What are Gravity Waves?
Can you imagine that there could be wrinkles in space and time caused by some natural phenomenon in the universe? A gravitational wave is a wrinkle caused by a stellar crash of neutron stars. A discovery that happened in September 2015 but has been predicted by Einstein more than a century ago. Einstein suggested in 1916 that his general theory of relativity pointed towards the occurrence of gravitational waves, which are caused when very massive objects in space spiral towards each other and distort the fabric of time and space. This space-time distortion then sends ripples across the entire cosmos. This article will define gravitational waves and look at the gravitational wave equation along with a few other essential characteristics of the gravitational wave theory.
What Causes Gravitational Waves
To give a gravitational wave definition, first, we need to understand what happens in the cosmos. Many violent and forceful processes in the universe cause gravitational waves. Something special happens when two massive accelerating bodies like black holes, neutron stars, or planets orbit each other. Such movements can disrupt time and space, which would travel like ripples. Gravity waves would travel from the source like water in a pond would spiral out when a stone is thrown in it. The gravitational radiation then propagates in directions away from the source, carrying information about its origins. Gravity is a wave that also carries with it clues to the nature of gravity itself.
Cataclysmic events produce the strongest gravity waves. A few examples are black holes colliding, supernovae, huge stars that explode once they reach the end of their lifetime, and neutron star collisions. The other less strong waves are predicted to be created by the movements of those neutron stars that are not perfect spheres. The remaining gravitational radiation is believed to be remnants of the Big Bang.
When Were Gravitational Waves First Found and How?
Einstein was not entirely convinced by his own idea, though many scientists accepted his theory. For the next few decades, Einstein fiddled with his theory and published many papers that refuted his original idea.
The initial proof of the existence of gravitational waves came in 1974, 20 years after the death of Albert Einstein. In the Arecibo Radio Observatory (Puerto Rico), two astronomers discovered a binary pulsar. Pulsars look like a blinking star from afar, but they are planets that orbit the rapidly rotating neutron stars. These seemed to them exactly like the system that was predicted earlier to generate gravitational waves. The astronomers felt that this could be proof of Einstein's prediction years ago. Hence they started measuring how the orbit of these stars changed over time.
After 8 years, they found that these stars were getting closer to each other at a rate which the theory of general relativity aptly predicted if these were radiating gravitational waves. Since then, many astronomers have tried studying the pulsar radio-emissions and found similar results, but these results did not come through direct contact but either as a mathematical deduction or other indirect ways.
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Finally, on September 14, 2015, LIGO (Laser interferometer gravitational-wave observatory) found a breakthrough and proved the existence of gravitational waves, which were caused by the collision of 2 black holes that were 1.3 billion light-years ago but reached Earth only in 2015. This could be deemed as one of humanity’s biggest scientific achievements.
On October 3, 2017, the founders of LIGO Rai Weiss, Barry Barish, and Kip Thorne won the Nobel Prize in Physics for this discovery.
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Measuring Gravity Waves
A gravitational-wave observatory or detector detects the gravity waves. As a gravitational wave passes earth, it goes on squeezing and stretching the space. LIGO can detect this movement of space by gravitational waves. A LIGO observatory consists of two ultra-sensitive detectors. These identical L-shaped detectors are 4 kilometers long and situated in Washington and Louisiana. By employing lasers and mirrors, each of these detectors can catch tiny aberrations in spacetime, which the gravitational waves cause. If a gravitational wave crosses these arms, their length changes slightly. The laser bouncing back and forth between the two mirrors can track how far apart these mirrors are to an incredibly precise degree. A real signal will show up in both the detectors.
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Now another observatory, the European gravitational observatory’s detector, is also live, which has a similar design as LIGO. So, there are a total of three working observatories for gravitation waves in the world. This would help scientists precisely identify the source of the gravitational waves in space. Similar observatories are anticipated soon in Japan and India too.
Characteristics of Gravitational Waves
Gravitational waves can not be seen; they are invisible.
They are very fast and travel at the speed of light, 186,000 miles per second.
The gravity waves stretch and squeeze everything on their way as they pass by.
The objects that cause gravitational waves are very far away from earth and sometimes might not reach the earth if they are very weak. That is why these waves are very difficult to detect.
Though destructive and violent events cause gravitational waves, they are much smaller when they reach the earth (thousands of billions of times).
The gravitational waves that reach the earth result from an event that occurred billions of light-years ago.
FAQs on Gravity Waves
1. What are gravitational waves?
Gravitational waves are invisible ripples in the very fabric of spacetime. First predicted by Albert Einstein's theory of general relativity, they are created when massive objects, such as black holes or neutron stars, accelerate through space. These waves travel outward from their source at the speed of light, carrying information about the powerful cosmic events that created them.
2. What are the main causes of detectable gravitational waves?
The most powerful and detectable gravitational waves are generated by the most violent events in the universe. The primary sources include:
- The merger of two black holes into a single, larger one.
- The collision and merger of two neutron stars.
- A supernova, which is the explosive death of a massive star.
- Any rapidly accelerating, non-symmetrical massive object.
3. How do scientists detect gravitational waves on Earth?
Scientists detect gravitational waves using highly sensitive instruments called gravitational-wave observatories, with LIGO (Laser Interferometer Gravitational-Wave Observatory) being the most famous example. These facilities use lasers bounced between mirrors over long distances. As a gravitational wave passes, it minutely stretches and squeezes spacetime itself. This causes an infinitesimally small change in the distance the laser travels, which the detectors are sensitive enough to register as a signal.
4. What is the difference between gravitational waves and gravity waves?
While their names are similar, these are two completely different phenomena. Gravitational waves are ripples in spacetime caused by accelerating massive objects in the cosmos. In contrast, gravity waves are physical waves that occur in a medium, like a planet's atmosphere or ocean. They are generated when buoyancy or gravity tries to restore equilibrium to a fluid, creating phenomena like ripples on a pond or certain cloud patterns.
5. Why was the first direct detection of gravitational waves considered a major scientific breakthrough?
The first detection of gravitational waves in 2015 was a landmark achievement for two main reasons. First, it provided the first direct experimental proof of a major prediction from Einstein's theory of general relativity, about 100 years after he proposed it. Second, it opened an entirely new field of gravitational-wave astronomy, giving scientists a new sense to observe the universe and study events, like black hole mergers, that are invisible to traditional telescopes.
6. Do gravitational waves affect humans or have any noticeable impact on Earth?
No, gravitational waves have no noticeable effect on humans or Earth. By the time they reach us from distant cosmic events, their effects are incredibly tiny—thousands of times smaller than the nucleus of a single atom. While they are constantly passing through us, the stretching and squeezing of space is far too minuscule to be felt or to cause any impact on our daily lives.
7. How are gravitational waves different from electromagnetic waves like light or radio waves?
Gravitational waves and electromagnetic waves are fundamentally different. Electromagnetic waves (like light, X-rays, and radio waves) are oscillations of electric and magnetic fields that travel through spacetime. Gravitational waves, on the other hand, are oscillations of spacetime itself. A key difference is that electromagnetic waves can be blocked or scattered by matter, while gravitational waves pass through almost everything unimpeded, offering a clearer view of their source.
