On Monday night, Elon Musk and his company SpaceX made history by vertically landing the first stage of its Falcon 9 rocket after blasting off into orbital space ­­- equivalent of launching a pencil over the Empire State Building and landing it in a shoebox back on the ground, in the words of one expert. It was an enormous victory, a moment of history and elation for Musk and his SpaceX engineers, Jeff Bezos, currently the chief of rival rocket-builder Blue Origin, reminded the world Blue Origin was already a member of the vertical-landing club:

Congrats @SpaceX on landing Falcon's suborbital booster stage. Welcome to the club!

- Jeff Bezos (@JeffBezos) December 22, 2015

Mashable says that, Bezos showed terrible sportsmanship by waiting barely half an hour before tweeting at Musk's company with some shade. By way of context, Bezos is locked an intense rocket-measuring contest with Musk and still smarting from some insults Musk lobbed his way last month.

There are actually two putdowns in fewer than 140 characters in that tweet, testifying to Bezos's love of efficiency.

The most obvious is, of course, "welcome to the club," which reminds Musk that Bezos first landed a rocket back on earth last month - even though Bezos's rocket did not go as high as Musk's did. Bezos also launched his rocket in secret, only publicizing it when it was successful, while Musk did it publicly, risking public failure (but of course, getting a victory).

The second, more subtle Bezos putdown is "suborbital." Space is thought to start at 100 km above the Earth. If you get there while going at 8 km/second, you're orbital. If you're not, you're suborbital, which is just a little less impressive. Billionaires who have sunk millions of dollars into achieving the dream of private space travel, these distinctions matter.

Bezos tweet sparked dozens of comments, almost all of which criticized him for suggesting that what Blue Origin had done was on the same scale as SpaceX.

According to CNN, SpaceX rocket that landed Monday successfully launched satellites into orbit. The Blue Origin rocket that landed upright in November made a much shorter sub-orbital flight. The SpaceX rocket also was much taller than the Blue Origin rocket.

Musk also said in November that SpaceX flights had achieved a much tougher objective of reaching orbit. But its attempts to land those orbital rockets upright had failed in spectacular crashes.

Landing rockets upright is crucial to cutting the cost of space travel, since that means the rockets can be reused. Most rockets that have carried people or satellites to outer space over the last 58 years have been discarded after their launch, often burning up upon reentry.

It is, of course, a matter of intense irony that, when it came to a rocket launch, Bezos failed to rise above - both morally and scientifically. While Musk is a prolific tweeter, Bezos is still a novice, despite the fact that he was an early investor in Twitter. He has only tweeted five times.