What Is The Lifetime Of A Photon?

As you may have read somewhere, light only takes 8 minutes to cover the distance between the Sun and the Earth. Yes, that’s an insanely short time, considering that we are talking about 150 million kilometres! But the light that reach us is actually produced at the centre of the Sun, in its core, where nuclear reactions occur. So, have you ever asked yourself how long does light take to reach the surface of the Sun, starting from its centre?
Well, we may attempt to find a rough estimate. Consider that the Sun has a radius of “only” 696,000 kilometres (compared to the 150 million kilometres that separates it from the Earth)… so we would expect light to reach the surface in, let’s say, a few seconds, is it?
…you may be surprised to hear that this estimate is totally wrong! In fact, light takes… (drums)…. Thousands of years to reach the surface of the Sun!
Wait, what? How is that possible?
…curious to know how? Stick with us and we will tell you the answer in this video!
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Before talking about the journey of light from the centre of the Sun to the Earth, we need to do a short digression about light. Stick with us, it won’t be that long.
What is light? Well, light is something fascinating: in fact, it has a “dual” nature. What does it mean? It means sometimes it behaves as a wave, and sometimes it behaves as a particle. Let me tell you more.
In the past centuries, scientists believed that light was a wave. And they were right, but.. that was only half of the story. At the end of the 19th century, and precisely in 1900, in order to explain some weird phenomena that were puzzling scientists, the German physicist Max Planck postulated that light was actually consisting of particles, called “photons”. Planck’s idea found confirmation five years later, in 1905, when Albert Einstein (this guy again!) managed to successfully explain the “photoelectric effect” by using Planck’s idea. The photoelectric effect is a well-known phenomenon that occurs when light is shone at a material (metals, in particular) and electrons are emitted from its surface as a result. By thinking light as a wave, some aspects of this phenomenon could not be explained. For instance, if the frequency of light was under a certain threshold, no electrons were emitted from the material, no matter how strong the intensity of the light beam is. However, by thinking light as a “bunch of particles”, the photons, this effect could then be explained. In fact, each photon in the light beam carries a certain amount of energy, and when the photon hits an electron in the material, it gives all its energy to the electron, which is now able to “escape” the material. The energy of the photon depends on the frequency of the light beam: so if this frequency is lower than a certain threshold, the photon has not enough energy to allow the electron to “escape” the material. The intensity of the light beam only determines the number of photons in the beam: so it doesn’t matter if we increase the intensity, we will only have more photons, but none of them will be able to “free” electrons from the material, because none of them has enough energy to do that. For realizing this, Einstein won the Nobel Prize.
Now that we have realized that light consists of photons, let’s go back to our original topic: why does light take so long to reach the surface of the Sun?
To answer this question, we have to start by looking at what happens in the core of the Sun. As in every other star, the core of the Sun is the “motor” that produces all the energy and the light emitted by our star.
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Credits: Ron Miller
Credits: Nasa/Shutterstock/Storyblocks/Elon Musk/SpaceX/Esa
Credits: Flickr

Video Chapters:
00:00 Introduction
01:14 Dual Nature of Light
02:13 Photoelectric Effect
03:13 Nuclear Fusion in the Sun's Core
04:17 Photon's Chaotic Path
05:10 Photon Absorption and Re-emission
07:57 Photon's Journey to Earth
09:15 Photons from Distant Stars

#insanecuriosity #photon #science

[InsaneCuriosity]

When you are looking at the universe, you are looking at the past, isn't that fascinating?

[cryptocoinkiwi]

What is the lifetime of a Photon?

Zero. From the perspective of the photon.

[horizonbrave]

Hey I just wanted to say thanks for shedding some light on this.

[leonreynolds]

This video is not correctly named. The life of the photon was never said.

[TheSmurfboard]

Thanks for shedding light on this topic.

[moltoniron]

I use sun photons to charge my airpods with my pocket sized solar panels

[elck]

It’s almost tragically poetic that you can look back into the past but can only do it from a really far back distance.

[thebrotha]

Sorry to disappoint but the first thing you said about making light was wrong it takes 4 not 2 hydrogen atoms to make one helium atom. The sun actually converts 600 million tons of hydrogen into 596 million tons of helium every second.

[shubhamrana]

For a photo there is no time...time exist for everyone which doesn't travel with the speed of light...only a bystander would say that photon took xyz time to reach a planet or a star..but for a photon it just happened within an instant...physics is crazy

[nicklaskowalski]

It indeed takes light 8mns to reach us from the surface of the sun. That’s from our point of view though, for the photon it’s actually instantaneous.

[kirklorange]

To whom it may concern: the irritating voice-over made me leave the page after a couple of seconds.

[khrawbobsyiemlieh]

Photons experience no time at all. They live forever

[ericephemetherson]

Some addition to the video: as I understand this I have to say that photons accelerate during this walk from the center of the Sun to its surface for a photon (or anything else for that issue) cannot attain the speed of light in 0 time. Nothing happens in zero time. So, the photon accelerates. Also, what causes the speed of light? The video did not explain that. Where does the speed of light come from?

[danielraymadden]

all i know is if I lay in the sun to long I feel a burn

[edweinb]

A photon is not a chunk of stuff hurtling across space. It is an energy transfer from an electromagnetic field.

[rickseiden]

You didn't mention that when the photon is traveling at 300, 000 m/s that it "experiences" no time. At the speed of light, time stop, due to relativity. So it takes 10, 000, 000 years to leave the Sun, and then suddenly, time just stops for it.

[vegdqjp]

what propels the electron on journey to begin with and what sustains it to continue the long flight and when will it lose energy to travel any further?

[Kombrig_]

I love your videos, but this time you've made a serious mistake. Speaking of the long way photon make from the Sun's core, you said that he absorbed and radiated back & forth with ATOMS!?? I'm sorry, but the Sun has no atoms -- it is a giant ball of plasma. So, photons are collide with protons and neutrons -- nuclear materials, which are denser than the lead 10 000 times.

[Canna_Science_and_Technology]

In the beginning of the video, you say light takes thousands of years(58sec) then at around (7.58) you say 10 millions years?/ huh?

[davidgifford]

Why use a photo of M13 for Proxima Centauri? Photons not really explained