Why Does Gravity Travel at the velocity of Light?
The dead cores of 2 stars collided 130 million yrs earlier in a galaxy somewhat far away.
The crash was so extreme that it originated a wrinkle in space-time– a gravitational wave. That gravitational wave and also the light from the stellar explosion traveled together throughout the cosmos. They arrived at Earth at the same time, at 6:41 A.M. Eastern on August 17th.
The occasion prompted worldwide headlines as the dawn of “multimessenger astronomy.” Astronomers got waited a generation for this moment. Nevertheless, it was also the first-ever direct confirmation that gravity travels at the speed of light.
The Speed of Gravity
We all know light obeys a speed limit– roughly 186,000 miles per second. Nothing travels faster. However, why should gravity travel at the same speed?
That question needs a quick dive into Albert Einstein’s general relativity, or concept of gravity– the same concept that predicted gravitational waves a century back.
Einstein overthrew Isaac Newton’s concept of “absolute time.” Newton believed time marched onward everywhere at an identical pace– regardless of how we people perceived it. It was unflinching. By that line of thinking, one 2nd on Earth is one second near a black hole (which he did not know existed).
Newton also believed gravity acted instantaneously. Distance did not matter.
It is All Relative
However, then Einstein revealed that time is relative. It changes with velocity and in the existence of gravity. 1 of the ramifications of that is that you can not have simultaneous actions at a distance. So the information of any kind has a finite speed, whether it is a photon– the light-carrying particle– or a graviton that carries the force of gravity.
“In relativity, there is a ‘speed of information’– the maximum speed that you can send information from one point to another,” says College of Wisconsin-Milwaukee physicist Jolien Creighton, an expert on general relativity and member of the LIGO group that first spotted gravitational waves.
Creighton explains that in electromagnetism, when you shake an electron, it produces a change in the electrica rea that spreads out at the speed of light. Gravity functions similarly. Shake a mass, and the change in the gravitational field– the gravitational wave– propagates at that same veloicty
“So, the fact that the veovcoty of gravitational waves is equal to the velocity of electromagnetic waves is mere because they both travel at the speed of information,” Creighton states.
There is an easy way to picture this, too. Imagine the sun vanished right now. Earth would not just drift into space instantly. After 8 minutes, Earth would go dark and simultaneously push off in a straight line.
Read the original article on discover magazine.
