# I heard that If anything travels at the speed of light space time warps ; then what about light...

wouldn’t light travel at infinite speed and time stop for it…that would mean that light would have an Infinite speed…and be everywhere in the universe at the same time? what about electricity which also travels at the speed of light?

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## 34 Answers

Maybe in the universe you design this should be so, but it’s not in the one we share. Light travels at a certain speed (in what we consider the “vacuum” of space—and which may not be so vacuous after all), and then it travels at different speeds as it enters air, water, glass, etc.

That’s just the way it is.

@talljasperman

Look into special relativity. Grossly oversimplifying it, time travels at the speed of light. But both time and light travel at a speed relative to the observer. Therefore, regardless of how fast we travel, we will always observe light traveling at the same speed.

But the problem with observing time at light speed is that you pretty much have to be light. Observations on that level fall under the realm of quantum mechanics, which is a separate discipline form general and special relativity. I’m certain that you’re aware that there is no present method to unify these theories…so behavior on the macro vs. the micro scale have to be subjected to different models. Therefore, applying concepts of perception of time from the special relativity standpoint don’t calculate at the quantum mechanical level (i.e., quantum mechanics would be the model to predict time at this level).

Let me know if I’m misconstruing anything.

I believe the theory that anything traveling at (or near) the speed of light warps space-time only applies to mass. Since light has no mass, it doesn’t apply.

Light most definitely does not have infinite speed.

I’ve developed, right or wrong, the view of relativity as light carries *information*. The information of an event cannot get somewhere any faster than light can carry it, so therefore no two events can be connected in ANY way until at least light can get there. This, and the fact that there is not enough energy in the universe to move something of greater mass than a photon to the speed of light.

@cockswain I think that about 90% of the married male jellies can tell you that information can travel faster than the speed of light. In fact, that occurs with depressing regularity.

When I was married and living with my wife, if I did anything that she thought was wrong, then she knew about it faster than it could be seen. Sometimes she knew about it before it even happened.

I’m sure that I’m not alone in this observation.

And gossip where I work approaches the speed of light.

@cockswain

Actually, contrary to special relativity, the one thing that travels faster than the speed of light is gossip.

Photons have no mass, so they can travel at the speed of light. Special relativity does apply though. If you’re a photon, time does not move for you. So from a photon’s perspective when it hits your eye, it’s exactly the same time as it left the star.

@Rarebear *So from a photon’s perspective when it hits your eye, it’s exactly the same time as it left the star.* Really? A photon from a star 4 vs 10 light years from an observer, from the photons perspective would reach both observers at the same moment as it left the star?

I didn’t know that. I’m going to have to cogitate on that one for a while.

I thought lint speed was the fastest

@Rarebear

But if it has no mass, it also requires no energy to move from one point to another. And theoretically, it exists in all points at the same time.

So isn’t that mostly because there’s a different concept of traveling in this context?

Wait a second, I thought a photon DID have mass. Isn’t that why the gravitational field of a black hole is able to pull in light?

@cockswain No. Photons have no mass. Black holes don’t “pull” in light. What they do is warp spacetime so strong that light will curve back to the mass.

Light ALWAYS travels by a straight path. Light paths are curved by stars because the spacetime is curved (and curved so strong that it curves in on itself in black holes). So light appears to “bend”. But from the light’s perspective, it’s travelling a straight line.

@iamthemob Correct. No energy is needed to move a photon from one point to another and theoretically a photon exists everywhere at once. Feynman actually describe this and called it the “Many-paths” hypothesis. Very well done for thinking of this on your own!

@Rarebear

I’m fairly certain I was pulling that from my reading of Brian Greene’s “The Elegant Universe” and Stephen Hawking’s writings as well. But I did reason through it myself, so I’m going to take the compliment as if it was all me. If I never read those again, I’ll not have proof to the contrary…;-)

Anything with zero mass travels at the speed of light as their natural state of motion. Relativity describes the motion of objects with mass, since it is all about gravity and space-time, relative to objects with zero mass.

@Rarebear Does that mean, relative to a proton, it is essentially the only proton in the universe and can observe all things everywhere at the same instant? If so, how would a proton observe an event transpiring in, for simplicity, over the course of a minute in our lives?

@cockswain

Are you confusing “protons” and “photons” here?

@cockswain It’s a complex question, actually, because in order to “observe” there has to be some sort of interaction and exchange of information. (Also, you wrote “proton”. I assume you meant “photon”). The photon doesn’t interact with anything until it does. A photon will travel merrily along its way until it gets caught by, say, your retina. Then the information gets transmitted via biochemical…yada yada.

So as far as the photon is concerned, it’s the only photon in the universe—in fact, it is its own universe since time does not exist for a photon.

I’m signing off for the day, guys. I’ll pick up the discussion tomorrow.

@Rarebear

Do you think it’s more accurate to say, rather than “time does not exist for a photon” that “space and time are the same thing to a photon”?

Answer if the whim siezes you when you return…;-)

Yes, I meant photon. I was just reading the recent pH thread and got those mixed up. @Rarebear You’ve given me a lot to contemplate. The idea a photon is everywhere in the universe all at once, then becomes “something else” as it interacts with something is hard to wrap my brain around. Does it go from being everywhere, to just a tiny packet of energy used in some interaction? Wild stuff. I don’t know why people need religion, this is satisfying and mysterious enough.

@iamthemob I like that statement.

@cockswain

I think that the problem you’re having is essentially the same as wrapping your head around the concept of “observing” a black hole. The one observable one that we’ve seen is of course, like any black hole as described in theoretical physics, not observable as anything beyond the event horizon never escapes, not even light. Therefore, information regarding the black hole, since it travels at the speed of light, is trapped beyond the event horizon as well.

We observe the black hole, therefore, by observing the effects on matter and energy surrounding the event horizon.

Time and space, from our perspective, are separated from each other and themselves so to prevent everything from happening at the same time in the same place. So, from our observational perspective, we separate out the photons from each other. From the photon’s perspective, it was already in your retina, and it’s the same one that just left the television, which is the same as the one that left the sun awhile ago.

For the photon, everything DOES happen at the same time and in the same place.

This is good stuff. I like your explanation. You’re a man (or woman, I guess I made that assumption) who wears many hats. This makes me wonder, is it possible to actually prove the existence of a black hole, or even are the ones we can observe, at best, theoretically there? Sort of like we have all this evidence suggesting other theories, but no proof (eh, like that connection)? That would be a strange event, to see something yet only be able to suggest it is theoretically there because we cannot observe it, only it’s effects. I suppose it’s like gravity in that regard, except the black hole transmits no information?

@cockswain

I know there is one black hole that scientists say has been observed, therefore proving their existence, which previously had been only mathematically theoretical.

However, I’m kind of with you on this one. I don’t really know what this means…but Stephen Hawking was certainly puffing his chest.

PS: was that man/woman comment to me? If so…why did you make the assumption that I was a woman? I’m not saying you’re wrong…but…

yes, how could I know your gender? I guessed you were male, but could have been wrong. Wouldn’t be the first time I got that wrong.

I’m back.

Okay, is the photon REALLY everywhere in the universe? It sort of boils down to the math of quantum mechanics, and the idea of probability wave functions of quantum particles. Realistically, though, it moves in a straight line. It’s just fun to think about.

But what does really happen is that light bends around gravitational fields, and it’s a reality of the curvature of spacetime.

And you can slow the speed of light really easily—just pour a glass of water. Light moves slower in water and then speeds up again when it leaves the water. That’s what causes refraction.

@Rarebear Actually, we might say that light travels in a straight line all the time. It just seems that a large gravitational well bends light because it bends the space time light is traveling through. Light still travels the shortest possible line through that area of space-time. It is much like flying a great circle on Earth between New York and Madrid. If you look at the two cities on a large map, they are on an almost identical line of latitude. But if a plane were to fly what appears to be the straight line of latitude, the two cities are 3707 miles apart. Flying the great circle (which is really a great ellipse) between them instead cuts the trip to 3605 miles.

@talljasperman Light travels at a very fast, but very finite speed of 186,000 miles per second. In his theory of Special Relativity, Einstein showed that that speed, taken as a constant C, can be used in an equation to show that Energy and Mass have an equivalency relationship. That formula is the familiar E = MC². But that seemingly simple formula has profound implications for any attempt to fly an object having mass at a speed approaching that of light, because as you pour more energy into a rocket ship’s engines to accelerate it faster and faster, its mass increases as a square of the energy input. And the greater its mass, the more energy it will take to accelerate it any more. So long before we reach the speed of light, any space ship with a finite mass would become so massive that even the total energy of our Sun couldn’t accelerate it.

We tend to think of photons as particles **and** waves, but those are only conventions for human convenience. Actually light is neither and partially acts like each. But that’s a discussion for a different question.

What matters to this discussion is that the photon isn’t bound by the rules that govern particles with mass. Suffice to say that the photon does not face the Universal speed COP of E = MC².

@ETpro Right. That’s what I thought I wrote, but thanks for clarifying.

Basically, you’re right to be confused. ;-)

@Parrappa Let me see if I can explain.

Let’s say you have two identical clocks. One clock stays on the ground, and the other goes into a very rapidly moving space ship. The spaceship travels out in space for awhile and then comes back home. The clocks are checked, and it is seen that the clock that was on the spaceship moved slower while it was in space. This is called “time dilation”.

As you get faster and faster to the speed of light, this time dilation gets more pronounced, so that when you get just under the speed of light, the clock will appear to be almost stopped if the observer on the ground were able to look at it.

The reason why nothing can accelerate to the speed of light is that it would take an infinite amount of energy to accelerate a mass to the speed of light.

But photons have no mass, so they the move at the speed of light. But relativity says that a clock moving on a photon AT the speed of light would be frozen in time (remember how time slowed as you got closer to the speed of light?). THAT’s what this discussion is about.

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