Mariah Carey and the holiday season are practically synonymous at this point.

While performing at the World AIDS Day Concert…Mariah took some time to sign a few autographs.

But to do that…she looked like she sat on a chair…except there was NO chair!

See the video evidence for yourself…how is she sitting on an invisible chair like that!?

In the video, her back and thighs form a perfect right angle.

Twitter has theories about how this move was even possible.

Some Twitter users speculated that it has something to do with the physics of her heels and the tight dress forming a resistance band-type effect.