Contents
What are gravitational waves?
According to Einstein's theory of general relativity, mass and energy curve spacetime.
When massive objects such as black holes or neutron stars move violently and asymmetrically, they create ripples that propagate through spacetime at the speed of light. Those are gravitational waves.
Why are they special?
- Do not require a medium to propagate.
- Can travel through a vacuum.
- Extremely difficult to detect due to the signal being incredibly weak.
In 2015, the LIGO observatory made the first direct detection of gravitational waves from the merger of two black holes, confirming a prediction that had existed for nearly 100 years from Einstein.
What are gravity waves?
Gravity waves are a type of mechanical wave that occurs when gravity acts as a restoring force to return matter to equilibrium.
Examples:
- Waves on the ocean surface.
- Tsunamis.
- Oscillations of air layers in the atmosphere.
In this case, it is the water or air that is oscillating, not spacetime.
Characteristics
- Must have a physical medium.
- Cannot propagate in a vacuum.
- Common in Earth's oceans and atmosphere.
Quick distinction
| Gravitational wave | Gravity wave |
|---|---|
| Oscillation of spacetime | Oscillation of water or air |
| Does not require a medium | Requires a physical medium |
| Can travel in a vacuum | Cannot travel in a vacuum |
| Generated by black holes, neutron stars, and extreme cosmic events | Generated by wind, gravity, terrain, or earthquakes |
Why are they often confused?
The primary reason is that their English names are very similar:
- Gravitational wave → Sóng hấp dẫn.
- Gravity wave → Sóng trọng lực.
Although both are related to gravity in some way, these two concepts belong to completely different areas of physics.
🌌 The simplest way to remember is: if the phenomenon can travel through a vacuum because spacetime itself is oscillating, it is a gravitational wave. If it requires water or air to oscillate, it is a gravity wave.
Further reading
References
- [1]Gravitational-Wave Transient Catalog (GWTC) — danh mục sự kiện và trạng thái các đợt chạy quan sát — LIGO–Virgo–KAGRA Collaboration / Gravitational Wave Open Science Center (2026)
- [2]The NANOGrav 15 yr Data Set: Evidence for a Gravitational-wave Background — The Astrophysical Journal Letters 951, L8 (2023)
- [3]Identification of strontium in the merger of two neutron stars — Nature 574, 497–500 (2019)
- [4]GW170817: Observation of Gravitational Waves from a Binary Neutron Star Inspiral — Physical Review Letters 119, 161101 (2017)
- [5]Multi-messenger Observations of a Binary Neutron Star Merger — The Astrophysical Journal Letters 848, L12 (2017)
- [6]Observation of Gravitational Waves from a Binary Black Hole Merger — Physical Review Letters 116, 061102 (2016)
- [7]A Joint Analysis of BICEP2/Keck Array and Planck Data — Physical Review Letters 114, 101301 (2015)
- [8]The Relativistic Binary Pulsar B1913+16: Thirty Years of Observations and Analysis — ASP Conference Series 328, 25 (2005)
- [9]Gravity wave dynamics and effects in the middle atmosphere — Reviews of Geophysics 41, 1003 (2003)
- [10]Capturing the ripples of spacetime: LISA gets go-ahead — European Space Agency (2024)
- [11]Glossary of Meteorology — mục “gravity wave” — American Meteorological Society (2024)
- [12]Tides and Water Levels — phân loại sóng mặt nước theo lực hồi phục — NOAA National Ocean Service (2024)
- [13]CODATA Recommended Values of the Fundamental Physical Constants — bán kính điện tích proton — National Institute of Standards and Technology (2022)
- [14]Phân biệt sóng trọng lực và sóng hấp dẫn — Thiên văn Việt Nam (VACA) — Đặng Vũ Tuấn Sơn (2017)
- [15]The Nobel Prize in Physics 2017 — Rainer Weiss, Barry C. Barish, Kip S. Thorne — The Nobel Foundation (2017)
Image: Brecht Corbeel - Unsplash
