KarrothMelu is correct! And thumbs up to Sizzle for being smart enough. Now continuing with the science theme..

Score Table:

Cypher: 4
KarrothMelu: 3
Pupairo12: 2
Kick: 2
Spy: 2
Weresloth: 1
Scoobysnack: 1
Corbeil: 1
Malebolgia: 1
Andrew: 1
Maul: 1

Riddle number 21:

Lost in the woods, you come upon a mysterious stranger who hands you two large spheres made of two kinds of opaque marble. The spheres look the same, are the same size and have the same weight and apparent density; however, one is solid and the other hollow. The hollow sphere contains a tiny map that will enable you to navigate your way home. Unfortunately, you cannot break the spheres. The stranger agrees to open the sphere that contains the map only if you can determine which sphere is hollow. How do you determine which sphere is hollow and why?

Note: Hitting them to hear hollow sound will not work, there may be a couple of possibilities but I will not accept any except the specific one I have here.

as they miraculously weigh same its out of question to try and bob them under water. it will float or drawn the same way.

i would go for a xray scan or a ultrasonogram for ffs.

other than that i got no clue.

spin the spheres the one with the map inside will be unbalanced due to the map being forced to one side by centripetal force

love2scoobysnack wrote:spin the spheres the one with the map inside will be unbalanced due to the map being forced to one side by centripetal force

This is one of the better answers and would work, however, the point goes to the person to provides my chosen answer.

you would shake both of them to see which one is hollow bc the map is in the hollow one so you would hear it bouncing inside

Use the Force?

Clearly science is the topic that is outsmarting you people.

I shall leave this 1 more day and if no one gets it, continue on.

id say something to do with light refraction or clarity...wish i could explain myself better

Physics

Spinning the spheres as love2scoobysnack would work, though there is a little bit extra which was missing,

Inertia

Two spheres, one is hollow and the other is solid. They both have a mass m, radius r and a moment of inertia I.

Solid Sphere: Hollow Sphere: Subsituting the same values for the two spheres will always produce a greater moment of inertia for the hollow sphere. (m>0 and r>0)

When both spheres are spun, the hollow sphere with the map inside will have a greater moment of inertia hence it will spin for more time than the solid sphere.

Another solution would be to roll the two sphere's on a flat surface, as the hollow sphere has more inertia, it will roll for a greater distance than the solid sphere.

Cypher is correct! Well done!

My answer was; Roll the spheres on a level flat surface. The hollow sphere will roll further because its mass is distributed away from the center giving it a higher moment of inertia

New addition - I will change the theme every 5 puzzles, this next one will be the third of the science theme.

Score Table:

Cypher: 5
KarrothMelu: 3
Pupairo12: 2
Kick: 2
Spy: 2
Weresloth: 1
Scoobysnack: 1
Corbeil: 1
Malebolgia: 1
Andrew: 1
Maul: 1

Riddle number 22:

How and why are a ruby and sandpaper alike?