| Elementary Particle:
A particle with no substructure (i.e. not made up of smaller particles) and which is therefore one of the basic building blocks of the universe from which all other particles are made.Quarks, electons, neutrinos, photons, muons and gluons (along with their respective antiparticles) are all elementary particles;protons and neutrons (which are made up of quarks) are not.
Energy:
Sometimes defined as the ability to do work or to cause change, energy is notoriously difficult to define. In accordance with the Law of Conservation of Energy, energy can never be created or destroyed but it can be changed into different forms, including kinetic, potential, thermal, gravitational, sound, light, elastic and electromagnetic. The standard scientific unit of energy is the Joule.
Entanglement:
The phenomenon in quantum theory whereby particles that interact with each other become permanently dependent on each other’s quantum states and properties, to the extent that they lose their individuality and in many ways behave as a single entity. At some level, entangled particles appear to “know” each other’s states and properties.
Entropy:
A measure of the disorder of a system and of its constituent molecules. More specifically, in thermodynamics it is a measure of the unavailability of a system’s energy to do work. The Second Law of Thermodynamics embodies the idea that entropy can never decrease, but rather will tend to increase over time, approaching a maximum value as it reaches thermal equilibrium. A classic example of increasing entropy is ice melting in water until both reach a common temperature.
Event Horizon:
A one-way boundary in space-time surrounding a black hole. Any matter or light that falls through the event horizon of ablack hole can never leave, and any event inside the event horizon cannot affect an outside observer.
Exogenesis:
The hypothesis that life on Earth was transferred from elsewhere in the universe. A related but more limited concept is that of panspermia, the idea that "seeds" of life exist already all over the universe, and that life on Earth may have originated through these "seeds".
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