# The hypothetical "top" and "bottom" of the Earth (better explained in OP) **URL:** \ **Category:** Factual Questions\ **Created:** [October 23, 2024, 11:26pm UTC](https://boards.straightdope.com/t/the-hypothetical-top-and-bottom-of-the-earth-better-explained-in-op/1009122 "2024-10-23T23:26:16Z")\ **Posts on this page:** 10\ **Page:** 3
**Author:** ![Little\_Nemo](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/little_nemo/32/3120_2.png) [@Little\_Nemo](https://boards.straightdope.com/u/Little_Nemo)\ **Post date:** [October 28, 2024, 12:26am UTC](https://boards.straightdope.com/t/the-hypothetical-top-and-bottom-of-the-earth-better-explained-in-op/1009122/41 "2024-10-28T00:26:45Z")
> [@Saint\_Cad](#): > > Little Nemo’s definition that the top is the direction of the Sun works perfectly on the flat earth if you assume gravity doesn’t exist. Wow, that is so far away from what I’ve been saying. ---
**Author:** ![Little\_Nemo](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/little_nemo/32/3120_2.png) [@Little\_Nemo](https://boards.straightdope.com/u/Little_Nemo)\ **Post date:** [October 28, 2024, 12:38am UTC](https://boards.straightdope.com/t/the-hypothetical-top-and-bottom-of-the-earth-better-explained-in-op/1009122/42 "2024-10-28T00:38:14Z")
> [@Pardel-Lux](#): > > That is how I understood it, but the tilt (that is why I wrote “inclined towards”, not “point in the direction of the sun”) is not always pointing towards the sun, it always points in the same sidereal direction, but as the Earth moves around the sun this direction (tilt) points towards the sun only once (or twice) a year. I’m not sure I’m following you here. As DPRK noted, the axis of rotation (the line connecting the two poles) never points directly at the sun. There is never any time when either the North Pole or the South Pole is the closest point to the sun. The Tropics of Cancer and Capricorn mark the northern and southern limits, respectively, of where the sun can be directly overhead at noon (which means that point if closest to the sun). As for axial tilt, it’s always counter-balancing. When one part of the Earth is tilted towards the Sun, it necessarily means another part of the Earth is tilted an exactly equal amount away from the Sun. So axial tilt is a local effect on Earth; some location on Earth might be tilted so it’s closer of father from the Sun. But the Earth as a whole is not closer or farther away. Again, maybe I’m misunderstanding the point you are making here. ---
**Author:** ![Irishman](https://avatars.discourse-cdn.com/v4/letter/i/b487fb/32.png) [@Irishman](https://boards.straightdope.com/u/Irishman)\ **Post date:** [October 28, 2024, 12:43am UTC](https://boards.straightdope.com/t/the-hypothetical-top-and-bottom-of-the-earth-better-explained-in-op/1009122/43 "2024-10-28T00:43:06Z")
> [@DPRK](#): > > OK, but I am not 100% certain how to parse that sentence. At any given moment, the Earth’s axis plus the Sun together define a plane, but what is its significance? I guess you are not talking about an equinox, because at that moment the axis is _perpendicular_ to an imaginary line connecting the Earth and the Sun. The Earth’s axis is tilted with respect to the sun. At equinox it is perpendicular to the line between the Earth’s center and sun. At solstice it is pointed toward/away from the sun. All other times it is at some angle to the line between the Earth’s center and the sun. ---
**Author:** ![DPRK](https://avatars.discourse-cdn.com/v4/letter/d/4491bb/32.png) [@DPRK](https://boards.straightdope.com/u/DPRK)\ **Post date:** [October 28, 2024, 1:04am UTC](https://boards.straightdope.com/t/the-hypothetical-top-and-bottom-of-the-earth-better-explained-in-op/1009122/44 "2024-10-28T01:04:22Z")
I thought we put paid to the idea that the axis is ever pointed _towards_ the sun, at solstice or at any other time. Declination at solstice is 23.4°, so that leaves 90 ± 23.4° degrees with respect to the axis. ---
**Author:** ![Irishman](https://avatars.discourse-cdn.com/v4/letter/i/b487fb/32.png) [@Irishman](https://boards.straightdope.com/u/Irishman)\ **Post date:** [October 28, 2024, 8:20am UTC](https://boards.straightdope.com/t/the-hypothetical-top-and-bottom-of-the-earth-better-explained-in-op/1009122/45 "2024-10-28T08:20:27Z")
I’m not saying the axis isn’t tilted from ecliptic vertical, I’m saying the tilted axis is co-planar to the line between the center of the Earth and the Sun. Define the reference axis on the Earth that is vertical to the ecliptic. Define a plane between the vertical axis and spin axis. Call it the Spin plane. When the spin plane points at the Sun, the rotation axis is 66.6° North/South of the line between the center of the Earth and center of the Sun. That’s what I mean by “pointed toward the Sun”. ---
**Author:** ![Machine\_Elf](https://avatars.discourse-cdn.com/v4/letter/m/82dd89/32.png) [@Machine\_Elf](https://boards.straightdope.com/u/Machine_Elf)\ **Post date:** [October 28, 2024, 9:30am UTC](https://boards.straightdope.com/t/the-hypothetical-top-and-bottom-of-the-earth-better-explained-in-op/1009122/46 "2024-10-28T09:30:50Z")
> [@Irishman](#): > > I’m not saying the axis isn’t tilted from ecliptic vertical, I’m saying the tilted axis is co-planar to the line between the center of the Earth and the Sun. _Any_ line through the center of the earth will be coplanar to the line between the center of the Earth and Sun, since they intersect at the center of the Earth. ---
**Author:** ![Pardel-Lux](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/pardel-lux/32/20182_2.png) [@Pardel-Lux](https://boards.straightdope.com/u/Pardel-Lux)\ **Post date:** [October 28, 2024, 10:31am UTC](https://boards.straightdope.com/t/the-hypothetical-top-and-bottom-of-the-earth-better-explained-in-op/1009122/47 "2024-10-28T10:31:58Z")
> [@Little\_Nemo](#): > > I’m not sure I’m following you here. It seems I am not able to explain it any better. Perhaps I’ll draw a sketch later, but it is not so important. ---
**Author:** ![Irishman](https://avatars.discourse-cdn.com/v4/letter/i/b487fb/32.png) [@Irishman](https://boards.straightdope.com/u/Irishman)\ **Post date:** [October 28, 2024, 11:16am UTC](https://boards.straightdope.com/t/the-hypothetical-top-and-bottom-of-the-earth-better-explained-in-op/1009122/48 "2024-10-28T11:16:53Z")
That’s why I went and defined the plane right after that. ---
**Author:** ![Irishman](https://avatars.discourse-cdn.com/v4/letter/i/b487fb/32.png) [@Irishman](https://boards.straightdope.com/u/Irishman)\ **Post date:** [October 28, 2024, 1:53pm UTC](https://boards.straightdope.com/t/the-hypothetical-top-and-bottom-of-the-earth-better-explained-in-op/1009122/49 "2024-10-28T13:53:02Z")
> [@DPRK](#): > > OK, but I am not 100% certain how to parse that sentence. At any given moment, the Earth’s axis plus the Sun together define a plane, but what is its significance? I guess you are not talking about an equinox, because at that moment the axis is _perpendicular_ to an imaginary line connecting the Earth and the Sun. Solstice. He means solstice. Earth’s spin axis leans in the direction of the Sun, or away from the Sun. Leans vs points. ---
**Author:** ![Timz](https://avatars.discourse-cdn.com/v4/letter/t/6a8cbe/32.png) [@Timz](https://boards.straightdope.com/u/Timz)\ **Post date:** [July 16, 2025, 11:48pm UTC](https://boards.straightdope.com/t/the-hypothetical-top-and-bottom-of-the-earth-better-explained-in-op/1009122/50 "2025-07-16T23:48:22Z")
“So imagine you pierced an orange from top to bottom with a metal straw, perfectly vertically. The holes at either end are the “top” and “bottom” of the orange. Now imagine you did that with the Earth.” You haven’t decided what you mean by “vertical”. When you’re holding the orange, you hang a plumb bob to see which direction is vertical, so you know which direction to run the straw thru the orange. The plumb bob points roughly toward Earth’s center. In other words, any line radiating from Earth’s center is (almost) vertical. And it’s still vertical out in space. A line from Earth’s center to Polaris – a line from Earth’s center to Rigel – a line from Earth’s center to Antares – they’re all vertical. So it’s up to you to decide what point on Earth is its top. Most of us imagine a line running thru Earth perpendicular to the plane of Earth’s orbit, and we think of Earth’s top as being the point where that line exits the Northern Hemisphere. But of course the other end is just as top. [Previous page](https://boards.straightdope.com/t/the-hypothetical-top-and-bottom-of-the-earth-better-explained-in-op/1009122.md?page=2)