# Questions tagged [one-way-speed-of-light]

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### One-way speed of light through long tube [duplicate]

Let's assume we have a long, narrow tube perpendicular to a wall that emits light (similar to the ones doctors use to look at radiology films). On the other side of the tube there is a sensor (mounted ...
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### Could we measure the one-way speed of light with two connected rotating apertures? [duplicate]

Can we measure the one-way speed of light by passing light through angularly shifted apertures in two disks solidly connected and spinning at a known angular velocity? Here is the apparatus I would ...
1 vote
122 views

### How do you calculate kinetic energy in a convention where the one-way speed of light is anisotropic?

The question about measuring the one-way speed of light has been debated in several posts in this forum, and are treated in detail on this wiki page. In relation to this debate, I wonder how you would ...
193 views

### One-Way Speed of Light and the Big Bang

Variations on this question have been asked a few times (e.g. here, here, and a few YouTube videos here and here). The claim seems to be that because we can only measure the round-trip speed of light, ...
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### Measuring one-way speed of light [duplicate]

Veritasium's video explains why we can't measure the one-way speed of light: https://youtu.be/pTn6Ewhb27k?si=60Q0AffVdt09lJSb However, I still don't completely get why this is the case. Let's say that ...
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### What's wrong with this One-Way Speed of Light experiment? [duplicate]

I can't tell what's wrong with it. Imagine the wheels of a car, jack the car, put a sensor on one wheel, a laser on another, start rotating, with enough speed the sensor will start to detect the laser ...
1 vote
284 views

### Clarification about the one-way vs two-way speed of light

I've just watched Why No One Has Measured The Speed Of Light by Veritasium, but I haven't really understood why this debate exists. The reason for my misunderstanding, I believe, is that the whole ...
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### Is it possible to measure the one way speed of light with redshift [duplicate]

By this I mean say you had and entire galaxy to work with, and you could measure the exact wavelengths of the waves you send out and record it. You would shoot this light beam across the galaxy and ...
73 views

### Why cant one-way speed of light be measured using a timer start that is electronically connected at midpoint? [duplicate]

Why can't one-way speed of light be measured using a timer start that is electronically connected at midpoint? I'm sure I'm missing something, but why can't an experiment be built with two timers that ...
1 vote
122 views

### Are the non-standard one-way speed of light conventions just transformations of coordinates?

There are a lot of posts and confusion regarding the fact that different standards of simultaneity result in different one-way speeds of light (OWSOL) (that may be non-isotropic). Of course, the ...
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### Why are 2 clocks needed to measure the 1-way speed of light? [duplicate]

Obviously with questions about the 1-way speed of light, I have an experiment in mind. Say you have 2 wheels connected with an axle and you have slots around the edge of each wheel (the slots are ...
435 views

### What is wrong with these ways of measuring one-way speed of light? [duplicate]

I thought of 2 ways of measuring one-way speed of light. Can somebody explain why these won't work please? Create a machine that emits a pulse of light and a sound from far away. Have a clock ready ...
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### Calculating the one-direction speed of light [duplicate]

According to Derek Muller from Veritasium, measuring the one-direction speed of light requires synchronised clocks, and that's a problem because moving one of the clocks will slow down its time. In ...
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### Understanding first order versus second order, specifically in context of relativity and optics experiments

I'm reading the following seminal paper on experiments in relativity: Krisher, Timothy P.; Maleki, Lute; Lutes, George F.; Primas, Lori E.; Logan, Ronald T.; Anderson, John D.; Will, Clifford M. (1990)...
114 views

### Time differential between two signals sent at two different near-relativistic speeds

There is something I don't quite get about relativistic velocities, which I am hoping to clarify with this question. Suppose you have an emitter and receiver both located somewhere far away from one ...
323 views

### Can this experiment successfully be used to find out one-way speed of light? [duplicate]

As with almost every question on this topic, this question is also inspired by the Vertiasium video Why No One Has Measured The Speed Of Light. This experiment tries to measure the one way speed of ...
107 views

### Upper and Lower Bounds on the One-Way Speed of Light

I know that the one-way speed of light cannot be measured due to clock synchronization. Knowing this, is it possible to place some kinds of maximum or minimum values on the one-way speed of light, and ...
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### What is the “conspiratorial anisotropy” if we would see no star redshifts in one direction of the sky? [closed]

Suppose we see no redshift of stars in one direction only (or better, in directions on a small patch around it). And suppose in that direction (on a patch of sky around it) we see a lot more stars ...
228 views

### If the speed of light is different in two opposite direction, wouldn't we see a bright and dim sky in opposite directions? [duplicate]

There have been asked a lot of questions about the direction dependence of the speed of light. The conclusion is that the speed of light can be different in two directions and we can't measure the ...
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### Velocity of light in different directions

From what I understand, we have not been able to measure unidirectional speed of light. It is said that theoretically it is possible for light to travel at c/2 in one direction and infinity speed in ...
362 views

### Would paradoxes arise if the one-way speed of light weren't $c$?

Introduction Let me start by saying that this is not a question about how to measure the one-way speed of light (OWSOL). It's about the physical implications of the idea that this speed is merely ...
1 vote
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### If I had a car which could go with a speed of light, could I drive it at night? [duplicate]

Just theoretically, when I turn on the lights in my super fast speed of light car, would I see the road if the light can't go faster than my car?
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### One-way speed of light confirmation, not measurement [duplicate]

So there's quite a few posts on here about the now infamous YT video about how the speed of light can only be measured as a round trip. I think I understand the issues with the proposed experiments I'...
226 views

### Does SR intend to postulate the one- or two-way speed of light?

I have read this question: It follows that the two-way speed of light is invariant (in the context of relativity, "invariant" is understood to mean "invariant with respect to Lorentz ...
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### Can you measure the one-way speed of light using gravity?

I recently learned that you can't measure the speed of light one way, only back and forth. I thought you might be able to use gravity to measure the speed one way. If you have to stations at the same ...
48 views

### Is time dilation applicable to different parts of the same object? (Related to figuring out speed of light in one direction) [closed]

I understand that same object is a bit of a vague and ambiguous term, but hear me out. Like many other people here I got an idea too for measuring the one way speed of light, after watching the ...
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### Potential one-way speed of light experiment [duplicate]

Exclaimer, I am in the high school physics range, in no way do I claim to know anything, nor expect to be right, this is just an idea I had when thinking about the one way speed of light so I was ...
2k views

### Can we measure the one-way speed of anything at all? [duplicate]

I know the one-way speed of light question has been exhausted, and I'm sorry for the naive question, but I would like to understand one thing. Can we measure the one-way speed of anything at all? If ...
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### One-way speed of light experiment, no clocks or mirrors (with simulation)

As can be seen in the many creative questions here, it is hotly disputed whether you can measure the speed of light in only one direction to the point where a infamous postulate was made that the ...
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### Couldnt we "race" light to determine its one-way speed?

From my (basic) understanding the biggest problem of measuring the speed of light is clock synchronization. But I question why this is necessary. To be more specific, what if, instead of measuring ...
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### Is Stellar Aberration a one-way speed of light measurement?

There is a discussion ongoing about the feasibility to measure the one-way speed of light, ever since a Veritasium video on the subject. There is also a wikipedia page about the subject. But ...
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### Did Ole Rømer measure the one-way speed of light or the two-way speed of light? [closed]

Simple question really. I'm having a convo with someone on Twitter who is a fan of the "Anisotropic Synchrony Convention" by dr. Lisle. It's a link to Answers in Genesis, so you know it's ...
1k views

### Meaning and validity of the mass-energy equivalence valid if we don't know the one-way speed of light?

I recently stumbled upon a video (1) which explained that what is assumed to be the speed of light is actually the two-way speed of light. As explained in the video, hypothetically the speed of light ...
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### Permissibility, permittivity and the one-way speed of light

Recently I came across a video, which states that it is impossible to experimentally measure the one-way speed of light. It was said that any attempts at directly measuring the one-way speed were ...
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### Measuring the one-way speed of light? [closed]

I know many people (including me) are bombarding this site with questions about the recent Veritasium video about the one-way speed of light, but I think I found a way. Here it is: (You can see sort ...
11k views

### Can One-Way Speed of Light be Instantaneous?

I recently watched this video by Veritasium where he talks about the One Way Speed of Light and talks about the limiting case where in one direction the speed of light is $c/2$ while it's ...
414 views

### Measuring one-way speed of light with gravitational lensing [duplicate]

This recent video from Veritasium (https://youtu.be/pTn6Ewhb27k), explored the problem of measuring one-way speed of light and covered a few possible (and practical) solutions. However my ...
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### Has the one-way speed of light really not yet been measured? Why wouldn't this work for example? [closed]

My understanding of what's said in the Veritasium video Why no one has measured the speed of light suggests that the one-way speed of light has not been measured and that it being isotropic has not ...
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### Is it possible to prove or disprove the Einstein Synchronization Convention with astronomy?

So, I just saw this Youtube video by Veritasium that discusses how it's impossible to measure the one-way speed of light from a light source to a detector, since it's impossible to synchronize clocks ...
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### Measuring the one-way speed of light

Could the following experiment help is to compare the one way and the two way speed of light. We sent a lightpulse from a clock in A. This lightpulse is reflected in B but also activates a lightpulse ...
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### Do photons slow down?

If $c$ is the 2-way speed of light and we can't measure the one-way speed, how do we know with absolute certainty that photons don't loose speed after a first bounce off of a reflective surface? If we ...
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### Is there any way to measure the one-way speed of light?

Is there any way (practical or theoretical) to measure the one-way speed of light? The two methods that come to mind are: Stellar aberration, and Using adiabatic clocks: synchronize clocks, then ...
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### Has anyone ever measured the one-way speed of light perpendicular to the Earth at the Earth's surface?

1 - Has anyone ever measured the one way speed of photons traveling perpendicular to the Earth at the Earth's surface? 2 - Given our current understanding of Physics is there any way both the upward ...
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