Consider the following GIF The bike driver gained relatively large momentum from the ride. My question is, how the flip he made helped him reducing his momentum and landing safely?

The radius of the observable universe is about 46 Gly. Is that figure true for all current observers in our universe? Is it true if the universe is finite or infinite, flat or curved?

This question has confused me for quite some time now. I have searched it up online, and the basic answer is: 'Mass is a form of energy. When black holes die they release the amount of energy that they should. Mass is conserved.' But there's a problem with that answer. Energy is conserved, but ma...