Elon Musk believes he knew who built the pyramids of Giza — and they were not human.

In a tweet on Thursday, the Tesla founder wrote, “Aliens built the pyramids obv.”

He followed up by writing that Pharoah “Ramses II was 😎.”

Musk continued, writing that the “Great Pyramid was the tallest structure made by humans for 3,800 years. Three thousand, eight hundred years.”

In a subsequent tweet, he seems to back off his theory a bit by linking to a BBC article about the mystery of who built the pyramids, which he said “provides a sensible summary for how it was done.”

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Following Musk’s tweets, Egypt’s Minister of International Co-operation, Rania al-Mashat, extended an invitation for Musk to “explore the writings about how the pyramids were built” and also “check out the tombs of the pyramid builders. Mr. Musk, we are waiting for you.”

Meanwhile, BBC News reports that Egyptian archaeologist Zahi Hawass responded to Musk’s tweet in a short video in Arabic, posted on Facebook, dismissing Musk’s argument as a “complete hallucination.”

According to a translation in Egypt Today, Hawass declared that the “pyramids [were] built by Egyptians and I will tell you quickly the evidence,” and continued by laying out a series of archeological information about the pyramids.

“I found the tombs of the pyramids builders that tell everyone that the builders of the pyramids are Egyptians and they were not slaves,” he added, pointing out that their construction was “a national project of the whole nation.”