A Question on Time Slowing Down at the Speed of Light

I have a question that I have been asking myself as I fall asleep the past few nights about how time slows down when moving at the speed of light. For example, the star Proxima Centauri is 4.2 light years from Earth. So, when the light from that star shoots off in all directions it takes 4.2 years to reach Earth, but because time slows down when traveling at the speed of light then those photons that traveled across space to Earth didn’t really take 4.2 years to get here. Sure, measuring the time from Earth, not moving at the speed of light, it took the photons 4.2 years to get here, however, if you were the photons the amount of time it took you to get here should be much less than 4.2 years because as you were traveling at the speed of light your time slowed down. So, how long were the photons really traveling?

Another example would be our Sun. It takes light from the Sun 8 mins to travel to the Earth. IF the Sun disappeared for whatever reason we would still have light for 8 mins because the Sun already ejected a steady stream of light towards us. If you shot a visible laser beam at the speed of light from the Sun to Earth and timed it from Earth it would take 8 mins to reach Earth. However, if you connected a stopwatch to the laser beam as you fired it and timed it, wouldn’t the time on the stopwatch read less than 8 mins because as it traveled at the speed of light towards Earth its time slowed down, while the time on Earth stayed constant?

I guess what I am trying to say is that from the outside observer it takes light from Proxima Centauri 4.2 years to reach the Earth. But if you are traveling at the speed of light with the photons from Proxima Centauri to Earth, how could the time it took you to cover the distance possibly equal the outside observer’s time if time slows down when traveling at the speed of light? Is the rate at which time slows down as you approach the speed of light so minuscule that it is barely noticeable? Or is the visible starlight that reaches Earth younger than we think?

(That made more sense in my head and I am even more confused now after writing it out.)
Could someone please steer me in the right direction?!?

time isn't real

reply to post by Ghost374


It is a made up concept, but there is no denying it exists in the universe. Thanks for the bump.

Just a stab in the, er, dark, but I imagine if you shrunk yourself down x 1 million and hitched a ride on the photon you would be travelling for millions of years.

Originally posted by Ghost374
time isn't real

Best response...

time is an illusion/tool that only exists through perception. so unless photons have the ability to perceive their own existence and or location (which I don't think they do) it didn't take them 4.2 years to travel because there is no such thing as time for photons.

If it were a human being traveling 4.2 light years (at the speed of light) then time would just simply APPEAR to slow down from that perspective when the "earth perspective" it would indeed have taken 4.2 years...

time is an illusion because it completely changes and depends on perspective. Time is not universal it cannot be because there is no universal perspective point or single place in which all things can be viewed from all angles/locations simultaneously.

its as difficult to understand as it is to explain.

reply to post by Ghost374


"Lunch-time" doubly so

If you were a photon, you would seem to collide as/soon as you left. Like being shot out a cannon into a wall that was infinitely close.

reply to post by tooo many pills


Time literally does not exist in the reference frame of the photons. If you were a photon traveling at speed "c" in a vacuum, it would seem to you like you traveled from point A to point B instantaneously.

You have to look at it in terms of spacetime. Everything is traveling through spacetime at the speed of light. This does not mean that is traveling through SPACE or TIME (seperately) at the speed of light. But that it is traveling through both. Your speed through space and your speed through time always add up to the speed of light. So if you travel at zero speed, you are going through time at the speed of light. If you are traveling through space at the speed of light (like a photon) then you do not travel through time at all. This is how space and time are related, and why time slows down the faster you go.

This is the real answer based on the special theory of relativity. Of course, in reality, only a massless object (like a photon with a rest mass of zero) can travel at the speed of light, because any other mass would take infinite energy to accelerate to the speed of light.

Hope that helps.

reply to post by Sly1one

If it were a human being traveling 4.2 light years (at the speed of light) then time would just simply APPEAR to slow down from that perspective when the "earth perspective" it would indeed have taken 4.2 years.

If a person travelling 99.99% the speed of light were to take a clock with them and measure how long a trip took, it wont equal 4.2 years. And if they were to reach the speed of light, they would theoretically go back in time (that's also part of why it's theoretically impossible to reach the speed of light, that and it requires and infinite amount of energy). Time isn't just "appearing" to slow down when your velocity increases, it's called time dilation, space and time are connected.

You dont gain time by traveling at the speed of light. You gain more distance in time.

If you have two clocks like i have illustrated in the image bellow. You can easily see it. The small clock represents time on earth. The Big clock represents speed of light.



There are two ways to see that if you gain time or distance.

1. On the Big Clock you can draw a line from 12 o'clock to the bar. On the small clock you do the same. Then you can measure time and distance. You will see that the time is equal but distance traveled is not.

2. If you measure the time or count the dots between 12 o'clock and the bar. You will count the exact same amount of dots or time on both clocks.

The big clock has a bigger radius then the smaller clock. And there is a greater distance between the dots. That is why you think time is slower when traveling at the speed of light.


If you travel at the speed of light you will have to use the Big clock. And when you look at it while traveling you will think! damn time is moving slowly.

Originally posted by WhizPhiz
reply to post by Sly1one

 

If it were a human being traveling 4.2 light years (at the speed of light) then time would just simply APPEAR to slow down from that perspective when the "earth perspective" it would indeed have taken 4.2 years.

If a person travelling 99.99% the speed of light were to take a clock with them and measure how long a trip took, it wont equal 4.2 years. And if they were to reach the speed of light, they would theoretically go back in time (that's also part of why it's theoretically impossible to reach the speed of light, that and it requires and infinite amount of energy). Time isn't just "appearing" to slow down when your velocity increases, it's called time dilation, space and time are connected.

edit on 22-12-2010 by WhizPhiz because: (no reason given)

You have illustrated my point perfectly without realizing it. Time is a Measurement...measurement of what? Its the measurement of movement, it is a tool used for the purpose of understanding MOVEMENT of MASS through SPACE. Time is an illusion and doesn't truly exist in the sense that mass, movement, and space do.

you can have mass, movement, and space without the concept of time, however you cannot have the concept of time without including all of the above (mass, movement, space).

time is a phenomena that is produced from the existence of mass/energy moving through space, you take ANY one of those three out of the equation and you will clearly see how time doesn't exist...its all perception.

Hmmm, I heard special relativity best explained like this;

This is kind of the short form, so bear with me...

Imagine you are driving on a road heading completely north, at about 70mph. You are moving north at 70mph, and them the road slightly bends to the right, so now your going 55mph north and 15mph east. You cannot go 70mph north again without increasing your speed. Now if the road bends once more and your heading fully east, then all of your speed is dedicated eastward. Now replace north and east with space and time, and the scenario is the same with the constant of the speed of light.

Time goes slower as you increase your speed to that of c, but it is relative to you. It seems normal time to you, your just covering a lot of space in that time. pun intended. If you went in a circle at light speed that's when time travel could be possible.

As for photons, it would take them 4.2 years to get here, as it would take a spaceship of people traveling at the speed of light 4.2 years to get there.

Now where it starts to bend brains a little is that if you were traveling at 250,000kps, beside light being shot out parallel to you at it's speed of 300,000kps, even though your traveling that fast, light would still whiz by you as if you were standing still. It would still pass you at 300,000kps even though you going with it. Same stands if you
are going away from the light.

Think about that a minute.

If I were to throw a ball at you at the speed of 20 kph, and you started running away at 8 kph then the ball would be coming at you with a speed of 12 kph. If you were running towards me at 8 kph the the ball would be going 28 kph. Interesting stuff.

I left it non technical on purpose people, no flaming.

When you get into stuff like this, that is where physics gets interesting.

Pred...

There is no medium in space for light waves to propagate across.

They are emissions from stars that are actually PUSHED out from stars. It takes say 4 years for light to get here from that star, because of no medium for light to propagate across.

Therefor the speed of light is like water coming out of your spicket. You can get from here to that star faster than light....if you can avoid it.

Its light and the emissions from that star that will slow you down, resulting in Time. Friction.

Avoid those emissions somehow to get to that star and there is no time. That's my theory which isn't based upon anything but....the fact there is no medium in space for visible light wave lengths to propagate across.

No time at all.

The Eternal Photon is Everywhere at Once.

Originally posted by Astyanax
No time at all.

The Eternal Photon is Everywhere at Once.

If a photon is everywhere at once that means it is infinite?

Mmm what do you think?

reply to post by Sly1one


reply to post by FalselyFlagged


reply to post by spy66


reply to post by predator0187


THANK YOU! All of you had great replies with perfect examples. Ya'll totally set me straight. Although, I don’t quite understand it completely, I see where my reasoning was flawed and definitely have a much better grasp of the concept. I am taking Physics for Engineers next semester so this was a good start. Hopefully, it will go in depth about Special Relativity, and I’ll come out of that class as smart as you Einsteins! :-p

Thanks again!

reply to post by tooo many pills


Well I'm glad you found what we all said helpful to expand your understanding of at least time. There are few things that can truly drive a man insane if he delves deep enough into them, one is the concept of time and the other is the concept of infinity.

If you think deeply enough about the concept of infinity within the universe you will find yourself going back and forth and back and forth between "Ah ha! This is how it works" moments and "Wait no, that's not right" moments...part of me believes infinity is just too abstract for the human mind to contemplate and make sense of.

Good luck with your journey into physics!

Originally posted by Sly1one
reply to post by tooo many pills

 

Well I'm glad you found what we all said helpful to expand your understanding of at least time. There are few things that can truly drive a man insane if he delves deep enough into them, one is the concept of time and the other is the concept of infinity.

If you think deeply enough about the concept of infinity within the universe you will find yourself going back and forth and back and forth between "Ah ha! This is how it works" moments and "Wait no, that's not right" moments...part of me believes infinity is just too abstract for the human mind to contemplate and make sense of.

Good luck with your journey into physics!

The infinite is easy. Its a constant and is always stationary. It never moves or changes.

Finite expands until it becomes infinite. The expansion of finite is also the reason why time travel is impossible.

Originally posted by spy66

Originally posted by Sly1one
reply to post by tooo many pills

 

Well I'm glad you found what we all said helpful to expand your understanding of at least time. There are few things that can truly drive a man insane if he delves deep enough into them, one is the concept of time and the other is the concept of infinity.

If you think deeply enough about the concept of infinity within the universe you will find yourself going back and forth and back and forth between "Ah ha! This is how it works" moments and "Wait no, that's not right" moments...part of me believes infinity is just too abstract for the human mind to contemplate and make sense of.

Good luck with your journey into physics!

The infinite is easy. Its a constant and is always stationary. It never moves or changes.

Finite expands until it becomes infinite. The expansion of finite is also the reason why time travel is impossible.

Infinity can get pretty complicated when you contemplate that within the space between your fingers an infinite number of measurements and space exists...THAT is very difficult to wrap your head around because it implies that distance in space is also an illusion....

reply to post by Sly1one


Oh definitely, the concept of infinity is a strange one especially when thinking about the darkness of space because our universe is 99.9% empty space. All that dark empty space seems to go on to infinity and most likely does because it is virtually nothing. Then only reason we have light in our universe is from nuclear fusion taking place in huge dense balls of flaming-hot gas. It turns out that there are anywhere from 100 billion to 500 billion of these things in our galaxy alone, and there are at least 100 billion galaxies in our universe. Then you realize that us humans as an advanced civilization have the ability to invent ways to travel to other places in the universe, except at the current timeline in our species 99.9% of us have no way of leaving our rock. The less than 0.01% that have been to outer space haven't even able to escape our own planet's gravity, and even if they did there are basically an infinite number of factors that could kill them any moment.

And all that is not even going into the sub-atomic and quantum levels which are 99.9% empty space themselves, so everything we've ever seen and will ever know is 99.9% nothing. It is also highly likely that the more and more we magnify the more levels of molecules we will find. So, it is possible that the universe is infinitely small and infinitely big. Then you realize that there are probably other universes outside of our own, and if they follow the trend of everything being 99.9% empty space then those universes are so far away from our own universe it is impossible to comprehend.

My head is spinning.

Originally posted by Astyanax
No time at all.

The Eternal Photon is Everywhere at Once.

But now your getting into quantum, we were focusing on special relativity.

And I'm sure you know how Einstein felt about the quantum world.

Damn smart people.

Pred...