Is the passage of three asteroids near Earth today just coincidental? I just saw in the advertisement-laden tabloid Express that three near-Earth astroids will pass the Earth today:


  
  The first of the three, dubbed Asteroid 2018 TU4, will come as close as 0.03637 astronomical units (au) or 14.16 lunar distances. around 3.13pm BST (2.13pm2 UTC)
  The next asteroid to pass the Earth is Asteroid SL3 at around 3.36pm BST (2.36pm BST).
  Lastly, Asteroid 2018 TS1 will come closest to Earth at around 3.45pm BST (2.45pm UTC) today.
  


Question: Is this just coincidental, or is there some relationship between these three particular asteroids, perhaps in the past, that would make their near-coincident arrival more likely?
It is just a coincidence, and isn't that uncommon of an occurrence. You can see a list of all such occurrences on this page. Looking at the specific orbital parameters, the orbits are very different. They range from an eccentricity of .2-.5, periods of 349-725 days, and otherwise are just plain different. There are 7 listed in the next week of a similar closeness, so having 3 on a single day isn't particularly uncommon. Much further then a week doesn't really matter because these were only spotted recently, they are all 3 quite small objects. The oldest detection of the 3 was only September 30, and one was only spotted on October 10th.