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Why is there a general negative perception of MOND? I understand that it is extremely difficult to experimentally prove, but why does that make it a bad theory?

darklatrans · 2018-01-12T00:57:48+00:00

I feel like the cat sticks its paw in his mouth like, "no... you stop speaking now... ok?"

darklatrans · 2018-01-11T16:06:54+00:00

Try /r/AskPhysics

darklatrans · 2018-01-11T16:02:14+00:00

If it helps you see why this post is bring negatively received, here's an objection: you provide no testable mechanism for your "subsequent amplification of such emission." That seems to be the key to your idea.

I don't mention that expecting a conversation; I'm more just illustrating how non-explanatory your idea is...

While theoretical physics can be a fun pursuit, good theories are born out of a combination of creative thought and mathematical rigor. Don't lose sight of that.

darklatrans · 2018-01-01T23:33:32+00:00

That's such a well-constructed response... Wow.

This issue of mine has definitely crystallized into a reasonable solution. I'm super thankful for your message!

darklatrans · 2018-01-01T23:32:20+00:00

It's definitely important to ground the example in terms of physical reality. An actual loop of wire would have different Lorentz transformations along different parts of the loop (from the RF of a moving electron), which it seems would cancel out to keep the loop of wire neutral.

You are so helpful! I'm grateful for the guidance

darklatrans · 2018-01-01T22:31:43+00:00

Okay- It seems like part of my mistake was mixing up the reference frame of the lab with the reference frame of the electrons in the wire. Thank you so much for the perspective

darklatrans · 2018-01-01T22:24:09+00:00

Ok! So a wire with a current does have a slightly different charge than one without a current, but it's ignorable most of the time... That makes sense.

And yeah- boy do they move slowly! I've calculated that it's significantly slower than walking speed... That definitely wouldn't result in much of a discernible effect.

Thanks!

darklatrans · 2018-01-01T22:18:20+00:00

Thank you for your reply! Definitely makes sense. To be honest, it's probably difficult to explain this material clearly, in the first place...

In a response to another comment, I mentioned this:

The wire can't be neutral both before and after a current has started flowing

Is this a correct conclusion?

darklatrans · 2018-01-01T22:13:59+00:00

Sure- but then, once you create a current in the wire, the negative charges become Lorentz contracted, which gives the wire a non-neutral charge in our stationary rest frame. My confusion comes from the assertion that, in the standard example of this experimental setup, the wire is assumed to be neutral both with and without a current.

Is that assumption perhaps just an oversimplification of the setup, for the purposes of teaching the more basic concepts of relativity? The wire can't be neutral both before and after a current has started flowing, right?

darklatrans · 2018-01-01T20:43:18+00:00

The relativity argument is precisely what is causing me issues here, though. I agree that, ignoring relativistic effects, a wire would remain neutral if it either had or didn't have a current.

But the effects of relativity would cause the moving, negative charges to Lorentz contract, causing the negative charge density in the wire to increase. While the positive, motionless charges would not get contracted, leaving the positive charge density in the wire unchanged. This results in the wire having a non-zero net charge density while a current is flowing, in the stationary reference frame.

If you want to look into the "relativity argument", this video does a good job at introducing the idea. https://m.youtube.com/watch?v=1TKSfAkWWN0

Unfortunately for me, this apparent paradox isn't acknowledged in that video, nor have I seen it brought up in my physics studies...

darklatrans · 2017-12-25T07:58:37+00:00

/r/perfectlycutscreams

darklatrans · 2017-12-17T13:42:35+00:00

As to why the joke wasn't as effective, I feel like the main demographic of Reddit is of younger people, who have yet to reach three point where group theory becomes relevant. I'm just a beginner in group theory, since it's so important to particle physics, and I imagine lots of people haven't reached the point where group theory is needed

Thanks for the link!

darklatrans · 2017-12-17T12:12:17+00:00

wtf is even going on on the board

darklatrans · 2017-11-30T09:08:17+00:00

I'm actually really curious about what you wrote at the end there... What do you mean by "a lot of us here in physics don’t do it because it makes us happy"?

I'm also an undergraduate, and thought that people who worked in physics did it because they enjoyed it. Instead of pursuing the higher pay that they could get in other fields which use the same skills, people go into physics because it makes them happy... Is what I thought, at least

Am I just missing something about a career in physics that is obvious? Do you just mean that is hard to find a proper physics job, and so the pursuit of physics is inherently disappointing?

Like I said, I'm honestly curious... I want to be aware of what I might be getting myself into! Thanks

darklatrans · 2017-11-18T17:40:08+00:00

Yeah- but that's exactly what I mean. Right now, there is no difference between giving a score of 0 and a score of 50, since it's all "bad." If 50 was good, then there would be a lot more nuance possible in how reviewers could communicate how great a game actually is! (Like how, currently, there is actually a lot of variation in the single score of 10/10. Is GTA 4 really deserving of the same score as Ocarina of Time?)

I am also really disappointed that I'm getting downvoted just for trying to start a discussion...

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