It's the question those inside Oracle Team USA camp have been contemplating over the past five days: how are Team New Zealand so fast?
Even those that had hopefully tipped Emirates Team New Zealand to win the 35th America's Cup match had not expected the level of dominance shown by the Kiwi crew over the opening weekend of the first-to-seven series.
Stepping off the water following his fourth successive loss to the Kiwi team, Oracle skipper Jimmy Spithill admitted "it's obvious these guys are faster than us".
On Sunday (New Zealand time) we will find out if the US team, who pulled off the most audacious comeback in America's Cup - and possibly sporting - history, have been able to overhaul that speed differential over the past four days.
Even with the wounds of San Francisco having barely scabbed over, those within Team NZ remain quietly confident they have the right "package" to continue their dominance through the rest of the Cup match.
The Herald asked a selection of yachting designers and experts where they think Team NZ has the edge.
It is about the bike
The most obvious difference between the Kiwi boat and their rivals is Team NZ's innovative cycle grinding set-up. Much has been made about the advantage this gives Team NZ in being able to generate more power with less energy output from the crew on board.
But there are other benefits.
The streamline positioning of the "peleton" has creates less windage - something some experts believes would be a drawback to the system.
As it has turned out however, with the short courses and narrow boundaries, the grinders are spending a lot of time on their feet in order to be able to generate the power needed, rather than crouching low and grinding in an arrow-like position.
"And a lot of things people thought might be a problem, haven't been a problem," said Mark Reid, contributing editor of Bay and Delta Yachtsman, adding the innovation was a "spoke of genius".
"Everyone says 'yeah we explored that concept and we decided we didn't want to go with it', but I think it has created a bit of a stir how effective it is."
"There's a lot less wind resistance and less drag with the way the cyclors are positioned, as opposed to the grinders."
Team NZ designer Dan Bernasconi said the other big advantage the pedal-powered system gives them is it frees up the hands of the sailors, allowing Blair Tuke to trim the foils, effectively controlling the flight of the boat. Andy Maloney also has the ability to control the rake of the daggerboards from his cycling station, taking over the duties while Tuke is transitioning between hulls.
"We decided really early on to look at cycling, but it wasn't so much for the power source, it was so it would allow the sailors to have their hands free. We knew that these boats right from the beginning were going to be really power hungry, but with only six guys we wanted to have the opportunity to have three guys fulltime controlling the boat," said Bernasconi.
While Team NZ's radical cycle grinding set-up captured the headlines when Aotearoa was launched in February, chief operating officer Kevin Shoebridge said at the time the real magic lay in the boat's sophisticated control systems that were not so obvious.
During the past few weeks of racing we have learned a lot more about these control systems, with each of the America's Cup race boats fitted with on-board cameras. It has become apparent that Team NZ's wing trimming system is also radically different to their rivals.
Glenn Ashby, Team NZ's skipper and wing trimmer, controls the shape of the wing using a nifty hand-held device he refers to as his "little x-box console". Whereas the other wings are controlled by traditional winches, Ashby is able to make micro adjustments to the wingsail simply by adjusting toggles on control panel.
"I think Glenn Ashby's x-box wing trimming set-up is genius. There's a lot of ingenuity there," says Reid.
"They're just able to maximize little things in the way that the wing is set-up and the angles of attack. They're not looking to make up 20 seconds on the race course, they're just looking to make a few metres here and it all adds up."
You don't have to be a naval architect to pick up that Team NZ's foils also have quite a different look to them from the other boats.
You probably do need to be a naval architect to properly grasp why.
The "kinky" foils, which have a 'C' shaped bend in the tips, have been used on the New Zealand boat in light airs.
"The emphasis is lift over drag," explains Reid. "The extra kink creates high lift, but it is actually quite unstable. But it's like a fighter jet. If you can master that instability and work out how those extra flaps work, you can make the boat go really fast."
"You could see early on that they would get themselves in certain situations and they would become unstable, and I think they've really had to learn how to sail that boat."
The human element
The equipment is pretty handy, but you can't overlook the talent of the crew on board in making Aotearoa fly.
In Peter Burling, Team NZ have a confident and composed helmsman, who brings youth, energy and an appetite for taking risks, while Ashby is widely considered the best in the game when it comes to the art of wing trimming.
Reid points out the people behind the scenes are also impressive.
Compared with their rivals, Team NZ were noticeably under-raced coming into the regatta, and made some costly mistakes early on - particularly in their first two outings against Oracle during the qualifying series.
During the past three weeks Team NZ's efforts in the pre-start, tactical decision-making and course management has improved vastly. Reid believes that is all down to the input of performance coach Ray Davies.
"For me, Ray Davies is the calming influence in that team. He gives the locker room pep-talks and I think he is an integral part of what is happening with the dynamics of this team on and off the water."
"I don't know what he puts in Peter Burling's ear, or Blair Tuke's ear, but clearly he is exerting great influence on what's happening out on the water."
Without getting your protractor out, you also might notice Team NZ appear to be flying their boat at a slightly different angle to their rivals.
The New Zealand boat flies bow down and is cranked to windward, which is difficult to achieve and even more difficult to do so stably for sustained periods.
The "nose down" attitude is based on a similar physics to why there are spoilers on a race car - it creates counter-forces on the boat to prevent it from getting too much out of the water.
Yachting commentator Peter Lester says most teams are sailing bow down, but Team NZ are able to get the boat pitched at a windward heel.
"This means the windward elevator is getting more grip, which creates righting moment, giving it stability and speed," he explains.