Hoc etiam magis haec animum te advertere par est
corpora quae in solis radiis turbare videntur,
quod tales turbae motus quoque materiai
significant clandestinos caecosque subesse.
multa videbis enim plagis ibi percita caecis
commutare viam retroque repulsa reverti
nunc huc nunc illuc in cunctas undique partis.
scilicet hic a principiis est omnibus error.
prima moventur enim per se primordia rerum,
inde ea quae parvo sunt corpora conciliatu
et quasi proxima sunt ad viris principiorum,
ictibus illorum caecis inpulsa cientur,
ipsaque proporro paulo maiora lacessunt.
sic a principiis ascendit motus et exit
paulatim nostros ad sensus, ut moveantur
illa quoque, in solis quae lumine cernere quimus
nec quibus id faciant plagis apparet aperte.
– Titus Lucretius Carus (Roman poet, 99BC-55BC),
The above are lines from Book II, lines 125-141, in Lucretius' De Rerum Natura.
Here is a prose translation to English, by John Selby Watson, 1851.
For you will see there, among those atoms in the sun-beam, many, struck with imperceptible forces, change their course, and turn back, being repelled sometimes this way, and sometimes that, every where, and in all directions. And doubtless this errant-motion in all these atoms proceeds from the primary elements of matter; for the first primordial-atoms of things are moved of themselves; and then those bodies which are of light texture, and are, as it were, nearest to the nature of the primary elements, are put into motion, and these latter themselves, moreover, agitate others which are somewhat larger. Thus motion ascends from the first principles, and spreads forth by degrees, so as to be apparent to our senses, and so that those atoms are moved before us, which we can see in the light of the sun; though it is not clearly evident by what impulses they are thus moved.
This is about Brownian motion. It was written a bit less than 2100 years ago.
[daily log: walking, 1km]