In what is surely the most captivating national balloon news since a Colorado couple falsely claimed their 6-year-old was trapped inside a runaway weather balloon in 2009, the Pentagon announced late Thursday that it is tracking a high-altitude Chinese balloon flying over the U.S., which is allegedly being used for reconnaissance. On Friday, China countered the allegation, saying it was a rogue weather balloon that had been blown off course. The Biden administration isn’t buying that line, calling the balloon a violation of U.S. sovereignty, and in response has postponed Secretary of State Antony Blinken’s upcoming trip to Beijing. While many are taking advantage of this rare opportunity to make balloon jokes, Republicans are attacking President Biden for not blowing it out of the sky. Below is what we know about this developing story.

What could China be trying to spy on?

Arms-control expert Jeffrey Lewis tells Intelligencer’s Matt Stieb that balloons are inexpensive longer-term alternatives to satellites:

A satellite is going to constantly be in motion. It’s going to fall, it’s going to peer over the horizon, it’s going to pass overhead, and it’s going to be gone. A balloon has a more persistent quality to its monitoring and detection.

But Lewis also notes that wouldn’t make much sense for China to be surveilling nuclear missile sites this way:

Satellites move but silos don’t. The locations of our missile silos and of Chinese missile silos are extremely well known to each party. If you’re talking about optical imaging, I don’t think there’s much of an advantage to a platform like this compared with a satellite. My guess is it could have some other payload on it to collect different kinds of information. I’m just speculating, but maybe a signals-intelligence payload. If you’re using a radio and you turn on marine radar, you can collect those signals from space or a drone. You could see if radio towers are transmitting, but again, we’re a free country. So you could take an RF detector and drive around Montana and you can get much closer to the silos than a balloon can.

Read the rest of Matt’s interview with Lewis here.

Where is the balloon now? Where has it been? Where is it going?

As of midday Friday, the balloon was hovering over the central U.S. and moving eastward at an altitude of about 60,000 feet, according to the Pentagon, which would not confirm the device’s exact location. The big white balloon, which is expected to remain in U.S. airspace for a few more days, was apparently visible over northwest Missouri around 12:30 p.m. on Friday:

Pentagon officials say they monitored the balloon hovering over Montana on Wednesday, where it had apparently traveled after flying into U.S. airspace in Alaska over the Aleutian Islands.

Montana Republican senator Steve Daines told the Pentagon in a letter that he was concerned about the balloon’s proximity to the heart of America’s nuclear-armed intercontinental ballistic missiles, which are scattered across multiple bases in the Great Plains.

Why isn’t the U.S. shooting down the balloon?

Although the military reputedly readied fighter jets to shoot it down, President Biden reportedly opted not to pop China’s balloon after Defense Secretary Lloyd Austin advised him against such a move. Pentagon officials were concerned that “any potential debris field would be significant and potentially cause civilian injuries or deaths or significant property damage.”

Nonetheless, the Biden administration is taking a lot of flak for not attempting to capture the balloon or take it out. “SHOOT DOWN THE BALLOON!” Donald Trump wrote in a Truth Social message on Friday. A number of top Republicans have said the same: