Light & Space: Investigating the Unknown

[john-of-the-divine]

how do we know light stays consistent when traveling through the "not nothingness of space"? how do we know the rate at which light degrades as it travels through the medium that has to be there?

 

[Arman777]

how do we know light stays consistent when traveling through the "not nothingness of space"? how do we know the rate at which light degrades as it travels through the medium that has to be there?

I want to help but I didnt understand your question

 

[john-of-the-divine]

Ok, isn't there a substance within "empty space" that was at least once called aether?

 

[Arman777]

Ok, isn't there a substance within "empty space" that was at least once called aether?

Theres no substance in empty space.Theres no aether.

In old days people thought that "waves" need medium to travel.Like sound need a medium etc.So people in those days thought light is a wave so it should need a medium to travel which they called it aether.But Michelson–Morley experiment showed us that, there's no aether.

 

[john-of-the-divine]

ah, but there was two conclusions derived from that experiment, or so I've read. I also read that Einstein said there has to be something or gravity itself didn't work. my understanding of that experiment was more or less deemed "inconclusive". if there is no medium, how does gravity work? I veiw gravity as pushing, not pulling. is that false?

 

[Comeback City]

ah, but there was two conclusions derived from that experiment, or so I've read. I also read that Einstein said there has to be something or gravity itself didn't work. my understanding of that experiment was more or less deemed "inconclusive". if there is no medium, how does gravity work? I veiw gravity as pushing, not pulling. is that false?

Is your question about light or gravity? It seems like you are mixing concepts together where you don't have to...
Indeed, scientists once believed there was a medium (which they called the aether) in which light needed in order to travel. This was disproved, as electromagnetic waves do not need a medium to travel through.
If you have questions about gravity, could you elaborate on them a little bit further?

 

[Arman777]

I also read that Einstein said there has to be something or gravity itself didn't work.

Where ? Any source ?

my understanding of that experiment was more or less deemed "inconclusive".

Its not inconclusive..Its a fact of nature..Light doesn't need a medium to travel.

if there is no medium, how does gravity work?

"Spacetime tells matter how to move; matter tells spacetime how to curve"(John Archibald Wheeler)
.Gravity is a fact of space-time curvature.

I veiw gravity as pushing, not pulling. is that false?

Pushing pulling is strange words to describe the situation I guess.I would say matters attract each other

 

[john-of-the-divine]

my question is how do they know how far light can travel? I think the term "space-time" needs further evaluation because I don't understand how gravity works if there's just nothing in space to bend. and if there is something, how do we know it's true effect on light?

 

[Vanadium 50]

I think the term "space-time" needs further evaluation because I don't understand how gravity works

The fact that you don't understand something doesn't make it wrong.

 

[john-of-the-divine]

do you understand what makes gravity? think of a surffer, does the wave push or does it pull him? so, what is it that mass bends to make gravity happen? I'm under the impression that science still doesn't understand gravity or what really causes this effect. how can something bend nothing?

 

[russ_watters]

my question is how do they know how far light can travel?

What is "known" so far is what has been observed: light has no problem traversing the entire width of the visible universe. So there is good reason to believe it travels forever.

...if there is something, how do we know it's true effect on light.

By observing how light behaves.

 

[russ_watters]

...how can something bend nothing?

The idea that space can be empty and yet have a geometry (and other properties) may be difficult to wrap your mind around, but it is well supported by observations.

 

[rootone]

... how do we know it's true effect on light?

Because GR predicted that predicted very massive objects would act as a gravitational lens,
Then some time later, as telescopes improved, that is exactly what was observed.
https://en.wikipedia.org/wiki/Gravitational_lens

 

[bahamagreen]

Per Wikipedia (Outer Space) referencing Davies, P. C. W. (1977), p. 93, The physics of time asymmetry

"...the mean free path of a photon in intergalactic space is about 10E23 km, or 10 billion light years."

It should be noted that at the Earth's surface a photon's mean free path (MFP) through air at standard temp and pressure is only about 2 meters, and the MFP is so short due to the vitreous humor in the eye that the photons that are absorbed by the retina are actually emitted within the eye itself (so even when star gazing these are brand new fresh photons, not "old ones" from outer space).

 

[john-of-the-divine]

ok, I guess what I should ask is what causes the force of gravity? mass has to interact with something to cause gravity. Einstein coined the phrase space-time, what is space-time? what makes up the fabric of space? and how on Earth can we say this "fabric" doesn't have more of an effect on light then we think? I don't care what the Michelson-Morley experiment says because to me it just says light is really fast.

 

[russ_watters]

ok, I guess what I should ask is what causes the force of gravity? mass has to interact with something to cause gravity. Einstein coined the phrase space-time, what is space-time? what makes up the fabric of space?

The general answer to the question of "what is...?" anything, is that the thing you want to know about "is" the sum of its known and theorized properties. This is likely to be unsatisfying to you because the known/theorized properties of space are probably less than you want to believe it has.

...and how on Earth can we say this "fabric" doesn't have more of an effect on light then we think?

By observing how light behaves in it.

I don't care what the Michelson-Morley experiment says because to me it just says light is really fast.

That isn't a very good approach to learning.

 

[john-of-the-divine]

you're right, it might not be the right approach. I'm saying the scale of that experiment is nowhere near big enough is why I say that. I just never put much thought into what is space-time until I asked myself who to say there isn't something reacting on the photons to slow them down or absorb or destroy them. I'm questioning how do we really know what the effect that this "fabric" has on light? the only way we could tell is to send a probe deep into space, shoot a laser at it and see what happens. then go further and see what happens. just because we made these tests and experiments on Earth and not truly in space. or am I missing something? i just had a thought that if this fabric does effect light more than we think it does, then the math is wrong.

 

[john-of-the-divine]

guess the real answer is I should have went to a school that I could never afford. thanks for trying to help me understand.

 

[russ_watters]

you're right, it might not be the right approach. I'm saying the scale of that experiment is nowhere near big enough is why I say that.

I'm not sure what you mean, but ok...

... who to say there isn't something reacting on the photons to slow them down or absorb or destroy them. I'm questioning how do we really know what the effect that this "fabric" has on light? the only way we could tell is to send a probe deep into space, shoot a laser at it and see what happens. then go further and see what happens. just because we made these tests and experiments on Earth and not truly in space. or am I missing something?

Yes; astronomy. We learn a lot about space by observing light that has traveled across the universe.

i just had a thought that if this fabric does effect light more than we think it does, then the math is wrong.

Clearly. But the math describes very well what is observed.

guess the real answer is I should have went to a school that I could never afford. thanks for trying to help me understand

You're welcome, but don't give up on learning just because you didn't go to school for it. It's true that you won't be able to learn it to the same depth as a college degree, but there is some good learning you can do.

 

[john-of-the-divine]

what if the math was forced just to fit a model? no I'm not a flat earther, but they have math that works too, or so it seems. what if our math is wrong too? I asked this question and all of a sudden everything moved in closer and got smaller. we are told what numbers we have to use, and it seems to me that there's a chance it could be wrong. would the math still work if everything is closer, I think it would. 2+2=4...unless one of the 2s is actually a 3. again, thanks.

 

[bahamagreen]

Sounds to me like you are wondering if the canonical light speed measurement (two-way with the "mirror and clock") has ever been performed in space (or in vacuum in the lab on Earth). Seems like Ole Rømer, radio com with lunar astronauts, GPS system, laser distance measures to the prisms on the Moon, et al... are approaching if not meeting that.

 

[john-of-the-divine]

what did you mean by op? I see that your reply got edited.

 

[berkeman]

what did you mean by op? I see that your reply got edited.

What did who mean? OP = "Original Post" (your first post in this thread) or "Original Poster" (you) in most cases on a discussion forum.

 

[john-of-the-divine]

this is my first time ever in a forum, don t know the lingo. the person above you used the abbreviation op but it was edited out. I just can't figure out the right question to ask.

 

[berkeman]

this is my first time ever in a forum, don t know the lingo. the person above you used the abbreviation op but it was edited out. I just can't figure out the right question to ask.

Ah, okay. I just now used my Mentor superpowers to read his previous version, and he was just saying that it sounded like you hadn't heard of several very accurate experiments that have been done in pretty different ways to verify the speed of light and no aether. Have you read the Wikipedia pages about the speed of light and various experiments done to verify that c is constant in a vacuum and not dependent on moving through some medium?

 

[berkeman]

Have a read through this article, and let us know if you have specific questions about it. Hopefully it helps you out...

https://en.wikipedia.org/wiki/Speed_of_light

 

[russ_watters]

what if the math was forced just to fit a model? no I'm not a flat earther, but they have math that works too, or so it seems. what if our math is wrong too?

It would be difficult for the math to be more than a little wrong because we use it to do practical things like navigate with Google maps and it works.

 

[john-of-the-divine]

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

 

[berkeman]

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

It's usually fine for well-understood stuff (which this is). For cutting edge theories, it can be a bit problematic (with lots of folks editing the articles). Give it a try and tell us what you think...

 

[john-of-the-divine]

It would be difficult for the math to be more than a little wrong because we use it to do practical things like navigate with Google maps and it works.

from here to the moon isn't very far when you consider the vastness of space. idk, I'm checking out the link that berkeman sent me

 

[russ_watters]

from here to the moon isn't very far when you consider the vastness of space.

I'm not sure what that comment is in reference to, but our observations impacting Relativity span the entire observable universe.

 

[berkeman]

I'm not sure what that comment is in reference to, but our observations impacting Relativity span the entire observable universe.

The post that @bahamagreen edited used to have reference to the experiments using the retroreflectors on the moon.

 

[john-of-the-divine]

how the heck came we see 46.5 billion light years when, as far as we can tell, the universe is only 14 billion years old. lol. guess the better guestiin to ask is what makes the force of gravity work? I see the model, I understand the model, what is the fabric of space time made of? it can't be nothing, because something can't bend nothing. 1×0=0

 

[john-of-the-divine]

I'm not sure what that comment is in reference to, but our observations impacting Relativity span the entire observable universe.

I'm saying that compared to the size of the universe, the distance to the moon is like an inch compared to 100 miles. I don't know the actual scale, but 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.

 

[berkeman]

I'm saying that compared to the size of the universe, the distance to the moon is like an inch compared to 100 miles. I don't know the actual scale, but 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.

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?