What the heck is a photon?

I recently stumbled upon a very interesting explanation about what a photon is.
The link to the video is after the transcription I decided to make (for people like me that prefer reading)

What is a photon?

It’s just a packet of energy.

Calling a photon a “packet of energy” isn’t wrong.
It’s just not very useful because everything is a packet of energy.

There’s a better way to describe photons.
Yes, it’s a packet of energy, but it’s the details about that energy that make it a photon.

Anyway, a photon is the smallest piece of light.

We need to break a beam into smaller and smaller parts until we find something we can’t break anymore.

Light beams are giant collections of many electromagnetic waves.

If we focus on one of those waves, we can see a repeating pattern.
One cycle of that pattern is one wavelength of that wave.
There really isn’t anything smaller than this for a wave.
Is that a photon then? No.

We have a slight problem.

Light waves can be anywhere on the EM spectrum including the low-frequency end like radio waves.
A single radio wavelength can be as large as a small city.
I find it hard to believe a single photon could ever be that big.
Maybe we’re looking at this all wrong.
Elementary particles like photons don’t really have size anyway.

This is about energy.
It’s the energy we have to break into pieces.

Let’s start with a standard incandescent light bulb, for example, a 60-watt bulb.
That means it transforms 60 joules of electrical energy into heat and light every second.

Incandescent bulbs are terribly inefficient though so only about 10% of that actually becomes light.
When you turn it on, 6 joules of light leaves the bulb every second but that spreads out in all possible directions.

Eventually, we’re going to see gaps between those pieces.
Those tiny pieces of light energy are called photons,
but the amount of energy they have is very small.

You can calculate it using E = h * f.

The “h” is Planck’s constant, which is extremely small.
The "f" is frequency tells you what type of light it is and, in the visible range, it tells you color.

So the energy of a photon is a constant times its color.

For that 60 Watt light bulb, that’s 10 million trillion photons/second.

That’s a lot of photons.

Because individual photons don’t have that much energy, you have to get really far away to notice the gaps between them.

Let’s say you move away from the Sun at an unimaginable speed and somehow manage to avoid any of Einstein’s relativity. Eventually, way out in space, you start to notice the Sun’s light flicker.

What you’re seeing are individual photons.

Actually, the human optic nerve doesn’t send a signal to the brain unless at least 9 photons arrive within 100 milliseconds.

Alright, so humans can’t see individual photons, but that actually explains a few things.
If you move away from the Sun like we did earlier you can’t see the flicker of the photons, so at about 750 light years
the Sun’s light will just fade away into the blackness of space.

That’s why the night sky is mostly black lit by just a few nearby stars. The rest of the photons are just too infrequent for us to see.

So, what is a photon?

There are a lot of little packets of energy floating around the universe.
What makes some of them photons is all in the details.

Photons have a specific set of properties that make them photons:

• A charge of zero,
• a spin of 1 with two possible orientations,
• a rest mass of zero, which makes many things about photons possible.
• their speed of almost 300 million meters per second.
• their energy being proportional to their momentum
• their inability to experience time or space.

Any little packet of energy with those properties is, by definition, a photon.

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