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It depends on size. And even larger asteroids, can become round.

Gravity is what causes celestial bodies to become round. I dont recall how large or massive an object has to be before it has a tendency to become round over time...

I recall someone once said that... Earth is smoother than a bowling ball.
That if you scaled up a typical bowling ball to be the size of earth... the surface of that bowling ball would actually be more irregular than Earth.

Jupiter and Saturn are both non-spherical--they rotate on their axes so fast they're notably ovoid.  Some stars are also non-spherical for similar reasons.

Celestial bodies with enough mass are drawn by their own gravity into spheroidal shapes.  Perfectly spherical, though?  Earth is not a perfect sphere either--its equatorial diameter is greater than its polar diameter, plus it's uneven, spheroidal, not spherical.

I knew there was a term for it but I could not remember what it was.

@PatriotAr15

Amusing with respect to the last.

Liberal is used in its true sense.  Classical liberalism was neither defined by Reagan nor is it the only form of true liberalism.  It is a particular set of philosophies and ideas within the broader liberal grouping and has its own particular traits (the sort of liberalism to which I subscribe is not classical) of which J.S. Mill is the best known flagbearer (a more modern example is Milton Friedman).  I don't use "liberal" to refer to Leftists outside of special or limited contexts, as generally Leftism is inherently illiberal.

The "fact" comes from the spec for billiard balls being badly written\ understood. The comparisons use the spec for allowable diameter as how spherical a ball is “All balls must be composed of cast phenolic resin plastic and measure 2 ¼ (+.005) inches [5.715 cm (+ .127 mm)] in diameter and weigh 5 ½ to 6 oz [156 to 170 gms].” They don't spec how round or smooth it is, just that it's a ball and can be up to .005 thou off on size.

Local variations in the earth moved down to scale of cue ball would be about as rough as sandpaper if you average it out more, it's about as smooth and round as a cue ball that would roll a little fucked up and would meet that misunderstood spec but not a new billiard ball.

here's some good nerd stuff on it: https://possiblywrong.wordpress.com/2011/01/03/is-the-earth-like-a-billiard-ball-or-not/

Then stuff gets squashed at the poles\ spreads at the equator due to spin so it go all oblate.

ETA: to answer OP question, mostly because they're really far away and our eyes suck. And the shit gravity everyone talking on.

An overstatement of sorts, but a good analogy to get people thinking about it.  The largest local bump on the surface of the Earth is going to be around 3 miles.  Hawaii, the Himalayas, Kilimanjaro, etc.  With the Earth's radius being roughly 4000 miles, that's a roughly 1:1000 deviation of scale - so, if you have a 4k monitor, you could draw a circle representing the Earth, say 2000 pixels in diameter (1000 pixels in radius).  Kilimanjaro would represent 3/4 of 1 pixel.

Our moon, on the other hand, the scale of the roughness of the surface is easily visible, just looking at the scale of the shadows of the craters during a waxing or waning lunar phase.  Then, going beyond that, the crater rims really stand out in profile during eclipses.

At max resolution, you can see the surface irregularities in profile.  Atmospheric distortion will play a role, too, but the Baily's Beads phenomenon just prior/after totality is a blinding example of just how pronounced the roughness is.





For scale of perspective, here's Jupiter, it's moons, and ours.  It's a composite photo only in that I moved the two closer together - original framing shown in the second photo...

[the red storm had moved out of view by the time I had set up to take this photo, and an eclipse shadow had also passed over the Jovian surface just an hour or so earlier - if I can get the focus absolutly spot-on, an eclipse might show up as one single dark pixel on the surface.]



and uncompressed framing ...



And even the sun has noticeable structure, even in unfiltered visible light....



Now, how much of the variance on the horizon is actual structure versus our own atmospheric distortion, or camera sensor/processing limits, I can't say.  But, I was able to get a lot of detail in the sun spots, so I think distortion was low(ish).

The best example I have of turbulent distortion is this one, as the moon is rising into Washington's wake...

Weird... when I first looked at Jupiter and its moons in your photo... I could have sworn I saw "orbit lines" encircling Jupiter/intersecting its moons. I was actually about to ask if you added the orbit lines in for demonstrative purposes, but then when I looked closely realized it was a strange optical illusion.

Possibly my brain filling in missing information. The cloud current "stripes" of Jupiter likely added to the illusion.

You took these photos yourself!? Man, I wish I could afford a decent telescope... but I live in a major metropolitan area... and light pollution would make it less worth it.

I miss seeing the night sky out in the country. People in cities and heavily populated areas in general, have *NO IDEA* what the night sky looks like out in the boonies. Its like a "night and day" difference. I remember when I lived in Wyoming, and I went into fairly remote areas...
In the city, you can only see a few star specks in the sky. But in the country, you can readily see nebula, and the spiral arm of the milky way galaxy.

They're my photos, yes.  But, just with a camera and a commonplace 80-400mm lens.  I don't have a telescope, though I'd like to have one.

Some of the photos were taken downtown, with no shortage of light pollution.  Bortle 7/7+ light pollution, or thereabouts.  So, light pollution, as much as I hate it, isn't necessarily a complete deal breaker in urban areas.

These two photos were taken after walking out of the bar.  Being able to show someone the 100% crop of the craters of the moon zipping across the LCD screen really made it worth it (and that's Jupiter to the left of the clock face).

 

DSLR.  And tripod.  At the bar.  Like an average, normal person.

Nikon D850 and an old 70-300 AF-D for the first photo, and a newer 80-400 AF-S for the second.

And usually a number of exposures are needed to be able to replicate what you might see in person.

If memory serves, the courthouse photo would have needed a focus on the moon, a focus on the clock tower, and even a separate focus on Jupiter if there is to be any hope of getting surface detail.  And two exposures settings, if you don't count the exposure on the focus frame for the clocktower - an exposure for the illuminated side of the moon, which would be good enough for the shape of Jupiter, and another brighter exposure for the stars/Jovian moons/earthshine.

So, that's about 4 frames, as everything is moving at a thousand miles an hour.

Somewhere, in all of that, there's going to be one frame that more or less captures the overall range of tones - that one frame may not have the best exposure for any one individual aspect, but it'll serve as a guide; something to ground the overall edit; hold it within reasonable bounds; usually.

Oh, and I was set up in the middle of the road, on the double yellow line to get the composition.

So, yeah, normal person stuff.  Perfectly.  Normal.

[looking back at my notes, the courthouse photo is a composite of 3 photos: a baseline photo for the illuminated side of the our moon and Jupiter; an exposure for earthshine on the shadowed side of the moon - and the earthshine exposure is the one where I pulled the stars and Jovian moons from; and an exposure/refocus on the clocktower, which was surprisingly close to my earthshine exposure setting in terms of exposure value.]

Or god created the mass and gravity and the relationship that results in spheres.

Saturn and Jupiter.  They're so choice.  If you have the means, I highly recommend swinging by...

Suck my balls, black-science man!

Hydrostatic equilibrium can help explain how gravity works over larger surfaces, you can also get impartial micro-gravity depending on how something is laid out (for instance, a hollow tube with one end being packed with uranium would have gravitational pull towards the uranium end). When you add a spin to water, the tension from van der waal (sp?) forces aren't in equalibrium in a sphere, so it will bulge on the circumference of spin and flatten on the axis.

"Oblate Spheroid"

Same way bubbles happen.

Bingo

There is a size/density mark where celestial objects become spheres, smaller astroids and formations haven't hit that mark yet.  

All celestial objects rotate because the cloud that formed them had a minuscule rotation cause by the gravity of passing objects.  As the cloud collapsed into a celestial object it spins faster and faster like a ice skater that pulls in her arms and spins faster and faster, the tighter her arms the faster she spins because her mass is closer to the axle.

So, magic.  Got it.

The opposite of that balloon.

For the same reason that a knife edge looks smooth, until you look at it under a microscope, but on the opposite side of the scale.  

The earth isn’t perceived as a perfectly round sphere when you’re in the mountains but you can’t see them on a planet when it’s 140,000,000 miles away.  

Because of scale and lack of gravity, a small asteroid is easier to see the imperfections in its shape.

Then gravity and rotation and shit.

Celestial bodies are just projections of light on the glass dome covering our flat earth.  If "they" wanted to, they could change them to be square shaped, or any other shape. It's just light from a giant projector. Ever seen a large telescope with a movable roof? It's not a telescope. It's actually a giant projector.

This one happens to have 2 projectors so it can project images in stereo for more realism.