Light - For Those Who Are More Educated In This Field

[Kenny]

That is one of a number of units of distance used in astronomy. There are also "AU" (= astronomical units), which are multiples of the mean radius of the Earth's orbit, and parsecs, which are related to the AU by being the distance from an observer at which light reaching the observer from opposite ends of something 1 AU across makes an angle of one arc second, approx 3.26 light years. There may be others: I'm not an astronomer.

But these are just units of distance, not methods of measurement. Measuring the distance is more complicated. One gets into parallax, standard candles and all sorts of stuff. And eventually, at long enough distances, red shift.

I am certainly out of my field.

With all the new discoveries that basically say:

10 New Discoveries That Could Radically Change The Universe - Listverse

Science is all about discovery. Uncovering fascinating new truths about the world around us. Finding original ways to explain some of the universe’s

listverse.com

(not that these discoveries apply to light)

I just wonder if a new discovery, as we measure distance and how it all started, can change all our figures.

I don't know if this is true, but as an example, if light can be elastic to where it actually stretches over time... LOL - I know it is a ridiculous thought, but as an example... what that would do to our thinking - black holes et al.

 

[exchemist]

I am certainly out of my field.

With all the new discoveries that basically say:

10 New Discoveries That Could Radically Change The Universe - Listverse

Science is all about discovery. Uncovering fascinating new truths about the world around us. Finding original ways to explain some of the universe’s

listverse.com

(not that these discoveries apply to light)

I just wonder if a new discovery, as we measure distance and how it all started, can change all our figures.

I don't know if this is true, but as an example, if light can be elastic to where it actually stretches over time... LOL - I know it is a ridiculous thought, but as an example... what that would do to our thinking - black holes et al.

Well the current theory of cosmic expansion does exactly that. The cosmological red shift is thought to be due to spacetime expanding and thus stretching the waves out over time, which makes them redder because with a longer wavelength the frequency goes down. Similarly the Cosmic Background Radiation, which pervades the universe in all directions, is the same as that given off by a body with a temperature of just under 3K. This is thought to have been originally emitted by a very early universe that was hot enough to glow, but because the expansion has stretched the radiation so much since, the effective temperature of the radiation has gone right down to a value close to absolute zero. The universe seems to be still expanding, so light presumably continues to be stretched over time. Not that the effect is one we can see over human timescales, though.

 

[Kenny]

Well the current theory of cosmic expansion does exactly that. The cosmological red shift is thought to be due to spacetime expanding and thus stretching the waves out over time, which makes them redder because with a longer wavelength the frequency goes down. Similarly the Cosmic Background Radiation, which pervades the universe in all directions, is the same as that given off by a body with a temperature of just under 3K. This is thought to have been originally emitted by a very early universe that was hot enough to glow, but because the expansion has stretched the radiation so much since, the effective temperature of the radiation has gone right down to a value close to absolute zero. The universe seems to be still expanding, so light presumably continues to be stretched over time. Not that the effect is one we can see over human timescales, though.

Thanks....

 

[wellwisher]

Not really in my experience. (I once went out with a particularly pretty and capable one - and I knew a lot of (mostly male) ones at Shell, two of whom are still occasional drinking companions.

But engineers as a breed are not the best experts when it comes to pure science research, because that's not what they do.

This is true of engineers, since they are sometimes asked to go outside the box, while initially being constrained by the known laws of science. What often happens is that the laws of known science, need to be expanded, to get the technology you need. Taller and taller buildings required advances in materials. This is not the case in pure science. Pure science theory can form it own closed loop, while technology often goes outside that loop, and has to expand the box of science.

Many innovations in industry are protected property. The data, questions and solutions, are locked away for now. Others will need to buy the invention, and try to reverse engineer it, with the pure science literature, not quite up to snuff, since the needed science is locked away in the company lockbox. They may need to reinvent the wheel. The can be a delay in terms of pure science getting up to steam.

Pure science experiments and details are much more shared among peers, while projects tends to be much more specific; count the genes on this mouse DNA, or look at the affects of oxygen on tungsten filaments within salt water environments. Engineering is given goals that can be more opened ended. This may require you jump around, the pure sciences, and modify and extend some areas of science beyond what is known.

The open ended goals and the unexpected walls, is how science gets pushed. This better describes R&D. Some forms of engineering are more routine; process tweaks and optimizations which can also improve mechanisms.

 

[wellwisher]

Well the current theory of cosmic expansion does exactly that. The cosmological red shift is thought to be due to spacetime expanding and thus stretching the waves out over time, which makes them redder because with a longer wavelength the frequency goes down. Similarly the Cosmic Background Radiation, which pervades the universe in all directions, is the same as that given off by a body with a temperature of just under 3K. This is thought to have been originally emitted by a very early universe that was hot enough to glow, but because the expansion has stretched the radiation so much since, the effective temperature of the radiation has gone right down to a value close to absolute zero. The universe seems to be still expanding, so light presumably continues to be stretched over time. Not that the effect is one we can see over human timescales, though.

One potential conceptual problem is connected to the concept of space-time and energy. The doppler shift is connected to distance; wavelength changes due to motion and velocity. However, within energy or photons, frequency; time, is the dynamic variable, and distance is the passive variable. We can measure distance with a meter stick which is a passive measuring device. Time needs a clock which needs energy; a dynamic tool is needed to measure the dynamic variable.

The red shift takes potential energy away from the photons; red defines less energy per photon than blue. Since time is the dynamic variable, that needs energy to be measured, a time shift should be leading any changes in photon energy, with the wavelength passively adjusting.

As a simple example of a time modulated doppler shift, say we have a train that first approaches us, then passes by us, and then moves away. We will hear the pitch of the train's whistle get higher; approaching, and then start to lower, after it passes us and moves away.

Picture this scenario. The train is stationary. We put on a blindfold. The engineer tweaks the pitch of his stationary whistle, so it sound like the train is approaching and then the train is moving away. The frequency tweak of the whistle can give us the same measured wavelength affect as motion, since the wavelength will change if we adjust the frequency. Light can be tweaked in both ways.

The moving train scenario, differs from the universe, in that the train stays within a single non changing space-time reference frame. The expanding universe, is changing the universal space-time reference frame continuously; expanding, with potential energy going into mass as gravitational potential. There appears to be a dynamic energy exchange going on that leads to less photon energy; red shift.

This suggest that there is a time tweak; exchange of the conserved energy in the photons. The expanding universe, by increasing complexity, as space-time expands, suggests universal entropy is increasing, which is endothermic.

Time has more in common with entropy than it does energy. Time moves in one direction; future. We do not get old and then get younger in cycles. We are born, age and die; one direction. Energy cycles like a wave and thereby repeats itself over time. The natural path for entropy is linear and always increases to the future; 2nd law is connected to the unidirectional flow of time.

Entropy times temperature has the units of energy; free energy. My guess is the flow of time, as space-time expands, leads to frequency modulation, mediated through entropy increase. This entropy changers times the background temperature T=3K, becomes the vehicle by which energy is traded.

 

[Polymath257]

I am certainly out of my field.

With all the new discoveries that basically say:

10 New Discoveries That Could Radically Change The Universe - Listverse

Science is all about discovery. Uncovering fascinating new truths about the world around us. Finding original ways to explain some of the universe’s

listverse.com

(not that these discoveries apply to light)

I just wonder if a new discovery, as we measure distance and how it all started, can change all our figures.

I don't know if this is true, but as an example, if light can be elastic to where it actually stretches over time... LOL - I know it is a ridiculous thought, but as an example... what that would do to our thinking - black holes et al.

1. Sure, it is possible for new discoveries to affect our current estimates. For example, if there is another force to deal with, that may affect our computations of the ages of stars or the development of the expansion.

The question is how much could it affect things. Will it change the fact that the universe is expanding? No. Will it perhaps affect the figure that it is 13.72 billion years into the expansion? possibly, but probably not by more than a billion years or so.

2. As @exchemist has explained, there is a sense in which the red shift in cosmology is exactly due to the expansion of space stretching out the light.

 

[exchemist]

Got it thank you exchemist. Is it special relativty?

Photons are traditionally said to be massless. This is a figure of speech that physicists use to describe something about how a photon's particle-like properties are described by the language of special relativity.
-snip-
As the particle is accelerated to ever higher speeds, its relativistic mass increases without limit. It also turns out that in special relativity, we are able to define the concept of "energy" E, such that E has simple and well-defined properties just like those it has in newtonian mechanics. When a particle has been accelerated so that it has some momentum p (the length of the vector p) and relativistic mass mrel, then its energy E turns out to be given by

E = mrelc2
What is the mass of a photon?

Yes, since we can't stop a photon without it being absorbed, the zero rest mass is a matter of inference from relativity. No physicist today uses relativistic mass, as it leads to confusion. In fact, though I don't intend to wade through a junk paper to find out, I imagine it's possible these people have used it, got themselves duly confused, and written twaddle in consequence.

 

[Ben Dhyan]

Actually, I have been very careful in how I say things to allow that the BB model is wrong and will need to be modified in the future.

Both of your questions, however, betray a serious misunderstanding of what the BB model says and, frankly, of what any serious model of cosmology would say. You are still working with misconceptions that are about a century out of date.

Logic is not decided by science! If nothing does not exist, and nor does spacetime until the BB, then logically, prior to the BB, absolute nothing existed.

 

[Ben Dhyan]

And it has already determined that tired light is a goat.

Spacetime continues, what some hacks declare is a goat in one generation may be the favored model in the next. You can't speak for future generations!

 

[Polymath257]

Spacetime continues, what some hacks declare is a goat in one generation may be the favored model in the next. You can't speak for future generations!

True enough. But the fact is that your viewpoint was the default prior to about a century ago. It was discarded because of the evidence. So it is incredibly unlikely to be revived, at least not without serious reworking.

The Ptolemaic viewpoint was accepted for well over a thousand years, but there is no conceivable scenario where it would be revived as a serious scientific theory. The same is true, but much less so, for Newtonian physics.

Your intuitions about space and time were standard until just over 100 years ago. But those of Aristotle were standard before that. The overthrow of both was an advance in our understanding and those ideas have been discarded for good reasons.

In particular, your intuition that time cannot have a beginning is one that we realize isn't required by logic or even by the evidence. It is logically quite possible that the notion of 'before the BB' is simply nonsense. It requires there to be time when time is impossible.

 

[Polymath257]

Logic is not decided by science! If nothing does not exist, and nor does spacetime until the BB, then logically, prior to the BB, absolute nothing existed.

Except that you have to show that the phrase 'prior to the BB' makes sense at all. That is NOT a philosophical question, but one of physics.

Logic *is* subject to science: we determine which rules of logic to use based on what works obervationally. If you doubt that, look up all the possible alternative logics, including paraconsistent and three-valued logics.

The real world is not limited to what you deem to be reasonable.

 

[Ben Dhyan]

True enough. But the fact is that your viewpoint was the default prior to about a century ago. It was discarded because of the evidence. So it is incredibly unlikely to be revived, at least not without serious reworking.
The Ptolemaic viewpoint was accepted for well over a thousand years, but there is no conceivable scenario where it would be revived as a serious scientific theory. The same is true, but much less so, for Newtonian physics.
Your intuitions about space and time were standard until just over 100 years ago. But those of Aristotle were standard before that. The overthrow of both was an advance in our understanding and those ideas have been discarded for good reasons.
In particular, your intuition that time cannot have a beginning is one that we realize isn't required by logic or even by the evidence. It is logically quite possible that the notion of 'before the BB' is simply nonsense. It requires there to be time when time is impossible.

Is it logical to believe that something could exist without time (pre-BB), I say no.

 

[Ben Dhyan]

Except that you have to show that the phrase 'prior to the BB' makes sense at all. That is NOT a philosophical question, but one of physics.

Logic *is* subject to science: we determine which rules of logic to use based on what works obervationally. If you doubt that, look up all the possible alternative logics, including paraconsistent and three-valued logics.

The real world is not limited to what you deem to be reasonable.

But physics must comply with the principles of logic, and you know that spacetime could not have a beginning in nothing, ergo there had to be something existing pre-BB, hence spacetime would exist.

 

[Polymath257]

Is it logical to believe that something could exist without time (pre-BB), I say no.

I agree. That is why it makes no sense to talk about 'before the BB' in some models. Nothing exists outside of spacetime. And the BB model describes the geometry of spacetime.

 

[Polymath257]

But physics must comply with the principles of logic, and you know that spacetime could not have a beginning in nothing, ergo there had to be something existing pre-BB, hence spacetime would exist.

To 'have a beginning' implies an earlier time. But that is precisely the point that is denied in the standard BB model: the phrase 'pre-BB' is literally meaningless. That is the point where logic says you need to show that the phrase 'pre-BB' is even meaningful: that time can be extended to before the BB.

 

[Ben Dhyan]

To 'have a beginning' implies an earlier time. But that is precisely the point that is denied in the standard BB model: the phrase 'pre-BB' is literally meaningless. That is the point where logic says you need to show that the phrase 'pre-BB' is even meaningful: that time can be extended to before the BB.

We are at an impasse, we are each sure of our respective positions, may we agree to disagree for now.

 

[metis]

If nothing does not exist, and nor does spacetime until the BB, then logically, prior to the BB, absolute nothing existed.

It is overwhelming believed by cosmologists that it did but was maybe only the size of a current day atom.

 

[Ben Dhyan]

It is overwhelming believed by cosmologists that it did but was maybe only the size of a current day atom.

And this atom sized universe existed in what? Iow, what was outside of it?

 

[Polymath257]

And this atom sized universe existed in what? Iow, what was outside of it?

The rest of the universe. That atom sized thing (if it existed--it is an extrapolation), was only what corresponds to the obsevable universe today.

 

[Polymath257]

We are at an impasse, we are each sure of our respective positions, may we agree to disagree for now.

Given that the exerts in the subject agree with me, I am not concerned.