Some say there are five fundamental interactions: gravitational, electromagnetic, strong, weak and the exchange of birthday greetings on Facebook. But even if you prefer paper to pixels, Symmetry is here to help you celebrate another year. Try these five physics birthday cards, available as both gifs and printable PDFs.

Like two beams of particles in the Large Hadron Collider, your lives intersected. Tell a friend you’re grateful:

Like a neutrino, they may change over time, but you still appreciate their friendship:

Whether it's dark energy or another force that pushes them forward, it’s an honor to see them grow: ​

Let them know that, like dark matter, good friends can be hard to find:​

And you’re so glad that, like a long-sought gravitational wave or a Higgs boson, they finally appeared:​

Can’t wait to send your first card? We happen to know of a laboratory with a big day coming up on June 15.

Fermilab
PO Box 500, MS 206
Batavia, IL 60510-5011

(Or reach them on Facebook.)

Print setting recommendations:

Paper Size: Letter
Scale: 100 percent

How to fold your card:

Fold your 8.5 x 11 inch paper in half on the horizontal axis, then fold in half again on the vertical axis. Voilà!