Does Light Experience Time? - Ask a Spaceman!

What does ‘time’ mean for light? What is the real lesson of the twin paradox? How can we all agree on the true age of the universe? Why is it all so technical? I discuss these questions and more in today’s Ask a Spaceman!

Keep those questions about space, science, astronomy, astrophysics, and cosmology coming to #AskASpaceman for COMPLETE KNOWLEDGE OF TIME AND SPACE! Music by Jason Grady and Nick Bain.

[clulesskid]

8 minutes just to be told that we're not allowed to ask that question.

[AstroRamiEmad]

You are so good that you make me doubt your logic ... If frame of reference can't go in the speed of light, it doesn't mean that light can't be it's own frame of reference outside relativity

I mean if relativity can't answer this question, it's a limit of the theory and not of light

[mrdooley]

Mind blown.
In addition to it being my wife’s favorite comeback. “Son, that was the question to ask.

[Fabi]

Nein Nein Nein Nein Nein Nein Nein Nein Nein Nein Nein Nein :D

[ariessweety]

Wow only 19k subscribers?? What the? You deserve so many many more. I know you'll get there though. Your so smart and an awesome great teacher too. Everyone would be so much smarter if they just watched your videos. Thats all you need ppl, is to watch Paul M Sutter and you'll have an EXTREMELY wrinkly brain 😝😝 I gotta say tho, this one really got me. I thought i had it but then i lost it. Pretty difficult for me to grasp. Anyway once again, great video teacher. My number one love in life is space science. So thank you for making these videos and spreading your smartness haha! Have a lovely day. ❤

[leighmcgaughy]

Mind blown!!! This makes me wonder if light is part of the fabric of the universe, or a function of it. Your content is my favorite on YouTube. It is your excellent ability to explain these concepts that makes me see how difficult these scientific questions are. Do you ever wonder if as science progresses will we just stack up unanswerable questions like cord wood? Either we find something more powerful than special relativity or we are at a dead-end. Special relativity will have to be replaced, but it works so perfectly I worry if it will ever happen.

[janap]

A photon/anti-photon pair created by pair creation through quantum fluctuations at the event horizon of a black hole produces Hawking radiation when the photon escapes to the far field and the anti-photon is absorbed into the black hole. How does that anti-photon decrease the energy content of the black hole to evaporate it since to the best of my understanding the anti-photon has positive energy…but negative frequency? Furthermore a photon with negative frequency and one with positive frequency are identical. Is the issue that allows the anti-photon to annihilate positive energy in any way related to the stoppage of time at the event horizon? Otherwise, the black hole just gets more energetic over time from this influx of anti-photons.

[gururajb]

Not only there is no concept of time but there is no concept of space either to the photon. Because the space shrinks in the direction of travel so much that it's length becomes zero at the speed of light. So photon has no time and no space.

[davidmurray]

You dont explain this very well, you have probably confused more people. From the perspective of a photon, it doesn't experience time or space, so that means the whole universe from the perspective of light is at a single point

[CoreyChambersLA]

Compared the the speed of light, humans and other animals are about as slow as plants. That's why our lifetimes seem long to us, but are a blink of the eye to the universe.

[BlueNeonBeasty]

What's the slowest you could move in space and thus the fastest in time?

[cigarobsession]

Movement in space relative to what? If a clock is in orbit passing overhead, for 1/2 the duration it’s moving toward you and away the other, relative to the ground. But the earth is moving through the solar system, again in different directions relative to other pints, in a corkscrew. Take that all the way through position in the galaxy, the galactic movement in the universe and speed relative to the center of the universe, if there is such a point.

[ScottMartinD]

I heard that Einstein said that from the perspective of light, you (all of us) have been dead for trillions of years (plural).

[classicalmechanic]

Shapiro time delay is a proof that massless light does experience time from spacetime curvature.

[mrloop]

Another - related - question though:
Say we discover a giant mirror ten lightyears from Earth, and this mirror is somehow in alignment with Earths trajectory. When pointing our telescopes towards the mirror and finding Earth there, are we looking twenty years into our own past?

[nooishe]

Hey Paul, Is it the wrong question or just non sensical like what's the marital status of the number 5?

Or what's the right question?

[alecgrolimond]

Yes but what about gravitation waves? Can that not effect light? If so light can slow down no?

[Mandrak]

Ok then, if the time doesn't exist for light, then the space does not exist either? From the perspective of photon who travelled 13 billion light years and just happened to hit our eyeball, it moved instantly in no time. Right?

[chrissscottt]

I don't get why you can't describe light as not being able to experience time. Light moves through space which I've been led to believe is really space-time so surely there must be some relationship even if conventional maths can't describe it?

[RichardT]

So they don’t experience time ... agreed ... then they do not experience distance/space either ... so light would therefore (as far as the photon is concerned) should not experience any aspects of our universe ... YET we can interact with photons. Mind is thus nicely blown ...