What's light actually made of?

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asked May 7 in Science by Penuspenus (680 points)
What's light actually made of?

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answered May 11 by GrahamPolk (4,030 points)
Light is made up of photons.

Light is made up of particles called photons.

The photon is a type of elementary particle that serves as the quantum of the electromagnetic field, including electromagnetic radiation such as light and radio waves, and the force carrier for the electromagnetic force.

Photons are massless, so they always move at the speed of light in vacuum, 299792458 m/s.

Light is actually both a wave and a particle.

Light behaves as both particles and waves at the same time, and scientists have been able to observe this duality in action using an ultrafast electron microscope.

Humans can see visible light.

The human eye can only see visible light, but light comes in many other "colors"—radio, infrared, ultraviolet, X-ray, and gamma-ray—that are invisible to the naked eye.

On one end of the spectrum there is infrared light, which, while too red for humans to see, is all around us and even emitted from our bodies.

The visible light spectrum is the segment of the electromagnetic spectrum that the human eye can view.

More simply, this range of wavelengths is called visible light.

Typically, the human eye can detect wavelengths from 380 to 700 nanometers.

Darkness is not really made up of anything other than the absence of light.

Darkness occurs when the sunlight is blocked out so when the earth spins and then tilts the earth gets dark and then as it spins around again towards morning the light or daylight comes out again.

Darkness doesn't have any source like light has source.

It is just an absence, an absence of light.

Darkness, the direct opposite of lightness, is defined as a lack of illumination, an absence of visible light, or a surface that absorbs light, such as black or brown.

The darkness is not light, as an object which does not emit or reflect energy is truly 'dark. '

Darkness is light radiation which is in thermal equilibrium with its environment.

(It would be fair to say, by this definition, that the interior of the sun is dark.)

Unlike normal matter, dark matter does not interact with the electromagnetic force.

This means it does not absorb, reflect or emit light, making it extremely hard to spot. In fact, researchers have been able to infer the existence of dark matter only from the gravitational effect it seems to have on visible matter.

And every day, as Earth turns on its axis, the part of the planet you're standing on turns for a time so that you face into Earth's shadow.

When you face into the shadow, it's night.

When Earth turns so that you again face the direction of the sun, it's day.

During the day, sunlight floods our atmosphere in all directions, with both direct and reflected sunlight coming to us from everywhere we can see.

At night, the sunlight doesn't flood the atmosphere, and so it's dark everywhere in the sky that there isn't a point of light at, like a star, planet, or the Moon.

One lunar side always faces Earth, or is tidally locked, because the moon's rotation and orbit is closely synced-up with our planet's.

The moon spins about its axis and orbits the sun with Earth, so its night or "dark" side is constantly moving.

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