Exploring Light & Matter: Questions & Answers

[vcandy]

TL;DR Summary

Simply thinking about the universe and correlation between light and matter...

Ok, so where do I begin? So I'll try to make this as short as possible sparing you all my issues.

I like thinking about what is. My math takes me as far as pre-calc, but have no training in this field. I have the utmost curiosity in understanding the functioning of everything. Specifically, the relationship between light and matter.

From the things I have read, light has a speed limit and for how vast the universe is, it appears rather slow.

I also know that at the smallest of levels things can happen instantly.

I am perplexed by this problem. By the way feel free to delete my account for sounding stupid.

I just want to understand this dilemma in my mind. So here it goes... Thanks in advance for anyone's thoughts.

If I were to replace our star, the Sun, with a star of greater mass such as Betelgeuse in our solar system what would happen? And what I mean by this is that if I hypothetically put myself on the outer surface of Betelgeuse what would happen if the star exploded? If I assume the core of this star was ground zero for the explosion and I reside 30 light minutes from the core would I explode with the star instantly or would the star explode and I would have to wait 30 light minutes to experience my explosion?

Or I even thought that if I were to take a ceiling fan and extend the blades out 100 light years long and turn it on, would not the blades on the outer edges speed beyond the speed of light?

I know this is a stupid idea, but cannot quite grasp what either outcome would be...

 

[PeterDonis]

Moderator's note: Moved thread to the relativity forum as the question appears to be better suited for that forum.

 

[DaveE]

I would have to wait 30 light minutes to experience my explosion?

Yes. Assuming we ignore lots of practical difficulties with your experiment.

if I were to take a ceiling fan and extend the blades out 100 light years long and turn it on, would not the blades on the outer edges speed beyond the speed of light?

No. Whether the blades are 100 light-years long or 1 meter long, it would take an infinite amount of energy to get the matter at the ends to move at the speed of light. You just can't spin it that fast, your motor isn't strong enough.

By the way feel free to delete my account for sounding stupid.

You absolutely don't sound stupid. You sound like you are learning some physics. These are reasonable questions, and this is a good place to ask them.

 

[PeterDonis]

If I were to replace our star, the Sun, with a star of greater mass such as Betelgeuse

You can't. Mass can't just disappear or appear or discontinously change in relativity. It has to be locally conserved. So there's no way of even formulating a scenario like you describe here in relativity.

However, it seems like the question you're actually asking could be framed by just asking "what if we were in the Betelgeuse star system watching that star explode?" without having to drag in "replacing" the Sun with Betelgeuse. So I'll assume that's the actual scenario in what follows.

If I assume the core of this star was ground zero for the explosion and I reside 30 light minutes from the core would I explode with the star instantly or would the star explode and I would have to wait 30 light minutes to experience my explosion?

The latter. The effects of the explosion would propagate outward from the core no faster than the speed of light. Actually, many of the effects would propagate much slower, but at the very least the burst of neutrinos from the core explosion would be traveling at or near the speed of light and would take 30 minutes to get from the core to you at the surface.

if I were to take a ceiling fan and extend the blades out 100 light years long and turn it on, would not the blades on the outer edges speed beyond the speed of light?

No, because the blades would not be rigid. When you turned the fan on, one end of the blade would start moving, but it would take 100 years (at least--the actual speed would probably be much slower, but we're imagining the blades to be made of some hypothetical super-material in which the speed of propagation of changes to the material's motion is the speed of light) for the other end to start moving. For those 100 years, the blade would be bent, and the bending would propagate down the blade. Depending on how fast you tried to spin the blades, the blades might even break. Certainly they would break if you tried to spin them fast enough for the outer edge to move faster than light.

 

[A.T.]

Or I even thought that if I were to take a ceiling fan and extend the blades out 100 light years long and turn it on, would not the blades on the outer edges speed beyond the speed of light?

 

[strangerep]

I also know that at the smallest of levels things can happen instantly.

Wrong. (I have no idea where you got this idea.) Physical effects do not propagate faster than lightspeed.

I am perplexed by this problem. By the way feel free to delete my account for sounding stupid.

If you suspect some part of your understanding is "stupid", it would help to mention what source(s) gave you that (mis-)understanding, so that it can be corrected in-context if possible.

 

[Delta2]

No, because the blades would not be rigid. When you turned the fan on, one end of the blade would start moving, but it would take 100 years (at least--the actual speed would probably be much slower, but we're imagining the blades to be made of some hypothetical super-material in which the speed of propagation of changes to the material's motion is the speed of light) for the other end to start moving. For those 100 years, the blade would be bent, and the bending would propagate down the blade. Depending on how fast you tried to spin the blades, the blades might even break. Certainly they would break if you tried to spin them fast enough for the outer edge to move faster than light.

What if the blades were made from an unknown to us yet material such that the speed of propagation is much greater than the speed of light (10^100 faster). Oops but I forgot we are in relativity forum, speed of light is the upper limit for all sort of waves even mechanical and sound waves.

 

[PeterDonis]

What if the blades were made from an unknown to us yet material such that the speed of propagation is much greater than the speed of light

No such material is possible. Relativity forbids the speed of propagation in any material from being faster than the speed of light.

I forgot we are in relativity forum

Even if you asked the question in another forum, it would just get moved here, because your question is outside of the domain of validity of non-relativistic physics to begin with.

 

[Delta2]

No such material is possible. Relativity forbids the speed of propagation in any material from being faster than the speed of light.

We don't know what materials there are out there. For example dark matter. I know dark matter is probably not rigid, since there is no EM interaction between particles which is responsible for making the matter rigid but anyway just saying, we don't know what the speed of wave might be inside a "fluid" made of dark matter.

Even if you asked the question in another forum, it would just get moved here, because your question is outside of the domain of validity of non-relativistic physics to begin with.

Δεν παίζεσαι... ε χεχε

 

[PeterDonis]

We don't know what materials there are out there.

We do know what limits relativity places on all materials. Please do not engage in unfounded speculation.

 

[Delta2]

Please do not engage in unfounded speculation

Ok well, just saying relativity might not be absolutely correct. But I might have crossed the barrier of mainstream physics ok i ll stop

 

[PeterDonis]

just saying relativity might not be absolutely correct.

Which, as I said, is unfounded speculation. And even founded speculation along these lines (such as discussion of papers on various hypothetical models of how Lorentz invariance might be violated) belongs in the Beyond the Standard Model forum, not here.

 

[Ibix]

We don't know what materials there are out there.

All materials are held together by EM forces, so the speed of light is the maximum possible speed for anything to propagate through mechanical means. When I poke an atom at the end of a rod, the next atom doesn't find out about it until the change in the EM field of the first atom propagates to its location, and EM field changes propagate at or below lightspeed. Even if you posit materials held together by forces other than EM, they all propagate changes at or below lightspeed. They have to, as anything faster would violate Lorentz covariance.

So, unless we find experimental evidence of violations of Lorentz covariance (and there is none to date, despite active research), then we can predict that there are no materials with sound speeds above light.

 

[vcandy]

Wow! All the cool responses! Thanks everyone... Now if only I could get my wife to respond proactively to my questions I could almost have a complete understanding of this crazy universe.

 

[vcandy]

Wrong. (I have no idea where you got this idea.) Physical effects do not propagate faster than lightspeed.

If you suspect some part of your understanding is "stupid", it would help to mention what source(s) gave you that (mis-)understanding, so that it can be corrected in-context if possible.

I thought quantum entanglement was just that. Two entangled particles having an affect on each other even over vast distances instantly. Not sure if this is accepted as truth or not in the science community.

 

[Ibix]

I thought quantum entanglement was just that. Two entangled particles having an affect on each other even over vast distances instantly. Not sure if this is accepted as truth or not in the science community.

Definitely not, although it's often presented as such in popsci, even by people who know better. An analogy is if I post you one of my shoes and send the other one to my mum. When you open the packet you'll find it's either a right shoe or a left shoe and you know instantly which shoe my mum has. No faster than light anything needed.

That analogy isn't perfect, since it relies on what are called "local hidden variables", and quantum physics doesn't. But it communicates the important point: you know instantly what the other shoe is and you cannot use that fact to communicate with anyone, let alone communicate faster than light.

 

[vcandy]

Nice piece... I see.

 

[strangerep]

I thought quantum entanglement was just that. Two entangled particles having an affect on each other even over vast distances instantly. Not sure if this is accepted as truth or not in the science community.

Emphasizing, and adding to, @Ibix's reply... the 2 particles cannot "affect" each other via entanglement alone. This is a classic misunderstanding of the fact that correlation does not imply causation. Even Brian Cox gets this wrong in one of his TV episodes where he suggests that an event here on Earth could have an instantaneous effect in the Andromeda Galaxy.

As Ibix implied, the crucial issue is whether information can be transmitted using the supposed FTL (faster-than-light) mechanism.

Now if only I could get my wife to respond proactively to my questions I could almost have a complete understanding of this crazy universe.

Good luck. Some things in life are forever non-understandable (sigh).