Spacetime Questions

• Can gravity form waves?
• Does every black hole contain a singularity?
• Does the influence of gravity extend out forever?
• Does the negative mass of antimatter mean that it's gravitationally repelled from stars?
• Does time go faster at the top of a building compared to the bottom?
• How can there be anything left in the universe? Don't black holes suck everything in?
• How can we travel to the past?
• How can you tell a black hole made out of antimatter from a black hole made out of matter?
• How does a black hole give off light?
• How does looking at distant galaxies allow us to look back in time?
• How does the expansion of the universe make outer space a vacuum?
• Is a black hole a 2D or a 3D object?
• When does light travel in a straight line?
• Why is gravity not a real force?
• Why is time frozen from light's perspective?