Fact check - number of ants related

I was reading Quora and an answer to one question states that if all the ants on earth were laid end to end they could circle “about five times the diameter of the entire solar system!”

That’s seems implausible. What say the TMs?

Doing some quick checks…

Estimated diameter of the solar system 4.545 billion km (or 4.545 quadrillion cm, for ease of later comparisons).
Estimated number of ants on Earth - 10 quadrillion.

Average length of an ant… I cannot find any hard numbers. A quick look through various species and casts within them…I’d guess about 1cm is a safe estimate. (Anyone who knows better, please correct me.)

So, the length of all ants laid mandibles to abdomen would be about 10 quadrillion cm. So…assuming I haven’t done a conversion wrong*…‘only’ a bit more than twice the diameter of the solar system…which is still pretty impressive.

  • My checks are saying I’m good, but if I’m brain-farting at a fundamental level, not just messing up numbers, I could be repeating the same mistake repeatedly.

The answer depends on what diameter you assign to the solar system. There’s several possibilities:

  1. Just the planets, so use the semi-major axis of Neptune (30 AU)
  2. The “old” solar system, i.e. considering Pluto as the edge (39.5 AU)
  3. The outer edge of the classic Kuiper Belt (50 AU)
  4. The furthest distance that a known object (except comets) gets (936 AU)
  5. Planet nine (we don’t know where that is, so we can’t give a number but likely somewhere between 500 and 1000 AU)
  6. the Oort Cloud (1 lightyear or more)

There are 100,000 centimeters in a kilometer, not 1,000,000. So the diameter is 454.5 trillion centimeters. An average ant is .7 centimeters. There are 10 quadrillion ants in the world. So they have a total length of 7 quadrillion centimeters, which is about 15 times the length of the diameter.

What does it mean to say that they would circle about five times the diameter of the solar system? A diameter is not a circle. That’s a circumference. The circumference of the solar system is about 2.856 quadrillion centimeters. The ants would circle the solar system more than two and a half times.

  1. That’s the radius of Neptune’s orbit, not the diameter.
  2. Your conversion from kilo- to centi- is off – 1 km = 100,000 cm = 1,000,000 mm.

So, the diameter should be 0.9090 quadrillion cm.

10 / 0.909 is about 11, but if ants are more like 4.5 mm (which is plausible, but I don’t know), Quora would be accurate.

[Edit on preview: what dtilque said, but I think Neptune’s aphelion is another reasonable [Edit #2: radius, with its implied diameter] to use.]
[Edit on post: ninjaed by Wendell Wagner]

Oops, I meant radius.

And this is somewhere around 8100 AU (plus or minus a bunch).

Re: Neptune’s aphelion: that planet has a very circular orbit, so 30 AU works for either perihelion or aphelion. Pluto, on the other hand has a very non-circular orbit. I gave the semi-major axis for that.

I’m not sure how you would even calculate the average length of an ant, since you would not only have to know the average length for each species (and many species are made up of various castes that vary enormously in length), as well as the number of ants in each species (and between species colonies can consist of a few dozen workers into the millions).

This said, the estimate of 1 cm seems high to me, since many ant species, and possibly the most numerous ones, are quite small. Something like 4.5 mm might be more like it.

At any rate, the calculations given here suggest that the figures are within the right order of magnitude, at least.

I screwed it up too. Insert the word “radius” wherever I wrote “diameter”. I think the final calculations are correct though.

Does it make a difference if they orbit clockwise or antyclockwise?

Oops…yep, that is definitely a fundamental brainfart.

And I should have doublechecked the radius/diameter thing, but that seemed to be the most solid number I was likely to get, and didn’t bother.:smack:

Too bad Dorothy Parker isn’t around to provide a snappy answer.

It doesn’t help that most of them are sterile females.



Replace ants with E Coli and i presume the results will be spectacular too.

Yes, part of the issue here is just simple dimensionality. If you take a 3-dimensional volume of anything made up of small pieces and lay the pieces end to end you are likely to get something counterintuitively long.

I wonder if the biomass of ants vs (say) humans is similarly impressive?

ETA: to answer my own question - no, similar or less than humans.
Per this article, earthworms appear to be the biomass kings.

correct url
see rightmost column in table

Another solar system comparison: “… all the DNA in all your cells put together would be about twice the diameter of the Solar System.”

So, the real question is if you took the DNA from those ants and put it end-to-end … who would clean up all that mess?

DNA is really impressive, because the dimensionality thing does not apply: each chromosome is a continuous linear structure within the cell. The figure often cited is that all the DNA in a human cell is about 2m long if stretched out. So it requires sophisticated molecular machinery to pack it all up so it fits, but then to unpack it as necessary for transcription, replication, meiosis…

So if there are 1 x 10[sup]31[/sup] Prokaryotes, and the average size were 1µm(just picking a feasible and easy to work with number, not saying it is the true average size), there would be a 1 x 10[sup]25[/sup] meter (10 ym line of them).