1. Astrophysicist Neil deGrasse Tyson talks about why there are limited Pyramids and the Eiffel tower

    Astrophysicist Neil deGrasse Tyson talks about why there are limited Pyramids and the Eiffel tower

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  2. Astrophysicist Neil deGrasse Tyson talks about the expansion of the Universe and the Big RIP

    Astrophysicist Neil deGrasse Tyson talks about the expansion of the Universe and the Big RIP

    3