The US government has shutdown. After Senators were unable to agree on a budget plan—even a temporary one—on Friday, most government branches closed their doors until a compromise is reached.

Unfortunately, the scientific process doesn’t wait for politicians to resolve their differences. As such, government shutdowns have a particularly devastating effect on federally funded scientific research, as well as the citizens this research serves.

During government shutdowns, only “essential” government employees—those whose jobs are the most vital for the maintenance of government agencies—continue to show up to work. Essential employees are mainly those whose jobs directly involve the safety of human life or the protection of government property. Therefore, scientists employed by the US Geological Survey to monitor earthquakes will still be working, for example.

Every other government employee whose paycheck depends on the federal budget, and whose work is considered “non-expected” (read: non-essential), is put on unpaid leave until the shutdown ends. This includes the thousands of scientists employed by government agencies ranging from the National Park Service to the Centers for Disease Control, National Institutes of Health, and NASA.

The last government shutdown occurred in 2013 and lasted for 16 days, costing the US a total of $2.5 billion dollars and the furlough of 850,000 government employees. Agencies heavily staffed with scientists were some of the hardest hit by the shutdown: 98 percent of the roughly 2,000 National Science Foundation employees, nearly three-quarters of 19,740 NIH employees and two-thirds of CDC employees were placed on indefinite, unpaid leave until a compromise was ultimately reached.

According to Nature, at places like the NIH campus in Maryland, only a handful of technicians were kept around to care for the 1.4 million rodents and nearly 4,000 non-human primates at the facility. At the same time, a few “desperately ill” patients were able to enroll in clinical trials, but most had to wait until the government shutdown ended.

At the same time, the CDC had to roll back its programs for tracking diseases like the flu, hepatitis, and measles, while the EPA had to stop inspections at 1,200 hazardous waste, chemical and drinking water facilities.

In 2013, NASA was also testing a bevy of instruments for the James Webb Space Telescope and the already budget-strapped agency had to halt the testing process at a cost of about $1 million per day. Work is ongoing on the telescope, which is one of the few NASA spacecraft to have weathered two government shutdowns. The shutdown could also delay the launch of the Parker Solar Probe, which entered a vacuum chamber to begin environmental testing earlier this month. If these tests are significantly delayed by the shutdown, the probe may not be ready to launch later this year.

The shutdown has also affected SpaceX’s Falcon Heavy, which was supposed to test fire its engines for the first time last weekend. The massive rocket is now stuck on the launch pad due to a lack of support personnel from NASA that it needs to perform the test.

The Department of Energy’s National Labs, on the other hand, are less affected by government shutdowns. These labs generally do work that is directly related to national security and are overseen by contractors, which is why they aren’t as quick to be shutdown. But even the physicists there aren’t immune to congressional politics. Although the National Labs continued operating as normal during the last shutdown (and plan to do the same this time around), if it had lasted just two days longer, it too would have succumbed to the budget crunch and shuttered all but the most critical operations.

Even if the work of some of these scientists may not be directly related to human safety, invaluable scientific work is inevitably lost in the process of the shutdown, and in many cases government employees are legally barred from working once they are placed on unpaid furlough. For scientists, this means not only being shut out of their labs, but also barred from attending scientific conferences, isolating scientists from their colleagues at home and abroad.