Here is a concise summary of the provided text:
**Title:** Discovery of Gravitational Waves
**Key Points:**
1. **Introduction to Gravitational Waves**: On Sept 14, 2015, a phenomenon occurred where space around the Earth expanded, slowed, accelerated, and contracted, revealing the passage of a gravitational wave.
2. **Evolution of Gravity Concept**:
* Aristotle: heavier objects fall faster
* Galileo: all objects fall at the same speed (without friction)
* Newton: introduced gravity as a force
* Einstein: revolutionized understanding with General Relativity, proposing gravity as space-time deformation
3. **Gravitational Waves**:
* Predicted by Einstein, but deemed undetectable due to their weakness
* Caused by massive, accelerating objects (e.g., black hole mergers)
4. **Detection on Sept 14, 2015**:
* Result of 50-year effort by over 1,000 physicists, mathematicians, and engineers
* Used laser interferometry (LIGO) to measure minute space deformations
* Confirmed by simultaneous detection across three gravitational interferometers
5. **Impact**:
* Confirmed General Relativity predictions
* Awarded three Nobel Prizes in Physics and one Abel Prize in Mathematics
* Now, gravitational waves are detected almost monthly, revealing a previously unseen aspect of the universe.
Here are the key facts extracted from the text, numbered and in short sentences:
**Historical Facts**
1. Aristotle believed heavier objects fall faster than lighter ones.
2. Galileo showed that, without friction, all objects fall at the same speed.
3. Newton linked the fall of bodies to planetary motion.
4. Albert Einstein developed the theory of General Relativity in the early 1900s.
**Scientific Concepts**
5. Gravity is a force that attracts objects with mass.
6. According to Newton, gravity acts instantaneously across distances.
7. Einstein's General Relativity posits that gravity is not instantaneous, but propagates at the speed of light.
8. Space and time are inseparable, and modifying one affects the other (per General Relativity).
9. Massive objects deform the space around them, affecting trajectories (e.g., asteroid orbits).
**Gravitational Waves**
10. Gravitational waves are ripples in space-time caused by moving massive objects.
11. Einstein predicted gravitational waves, but thought they might be too weak to detect.
12. Gravitational waves were first detected on September 14, 2015.
**Detection Methodology**
13. The detection used an interferometer with two 4 km long vacuum tubes and mirrors.
14. The setup measured tiny changes in space-time by comparing laser beam paths.
15. To ensure accuracy, the mirrors were smoothed to the atomic level, and the device was suspended to avoid seismic vibrations.
16. Three gravitational interferometers on Earth confirmed the detection to rule out other explanations.
**Event of September 14, 2015**
17. The detected gravitational wave was from the merger of two black holes, each approximately 330,000 times the mass of Earth.
18. The event released energy equivalent to the mass of three suns, instantly vaporized into pure energy.
19. The wave traveled over 2 billion years before being detected, with a displacement of ~1/10,000th of a proton's diameter.
**Awards and Legacy**
20. The discovery led to three Nobel Prizes in Physics and one Abel Prize in mathematics.
21. The detection of gravitational waves has become relatively frequent, with almost monthly occurrences.