GPS satellites would become significantly inaccurate within hours if they didn't recalibrate according to Einstein's theories of relativity.

Scientists showed that the relativistic effect of time dilation was real after comparing atomic clocks flown around the world with stationary ones on Earth's surface.

Earth's core is about 2.5 years younger than its surface according to relativity

Gravity Probe B verified that rotating objects drag spacetime

The extreme precision of atomic clocks highlights gravitational time dilation

The underlying fabric of the universe—spacetime—changes shape in the presence of mass and energy, which affects measurements of space and time.

Uncertainties in measurements make finding gravity's Newtonian limit unclear

When GPS and sonar are unavailable, submarine navigation relies on a fiber-optic gyroscope to determine the vessel's orientation and an accelerometer to calculate distance traveled.

For the speed of light to be constant for all observers, space and time cannot be absolute, universal dimensions that are identical for everyone.

Satellites in low Earth orbit can experience changes in their orbits due to shifts in solar activity, which alter the amount of energy Earth's atmosphere receives and its resulting density.

Where you are located in a gravitational field affects how quickly you age

Scientists validated Albert Einstein's theory of gravity by measuring the apparent positions of stars via their starlight as it traveled near the sun on its way to Earth during a total solar eclipse.

According to the special theory of relativity, the faster objects move through space, the less they move through time, and therefore age more slowly.

Quantum mechanics and general relativity—two of the most successful explanations of the physics seen across the universe—are logically incompatible with one another because they use contradictory models for space and time.

Visualize how the order of events changes, according to special relativity, when the perspective is changed between observers who move relative to one another.

By discarding absolute space and time, special relativity introduces apparent paradoxes—scenarios in which different, equally valid observers obtain conflicting measurements.

Almost three centuries before Albert Einstein presented the special theory of relativity, Galileo Galilei devised a principle of relativity involving uniform motion.

Why time ticks faster on the moon, which may need its own time zone

The geoid depicts what Earth would look like if not for tides and currents, given the planet's rotation and uneven gravitational field.

Although the color of light changes due to motion between a source and an observer—the Doppler effect—relativistic motion further alters it due to time dilation.

While special relativity describes motion along flat spacetime—the underlying fabric of the universe—general relativity extends this theory to explain motion through curved spacetime.

Earth's rotation rate constantly changes, which drove the need for leap seconds to synchronize a solar day with timekeeping tools.

No map of the Earth is perfect because each introduces inaccuracies in the shape, size, or orientation of landmasses and oceans by trying to flatten the planet's curved surface.

Albert Einstein's theory of gravity arose from what he described as 'the happiest thought of his life': realizing that a person who fell off the roof of their house would not feel their own weight as they fell.

Experimenting with space-time

By measuring radio signals transmitted to and received from distant spacecraft, NASA's Deep Space Network can determine a spacecraft's position and speed and send commands to alter its trajectory.

Walk around Relativity Park—a virtual theme park where you can experience relativistic effects by slowing down the speed of light.

A breakdown of the experimental test results supporting the general theory of relativity

Individuals moving at different speeds may disagree on the order of observed events because each experiences the passage of time differently, according to special relativity.

Five surprising things your GPS can do

According to the equivalence principle, objects in a closed space cannot tell the difference between whether they are accelerating or experiencing a uniform gravitational field.

Discoveries in electromagnetism, which suggested that light traveled at a single speed, became the catalyst for overturning Isaac Newton's view that all speeds are relative.

Watch a visualization of what it would look like to move along Earth's surface as fast as the International Space Station, or about 23 times the speed of sound.

How neutron stars serve as laboratories for testing Einstein's theory of gravity

Although associated with his theories of relativity, Albert Einstein initially viewed the concept of spacetime, which originated with his teacher, Hermann Minkowski, negatively.

Observations of colliding neutron stars by the Laser Interferometer Gravitational-Wave Observatory in 2017 confirmed that gravity travels at the speed of light.

The moon is moving 3.8 centimeters farther away from Earth each year

Simulate the precession of Mercury's perihelion—the gradual shift in the closest point of Mercury's path around the sun as its elliptical orbit rotates.

Random positioning machines simulate the weightlessness of space, allowing researchers on Earth to study how space affects living things.

Potential LIGO sites were selected in pairs, approximately 3,000 kilometers apart

Scientists determine earthquake locations by comparing how long it takes different seismic waves to be detected at three stations around the world, from which an origin, or hypocenter, can be triangulated.

A spaceship traveling near the speed of light would experience relativistic aberration—its field of view will seemingly narrow into the direction of travel.

Railroads and long-distance communication led to the development of time zones, with Greenwich established as the prime meridian—the longitude of 0 degrees—due to British advancements in star mapping and navigation.

Because they move at the cosmic speed limit through space, photons—particles of light—do not 'perceive' distance or the passage of time.

The construction of LIGO needed to compensate for Earth's curvature

Gravity assists are crucial for space travel beyond Mars

If the Earth stopped spinning, about 85% of the world's population would experience supersonic winds.

Scientists define sea level as the elevation to which water would settle on Earth's surface, given the planet's gravitational field and rotation.

Watch some effects of special relativity become increasingly more apparent in 'A Slower Speed of Light,' a video game prototype from the MIT Game Lab.

Why do some people always get lost?

Mathematician David Hilbert developed general relativity equations before Einstein