<p>Of course it would have had some effects! Gravity obeys the mathematical function:</p>
<p><span class="math-container">$F = {G\ m_1\ m_2\over D^2 }$</span></p>
<p>where G is the constant of gravity (approx. <span class="math-container">$6.67430 \times 10^{-11} N m^2 kg^{-2}$</span>), <span class="math-container">$m_1$</span> and <span class="math-container">$m_2$</span> are the masses of each body, and <span class="math-container">$D$</span> is the distance between each body (center-of-mass to center-of-mass).</p>
<p>Supposing the robot’s mass is about as much as the planet’s mass, it would definitely have thrown it off-course as it approached the planet—but, then again, the planet would also have affected the robot’s course.</p>
<p>It would not, however, have “affected the planet’s gravitational forces,” as the gravitational force exerted by a body depends only on its mass.</p>
<p>I would presume, though, that there are,  on planet Cybertron (though we can’t see them on this image) bodies of water, or simply loose objects. These would have been affected by Unicron’s presence/approach, and would have been somewhat displaced by his presence/approach, as there was a force (basically) as strong as Cybertron’s gravity pulling them in the direction where Unicron was at that moment. Such objects on the opposite side of Cybertron may have been crushed (if they were not made very resistant), for example, and such objects on the side of Cybertron facing Unicron would have “lost their weight” (at least partly) and—no, not <em>float</em>—being easier to displace…</p>
<p>A lot is not know in the context of your question. Maybe reading the comix where this comes from would help know Unicron’s trajectory, etc., but I’ll leave that for others.</p>
<p>Be well!</p>

CC BY-SA 4.0
2020-11-29T23:29:29.180Z
In the context of the comic, Cybertron does not have bodies of water, which is made clear by its inhabitants not knowing what water is. It definitely does have loose objects though, as there are plenty of vehicles and computers and things like that. It probably also has large liquid bodies but these are of some other liquid than water.
user53739
CC BY-SA 4.0
2020-11-29T23:32:27.497Z
So, as I said, these “mobile” things would mostly and definitely be affected.

I also forgot to mention tidal forces. Parts of Unicron would obviously be closer to Cybertron than others — for example, on your image, is feet touch the planet, but his head is further. *HE* would be subjects to tidal forces, but so would *Cybertron*. This would have devastating effects on both.

In other words, this is completely fictitious and wouldn’t be possible in real life. ;-)
Pierre Paquette
CC BY-SA 4.0
2020-12-22T17:45:26.717Z
No reasonable assumption was made about the robot’s mass. Downvote.
Incnis Mrsi
CC BY-SA 4.0
2020-11-29T23:24:16.893Z
2020-11-29T23:24:16.893Z
Pierre Paquette
<p>I originally asked this at the sci-fi exchange but was told it was off-topic as it was about real-world science.</p>
<p><a href="http://www.unicron.com/images/background-full/1988_TFComics-bg2.jpg" rel="nofollow noreferrer">Here</a> is a picture of Unicron standing on top of the planet Cybertron, as written by Simon Furman and drawn by Geoff Senior in issue #75 of the Transformers comic.</p>
<p>Notice how Unicron is pretty much as tall of the planet's diameter. Assuming he was able to land there without causing the entire planet and himself to explode, wouldn't this have affected the planet's gravitational forces and possibly thrown it off its orbit?</p>

CC BY-SA 4.0
2020-11-30T03:46:06.453Z
It would be a great nuisance to be a space faring robot with mass close to that of a planet.  That massive, stuff would be gravitationally attracted to the robot and fall towards it.  Just maintaining a non spherical physical shape would be difficult.  Metal isn't strong enough to be a robot shape and a planet's mass.   Unless the robot was largely hollow and as a result low density, it would be very problematic and probably impossible.    Maybe this is better for world building?
userLTK
CC BY-SA 4.0
2020-11-30T04:18:32.220Z
@userLTK If we replace the robot with an inert object  that coalesces with the planet then it becomes an interesting orbital mechanics problem. All the time that it approaches it deflects the planet. But I guess the answer is (as always) yes, everything is always affecting everything gravitationally, and no, there's no specific orbit to be "thrown-off" of. So probably there's a good previous question to dupe this to.
uhoh
CC BY-SA 4.0
2020-11-30T14:17:44.290Z
Unicron (the robot in question) is able to transform into a spherical shape, so that would make it easier for him, I think.
user53739
CC BY-SA 4.0
2020-12-22T17:43:41.057Z
A planet-sized robot does not necessarily have such a great mass; it can—and should to be functional—be largely hollow. BTW worldbuilding.stackexchage.com would accept such a question.
Incnis Mrsi
CC BY-SA 4.0
2020-12-30T00:04:28.120Z
Voted to close. This has nothing to do with Astronomy. Worldbuilding.SE is the closest site, I think.
Rory Alsop
CC BY-SA 4.0
2020-12-30T00:23:48.593Z
I’m voting to close this question because planet sized robots are beyond the bounds of what is reasonable to manufacture. There can't be a reasonable answer to this that accepts the assumptions. and doens't invoke "magic"
James K
<planet><gravity><astrophysics>
How does a planet-sized robot standing on a planet affect its gravity?
user53739
# How does a planet-sized robot standing on a planet affect its gravity?

(Asked by: username_0 on 2020-11-29)

I originally asked this at the sci-fi exchange but was told it was off-topic as it was about real-world science.

[Here](http://www.unicron.com/images/background-full/1988_TFComics-bg2.jpg) is a picture of Unicron standing on top of the planet Cybertron, as written by Simon Furman and drawn by Geoff Senior in issue #75 of the Transformers comic.

Notice how Unicron is pretty much as tall of the planet's diameter. Assuming he was able to land there without causing the entire planet and himself to explode, wouldn't this have affected the planet's gravitational forces and possibly thrown it off its orbit?

**Tags:** planet, gravity, astrophysics

> **Comments:**
> **username_1**: It would be a great nuisance to be a space faring robot with mass close to that of a planet.  That massive, stuff would be gravitationally attracted to the robot and fall towards it.  Just maintaining a non spherical physical shape would be difficult.  Metal isn't strong enough to be a robot shape and a planet's mass.   Unless the robot was largely hollow and as a result low density, it would be very problematic and probably impossible.    Maybe this is better for world building?  
> **username_2**: @username_1 If we replace the robot with an inert object  that coalesces with the planet then it becomes an interesting orbital mechanics problem. All the time that it approaches it deflects the planet. But I guess the answer is (as always) yes, everything is always affecting everything gravitationally, and no, there's no specific orbit to be "thrown-off" of. So probably there's a good previous question to dupe this to.  
> **username_0**: Unicron (the robot in question) is able to transform into a spherical shape, so that would make it easier for him, I think.  
> **username_3**: A planet-sized robot does not necessarily have such a great mass; it can—and should to be functional—be largely hollow. BTW worldbuilding.stackexchage.com would accept such a question.  
> **username_4**: Voted to close. This has nothing to do with Astronomy. Worldbuilding.SE is the closest site, I think.  
> **username_5**: I’m voting to close this question because planet sized robots are beyond the bounds of what is reasonable to manufacture. There can't be a reasonable answer to this that accepts the assumptions. and doens't invoke "magic"  

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## 1 answers

### Answer by username_6 on 2020-11-29. Score: 1

Of course it would have had some effects! Gravity obeys the mathematical function:

$F = {G\ m\_1\ m\_2\over D^2 }$

where G is the constant of gravity (approx. $6.67430 \times 10^{-11} N m^2 kg^{-2}$), $m\_1$ and $m\_2$ are the masses of each body, and $D$ is the distance between each body (center-of-mass to center-of-mass).

Supposing the robot’s mass is about as much as the planet’s mass, it would definitely have thrown it off-course as it approached the planet—but, then again, the planet would also have affected the robot’s course.

It would not, however, have “affected the planet’s gravitational forces,” as the gravitational force exerted by a body depends only on its mass.

I would presume, though, that there are, on planet Cybertron (though we can’t see them on this image) bodies of water, or simply loose objects. These would have been affected by Unicron’s presence/approach, and would have been somewhat displaced by his presence/approach, as there was a force (basically) as strong as Cybertron’s gravity pulling them in the direction where Unicron was at that moment. Such objects on the opposite side of Cybertron may have been crushed (if they were not made very resistant), for example, and such objects on the side of Cybertron facing Unicron would have “lost their weight” (at least partly) and—no, not *float*—being easier to displace…

A lot is not know in the context of your question. Maybe reading the comix where this comes from would help know Unicron’s trajectory, etc., but I’ll leave that for others.

Be well!

> **Comments:**
> **username_0**: In the context of the comic, Cybertron does not have bodies of water, which is made clear by its inhabitants not knowing what water is. It definitely does have loose objects though, as there are plenty of vehicles and computers and things like that. It probably also has large liquid bodies but these are of some other liquid than water.  
> **username_6**: So, as I said, these “mobile” things would mostly and definitely be affected.  I also forgot to mention tidal forces. Parts of Unicron would obviously be closer to Cybertron than others — for example, on your image, is feet touch the planet, but his head is further. *HE* would be subjects to tidal forces, but so would *Cybertron*. This would have devastating effects on both.  In other words, this is completely fictitious and wouldn’t be possible in real life. ;-)  
> **username_3**: No reasonable assumption was made about the robot’s mass. Downvote.  

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