Ask any question you want about Physics

originally posted by: ImaFungi

Yeah I understand your comment because you have used it in my vicinity before, its not as clever as you think and it is more a tool of deflection than anything else, an example of anything else being actually brave up and walk towards the pain of having a discussion with me in which I prove what you are saying to be incorrect.

You often mistake the map for the territory. Like now.

a reply to: Arbitrageur

What is the process that originated some of the Ultra High Energy Cosmic Rays detected on the evening of 15 October 1991 over Dugway Proving Ground, Utah, by the University of Utah's Fly's Eye Cosmic Ray Detector?

Its observation was a shock to astrophysicists (hence the name), who estimated its energy to be approximately 3×1020 eV (3×108 TeV, about 20 million times more energetic than the highest energy measured in radiation emitted by an extragalactic object)

Thanks!

Is there a point at which the number of photons emitted from a source stops acting at particles and starts acting like a wave? And what is that point and is it always the same?


Also, We know that time appears to slow down for an observer travelling at speed, and the closer you get to light speed, the more it slows, but what is the "speed of time" for an object at rest? (Ie, not part of a galaxy travelling through the universe at x mph).

a reply to: ATSAlex
Great question, because I'd also like to know the source(s) of the highest energy cosmic rays.

High energy cosmic rays are a subject of ongoing research and we don't have all the answers and don't know the source of that event. We do detect a handful of very high energy particles each year, and think they are probably accelerated by giant natural accelerators, but until we can more accurately determine the sources, we have to say we don't know. One common thought is that black holes may be involved. I think the ongoing research will eventually be fruitful and give us some better answers.

originally posted by: SprocketUK
Is there a point at which the number of photons emitted from a source stops acting at particles and starts acting like a wave? And what is that point and is it always the same?

Not based on the number of photons, but based on the frequency of the photons, yes. I don't know of an exact "cutoff" as the electromagnetic spectrum is continuous so it's more of a gradual transition, but long wavelength photons in radio wave frequencies act more like waves, and short wavelength photons like X-Ray or Gamma Rays tend to be more particle-like. Theoretically all photons should have wave particle duality, so it's really a matter of how easily such behaviors are observed. It turns out to be very difficult to observe the particle-like behavior of photons in the radio wave spectrum.

Also, We know that time appears to slow down for an observer travelling at speed, and the closer you get to light speed, the more it slows, but what is the "speed of time" for an object at rest? (Ie, not part of a galaxy travelling through the universe at x mph).

There is no answer to this in general relativity, which doesn't say there is any ultimate reference frame. If you want to establish the cosmic microwave background as a standard reference frame, you could try to estimate how much slower the clocks on Earth run from the perspective of an observer stationary relative to the cosmic microwave background, in a low gravitational field.

I never tried to calculate this, but just guessing I'd expect the amount our clocks run slower to be some fraction of a second per 24 hour day, so our clocks are slowed down a tad by our motion and gravitational field, but not a whole lot. Actually I'm extrapolating that guesstimate partly from what we use to calibrate GPS clocks, so it's not a completely uneducated guess. If you wanted to make some assumptions and do some calculations you could probably come up with a number, but I've not yet run across anybody who has done that. Part of the problem with trying to find a reference to compare with Earth is that there is nowhere with a zero gravitational field, so even an observer stationary relative to the cosmic microwave background will have their clocks slowed down by some small gravitational field that exists wherever they are, even in the void between galaxies.

a reply to: Arbitrageur
Thanks for that. I realise that they may have been rather left field questions and that things dont always translate form human experience into the strangeness of the physical universe, it's just something that bugged me since I watched a show saying that galaxies move at a massive speed through the universe.

originally posted by: SprocketUK
a reply to: Arbitrageur
Thanks for that. I realise that they may have been rather left field questions and that things dont always translate form human experience into the strangeness of the physical universe, it's just something that bugged me since I watched a show saying thet galaxies move at a massive speed through the universe.

The speed of the Milky Way galaxy (552 kilometers per second according to this source) is fast compared to the speed of a car or a plane. Let's say the SR-71 traveled about 1 kilometer per second.

But, relative to the speed of light, which is 299,792 kilometers per second, 552 kilometers per second isn't all that fast. We can calculate that effect on clocks exactly, just put 552/299792 = .00184 into this relativity calculator:

www.1728.org...

The answer is that for every million seconds on the "stationary" CMB clock, a clock traveling with the Milky Way galaxy will only show 999,998.3 seconds, so you lose nearly 2 seconds out of every million due to the speed of the Milky Way, from the perspective of an observer stationary with respect to the CMB. Not much, right?

a reply to: PhotonEffect

There's data. Then there's interpretation of that data. And invariably, the interpretations will differ amongst the subjective entities processing such data. There are differing opinions amongst scientists all the time. It is these differing views that can lead to progress, and can show just how wrong the previous data was, or just how wrong our interpretation of that data was. I guess, this is science. A realization of a different way to see the world.

Yes, there are differing opinions based on the experimental evidence, but that isn't philosophy. That's just exploring the evidence. Repeating the experiment and confirming the data is what validates the evidence. Of course, depending on what branch of hard science you're in, the type of experimental data you have is going to differ. If you look at the spectra below (and I just picked this up from Wikipedia - it's not mine), whoever repeats the 13 C NMR spectrum of
diphenyl selenide should come up with the same spectra. That might be overly simplistic, but the key point is that results of any experiment must be repeatable. If it isn't then you find out why it isn't. This is a very basic rule of scientific research.

Nima Arkani-Hamed has very controversial theories in QM. He disagrees with some of the top stars in the field. But he can speculate all he wants because in the end, it's his equations and experimental data (if he can get it) that count.
BTW, he's a very interesting guy - here's a link to a couple of his YouTubes:
www.youtube.com... - if you scroll to 52 minutes, you'll get the jist of his ideas.
www.youtube.com...

But science and humans are intimately connected. It is, after all, written by the human for the human. We describe the world with our own language and concepts. We think that gravity is a force, and the world is made of particles. These are all human ideas.

Gravity and particles are not "human ideas". They are phenomena discovered first by theoretical work and then by experiment. Humans didn't make up gravity. It is a fundamental part of our universe. If there were no humans, gravity would still be there. Humans have no effect on gravity. Gravity and "particles" (we'll have to get rid of that word some day) are independent of human intervention.

Mathematics is a human construct - I agree with this. It's a tool. But again, new mathematical proofs have to be challenged.

We have processes in place to analyze data objectively. I don't see a role for philosophy in the lab.

originally posted by: Bedlam

You often mistake the map for the territory. Like now.

No.

I only, question how accurately the map represents the territory.

a reply to: Phage

i.e. what is a one?

I got a feeling he might be incorrectly showing you with his finger. Sorry couldn't resist.

originally posted by: Arbitrageur

originally posted by: SprocketUK
a reply to: Arbitrageur
Thanks for that. I realise that they may have been rather left field questions and that things dont always translate form human experience into the strangeness of the physical universe, it's just something that bugged me since I watched a show saying thet galaxies move at a massive speed through the universe.

The speed of the Milky Way galaxy (552 kilometers per second according to this source) is fast compared to the speed of a car or a plane. Let's say the SR-71 traveled about 1 kilometer per second.

But, relative to the speed of light, which is 299,792 kilometers per second, 552 kilometers per second isn't all that fast. We can calculate that effect on clocks exactly, just put 552/299792 = .00184 into this relativity calculator:

www.1728.org...

The answer is that for every million seconds on the "stationary" CMB clock, a clock traveling with the Milky Way galaxy will only show 999,998.3 seconds, so you lose nearly 2 seconds out of every million due to the speed of the Milky Way, from the perspective of an observer stationary with respect to the CMB. Not much, right?

Well i was thinking about this and yes you can get a basic time unaffected by speed. Einstein allowed us to do this, Adding the total movement through both space and time always equals light speed. Spacetime is interlinked you the faster you move through space the slower time becomes or the faster time becomes the more space increases. Your movements through time and space is a give and take a body at rest is only moving through time.This is why yeah i can say we can calculate that heck might get a student to do it lol.

Spam removed by admin.

a reply to: Arbitrageur

That's a cool way to look at it. Would there be much Change if you factored in the spin of the earth, it's orbit about the sun and the solar systems orbit around the galactic centre? Or does that not really affect things?

a reply to: dragonridr

Awesome. Glad I provided someone with homework :-D

a reply to: dragonridr
Isn't that what I calculated? That considered only velocity.

The calculation that would be more difficult is in general relativity where you consider gravitation also, because then where do you put the reference observer, and what kind of gravitational field do they experience? It's a lot easier if we can disregard gravity, but as I'm sure you know the strength of the gravitational field also affects the passage of time.

originally posted by: SprocketUK
a reply to: Arbitrageur

That's a cool way to look at it. Would there be much Change if you factored in the spin of the earth, it's orbit about the sun and the solar systems orbit around the galactic centre? Or does that not really affect things?

In an apparent paradox, you will actually get less time dilation when you factor in the other motions, at least at our current position in our orbit around the Milky Way galaxy.

If you walk while twirling a ball on a string over your head, the speed of the ball relative to Earth is added to your walking speed when the ball travels forward (in the same direction as you're walking), and is subtracted from your walking speed when the ball is moving backward. The point of the sun's orbit of the Milky way is more like the latter at the moment. As a result the the sun's estimated velocity relative to the CMB at about 370km/s is actually slower than the Milky Way's velocity relative to CMB of 552 km/s.

The other factors you mention can be calculated but aren't all that significant. For example, the Earth's rotation, even at the equator, amounts to less than 0.5km/s, and the velocity from the Earth's orbit around the sun is a little more significant (about 30 km/s) but still not that much compared to 370 km/s. Once again you may find that part of that velocity is added or subtracted depending on where the Earth is in its orbit. Not counting gravity, I'd expect just the velocity related time dilation we experience relative to the CMB is a little less than 1 part in a million, overall, but it will be quite a bit more in 120 million years when the Sun is on the other side of the Milky Way (that's about half the time of one orbit of the sun around the Milky Way). Then the sun will be moving faster than the Milky Way, when the sun's orbital motion will be better aligned with the Milky Way's motion, and our time dilation relative to the CMB will be more like 2.5 seconds out of a million seconds, instead of less than 1 second per million seconds currently.

a reply to: Arbitrageur

I was thinking of starting with a simple base like the drop tests they did removes gravity out the mix. From there just means factoring in variables. But even with this I suspect the diffrence to be a million billionth of a second or so from the drop test.

Hi all,

I am only getting to the basics of physics. With that said, I have noticed ongoing debate on say, photon duality, is it a wave or a particle.
Problem as I see it is that if its a wave then there must be medium what is waving, with the particle it is unclear what keeps photon (energy) as such having scientist to come up with point like stuff.

Can someone tell me if my guess is right in regards what I am about to say...

Personally it seems to me that energy outside an atom is a wave, it spreads and interacts following the known rules of the wave becoming 'white noise' over billion of years, sort of like a background uniform fluctuation resulting in uniform general frequency after so many wave overlapping and what not.

If we for a second stop right here, is it possible that the medium for the light wave is....light wave.

Imagine energy on the loose wondering across cosmos, interacts, bounces, creating new patterns but always tends to 'flat line', as is to become as 'red' as possible, find rest in total calm, absence of frequency.

Ancient, primordial light in this scenario could be serving as a 'medium' for other light wave to be born and spread when photon is released.

I will attempt to make a prediction based on what I said)))

If we create lab conditions where inside the collision chamber will be no energy (no waves), cancel out it somehow than, say electron - positron annihilation wont tale place because resulting photon will have no 'medium' to escape into.


cheers!!!!!

originally posted by: darkorange
If we for a second stop right here, is it possible that the medium for the light wave is....light wave.

Sort of, we say it's self-propagating, so you can say the light is what's propagating itself, though I wouldn't use the term "medium", which is why I said "sort of".

Ancient, primordial light in this scenario could be serving as a 'medium' for other light wave to be born and spread when photon is released.

The primordial EM radiation is called the cosmic microwave background and its way too low a frequency to be in the range of visible light. I've seen no evidence it's any medium for propagation. You could do an experiment in a faraday cage designed to block out the CMB and all other primordial EM radiation to test your idea.

I will attempt to make a prediction based on what I said)))

If we create lab conditions where inside the collision chamber will be no energy (no waves), cancel out it somehow than, say electron - positron annihilation wont tale place because resulting photon will have no 'medium' to escape into.

Even if you could make a chamber with no energy (nearly impossible as you always have some thermal radiation since nothing is at absolute zero), as soon as the electron and positron annihilated, there would be energy.

Here's a flash demonstration showing how EM radiation propagates itself without any medium:

math.ucr.edu...

a reply to: darkorange


According to my understanding there are a few reasons the nature of light is confounding;

If light was only; separate balls which traveled from point A to Z to be caught in a system of matter, and the ball of light always existed and than that system of matter could toss the ball away creating a new point A to Z traveling of that ball; Then the nature of light would be quite easy to comprehend.

If it is not only that; Then that forces us to assume the nature of light must be some more complex, sophisticated, intricate, intriguing way; at least, not the simplest way it could be; which would be, light balls which are separate from each other, which travel from points A to Z.

I will stop here; The universe is 3d/4d; If the aspect of the universe we refer to as light, is not light balls as described above; what are some of the possible ways we may think in which light might exist?

A physical, bodily finite object that moves as a separate object unto itself.

As a light like particle, like wave; can we imagine a see-saw that fits in your hand, and when you throw it, it see-saws up and down while moving forward?

Or like if you were to throw a big water balloon, and we can imagine its inner contents moving forward around its center, and then this forcing the material casing at the poles to whiplash forward, which would then be in front of the center, and pull the center forward, and vice versa back and forth;

This is the kinds of way I can think of a particle like wave like, self motivating self propagating object;

a reply to: Phantom423

Gravity and particles are not "human ideas". They are phenomena discovered first by theoretical work and then by experiment. Humans didn't make up gravity. It is a fundamental part of our universe. If there were no humans, gravity would still be there. Humans have no effect on gravity. Gravity and "particles" (we'll have to get rid of that word some day) are independent of human intervention.

Yes yes. I didn't mean to suggest that the phenomena that underlies these concepts don't actually, physically exist. There clearly is something there that acts on matter in a particular manner. We didn't discover it. It's always been. We just realized it, gave it a name and described in certain human terms how it might work. But we don't know what gravity really is, nor do we with particles.

If there were no humans then our concept of gravity ( as a force which causes things to attract) and the maths used to measure it would not exist. Sure, the true objective thing is there, but it's not gravity, nor is it a force of attraction. It's something else entirely.

We have processes in place to analyze data objectively. I don't see a role for philosophy in the lab.

Sure. I get all of that, and understand why philosophy is useless in a lab. But again anything created by humans must in some sense involve human subjectivity. The processes themselves came from human brains. The data is perceived, analyzed and interpreted by humans. How do we get a true objective sense of what is out there? We can't. And a computer can only do what we tell it to. ( at least for now )

Thanks for the chat. Don't mean to derail things here. Cool convo going on.

Cheers~

originally posted by: darkorange
Hi all,

I am only getting to the basics of physics. With that said, I have noticed ongoing debate on say, photon duality, is it a wave or a particle.
Problem as I see it is that if its a wave then there must be medium what is waving, with the particle it is unclear what keeps photon (energy) as such having scientist to come up with point like stuff.

There isn't any medium that is waving. We got rid of aether back in 1905. You don't need anything for it to wave in. It is sort of a pushme-pullyu.