I think that doesn't account on the effect of gravity on the cardboard. That mass would crush the center of the sphere, making it smaller. So more material would be needed, and more pressure to the core.
I don't get your concern.
Cardboard cutout is flat. We set the cutout to be the size of the sun. When the time starts affecting it, yes the gravity tries to collapse it onto the sphere but mass stays the same and gravity exerted "outside" is the same.
Even if it's flat, gravity works in that direction (radial).
Yes, and?
Put a sheet of paper vertical and let gravity do its work. What happens? Then think about a BIG "sheet" that has gravity by itself. You end up with a ball.
yes:
Is there even enough carbon on earth to form all the neccessary wood?
according to this paper all plant biomas would be 10^3^ times short
I’m just imagining earth as a flaming marshmallow now
Manual curation of great Lemmy discussions and threads
