Table of Contents
Co-founder and editor of Astronomy Hub.
Amateur astronomer over 20 years.
In 1905, Albert Einstein stated that the laws of physics are the same for all non-accelerated observers and that the speed of light in a vacuum is independent of the movement (speed) of the observers.
This theory is Albert Einstein’s “Special Theory of Relativity”. This theory gave a new structure to all physics and put forward the concepts of space and time together.
After 10 years, he added the concept of acceleration (g) to his theory and published the “General Theory of Relativity” in 1915. In this theory, Einstein determined that giant massive bodies cause bending in space-time due to intense gravity.
New Definition of Gravitational Force
Two objects exert a gravitational force to each other. This is called gravity. Your center of mass exerts a gravitational force on the Earth as the Earth pulls you towards its center — which allows you to stay on the ground without flying — but with less force.
Isaac Newton explained the force of attraction between objects with three laws of motion. However, Newton’s laws explain gravity as a natural force in which an object acts at a certain distance.
Albert Einstein stated in the “Special Theory of Relativity” that the laws of physics are the same for all observers, and the speed of light in a vacuum never changes regardless of the speed of the observers.
As a result, Einstein found that space and time are not independent of each other, but are intertwined space-time continuity. This theory suggests that the moment events occur for one observer may also occur at different moments for other observers.
While working on the “General Theory of Relativity”, Einstein realized that giant objects cause distortions in the space-time fabric. You can compare it to a trampoline with a large weight on it.
The weight placed on the trampoline will press down on the trampoline fabric and cause it to stretch.
Credit: NASA
Evidence of General Relativity
Although observation instruments cannot see or measure spacetime, several events related to spacetime warping have been experimentally confirmed.
Gravitational lensing:
A light source behind a massive body like a black hole bends due to the intense gravity of the black hole and creates a lensing effect. Astronomers use this method to study the stars and galaxies behind dense massive bodies.
The quasar called Einstein’s Cross in the constellation Pegasus (Winged Horse) is a very good example of gravitational lensing. This quasar is located about 8 billion light years from Earth and 400 million light years beyond a galaxy. (Galaxy between Earth and quasar)
Due to the gravitational lensing created by the galaxy, it refracts the light of the quasar and causes four points to be seen around the galaxy as shown in the picture.
Changes in the orbit of Mercury:
The orbit of Mercury changes over time due to the warping of space-time created by the Sun. It is possible for Mercury to collide with Earth in a few billion years.
Frame-dragging of the space-time frame around rotating objects:
Large-mass objects such as the Earth cause bending and distortion in space-time during their rotation around themselves.
The gyro axis of the precision-caliber Gravity Probe B satellite, which NASA sent in 2004, deviated over time, which confirmed Einstein’s theory.
Gravitational Redshift:
The electromagnetic radiation of an object extends slightly into the gravitational field.
When we think of the siren sound from an emergency vehicle; When the vehicle approaches the observer, the sound waves emanating from the vehicle are compressed, and when the vehicle moves away, the sound waves begin to expand. (This term for electromagnetic waves is called redshift.)
This phenomenon, called the Doppler Effect, occurs at all frequencies of the light wave. In 1959, two physicists, Robert Pound and Glen Rebka, sent a gamma ray of radioactive iron from a tower at Harvard University. They found that the beam had a lower frequency than its natural frequency due to gravity.
Gravitational Waves:
Violent events such as the collision of two black holes are thought to create gravitational fluctuations in space time. Laser Interferometer Gravitational Wave Observation (LIGO) detected first gravitational waves in 2015.
References
- Cover Image: One of the most perfect spheres ever created by humans. A fused quartz gyroscope for the Gravity Probe B experiment which differs from a perfect sphere by no more than a mere 40 atoms of thickness as it refracts the image of Albert Einstein in the background.
- Newton’s Law of Universal Gravitation Formula; licensed under the Creative Commons Attribution-Share Alike 4.0 International
- Einstein’s theory of general relativity predicted that the space-time around the Earth was not only deflected but also bent. Gravity Probe B satellite confirmed this prediction. Credit: NASA
- The image, which is thought to be a black hole, distortions occurred in the galaxy image behind the black hole due to gravitational lensing.licensed under the Creative Commons Attribution 4.0 International
- Numerical simulation of two merging black holes performed by the Albert Einstein Institute in Germany. (licensed under the Creative Commons Attribution 2.0 Generic)
Great article it presents evidence, but will there ever be proof of the General Relativity theory? What does it take to conclusively prove that it is true? Are there any plausible alternative theories proposed ?