<p>If we assume the 15 CM per year is accurate (which I'm not 100% sure it is), then it's possible to answer this.  In a loose sense, yes, the pressure should move the moon away from the sun faster, but more accurately and the real answer is that doesn't happen because there are 3 bodies in play and when you have 3 body gravitation, things get a lot more complicated.</p>

<p>First, just for fun, a <a href="https://www.newscientist.com/article/dn17228-why-is-the-earth-moving-away-from-the-sun/" rel="nofollow noreferrer">source</a> for the 15 CM.</p>

<blockquote>
  <p>The moon away each year by photon momentum.The moon is the perfect
  color,size and The moon has a mass of 7.35 x 10²² kilograms. It is
  only about 60 percent as dense as Earth so it should be effected by
  the photons from the sun causing movement.And that movement should be
  combined with earths 15cm giving a new total distance a year right</p>
</blockquote>

<p>If we only look at equal force per surface area, which is what you're describing, it's not density, it's the ratio surface area to mass.  The Moon's surface area is about 7.4% of Earth's (about 1/13.5) and it's mass about 1/81st of Earths.  <a href="http://www.universetoday.com/20489/moon-compared-to-earth/" rel="nofollow noreferrer">Source</a>.  81/13.5 = about 6.  That means given equal pressure, the moon should accelerate 6 times as much which corresponds over small distances to 6 times the distance or 90 CM per year - BUT, that's if you ONLY take into account the pressure.</p>

<p>The effect of the sun losing mass has equal effect on both the Earth and the smaller Moon.  </p>

<p>And a 3rd factor to consider is the tidal bulge on the sun caused by the Earth-Moon system, which is very small but all these effects are small.   The Earth-Moon system creates a tiny bulge on the surface of the Sun and because the Sun rotates ahead of the Earth-Moon, that tiny tidal bulge has a tiny pull on the Earth-Moon system that slowly accelerates them and pushes them slowly away from the sun.  That effect is equal for both the Moon and Earth too.   </p>

<p>All 3 of those are factors in the 15 CM per year estimate and only one of them has 6 times the effect on the Moon than the Earth.   The planets Venus and Jupiter might also be factors in that 15 CM per year estimate too, but lets leave that alone for now.</p>

<p>If we consider the 3 body problem it gets very mathy, but I'll just talk about how it applies to solar pressure.   Lets start with a picture.  </p>

<p><a href="https://i.sstatic.net/OAdJP.jpg" rel="nofollow noreferrer"><img src="https://i.sstatic.net/OAdJP.jpg" alt="enter image description here"></a></p>

<p>When the Moon is waning its moving towards the sun and any pressure from the sun slows the moon down, (a tiny bit) and that slow-down moves the Moon closer to the Earth which speeds it up even more - funny how that works, pushing to slow something down in orbit and it goes faster - but that's how it works, cause potential energy converts to kinetic as the orbit drops, kinda like how falling makes things go faster.</p>

<p>When the Moon is waxing, it's moving away from the sun and any pressure from the sun speeds it up which moves it away from the earth and that in turn, slows it down.  So that's your answer in a nutshell.  The solar pressure doesn't push the moon away from the sun so much as it pushes the moon into a lower and then higher orbit around the Earth depending on where the Moon is in it's orbit around the Earth and the various positions in both the Moon's and Earth's elliptical orbits.  The overall effect is very difficult to calculate and I suspect it could go either way depending in part on the timing of large coronal mass ejections hitting the moon and in part on any possible resonance between the eccentricity of the Moon around the Earth and the Earth around the sun, er, I think.</p>

<p>What is safe to say is that the Earth-Moon system obeys the same surface area to mass ratio the Earth alone because that's simple momentum which needs to be conserved.    The Earth-Moon system has a combined surface area of 1.074 Earths and a combined mass of 1.012 Earths, so the Moon being in the Earth-Moon system makes the Earth move away due to solar pressure about 6% faster.  15 CM to 15.9 CM.  Not a very big change, and it's possible that the 15 CM estimate is based on the Earth-Moon barycenter not the Earth itself.</p>

<p>So, the effect is more of a wobble in the Moon's orbit around the earth than an actual force that pushes the Moon away from the sun faster than it pushes the Earth away.</p>

<p>All this, is, of-course, unimportant compared to the much bigger solar tidal force on the Earth-Moon system.   As the Moon gets closer to the sun (new moon in the picture above) The sun effectively pulls the Moon a little bit away from the Earth and when it's further from the sun (full moon), The Moon is effectively pulled towards the earth.  The net effect of this solar tide is a measurable wobble in the Moon's orbit around the earth.  The effect on the Moon's orbit around the earth due to photon pressure and coronal mass ejection pressure - basically insignificant.</p>

<p>Hope that's clear.</p>

CC BY-SA 3.0
2015-11-07T06:17:49.287Z
2015-11-08T12:00:48.933Z
2015-11-08T12:00:48.933Z
userLTK
<p>Could a planet's main use for natural satellites be that of a photon sail?<a href="https://i.sstatic.net/ehRuF.jpg" rel="nofollow noreferrer"><img src="https://i.sstatic.net/ehRuF.jpg" alt="enter image description here"></a></p>

CC BY-SA 3.0
2015-11-05T16:29:55.173Z
Are you confusing protons with photons from radiation pressure? If not, can you give sources for that number (15 cm)?
HDE 226868
CC BY-SA 3.0
2015-11-05T16:32:58.673Z
@-HDE 226868-I was in the moment,thanks for helping me
user5434678
CC BY-SA 3.0
2015-11-05T16:47:01.213Z
There is no mention of photon pressure in the link you provide: *...One idea is that the Sun is losing enough mass, via fusion and the solar wind, to gradually be losing its gravitational grip... Other possible explanations include a change in the gravitational constant G, the effects of cosmic expansion, and even the influence of dark matter. None have proved satisfactory.
... But Takaho Miura of Hirosaki University in Japan & three colleagues think they have the answer. In an article, they argue that the sun and Earth are literally pushing each other away due to their **tidal** interaction.*
Eubie Drew
CC BY-SA 3.0
2015-11-05T17:02:24.687Z
There's a formatting error in the link you put in the above comment. Click the blue 'help' at right when you are writing a comment to get formatting tips, including how to insert a link.
kim holder
CC BY-SA 3.0
2015-11-05T17:06:59.690Z
I believe that the moon is more responsible for this movement than the earth due to its color,size and tidal lock with the earth Aabaakawad the sun's photons are causing the increasing distance.The earth and moon are moving farther in distance due to the tidal interaction.The sun could never interact in the same way as the earth does with the moon.The sun does not treat planets like natural satellites there far to small.
user5434678
CC BY-SA 3.0
2015-11-05T17:12:37.307Z
The sun pushes the earth 15 cm away with photons each year link <https://www.quora.com/Do-photons-from-the-sun-push-the-Earth-with-a-significant-force> Is this source enough? or should I post another?
user5434678
CC BY-SA 3.0
2015-11-05T17:28:39.253Z
<http://ib-physics-ii-6b-e.aspen.high.schoolfusion.us/modules/locker/files/get_group_file.phtml?gid=4397333&fid=19334358>
user5434678
CC BY-SA 3.0
2015-11-05T17:37:20.007Z
@Mr.Cruz your quora link comes up page not found, you other long URL link creates a blank page.
Eubie Drew
CC BY-SA 3.0
2015-11-05T17:49:17.807Z
@kimholder I was referring to the link Mr. Cruz used to have in his Q. He has now removed it. That link was http://www.newscientist.com/article/dn17228-why-is-the-earth-moving-away-from-the-sun/ Mr. Cruz currently has the link http://ib-physics-ii-6b-e.aspen.high.schoolfusion.us/modules/locker/files/get_group_file.phtml?gid=4397333&fid=19334358 in his Q, which is a bunch of very good Physics problems, but there is nothing about the sun pushing the Earth.
Eubie Drew
CC BY-SA 3.0
2015-11-05T17:52:42.697Z
@Aabaakawad - Sure, i commented more in order to help Mr. Cruz get used to the ins and outs of posting.
kim holder
CC BY-SA 3.0
2015-11-05T17:54:17.923Z
@Mr.Cruz A further quote from the New Scientist article: *It’s the same process that’s gradually driving the moon’s orbit outward: Tides raised by the moon in our oceans are gradually transferring Earth’s rotational energy to lunar motion. As a consequence, each year the moon’s orbit expands by about 4 cm and Earth’s rotation slows by 0.000017 second.

Likewise, Miura’s team assumes that our planet’s mass is raising a tiny but sustained tidal bulge in the sun... According to their explanation, the distance between the Earth and sun is growing because the sun is losing its angular momentum.*
Eubie Drew
CC BY-SA 3.0
2015-11-05T17:57:08.100Z
@Mr.Cruz could you have confused photon momentum with angular momentum?
Eubie Drew
CC BY-SA 3.0
2015-11-05T22:20:54.580Z
No angular momentum happens every day in the oceans when photons collide with the oceans. Water reflects light best at a angle and that only occurs for such a short time of the day.So a body of water may look like a giant mirror but its is useless as a reflector or photons.
user5434678
<the-moon><the-sun><earth>
Does the Moon capture radiation pressure from the sun causing momentum from photon propulsion?
user5434678
# Does the Moon capture radiation pressure from the sun causing momentum from photon propulsion?

(Asked by: username_0 on 2015-11-05)

Could a planet's main use for natural satellites be that of a photon sail?[![enter image description here](https://i.sstatic.net/ehRuF.jpg)](https://i.sstatic.net/ehRuF.jpg)

**Tags:** the-moon, the-sun, earth
> **Comments:**
> **username_1**: Are you confusing protons with photons from radiation pressure? If not, can you give sources for that number (15 cm)?  
> **username_0**: @-HDE 226868-I was in the moment,thanks for helping me  
> **username_2**: There is no mention of photon pressure in the link you provide: *...One idea is that the Sun is losing enough mass, via fusion and the solar wind, to gradually be losing its gravitational grip... Other possible explanations include a change in the gravitational constant G, the effects of cosmic expansion, and even the influence of dark matter. None have proved satisfactory. ... But Takaho Miura of Hirosaki University in Japan & three colleagues think they have the answer. In an article, they argue that the sun and Earth are literally pushing each other away due to their **tidal** interaction.*  
> **username_3**: There's a formatting error in the link you put in the above comment. Click the blue 'help' at right when you are writing a comment to get formatting tips, including how to insert a link.  
> **username_0**: I believe that the moon is more responsible for this movement than the earth due to its color,size and tidal lock with the earth Aabaakawad the sun's photons are causing the increasing distance.The earth and moon are moving farther in distance due to the tidal interaction.The sun could never interact in the same way as the earth does with the moon.The sun does not treat planets like natural satellites there far to small.  
> **username_0**: The sun pushes the earth 15 cm away with photons each year link <https://www.quora.com/Do-photons-from-the-sun-push-the-Earth-with-a-significant-force> Is this source enough? or should I post another?  
> **username_0**: <http://ib-physics-ii-6b-e.aspen.high.schoolfusion.us/modules/locker/files/get_group_file.phtml?gid=4397333&fid=19334358>  
> **username_2**: @Mr.Cruz your quora link comes up page not found, you other long URL link creates a blank page.  
> **username_2**: @kimholder I was referring to the link Mr. Cruz used to have in his Q. He has now removed it. That link was http://www.newscientist.com/article/dn17228-why-is-the-earth-moving-away-from-the-sun/ Mr. Cruz currently has the link http://ib-physics-ii-6b-e.aspen.high.schoolfusion.us/modules/locker/files/get_group_file.phtml?gid=4397333&fid=19334358 in his Q, which is a bunch of very good Physics problems, but there is nothing about the sun pushing the Earth.  
> **username_3**: @Aabaakawad - Sure, i commented more in order to help Mr. Cruz get used to the ins and outs of posting.  
> **username_2**: @Mr.Cruz A further quote from the New Scientist article: *It’s the same process that’s gradually driving the moon’s orbit outward: Tides raised by the moon in our oceans are gradually transferring Earth’s rotational energy to lunar motion. As a consequence, each year the moon’s orbit expands by about 4 cm and Earth’s rotation slows by 0.000017 second.  Likewise, Miura’s team assumes that our planet’s mass is raising a tiny but sustained tidal bulge in the sun... According to their explanation, the distance between the Earth and sun is growing because the sun is losing its angular momentum.*  
> **username_2**: @Mr.Cruz could you have confused photon momentum with angular momentum?  
> **username_0**: No angular momentum happens every day in the oceans when photons collide with the oceans. Water reflects light best at a angle and that only occurs for such a short time of the day.So a body of water may look like a giant mirror but its is useless as a reflector or photons.  

---

## 1 answers

### Answer by username_4 on 2015-11-07. Score: 3 | Accepted answer

If we assume the 15 CM per year is accurate (which I'm not 100% sure it is), then it's possible to answer this. In a loose sense, yes, the pressure should move the moon away from the sun faster, but more accurately and the real answer is that doesn't happen because there are 3 bodies in play and when you have 3 body gravitation, things get a lot more complicated.

First, just for fun, a [source](https://www.newscientist.com/article/dn17228-why-is-the-earth-moving-away-from-the-sun/) for the 15 CM.

> The moon away each year by photon momentum.The moon is the perfect
> color,size and The moon has a mass of 7.35 x 10²² kilograms. It is
> only about 60 percent as dense as Earth so it should be effected by
> the photons from the sun causing movement.And that movement should be
> combined with earths 15cm giving a new total distance a year right

If we only look at equal force per surface area, which is what you're describing, it's not density, it's the ratio surface area to mass. The Moon's surface area is about 7.4% of Earth's (about 1/13.5) and it's mass about 1/81st of Earths. [Source](http://www.universetoday.com/20489/moon-compared-to-earth/). 81/13.5 = about 6. That means given equal pressure, the moon should accelerate 6 times as much which corresponds over small distances to 6 times the distance or 90 CM per year - BUT, that's if you ONLY take into account the pressure.

The effect of the sun losing mass has equal effect on both the Earth and the smaller Moon.

And a 3rd factor to consider is the tidal bulge on the sun caused by the Earth-Moon system, which is very small but all these effects are small. The Earth-Moon system creates a tiny bulge on the surface of the Sun and because the Sun rotates ahead of the Earth-Moon, that tiny tidal bulge has a tiny pull on the Earth-Moon system that slowly accelerates them and pushes them slowly away from the sun. That effect is equal for both the Moon and Earth too.

All 3 of those are factors in the 15 CM per year estimate and only one of them has 6 times the effect on the Moon than the Earth. The planets Venus and Jupiter might also be factors in that 15 CM per year estimate too, but lets leave that alone for now.

If we consider the 3 body problem it gets very mathy, but I'll just talk about how it applies to solar pressure. Lets start with a picture.

[![enter image description here](https://i.sstatic.net/OAdJP.jpg)](https://i.sstatic.net/OAdJP.jpg)

When the Moon is waning its moving towards the sun and any pressure from the sun slows the moon down, (a tiny bit) and that slow-down moves the Moon closer to the Earth which speeds it up even more - funny how that works, pushing to slow something down in orbit and it goes faster - but that's how it works, cause potential energy converts to kinetic as the orbit drops, kinda like how falling makes things go faster.

When the Moon is waxing, it's moving away from the sun and any pressure from the sun speeds it up which moves it away from the earth and that in turn, slows it down. So that's your answer in a nutshell. The solar pressure doesn't push the moon away from the sun so much as it pushes the moon into a lower and then higher orbit around the Earth depending on where the Moon is in it's orbit around the Earth and the various positions in both the Moon's and Earth's elliptical orbits. The overall effect is very difficult to calculate and I suspect it could go either way depending in part on the timing of large coronal mass ejections hitting the moon and in part on any possible resonance between the eccentricity of the Moon around the Earth and the Earth around the sun, er, I think.

What is safe to say is that the Earth-Moon system obeys the same surface area to mass ratio the Earth alone because that's simple momentum which needs to be conserved. The Earth-Moon system has a combined surface area of 1.074 Earths and a combined mass of 1.012 Earths, so the Moon being in the Earth-Moon system makes the Earth move away due to solar pressure about 6% faster. 15 CM to 15.9 CM. Not a very big change, and it's possible that the 15 CM estimate is based on the Earth-Moon barycenter not the Earth itself.

So, the effect is more of a wobble in the Moon's orbit around the earth than an actual force that pushes the Moon away from the sun faster than it pushes the Earth away.

All this, is, of-course, unimportant compared to the much bigger solar tidal force on the Earth-Moon system. As the Moon gets closer to the sun (new moon in the picture above) The sun effectively pulls the Moon a little bit away from the Earth and when it's further from the sun (full moon), The Moon is effectively pulled towards the earth. The net effect of this solar tide is a measurable wobble in the Moon's orbit around the earth. The effect on the Moon's orbit around the earth due to photon pressure and coronal mass ejection pressure - basically insignificant.

Hope that's clear.


---

