Albert Einstein's theory of special relativity explains how space and time are linked, but it doesn't include acceleration. By including acceleration, Einstein later developed the theory of general relativity, which explains how massive objects in the cosmos distort the fabric of space-time. The theory explains how this distortion is felt as the force of gravity, as it predicts how much the mass of an object curves space-time. Scientists test relativity by observing objects in space and seeing if their behaviors match up with Einstein's explanations of space-time and gravity, for instance by observing how light bends around massive objects as it travels towards Earth.
The discovery that space and time combine to make a single continuum has permitted numerous breakthroughs in physics. Will scientists ever understand it at the small-scale levels?
An ancient supernova that was serendipitously captured in four Hubble space telescope images thanks to a naturally occurring cosmic magnifying lens has reappeared, as astronomers predicted.
Astronomers wanting more accurate measurements of distant black holes have some new assistants — robots that can tackle the tedious task of monitoring black hole neighbor clouds’ glow.
A quest to find ripples in space-time took a major step forward this week when the European Space Agency successfully launched the LISA Pathfinder mission into space.
Our universe is actually really simple, it's just our cosmological theories that are getting needlessly complex, argues one of the world's leading theoretical physicists.
Two black holes, circling one another on their way to merging together, can create ripples in spacetime, but the waves are weaker than previously thought.
Hawking and two colleagues propose that information isn't destroyed at the heart of a black hole; it's stored at the black hole's boundary in holographic form.
The famous theory, which Einstein published in 1915, remains the bedrock upon which scientists' understanding of the origin and evolution of the universe rests.
Albert Einstein's General Theory of Relativity celebrates its 100th anniversary in 2015. See the basic facts of Einstein's relativity in our infographic here.
A new way to reconcile quantum mechanics and general relativity could imply that the age of the universe is infinite, and that there was no true Big Bang that started it all.
Gravitational waves, invisible ripples in the fabric of space and time, might be detected by looking for the brightening of stars, researchers say.