chose the Earth as the origin of the coordinate system, then the sun would indeed revolve around the Earth.....but NOT the other planets.  They would appear to have strange, unexplainable loopy orbits.  This was in fact the very reason the heliocentric model was discovered, because the orbits of the other planets were unexplainable, unless one posited the sun as the center of the system....then everything made sense.

[Gnu Ordure]

^^^

Actually, a girlfriend once said, as she was walking out the door one day, that I seemed to think the world revolved around me.

Not sure what she meant. She never came back to explain.

[Cyberia]

Oh that.....


Yes, the proper reference point for women is to assume the world revolves around them.  This solves many problems and is the scientific consensus. 

[Quesi]

Now I am NOT a scientist, so please correct me if I am wrong, but it seems to me that the spiral that they are talking about in the videos is just because the sun is actually moving along in the galaxy.  And so the planets are moving along with it to keep up.

Am I right?  Please tell me if I have no idea what I am talking about. 

And if so, they didn't take into account the fact that the whole galaxy is moving, so the diagram *could* become exponentially more complex. 

[Azdgari]

The sun isn't so much "pulling the planets along", as the planets are influenced by nearly the same external forces as the sun is.  The vector of gravitational pull on the sun strictly from the other objects in our galaxy is nearly indistinguishable from that on any of its planets, them being so close together and all.

[Gnu Ordure]

Oh that.....

Yes, the proper reference point for women is to assume the world revolves around them.

Really? Now you tell me. That explains a lot.

The fact that I'm still single. And the law-suits.

Yes, it's all making sense now...