In today’s Bulldog wrapup of science and technology news:

  • Facebook apologizes for overstating video view times
  • SpaceX indicates breach in helium system may have caused blast
  • Plus: Watch a slow-motion video replay of the launch pad blast
  • G-7 partners welcome U.S. robotic car guidelines
  • What were the reasons behind the Yahoo hack?

The details:

  • Facebook apologizes to advertisers for counting error

Facebook is apologizing to advertisers for what it calls an error that overstated the average length of time users watched videos on the site.

The measurement didn’t affect how much Facebook charges to run video spots, but analysts say ad agencies may have used the Facebook estimates as a key metric when they plan campaigns and decide how much advertising to place on Facebook or competing sites.

Facebook executive David Fischer said his company recently discovered its method of calculating the average viewing time didn’t include times when people watched a video for less than three seconds. That had the effect of making average times seem longer.

Fischer said Facebook has corrected the error, but analysts say it underscores the need for independent verification of such advertising metrics.

  • SpaceX: Accident points to breach in rocket’s helium system

SpaceX said Friday that evidence points to a large breachin the rocket’s helium system during a routine prelaunch test that turned into a devastating fireball three weeks ago.

The Falcon rocket and a satellite were destroyed in the Sept. 1 explosion, which occurred on the pad two days before the scheduled liftoff. Most of the wreckage has been recovered and is being analyzed.

In an update Friday, SpaceX said it’s still poring through video, audio and data from the moment the first sign of a problem occurs, until the actual fireball. That timeline covers less than one-tenth of one second. The data and debris indicate “a large breach” in thehelium system of the second-stage liquid oxygen tank.

  • VIDEO: Watch a replay of the explosion in slow motion at:

“All plausible causes are being tracked,” the company said on its website. There is no connection, the company stressed, with last year’s failed launch. That Falcon 9 rocketwas enroute to the International Space Station with supplies when it ruptured a few minutes into flight.

In that case, a support strut for a helium bottle apparently snapped in the second-stage oxygen tank, dooming the rocket. Helium is part of the pressurization system.

While the launch pad was damaged, nearby support buildings and fuel tanks were unscathed, according to the company. The control systems at the pad are also in decent condition. No debris appears to have strayed beyond the SpaceX-leased Launch Complex 40 at Cape Canaveral Air Force Station. Ground crews had been fueling the Falcon for a brief test-firing of the rocket’s engines; the launch pad was clear of workers for the test.

SpaceX continues to work on another pad, this one at neighboring Kennedy Space Center and once used to launch shuttles. It could be ready to support Falcon launches as early as November, depending on how the investigation goes. It is also preparing a launch pad in California.

Launches will resume “as quickly as responsible” once the cause of the accident is pinpointed, the company said.

SpaceX chief Elon Musk has called this the most difficult and complex failure in the private company’s 14-year history. Meanwhile, he is scheduled to address the International Astronautical Congress in Mexico on Tuesday, presenting his ideas for colonizing Mars and making humans an interplanetary species — his overriding ambition.

  • US guidelines on self-driving cars get good reception at G-7

U.S. Transportation Secretary Anthony Foxx said Sunday that his counterparts in the Group of Seven nations welcomed U.S. guidelines on regulating self-driving cars and have agreed to work together on creating such standards to maintain safety.

“There was actually a very enthusiastic reception to the policy,” he said. “We did a good job of inventorying what each country is doing and laying out areas that we want to explore further.”

Such issues include cybersecurity, ethics and privacy, wireless spectrum questions and many other issues, he said, while noting that reaching a resolution might take years, meaning the technology would be moving faster. Foxx called the U.S. guidelinesr eleased earlier this month the most comprehensive on autonomous vehicles, coming out ahead of the rest of the world.

Foxx and other transportation officials from the G-7 met over the weekend in the Japanese resort town of Karuizawa. Speaking by telephone with The Associated Press, Foxx stressed road tests on autonomous vehicles must continue to encourage innovation.

U.S. electric car maker Tesla’s Model S that was using the semi-autonomous mode crashed in May. The driver died after crashing into a tractor-trailer. Tesla is introducing improvements to its Autopilot system to make it safer.

“One of the things I think that autonomous vehicles suffer from is that they get compared to perfection, and not to the 94 percent of car crashes that are attributable to human factors. We have to make the right comparisons,” Foxx said, while declining comment on the ongoing investigation on Tesla. “These vehicles will not be absolutely perfect in terms of having no accidents, but by comparison they can be markedly better.”

Many automakers besides Tesla are testing or have rolled out automated vehicles, including Ford Motor Co., based in Dearborn, Michigan, and Nissan Motor Co. and Toyota Motor Corp. of Japan.

The new U.S. guidelines are meant to bring order to the technology’s development. Proponents say such technology can make cars safer because machines can react faster and they are less prone to human error. But even experts remain cautious.

  • What was motivation for Yahoo hack?

If a foreign government is behind the massive computer attack that compromised a half billion user accounts at Yahoo, as the company says, the breach could be part of a long-term strategy that’s aimed at gathering intelligence rather than getting rich.

Yahoo says the breach involved users’ email addresses, passwords and other information — including birthdates — but not payment card or bank account numbers. Although the stolen data could still be used in financial crimes, such as identity theft, experts say a foreign intelligence agency might combine the Yahoo files with information from other sources to build extensive dossiers on U.S. government or corporate officials in sensitive positions.

“With state-sponsored attacks, it’s not just financial information that’s of value,” said Lance Hoffman, co-director of the Cyberspace Security and Privacy Institute at George Washington University. “In the long run, if the state accumulates a lot of information on you, and especially if it corroborates that with other sources, it can assemble a pretty good profile.”

Governments have also been known to hack email accounts to keep tabs on their own citizens or dissidents. Experts believe that was one motive behind a 2010 hacking of Google Gmail accounts used by Chinese human rights activists.

Yahoo hasn’t revealed the evidence that led it to blame a “state-sponsored actor” for the latest attack, which the Sunnyvale, California, company said occurred two years ago and was discovered only in recent weeks.

Some analysts warn that “state sponsored” can be a vague term. It might also be an easy excuse to deflect blame for a company’s own security lapses, by suggesting it had no hope of defeating hackers who had all the resources of a government intelligence agency behind them, warned Gunter Ollmann, chief security officer at Vectra Networks, a San Jose, California, security firm.

Yahoo declined comment, but its top security official, Bob Lord, has said the company would make that claim only “when we have a high degree of confidence.” In a policy statement last year, Lord also said the company wouldn’t release details about why it believes attacks are state-sponsored because it doesn’t want to risk disclosing its methods of investigating breaches.