Twitter can be a terrible place, but it’s also full of fun facts. Here’s one for today: it’s impossible to exceed the 70 pound weight limit of the US Postal Service’s (USPS) small flat rate box. The amount of osmium, a super dense metal, it would take to fill the box only weighs 61.5 pounds. Osmium is twice as dense as lead and about three times as dense as iron, which is what most dumbbells are made out of. Someone did the math, which is relatively simple.

The original poster was quick to point out that osmium is the densest substance on Earth. Before Neil deGrasse Tyson could hop into his mentions, he shared that filling the box with a neutron star would put the package about 30 trillion kilograms overweight. Twitter can be a fun place sometimes.

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If you remember your high school chemistry (I had to look it up), osmium is pretty much smack dab in the middle of the periodic table. Most of which don’t include density, only the symbol, atomic mass, and atomic number.

Osmium’s density is 22.6 grams per cubic centimeter. OP measured the inside dimensions of the small flat rate box and multiplied them to get the volume, 75.3 cubic inches. This is equal to 1,234.5 cubic centimeters. So all we have to do is multiply 22.6 x 1234.5. This gives us 27,899.7 grams, which is 61.5 pounds.

Because this is Twitter, people had opinions. Per the thread, we need to be even more specific. Osmium is the densest stable element on Earth. Scientists can make unstable elements in a lab, but they are radioactive and would instantly neutralize the box. And the people packing it for that matter. Other suggestions including filling the flat rate box with particles from the Large Hadron Collider, the weight of their mother’s expectations, or guilt. Definitely weighty items but again, hard to pack.

It also turns out that the osmium shipment would be worth over \$350,000, which will deter anyone from casually trying it. Someone did pack a chunk of tungsten into a small flat rate box, though. It weight 48 pounds and the videos of people trying to lift it are amusing.

Osmium was discovered in 1803 and early uses included gramophone needles and pen nibs. It gets its name from the Greek osme, meaning smell. Because apparently it smells bad. Speaking of osme, on Futurama, Nibbler poops dark matter. No word on whether Planet Express has a higher weight limit for packages than the USPS.

Melissa is Nerdist’s science & technology staff writer. She also moderates “science of” panels at conventions and co-hosts Star Warsologies, a podcast about science and Star Wars. Follow her on Twitter @melissatruth.