As humanity’s furthest reach into the Universe so far, the two Voyager spacecraft’s well-being is of utmost importance to many. Although we know that there will be an end to any science…
Here’s a fun fact that I think of every time I read about light delay.
We assume the speed of light is the same in all directions but there’s no way to prove that it is.
It could be light speed is instantaneous in one direction, and half the speed we think it is in the reverse. Any test we could devise depends on information traveling in two directions, nullifying any discrepancies in light speed.
The speed of light in a vacuum unaffected by external forces such as gravity should be the same no matter what direction it is in. I’m not sure why it wouldn’t be. That’s like saying a kilometer is longer if you go East than if you go West.
However, it’s actually far more complicated than that, and much of it beyond my understanding.
There’s no reason it wouldn’t be. The point is that it’s impossible to prove that it is. There is no conceivable experiment that can be performed to prove the two-way speed of light is symmetric.
That’s not how anything works. It’s impossible to prove that the universe wasn’t created last Thursday with everything in place as it is now. There’s no point in assuming anything that can’t be proven has validity.
It’s just a thought exercise. There are several reputable YouTube videos on this topic. None of them claim that the speed of light isn’t the speed of light. They’re just demonstrating that we can’t prove it with current technology. Similar to the difficulty it took to finally prove that one plus one equals two. We know that’s correct, but it took years to prove it.
Couldn’t we send out two devices in different directions, wait a decade, have them shine light at eachother simultaneously, record when they receive the light, then send the times back to earth?
Your question is good. You’re missing understanding of time dilation and frame of reference. An explanation of the theory of relativity is at least pages long.
The first book I ever read on the subject, and IMO the best introductory text for any non-physiscist, is Stephen Hawking’s “A Brief History of Time”. But, any introduction to relativity should answer your question.
One of the more memorable physics classes I’ve had went into the history of discoveries that led to our understanding of relativity. The relevant story here, starts with how sound travels though air.
Let’s say you’re standing at the bottom of a building shouting to your friend peeking out a window on the 5th floor. On a calm day, that friend will hear you at pretty much the same time as someone standing the same distance away, but on the street. However, if it’s windy, the wind pushes around the air through which the sound of your voice is traveling, the friend up in the window will have a slight delay in receiving that sound. This can of course be verified with more scientific rigor, like a sound sent in two perpendicular directions activating a light.
Scientist at the time thought that light, like sound, must travel though some medium, and they called this theoretical medium the Aether. Since this medium is not locked to Earth, they figured they must be capable of detecting movement of this medium, an Aether wind, if you will. If somehow the movement of this medium caused the speed of light in one direction to be faster than another due to the movement of this medium, measuring the speed in two directions perpendicular to each other would reveal that difference. After a series of experiments of increasing distances and measurement sensitivities (think mirrors on mountain tops to measure the time for a laser beam to reflect), no change in the speed of light based on direction was found.
Here’s a fun fact that I think of every time I read about light delay.
We assume the speed of light is the same in all directions but there’s no way to prove that it is.
It could be light speed is instantaneous in one direction, and half the speed we think it is in the reverse. Any test we could devise depends on information traveling in two directions, nullifying any discrepancies in light speed.
The speed of light in a vacuum unaffected by external forces such as gravity should be the same no matter what direction it is in. I’m not sure why it wouldn’t be. That’s like saying a kilometer is longer if you go East than if you go West.
However, it’s actually far more complicated than that, and much of it beyond my understanding.
https://math.ucr.edu/home/baez/physics/Relativity/SpeedOfLight/speed_of_light.html
That said, direction should not matter.
There’s no reason it wouldn’t be. The point is that it’s impossible to prove that it is. There is no conceivable experiment that can be performed to prove the two-way speed of light is symmetric.
That’s not how anything works. It’s impossible to prove that the universe wasn’t created last Thursday with everything in place as it is now. There’s no point in assuming anything that can’t be proven has validity.
It’s just a thought exercise. There are several reputable YouTube videos on this topic. None of them claim that the speed of light isn’t the speed of light. They’re just demonstrating that we can’t prove it with current technology. Similar to the difficulty it took to finally prove that one plus one equals two. We know that’s correct, but it took years to prove it.
Couldn’t we send out two devices in different directions, wait a decade, have them shine light at eachother simultaneously, record when they receive the light, then send the times back to earth?
Your question is good. You’re missing understanding of time dilation and frame of reference. An explanation of the theory of relativity is at least pages long.
The first book I ever read on the subject, and IMO the best introductory text for any non-physiscist, is Stephen Hawking’s “A Brief History of Time”. But, any introduction to relativity should answer your question.
… but there is a way, and it has been proven.
One of the more memorable physics classes I’ve had went into the history of discoveries that led to our understanding of relativity. The relevant story here, starts with how sound travels though air.
Let’s say you’re standing at the bottom of a building shouting to your friend peeking out a window on the 5th floor. On a calm day, that friend will hear you at pretty much the same time as someone standing the same distance away, but on the street. However, if it’s windy, the wind pushes around the air through which the sound of your voice is traveling, the friend up in the window will have a slight delay in receiving that sound. This can of course be verified with more scientific rigor, like a sound sent in two perpendicular directions activating a light.
Scientist at the time thought that light, like sound, must travel though some medium, and they called this theoretical medium the Aether. Since this medium is not locked to Earth, they figured they must be capable of detecting movement of this medium, an Aether wind, if you will. If somehow the movement of this medium caused the speed of light in one direction to be faster than another due to the movement of this medium, measuring the speed in two directions perpendicular to each other would reveal that difference. After a series of experiments of increasing distances and measurement sensitivities (think mirrors on mountain tops to measure the time for a laser beam to reflect), no change in the speed of light based on direction was found.
Please enjoy this wikipedia hole: https://en.m.wikipedia.org/wiki/Michelson–Morley_experiment , and please consider a bit of caution before you refer to things as facts in the future!
How does the double slit experiment work into this?