How to Make Sure Your Eclipse Glasses Are Safe

Fox Photos/Getty Images
Fox Photos/Getty Images

You’re probably already preparing for the August 21 solar eclipse, right? It’s going to be spectacular, especially for those in the path of totality, which stretches across the U.S. from South Carolina to Oregon. No matter where you live, though, if you want to watch the eclipse, you should get ahold of some eclipse glasses. To make sure your glasses are up to safety standards, your specs need to follow a few guidelines from NASA before you look up.

First, you should be able to see the manufacturer’s name and address somewhere on the glasses. There are five brands of eclipse glasses that the American Astronomical Society has verified as meeting eclipse safety standards:

  • American Paper Optics
  • Baader Planetarium (only the AstroSolar Silver/Gold film)
  • Rainbow Symphony
  • Thousand Oaks Optical
  • TSE 17

You should also verify that the glasses list the correct certification information, confirming that they’re safe to use when looking directly at the sun. Somewhere on the glasses it should say that the glasses meet the ISO 12312-2 transmission requirements, and you’ll see an ISO logo from the International Organization for Standardization.

This is what your glasses should look like, according to NASA’s guidelines [PDF]:

An illustration of paper eclipse glasses with the necessary safety standards information circled in red

Even if your glasses have all the right information written on them, make sure to take a second look. Be careful not to use lenses that are wrinkled or those that have scratches on them. They should also be relatively new—don’t use any that are more than three years old.

We previously wrote about Warby Parker's free eclipse glasses, which you can pick up in the company's stores in August. We've reached out to the company about whether their glasses meet these guidelines and will update the story when we hear back.

Read the rest of NASA's eclipse safety recommendations here.

Update: Warby Parker has confirmed that their free eclipse glasses are made by American Paper Optics, a certified brand. View away!

Newly Uncovered Galileo Letter Details How He Tried to Avoid the Inquisition

Galileo Before The Papal Tribunal by Robert Henry. Hulton Archive, Getty Images
Galileo Before The Papal Tribunal by Robert Henry. Hulton Archive, Getty Images

Galileo Galilei was one of the Roman Catholic Inquisition’s most famous targets. As a result of his outspoken support for the theory that all the planets, Earth included, revolve around the Sun, the Catholic Church charged him with heresy and he spent the last years of his life under house arrest. Galileo was well aware that he was on the Church’s hit list, and a newly discovered letter shows that at one point, he tried to tone down his ideas to avoid persecution, according to Nature and Ars Technica.

The letter in question, written in 1613, solves a long-held mystery for Galileo scholars. It was found in the library of the Royal Society, where it has been for at least 250 years.

Galileo’s beef with the Catholic Church came about because of his support for heliocentrism—the idea that the solar system centers around the Sun—as advocated in Nicolaus Copernicus’s book De Revolutionibus. Galileo’s scientific writings clearly endorsed Copernicus’s theory of the world, including in personal correspondence that was widely disseminated, and in some cases, he directly questioned the scientific merit of Biblical passages.

In 1613, Galileo wrote to a friend and former student named Benedetto Castelli who was then teaching mathematics at the University of Pisa. The letter was a long treatise on Galileo’s thoughts on Copernicus’s ideas and religion, arguing that science and astronomy should not be overpowered by religious doctrin . (He would later expand this into his Letter to the Grand Duchess Christina.) As with many of Galileo’s writings at the time, the letter was copied and disseminated widely, and eventually, a friar named Niccolò Lorini forwarded it to the Inquisition in Rome in 1615.

This is where things get tricky. Galileo claimed that the version of the letter Lorini sent was doctored to be more inflammatory. He sent a less controversial version of the letter to a friend, saying that it was the original document and should be forwarded to the Vatican, essentially to clear his name. But scholars have never been able to be totally sure if he was telling the truth about the letter being doctored.

This newly discovered letter suggests that he was lying, and that he himself was looking to tone down his rhetoric to appease the Catholic Church and keep authorities from quashing the spread of heliocentric ideas. The original copy found in the Royal Society archives shows changes to the wording in what appears to be Galileo’s handwriting. The seven-page letter, signed “G.G.,” includes changes like swapping the word “false” for the more slippery “look different from the truth,” changing “concealing” to “veiling,” and other edits that seek to tone down the rhetoric that inflamed Church leaders. The wording and handwriting corresponds to similar writing by Galileo at the time. Based on this finding, it seems that Galileo did seek to make his ideas more palatable to the Catholic Church in the hopes of escaping persecution by the Inquisition.

Discovered on a research trip by science historian Salvatore Ricciardo of Italy's University of Bergamo, the letter may have been overlooked in the Royal Society archives because it was cataloged as being dated October 21, 1613 rather than the date it actually bears, December 21, 1613. However, it’s unclear how it came to the Royal Society in the first place. The document is the subject of a forthcoming article by Ricciardo and his colleagues in the Royal Society journal Notes and Records, according to Nature.

The minor changes Galileo made did not successfully hold off the Church’s crackdown on heliocentrism. In 1616, the Inquisition ordered Galileo to stop teaching or defending the theory, and several of his books were subsequently banned. He would stand trial again almost two decades later, in 1633, on suspicion of holding heretical thoughts. He was found guilty and sentenced to house arrest, where he remained until his death in 1642.

[h/t Ars Technica]

This Amateur Rocketeer Builds Functioning, Miniature Replicas of SpaceX Rockets

Jeff J Mitchell, Getty Images
Jeff J Mitchell, Getty Images

Amateur rocketry is a hobby that predates NASA. Hobbyists have successfully made it to space using rockets built without the massive budgets and resources available to larger organizations. And some of these rockets do more than reach incredible heights: As Motherboard reports, Joe Barnard, a 25-year-old rocketeer from Nashville, Tennessee, is working on making model rockets capable of propulsive landings, the same trick that makes some SpaceX rockets reusable.

Most rocket boosters that propel loads past the Earth's atmosphere are designed to go only one way. In 2015, Elon Musk's space exploration company SpaceX made history when it successfully maneuvered the boosters used to launch its Falcon 9 rocket back onto the landing pad. SpaceX says its latest version of the rocket can be re-flown up to 100 times, saving the company millions of dollars per launch.

Joe Barnard is bringing this same level of innovation to the amateur rocketry world. He first became interested in aerospace engineering after watching early SpaceX videos, and instead of earning a degree in the field, he taught himself the basics. He's since made rocketry into a career, founding Barnard Propulsion Systems (BPS), a small business that sells supplies to other hobbyists, and working on rockets of his own.

Like the rockets at SpaceX, Barnard's creations use thrust vectoring—the technology that makes it possible to navigate and stabilize a rocket after launch—only on a much smaller scale. He's built miniature models of SpaceX's Falcon 9 rockets, and as is the case at SpaceX, his launches don't always run smoothly.

Barnard is still perfecting propulsive landings in amateur rockets, but for now he says each failure is a learning experience. You can watch the progress of his experiments on his YouTube channel.

[h/t Motherboard]