By 'waves' do you mean sound waves? If so sound waves need to travel through things like solids, liquids and yup <u>gases. </u>When the waves travel they are vibrating the molecules in the matter. By doing this he molecules in solids are packed very tightly.
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I Would bc it's the better opportunity
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You get some type of pressure that you start to feel in your muscles and joints from gravity and movement. How do they say it? Something called "seat-of-the-pants" (something like that). You get some type of pressure, and your body senses it, and it knows when you are upside-down or not, because if you're not, then you won't get any pressure in your muscle.
Hope this helped!
Have a supercalifragilisticexpialidocious day!