At particle colliders just like the Giant Hadron Collider, researchers faucet into Einstein’s equations within the seek for darkish matter particles. Credit score: Daniel Turbasa/Dreamstime.com
Does E = mc2 maintain true for darkish matter and darkish power?
Gary George
Cincinnati, Ohio
Sure — in brief, that is true for all types of matter and power, together with darkish matter and darkish power. However there are some vital particulars to contemplate.
E = mc2 is a particular case of the complete equation E2 = (mc2)2 + (computer)2. The time period computer represents the kinetic power of an object, which implies the acquainted E = mc2 is barely precisely true for objects at relaxation or in the identical relaxation body, the place the momentum p is zero. That’s why the mass (m) within the equation can be known as relaxation mass.
Normally, the a part of the equation containing the remainder mass is way bigger than the kinetic power. Then E = mc2 is an efficient approximation for every part that doesn’t transfer at a major fraction of the velocity of sunshine. And talking of sunshine, photons (the particles of sunshine and electromagnetism) are the opposite excessive of the complete equation. They haven’t any relaxation mass (in order that time period turns into zero) however they nonetheless have momentum and thus power.
The truth that kinetic power can be a part of the full power of particles is exploited by scientists at particle accelerators, just like the Giant Hadron Collider at CERN. By accelerating particles to almost light-speed, new particles will be created in head-on collisions which have much more relaxation mass than the unique ones. Researchers use this technique to seek for darkish matter particles by attempting to create darkish matter from the mass and power of different particles.
The equation even holds true for darkish power. The best technique to perceive darkish power is because the power held by the vacuum of area itself. So, even in essentially the most excellent vacuum with out a single particle of matter, there’s some tiny quantity of power. For instance, the darkish power content material for a sphere enclosed by the Moon’s orbit would solely equate to a mass of about 3 kilos (1.4 kilograms), which is definitely overshadowed by just about every part else inside that quantity. Nonetheless, because the universe is usually lots of empty area, this tiny quantity of power held by the vacuum of area quantities to nearly all of the full power content material within the universe. As a result of odd properties of darkish power, the gravitational pull generated by its mass equal is definitely overcome by its detrimental stress, which is the pressure driving the accelerated growth of the universe.
Christoph Saulder
Cosmologist, Korea Astronomy and House Science Institute, Daejeon, South Korea
