Light & Space: Investigating the Unknown

[russ_watters]

I'm saying we can't know the true effects on light until we can go a light year away, shoot a laser back to earth, and study that light.

It may not give quite the same information, but studying light that has traversed much of or all of the universe is plenty helpful.

 

[john-of-the-divine]

We've basically done that. We can look at the light from certain light sources (different kinds of stars and related bodies) at very different distances and compare them. What do you think the main difference is in the light coming from a nearby star and one a few billion light years (LY) away?

ah, but all that is based on the belief that in space, the light takes x amount of time to travel x amount of miles, when we really don't know what the "fabric" of space time is made out of? I don't know, maybe I'm thinking too high for my tiny mind

 

[berkeman]

ah, but all that is based on the belief that in space, the light takes x amount of time to travel x amount of miles, when we really don't know what the "fabric" of space time is made out of? I don't know, maybe I'm thinking too high for my tiny mind

If you're really asking what the "fabric" of spacetime is, I think I'll move this thread to the Relativity forum, where you can get more knowledgeable replies. I'll mark it with a "B" prefix to let others know that you'd like responses on a Basic level.

 

[john-of-the-divine]

guess my guestiin can't be answered till we go out and see. not just

If you're really asking what the "fabric" of spacetime is, I think I'll move this thread to the Relativity forum, where you can get more knowledgeable replies. I'll mark it with a "B" prefix to let others know that you'd like responses on a Basic level.

lol. thanks guys.

 

[Ibix]

There isn't an answer to "what is spacetime" in relativity. Relativity just says that spacetime has non-Euclidean geometry and predicts the rules of that geometry based on the mass and energy present. It doesn't say what spacetime is or how mass and energy modify geometry, only that they do.

"We don't know, we're working on it" is probably the high level answer. I don't know enough about quantum gravity theories to comment authoritatively, but I think explaining at least some of "what is spacetime" is part of what they are supposed to do. But we don't have a complete quantum gravity theory yet, let alone a complete and tested one.

 

[john-of-the-divine]

ah, see, now that's what I'm trying to understand. I see the model of how gravity works in space-time, and I understand it, somewhat. so my original question is, how do we know that the "fabric" doesn't, over time, absorb, break down, destroy or even slowdown a photon of light? the math might work within our solar system but, what about the vast distance of space. if light is traveling through space-time, how can we know that there is no effect on the photon that is unseen, as of yet?

 

[rootone]

,,, I'm not a flat earther, but they have math that works too

No they don't.
Aside from which the Earth is observed to be a spheroid, unless you think satellites are fake or something.

 

[john-of-the-divine]

No they don't.

hence the reason why I said "or so it seems"

 

[Dale]

how do we know that the "fabric"

There is no fabric in GR. That is a very misleading pop-sci trope and is utterly useless for actually doing GR.

Spacetime is the geometry of physics. It consists of distances and angles. Since spacetime includes time the spacetime notion of distance includes duration and the notion of angles includes relative velocity. The math of spacetime is simply the math of a specific type of curved surfaces.

 

[john-of-the-divine]

empty space really is just empty space?

 

[rootone]

No, Quantum field theory suggests that everywhere in space has some or more or less of the same field stuff,
though the field is not itself a physical object, it is a distribution of probabilities.
If you think that's weird, a lot of people agree.

 

[Nugatory]

guess the real answer is I should have went to a school that I could never afford. t

There's some serious good news here: Thanks to the internet you don't have to go to a ridiculously expensive top-flight school to learn this stuff. Textbooks and lecturers' notes from very strong academic programs are available online; for example, Sean Carroll and Gerard t'Hooft have both placed first-rate general relativity textbooks on the web, and there are many more good online resources.

On the other hand, you do have to work at it. Plan on spending several years of the same sort of effort that you'd put into learning anything else worthwhile, and resist the impulse to skip learning the math that's needed to deal with all of physics since Newton (who more than three hundred years ago invented calculus because he needed it to solve the open physics problems of his era). Nonetheless... A few years of concentrated effort will give you what some of the smartest people who ever lived spent centuries developing... That's good news.

 

[john-of-the-divine]

I know there has to be something that mass effects to create gravity. I used the term "fabric" as a reflection of that something knowing it's really not a fabric, hahaha. But, this field, do you think it's the "aether", just different then what was once thought to exist?

 

[Dale]

empty space really is just empty space?

Yes, tautologically. X really is just X for any X.

 

[Dale]

But, this field, do you think it's the "aether", just different then what was once thought to exist?

The Michelson Morley experiment ruled out a rigid aether and ring interferometer experiments ruled out a dragged aether. The only aether that remains compatible with experiments is experimentally indistinguishable from no aether.

 

[john-of-the-divine]

There's some serious good news here: Thanks to the internet you don't have to go to a ridiculously expensive top-flight school to learn this stuff. Textbooks and lecturers' notes from very strong academic programs are available online; for example, Sean Carroll and Gerard t'Hooft have both placed first-rate general relativity textbooks on the web, and there are many more good online resources.

On the other hand, you do have to work at it. Plan on spending several years of the same sort of effort that you'd put into learning something else worthwhile, and resist the impulse to skip learning the math that's needed to deal with all of physics since Newton (who more than three hundred years ago invented calculus because he needed it to solve the open physics problems of his era). Nonetheless... A few years of concentrated effort will give what some of the smartest people who ever lived spent centuries developing... That's good news.

I've gotten most of my knowledge from science, discovery, ext. can see and I understand the theories, until I asked the great "what if" question. now I want to know what "it" is that mass effects to make gravity. guess I need to understand the math

 

[Dale]

I understand the theories

if that were true then you wouldn't be asking about fabric and aether. Pop sci sources are entertainment, not education. They make you feel good, but they don't teach you the theory.

It is good that they motivated you to ask more, but you need to recognize that if you are interested in the answers then you are going to have to unlearn a bunch of pop-sci baggage

I want to know what "it" is that mass effects to make gravity.

"It" is the geometry of physics

 

[Nugatory]

no, I haven't. how reliable is Wikipedia?

As @berkeman says, wikipedia is generally OK for well-understood stuff that's not near the cutting edge. A pretty good rule of thumb is that wikipedia coverage at the undergraduate level in math and science (but emphatically not the social sciences!) is probably reasonably good. Anything beyond that... Not so much. It is prudent to read the "Talk" section of any wikipedia article before you decide how trustworthy it is.

The Physics Forums policy is that wikipedia is not in general an acceptable source, but we routinely allow and provide links to wikipedia articles that the mentors have found to be good.

 

[john-of-the-divine]

The Michelson Morley experiment ruled out a rigid aether and ring interferometer experiments ruled out a dragged aether. The only aether that remains compatible with experiments is experimentally indistinguishable from no aether.

that's why i put it in quotations.

if that were true then you wouldn't be asking about fabric and aether. Pop sci sources are entertainment, not education. They make you feel good, but they don't teach you the theory.

It is good that they motivated you to ask more, but you need to recognize that if you are interested in the answers then you are going to have to unlearn a bunch of pop-sci baggage

"It" is the geometry of physics

that's why I'm here. and I ment I might not know the math, but I can invision it. beyond what their cg shows us

 

[Dale]

that's why I'm here

Excellent!

What is your math background? If you know algebra and vectors you can start with special relativity and spacetime.

 

[john-of-the-divine]

Excellent!

What is your math background? If you know algebra and vectors you can start with special relativity and spacetime.

see, that's my biggest problem, I've never been able to make myself do math. I've always had a great imagionation, and that's good, till it takes me away from what I'm trying to consentrait on.

 

[Dale]

I've never been able to make myself do math.

Then realistically I think that you have to pick a different goal. At least I don't know of a way to learn physics without doing math.

 

[rootone]

You were asking earlier about knowing the math.
I am not any kind of math expert, but I think if you can grasp Newton's Principia, then you are doing OK.
If you want to build a bridge over a river it works just fine.

 

[john-of-the-divine]

honestly, I'm trying to figure out why you think light coming from billions of light years away hasn't been altered by the space it's traveled through. if you can explain, without math, exactly what causes the effect of gravity and how it effects light, I will understand. if you can't explain without numbers, then what makes the math so infallible? but I guess that's why it's all only theoretical, which makes none of it fact. I just wanted to know how do you know %100 that the light from billions of light years away, when in fact, it's nothing more than a best guess? even though I'm no math expert, it really isn't that far fetched to believe the math could have been forced to fit a model. just because the math works doesn't make it anything less then a best guess. but, like I said, we won't know for sure till we go out there and look.

 

[rootone]

https://en.wikipedia.org/wiki/Tired_light
Probably not.

 

[john-of-the-divine]

like I said earier, I'm thinking bigger than my tiny brain can handle. thank you for the info you have shown me

 

[rootone]

You might find this is interesting,

 

[Dale]

. if you can explain, without math, exactly what causes the effect of gravity and how it effects light, I will understand

I cannot explain it without math. What good reason could you possibly have for rejecting a valid answer simply on the grounds that it contains math?

. if you can't explain without numbers, then what makes the math so infallible?

Because the math accurately predicts the results of our best physical experiments and astronomical observations. How do you expect to predict something quantitative without math?

just because the math works doesn't make it anything less then a best guess

That is why we do experiments too. To ensure that the math correctly describes part of nature.

I just wanted to know how do you know %100

"100%" is math. So you can clearly do some math

like I said, we won't know for sure till we go out there and look.

And when we do go out there and look we will have to use math to understand what we see.

Frankly, your anti math stance just comes off poorly here. If you don't want to learn math, that is fine, but don't delude yourself into thinking that an answer doesn't exist when you are simply unwilling to learn it. The deficiency is not in the answer.

 

[john-of-the-divine]

You might find this is interesting,

I'm deffenetly going to finish that later. thanks

 

[john-of-the-divine]

I cannot explain it without math. What good reason could you possibly have for rejecting a valid answer simply on the grounds that it contains math?

Because the math accurately predicts the results of our best physical experiments and astronomical observations. How do you expect to predict something quantitative without math?

That is why we do experiments too. To ensure that the math correctly describes part of nature.

"100%" is math. So you can clearly do some math

And when we do go out there and look we will have to use math to understand what we see.

Frankly, your anti math stance just comes off poorly here. If you don't want to learn math, that is fine, but don't delude yourself into thinking that an answer doesn't exist when you are simply unwilling to learn it. The deficiency is not in the answer.

I'm not necessarily anti math, and I'm not unwilling to learn it, i was just looking for explanations that don t evolve math. sorry to waste your time. thank you for at least trying.

 

[Orodruin]

I'm not necessarily anti math, and I'm not unwilling to learn it, i was just looking for explanations that don t evolve math. sorry to waste your time. thank you for at least trying.

To be quite blunt, trying to accurately explain physics without math is like trying to explain the color green to a blind person.

 

[shihab-kol]

You have to take maths into the picture.
Maths is the car which shall make your physics ride more interesting and comfortable
To get to the point:
Photons have energy and energy generates gravity according to general relativity. However the gravity force is an extremely weak force for small objects, so for the gravity between individual elementary particles or between photons the force of gravity would be completely negligible and unmeasurable.

 

[Dale]

i was just looking for explanations that don t evolve math

I don't have such answers. Scientific answers involve assumptions, math, and experiments.

 

[nitsuj]

To be quite blunt, trying to accurately explain physics without math is like trying to explain the color green to a blind person.

wow...just wow.

 

[nitsuj]

I just wanted to know how do you know %100 that the light from billions of light years away, when in fact, it's nothing more than a best guess? even though I'm no math expert, it really isn't that far fetched to believe the math could have been forced to fit a model. just because the math works doesn't make it anything less then a best guess. but, like I said, we won't know for sure till we go out there and look.

You seem to be taking a philosophical position regarding "proof "
It is far fetched to think that the math was "forced" to fit a "model"...particularly when the "model" is described by math lol

"Forcing to fit" the model is when we use words to describe the model, instead of math. Such as forcing the word "fabric" into the concept of spacetime geometry.

I explored square root once so I could understand it better. Like in all of physics math, the concept of square root has basis in the physical world.

Read about math, the concepts ect. Follow along reading the equations, look up what they mean...until you find an example of "forced to fit" and present it here; as of now I don't think "forced to fit" is well defined if at all.