# Light and Time

Alex (@hollowinfinity) 5 years, 9 months ago

My question is do we simply base time measurement off of light? Is it possible to measure time at all without light and its constant speed? If so, how can we be sure of time at all? We measure our time based on light from the sun, and its not constant because of all the mediums it must pass through. Since the sun is the source of light, then do stars have no sense of duration at all?
Secondly, if distances literally converge when going the speed of light, or really fast, and we measure things based off of light, then how are we certain there is actually space at all? All distances could be converged upon itself into a point, yet there is no way for us to know because we don’t move fast enough.

April 18, 2012 at 9:40 am
Jack (21) (@jackflash) 5 years, 9 months ago ago

Would it be more accurate to say it is not necessarily light that is the main factor in time, but speed?

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Ray Butler (1,422)M (@trek79) 5 years, 9 months ago ago

Telling time depends on light so we can see the hands of the clock but we can keep time by the rotation of the Earth. Fundamentally it is the day and night cycle that time is based on so knowing the relative position of the Earth to the sun, or even the planets, I suppose you could use some kind of electromagnetic or a gravitational eddy sensor.

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Anonymous (53) (@) 5 years, 9 months ago ago

Telling time depends on light, yes, but seeing light depends on speed. Speed depends on how fast something is moving per given unit of time. Thus, I agree with Ray in that it’s all relative. This is why time moves slower on the moon. This is why time moves slower the further away a planet is to the sun. The way I understand it (and I could be wrong/talking out of my ass) but, the way I understand it: light from the sun reaches us quicker than Jupiter for example, so time is faster for us and slower on Jupiter. So to answer your question (‘Can we measure time without speed and light?’), I don’t see how. It is interesting to me that we measure time based on its rotation around the sun though. I wonder what our life would be like without having time. How would we meet people for lunch? How would we know when to go to class? Hmm..

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Kushna Mufeed (2) (@kushna) 5 years, 8 months ago ago

@hollowinfinity, How we experience time is entirely relative to some other (celestial) body moving relative to us. If someone is moving fast relative to the earth, they experience time slower than those on earth. If you could possibly reach the speed of light relative to the earth, time stops for you relative to earths time frame. However this is impossible since your relative mass approaches infinity as you approach the speed of light and no force can accelerate an infinite mass.

So in essence, it is light’s constant speed as well as the relative motion between bodies which determine the passage of time of these bodies relative to each other. Something I find absolutely fascinating is that no matter how fast you go the speed of light relative to you will always be c.

The sun does experience time because it is a body with mass with a speed less than the speed of light. However, photons do not experience time or space. From the perspective of a photon, it is created and destroyed (or emitted and absorbed) at the same instant in the same position. So you are correct: this does call into the question the true existence of time and space as these conclusions to make them seem to be illusory. This is something I myself need to contemplate further.

@mybee42, According to what I have just said, time is not slower on Jupiter relative to earth because of the distance from the sun. If it is slower, it is because of the relative speeds between the Earth and Jupiter. Conversely, time would also slow down on Earth from Jupiter’s perspective. I do not trust myself to give a proper explanation of this, but Brian Greene explains this phenomenon excellently in his book The Elegant Universe

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Roseanne (12) (@rsupernault) 5 years, 8 months ago ago

Under the presumption that other beings or races exist in the universe (which they do, if you don’t think that, just go away) and that the manner in which we experience and measure the rate of time is actually relative to our distance to the sun, and other beings in the celestial galaxy experience it at a different rate due to their distance to whatever sun may be in their galaxy, then theoretically, wouldn’t these other beings or races evolve or develop faster or slower than us because of it?

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Alex (550) (@hollowinfinity) 5 years, 8 months ago ago

@rsupernault, unless perhaps life itself is relative as well! I’ve thought about alien life a lot, and perhaps if the Universe is all mental, then as far away as you go from yourself, the less ‘life’ there is.
I really believe that ALL things are relative. Even understanding.

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R.V. Star (151) (@rickvonstar) 5 years, 8 months ago ago

time is really just the description of motion through space right?

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Roseanne (12) (@rsupernault) 5 years, 8 months ago ago

@hollowinfinity I thought of that when I just walked to the store after I posted… How life is experienced relative to who or what is in it’s space. Even if I am perceiving time in a specific way, it does go faster in some spaces and slower in others. I agree with everything being relative. And how everything just IS. Things just ARE, and how we perceive them is also relative. I also ran into a friend and we started talking about it (weird how many things happen on the way to the store), and he talked about how if human beings have genetic memory, than so does the earth because we come from the earth. Maybe the earth remembers all our history as this race, from amphibian to homo sapien, and knows just when to do what she needs to scare us or shove us along. Or replenish herself and make us start over…

@rickvonstar I believe so.

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Kushna Mufeed (2) (@kushna) 5 years, 8 months ago ago

@mybee42, It appears I was incorrect in my assertion that distance from the sun does not effect the passage of time. The phenomenon is called gravitational time dilation. However, it works the reverse of what you were saying, and time passes slower for planets closer to the sun, and vice versa. https://en.wikipedia.org/wiki/Gravitational_time_dilation

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Eric (1,818)M (@blankey) 5 years, 8 months ago ago

@hollowinfinity,
It is all one cycle. There is no tomorrow and there is no yesterday.
The fact that time is relative and can thus be manipulated for an individual shows it is an illusion.

Also, the most objective thing in the universe would probably be a black hole. Black holes experience everything at once. Time and space are interconnected and they both can be sucked into a black hole and theoretically spit out the other end and create another universe. And since time does not “exist” then this is happening constantly, correct? I feel like there is something here, someone help me out.

@rsupernault, Definitely, the earth is a living, breathing organism. I think mother nature might of had enough of us.

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Eric (1,818)M (@blankey) 5 years, 8 months ago ago

@kushna, Time passes slower for an individual or organism when near something of great mass. If you were to stand on the Egyptian Pyramid, time would be going slower for you than your brother in the sand a few hundred away. The fact that this is possible, shows that time only exists for us, for this reality.

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Anonymous (53) (@) 5 years, 8 months ago ago

Sorry if this sounds completely ignorant: So Jupiter has about a 9 hour day cause it’s farther away from the sun (time is faster when it’s further away from a giant mass) but it’s days are longer because it’s further away from the sun and it takes longer to make one complete rotation around the sun. … So time moves faster on jupiter and slower on Mercury… and time moves faster on the moon even though at some points in time it’s closer to the sun than the earth… ?

Also, look what I found http://www.youtube.com/watch?v=7NWoxdJ1sIk

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Nick (195) (@nickc2007) 5 years, 8 months ago ago

Honestly had never considered light having to travel through regions of different density before. Mind=blown.

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Kushna Mufeed (2) (@kushna) 5 years, 8 months ago ago

In actuality, light travels at the same speed through every medium. The only reason that it appears to go through certain mediums slower than c and others faster than c (an impossibility according to the theory of relativity!) is due to the interactions of the electromagnetic waves of light with the electrons of the atoms of the medium it passes through, resulting in a phase shift of the original wave.

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Alex (550) (@hollowinfinity) 5 years, 8 months ago ago

‘It only seems to slow down–although I wouldn’t call it bouncing. It’s more like continually getting absorbed and re-radiated. Electromagnetic radiation travels at one speed only–c. The stuff we call light traveling through an optically dense medium is a combination of EM radiation and accelerating charged particles. That disturbance can, of course, travel slower than c, which is what someone means if they say light slows down in a medium even though that isn’t quite correct, strictly speaking.’

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Alex (550) (@hollowinfinity) 5 years, 8 months ago ago

So, light only follows the straight line going C if there is no medium (A vacuum) otherwise, its always “bouncing around”

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Anonymous (2,833) (@) 5 years, 8 months ago ago

The most fascinating thing I find about light and time, is a photon has experienced all of time, yet it doesn’t move infinitely fast.

As soon as a photon goes into existence, it has experienced ALL of time, yet it (can) only experience a finite distance (say from the sun to the earth or the screen of your computer to your eyes).

This doesn’t make any sense!

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Kushna Mufeed (2) (@kushna) 5 years, 8 months ago ago

@ijesuschrist, All of time? The way I understand is that it experience no time, since time stops at the speed of light. It experiences emission and absorption at the exact same instance. It also experiences no space since space contracts to nothing at the speed of light.

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Alex (550) (@hollowinfinity) 5 years, 8 months ago ago

@kushna, Which brings up my original question. If the speed of light constricts space to nothing, then can’t we infer that space may not even exist at all? Everything is at one point, so therefore everything is a singularity.

@blankey, This brings in your black hole idea, because a black hole is like a singularity point right?

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Eric (1,818)M (@blankey) 5 years, 8 months ago ago

@hollowinfinity, I suppose we are creating this universe and infinite other/parallel universes simultaneously and constantly.

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Alex (141)M (@alexishungry) 5 years, 8 months ago ago

@hollowinfinity Space converges for LIGHT, but not us, because we aren’t going the speed of light. The fact that all of this is happening right now and that we exist the way we do, means space does exist.

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Alex (550) (@hollowinfinity) 5 years, 8 months ago ago

@alexishungry, Light is on either side of us though. Space constricts for light. Space is irrelevant for light then. We are only able to be because of light. Light just may be the most important thing in our existence. We have an ILLUSION of space because of our speed. I would agree to that.

But it means on a grander scale in the Universe too, that space is both a point, and infinite at the same time. Space is relative, as much as time is.
Why does everything seem to come to a point? One of the things that intrigues me the most are singularities. 1/0? 10th dimension? 1dimension. 0dimensions?
Shit, maybe it is all binary. 0.0

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Alex (141)M (@alexishungry) 5 years, 8 months ago ago

@hollowinfinity But things can exist without light. There was a long period after the big bang during which particles existed without light. Yet there was still movement and speed and time and space. I have to say speed is an ‘illusion’ of spacetime, not the other way around. (Because speed is just distance/time.)

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Eric (1,818)M (@blankey) 5 years, 8 months ago ago

@hollowinfinity, One thing is for sure, everything was at one small, condensed point before the big bang.

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Kushna Mufeed (2) (@kushna) 5 years, 8 months ago ago

@alexishungry, Can you back up this claim? As far as I know, this is completely false. Regardless, I would imagine the limiting property of the speed of light would still exist with or without the presence of photons, since it is so key to the theory of relativity.

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