The UniverseAnswer
Is gravity a force, or a bend in space and time?
The force picture and the spacetime picture explain the same world at different levels of detail.
TOPIC
relativity.
Stories and answers about #relativity
FROM THE QUESTION LIBRARY
Short answers, with sources.
The UniverseAnswer
Is time travel possible?
Travel into the future happens every day and has been measured; travel into the past is still an open question in physics, and here is why.
The UniverseAnswer
What is time, and why does it only seem to move forward?
Clocks really do disagree, rising entropy seems to give time its direction, and whether time flows is still debated, so here is what is measured, what is explained and what is open.
The UniverseAnswer
Why is the speed of light the universe’s speed limit?
The limit belongs to the structure of space and time; light in a vacuum travels at that limit because it has no rest mass.