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The one way speed of light is instantaneous

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Voting Style: Open Point System: 7 Point
Started: 7/7/2015 Category: Science
Updated: 1 year ago Status: Post Voting Period
Viewed: 695 times Debate No: 77376
Debate Rounds (5)
Comments (5)
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The one way speed of light is instantaneous. I am to argue FOR this statement, and my opponent will argue AGAINST this statement.


Light- Visual electromagnetic waves, which in the electromagnetic spectrum have a wavelength from 380 nm to 780 nm. But may refer to other electromagnetic waves in some other cases.

Instantaneous- occurring, done, or completed in an instant.

*Also, the argument for "the speed of light" is its speed within a VACUUME. Please remember this, as there are many factors that effect the speed of light.

**First round is for acceptance AND presenting your side of the argument

***If there are any questions, or if you want clarifications or changes, please say so in the comments.


*---We are observing new stars---*

We are still observing new stars appearing. If the speed of light was instantaneous, we would already see all the stars in the universe. Space is a vacuum.

*---Ole Roemer's Observations---*

Roemer observed a shadow of Jupiter's moon Io very precisely. He knew Io's orbit took 1.76 days. However the speed seemed to vary. It looked like Io was moving faster when Earth was moving toward Jupiter, and the opposite when Earth was moving away. This is consistent with the speed of light being finite.

*---Modern experiments---*

Astronauts placed a mirror on the moon. Scientists then pointed a laser at it and measured the delay for the signal to come back. This took about 2.5 seconds round trip, but the fact that it took any time at all means light is not instantaneous.

*---Black Holes---*

Around a black hole, a circle is formed. This is because all the light in that hole has been pulled in by the tremendous gravity of the black hole. If light traveled instantly, this would not happen.
Debate Round No. 1


First, before I go into disproving your claims, I need to clarify something about the speed of light. The way people measure the 2 way speed of light is by shining a light in a vacuum, and measuring how long it took it to come back. If you assume that the speed is constant, then it traveled 299,792,458 m / s (by calculating the time it took and the distance traveled). But if you assume that it was instant the way there, it would hypothetically travel at 149,896,229 m / s on the way back. In both hypothetical cases, light would take the same time to travel the same amount of distance.

Now, when you say we are observing "new stars", that is completely irrelevant to the topic. As you say, "...we would already see all the stars in the universe.". How do you know that this isn't how the universe looks like? What if we see how the universe truly looks like in current time? Also, what if I'm right, and we indeed DO see all the stars in the universe. I see no real proof against my position in that claim, only you stating what would be true if I was right, which I agree with.

About the Ole Roemer's Observations, I do not see how planetary orbits are at all related to the speed of light. You simply just described the gravitational effects of Earth and Jupiter. How is that at all related to a finite speed of light? I need a reason if I am going to accept you claim.

About the modern experiments, I was talking about the ONE way speed of light. You are confused about what I meant about the topic. I was saying one way is instant. I never said the other way was not. Those experiments are consistent with the speed of light being instant one way, and being 149,896,229 m / s the other way. Therefor, proving that it is possible for the speed of light to be instant one way.

And about black holes. Yes, the "point of no return" prevents light from getting away. But what if it only prevented the reflected light from escaping? That light would be traveling at 149,896,229 m / s, and would easily be affected. Also, light traveling instantly could be catastrophically effected from such gravitational energy, or be veered off course, so we cant observe it. We still have a lot to learn about the speed of light, and black holes. Many theory's are still being made, so the possibility of my claim still stands.

I believe there is no way you can disprove my claim. Any way you can try to do that would either previously assume the speed of light, or just be an irrelevant claim. I suggest you research what Einstein said on the speed of light.

I suggest you read this article, which may help you understand my position


Okay. So Roemer and the Hubble Sphere are the ways we know One way speed of light is not instantaneous.

Roemer was observing Io's orbit very carefully. When the Earth was going toward Io, Io appeared to be orbiting slightly faster. This is because the Earth was intersecting the light coming from Io. The opposite effect happened when Earth was moving away. This is because, now Earth is going away from the light coming from Io. Think of it like frames of a movie. Where Io is the movie, and it is sending out frames at the speed of light. If Earth was going toward Io, it would see more frames in a second. If you play more frames in a second, it would appear to be speeding up.

The Hubble Sphere is the stars we can currently see. This one is pretty easy to explain. If light were instantaneous, we would see every star in the universe. But since light is not, we can only see the stars in our Hubble Sphere.
Debate Round No. 2


I still disagree with you. Romer did not prove that in his experiments. Here is my reason why.

"The first experimental determination of the speed of light was made by Ole Christensen Romer. It may seem that this experiment measures the time for light to traverse part of the Earth's orbit and thus determines its one-way speed, however, this experiment was carefully re-analysed by Zhang, who showed that the measurement does not measure the speed independently of a clock synchronization scheme but actually used the Jupiter system as a slowly-transported clock to measure the light transit times.[31]
The Australian physicist Karlov also showed that Romer actually measured the speed of light by implicitly making the assumption of the equality of the speeds of light back and forth. "

Also, I do not see how the "Hubble Sphere" disproves my point. How do you know that you can't see all the stars? What if we do see every star in the universe? Even if we don't, doesn't that just mean that there isn't enough light emitting from the stars? What about things that prevent the light from arriving here?
There are many questions to the Hubble Sphere still. It in no way disproves my claim.

Also, I speculate that the Hubble Sphere doesn't exist like you say.
The universe's expansion is assumed from redshift in the light. Scientists think that the Doppler Effect is what leads to/causes redshift, and therefore shows that the universe is expanding. (I suggest reading on what the Doppler Effect and Redshift is).

But what if the redshift in the light wasn't from the Doppler Effect, but from light being affected by the universe around it? This is called the Tired Light Model. Even Edwin Hubble, who discovered redshift, believed that it was possible that redshift was due to distance, and not the universe expanding.

". . . the possibility that red-shift may be due to some other cause, connected with the long time or distance involved in the passage of the light from the nebula to observer, should not be prematurely neglected." (Hubble and Tolman 1935, p. 303)

Now, you cannot say that absolutely that the Hubble Sphere disproves my position. The Hubble Sphere isn't even guaranteed to be true. It depends on an interpretation of redshift of light, which I would say is due to light decay. Therefore, the Hubble Sphere does not disprove my position.

Here is an illustration of why I think that the speed of light is instantaneous.

Lets say, hypothetically, that
*The Hubble Sphere exists in the way people say it does, and
*The speed of light is NOT instantaneous one way, but is constant.

That would mean that there are things inside our universe that are technically outside our universe! That is because the universe is expanding faster than the speed of light.

"Space itself is pulling apart at the seams, expanding at a rate of 74.3 plus or minus 2.1 kilometers (46.2 plus or minus 1.3 miles) per second per megaparsec (a megaparsec is roughly 3 million light-years). If those numbers are a little too much to contemplate, rest assured that's really, really fast"

Nothing (besides space, because of Special Relativity), can go faster than the speed of light (think of it like the speed limit). So it"s impossible to interact with those things that the universe separates us from past a certain point. The point of separation comes from the universe expanding at speeds faster than the speed of light. The speed of light, being a universal constant and from other factors, is the fastest something can travel. Because things cannot travel faster than the speed of light, then those same things cannot travel as fast as the universe. Therefore, nothing can move as fast as the expansion of the universe. Therefore, the universe can keep things completely separated because they can never travel fast enough to ever meet.

That means that there are things in our expanding universe that we can never be in relation with within time and space. Then how can those things be defined as being within the same universe then? It seems strange that things within our universe would be considered not in our same universe. How can something be defined as in our universe, but be unapproachable, and basically nonexistent to us? It might as well not exist, because nothing in physics can bring us to those objects in any way. No observation, direct or indirect, using any known action that physics allows, could make those objects known. In your position, something can be within our universe, but never be known and be outside our reaches of the universe (because of the speed of the expansion of the universe)! This is some kind of hybrid-multiverse kind of idea, which I disagree with. I do not agree with this interpretation of the universe . So therefore, I do not agree with your interpretation of the universe, as that is the ultimate conclusion if you hypothetically correct.

But what if the speed of light was instant? Whether or not the universe is expanding at the rate that redshift predicts, all things would be within light"s limits of reaching. Then, all things in the universe are within reach. That would make a single, unified universe (whether or not the universe is expanding at the suspected speeds). This interpretation of the universe is more appealing.

So, the idea of a Hubble Sphere is questionable. Also, the idea leads to that the universe is expanding faster than light, which creates strange ideas of our universe.

I believe my position makes more sense, and is scientifically plausible at the same time. While your position, while also being possible, doesn't appear as well as mine.


No, The fact that we are observing new stars appearing in the sky proves that the speed of light is not instantaneous. If it was instantaneous, we would already see all the stars in the sky because the light would have already reached here.

I realize I am retracting some of my claims. This is because I did not fully understand what you meant in the debate topic. I also do not understand why Roemer's discoveries are wrong (and would like you to expand on that), but for now I will take it that it does mean Roemer's discoveries do not disprove your point, because... Wikipedia.
Debate Round No. 3


Sorry for not being specific in some of my claims.
Also, could you please give examples of new stars just "appearing" in the sky? I don't know any instances of stars appearing and would need some more information on this.

Now about Romer's experiments, the problem is that he assumed that space is isotropic, and that light is constant/consistent.

Physics. of equal physical properties along all axes.
having uniform physical properties in all directions

Your description of Roemer's experiments are wrong. It wasn't like frames in a movie. Io's orbit appeared different depending on the position/movement of the earth and Jupiter. Roemer just blamed it on the light, and claimed that it was because it took light longer because of earth's position. Why did he do that? Why is light the reason, and not something else? What if its because of Io just traveling slower? What if its because of the planets moving differently? What if it is because the space isn't isotropic? Why does that mean light took longer to travel? There are many assumptions that Roemer made, and that is why his conclusion isn't guaranteed.
You can find other references then Wikipedia, too. Just because its on Wikipedia doesn't mean it's wrong. I just used Wikipedia because the web page had useful information for everyone in understanding the subject more.


Roemers observations were of an increasing speed in Io's orbit when Earth was heading toward Jupiter and of decreasing speed when Earth was moving away from Jupiter. This is consistent with light getting to the Earth a tad bit faster because the Earth is moving toward Jupiter, and a tad bit slower in the opposite.

The solar system, for the most part is isotropic. Unless you can show that it isnt, it is assumed physics apply to everything.

The Hubble Sphere, is the result of the Speed of Light. The universe is expanding. Outside of the Hubble Sphere, stars are receding from Earth faster than light. Therefore we cannot see them. I do not have the credentials to explain it much better. Look it up. Anyways, we know there are more stars in existence than we can see. Once again, look it up.
Debate Round No. 4


Here is the question, how do you know it was because of the speed of light? You say it is consistent with light moving slower, but that doesn't mean that is the reason. You might like that explanation, but liking it doesn't make it true.

Also, you assume that space is isotropic, but you cannot prove it is. Io could just take longer to orbit. When I say that space isn't completely isotropic, I mean that it not being isotropic could lead to effecting the planet. You are assuming that the planets and moons orbit perfectly around the sun, in a fashion that we can predict with absolute certainty in such a specific way that we can make judgments on the speed of light. I don't assume that. I disagree with you on that assumption.

How do you know that the Hubble Sphere exists? It is a description of what we CANNOT see. But how do you know that it is true? How do you know that there are stars we cant see? You would have to know about them in order to say you can't see them. Also, how do you know that the universe is expanding? I did look up what you are claiming, and I could not find a satisfactory explanation for my questions. You assume the universe is expanding, assume that the speed of light is equal in both directions, and from that assume that there is a Hubble Sphere.

That is the problem. Before you claim there is a Hubble Sphere, you have to assume that I'm wrong, then use that as proof against me. That is the fallacy of begging the question.


But Io takes longer to orbit when Earth is moving away, not consistent with any other clocks besides that. It is correlated with the motion of Earth relative to Io.

If we can not assume space is isotropic, we can not conclude anything about space. What explanation makes more sense? The speed of light not being instant, or Physics being suspended at Io so it looks like the speed of light is not instant.
Debate Round No. 5
5 comments have been posted on this debate. Showing 1 through 5 records.
Posted by kkris1 7 months ago
I think we can synchronize distant clocks:
Let"s have a flashlight which rotates with angular velocity "w" while emitting the light. At a distant r from the flashlight let"s have two clocks A and B separated by distance d. Linear velocity of the beam at r from the flashlight will be v=wr. So rotating beam of light will activate the clock A and a certain time later will activate clock B. For our experiment to yield high enough accuracy we would need r and was as large as possible. So we would need fast spinning powerful flashlight which could shine the light visible from the big distance.
Luckily the Creator left such a flashlight for us. It is called a pulsar. As we know pulsars can spin extremely fast (even more than 700 rotations/s) and are very stable, rivalling accuracy of atomic clocks.
Let"s make a rough calculations: if r=1100ly(=~10^19m, w=10hz our linear speed will be 6.28x10x10^19m/s=6.28"10^20m/s.
If our distance d from A to B is 6.28x10^6m (less than 0.1s for the light to travel from A to B and back; this is important that we are able to exchange information between clocks A and B within the time shorter than one full rotation of the pulsar), the signal from the pulsar will arrive at A 10^-14s earlier than at clock B. I think that if we are not very fussy, we could say the signals arrive at A and B simultaneously.
Now to synchronize the clocks, at the beginning of the pulse from the pulsar detected at A we send the information from A to B that at the beginning of the next pulse from the pulsar clock at B should be started. When the next pulse from the pulsar arrives, we start both clocks A and B which will now be (almost perfectly) synchronized.
Having two clocks synchronized, we can easily measure one way speed of light.
Kind regards,
Posted by hldemi 1 year ago
The reason why black hole has effect on photon is because black hole is not moving at the speed of light. If both black hole and photon moved at the speed of light their interaction would be physically impossible.
Posted by hldemi 1 year ago
This is a trick debate. The pro is right, but only relative to photon traveling at the speed of light in vacuum. To the observer that photon is traveling at the speed of light but to the photon its instant. Time only stands still for photons moving through a vacuum, where their speed through space equals c (the speed of light in vacuum) and thus their speed through time equals 0. So for photon time is stopped= moving is instant.
Posted by Ramshutu 1 year ago
I'm assuming you take the burden of proof to show as you are making the positive claim? I'm interested in taking this one up.
Posted by Couchsessel 1 year ago
Uhm, what exactly are you trying to say? Could you explain your point some more?
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