Is Time Travel (going backwards) Possible?

[Morrus]

Going back a few days, here's one example of the "not before the time machine was built" stuff:

I only watched the first few seconds but - is that Tom Baker? If so, awesome!

 

[KarinsDad]

By that logic, I may as well say "messageboard posters are dishonest". What you're saying has nothing to with science or scientists at all; it's just people. Why did you choose to attach it to statement about scientists in particular, as opposed to football players or chess players?

I mean, it sounds like you have a beef with "scientists". That's three posts in a row where you've levelled different accusations at them. First it was their fault that educators and media portrayed hypothesis as fact; when I pointed out that it was unfair to blame them for that, you moved on to claiming they were all narrow-minded and opposed to new theories; and when I pointed out that they're not generally opposed to new theories, you say you didn't mean all of them, and switched to accusations of dishonesty. And before all that, you were attacking perfectly reasonable behaviour regarding hypothesis and interpretation of data because "it's possible" something could be wrong (which is obvious, but not a useful statement in any way). It really, really sounds like you hold some kind of grudge against the broader scientific community; I can't imagine what, though.

Yeah, sure, there are bad apples in every vocation. So what? That's not a useful commentary on science, scientists, or scientific practice in any meaningful sense. I mean if that's all that those posts were building too - yeah, sure.

I think that open discourse is a staple of scientific integrity and that includes how scientific knowledge gets disseminated to the public at large. I think that there are some scientific fields (ones where we cannot experiment in the lab, or are limited in the types of lab experiments that we can perform) where the theories are susceptible to both more rigid dogma and to a higher probability of incorrectness. Sorry, but having (possibly) hundreds of scientists looking for Dark Matter for 80 years (seriously looking for 40 years) and failing, and having every Dark Matter equation ever thought of only working for some galaxies and not for others, should give someone a clue to look for something else. That to me IS a definition of close mindedness.

Interestingly, there has been quite a bit in the literature recently about more and more astronomers siding with the idea that some form of modification to Einstein's general relativity and/or Newton's gravity equations as more reasonable explanations than Dark Matter.

With regard to educators and the media, scientists should hold their feet to the fire. Scientists should especially not let the media misrepresent their work in any way. I doubt scientists can do anything about educators since a lot of that tends to be hidden from their view. Course, a scientist who writes an educational book does get a share of the $100 to $200 per book sold, so they should be motivated to keep their books up to date with the latest theory and should indicate it as such.

As for my second post, you ignored most of it and concentrated on one specific sentence and decided to continue to only discuss it.

With regard to science, I think a lot of science is very solid. We wouldn't be having this conversation (or heating our dinner or doing hundreds of everyday things) without technology that resulted directly from solid science.

But, I do think that some of the more theoretical and not quite proven (or hard to prove or disprove) science tends to be a bit more dogmatic (when it shouldn't) and resistant to change. And some of this is the way it should be. We should not throw out the baby with the bath water every time a glitch comes along. But, we should also explore other alternatives because glitches do come along.

Anyway, I'm not really trying to attack anyone, but you seem to be taking it that way, so I'll just drop it.

 

[Morrus]

Sorry, but having (possibly) hundreds of scientists looking for Dark Matter for 80 years (seriously looking for 40 years) and failing, and having every Dark Matter equation ever thought of only working for some galaxies and not for others, should give someone a clue to look for something else. That to me IS a definition of close mindedness.

Is that your scientific opinion? That sounds like a statement that you'd need to really understand the science and the math to make. I wouldn't dream of proclaiming that "scientists" (again, there are many and they all do different things) are all wrong to be pursuing the theories they are, because I know I don't understand their theories - or, more specifically, what might be wrong with their theories.

And you've said that you don't, either. Yet you know they're being close-minded in pursuing them? What qualifies you - above them, no less - to proclaim the correct allocation of research resources?

I'm honestly not trying to get into a fight here. I just literally cannot fathom your perspective. I feel like I've encountered an alien species whose mind works in an utterly baffling way!

Interestingly, there has been quite a bit in the literature recently about more and more astronomers siding with the idea that some form of modification to Einstein's general relativity and/or Newton's gravity equations as more reasonable explanations than Dark Matter.

Huh? So now you're saying they are considering other theories?

Yikes, man. I can't even follow this conversation any more.

That said - why do you keep returning to dark matter in particular? It seems to be your point of contention, despite not being the subject of this thread (or even dark energy, which the thread later drifted into) - that you personally feel aggrieved because the majority of tiny number of scientists working on that particular field of research are not focused on a different theory of which you're enamoured? Is that your data set?

 

[Umbran]

If I may: A photon starts a billion light years away. In the frame of an observer on the earth, is the photon already red shifted, or does the red shift occur as the photon travels to the earth?

Um, neither? Doppler shifting is best modeled by thinking of the wave nature of light, not the particle nature. Then, it the shifting Hubble observed is a result of relative motion between the source and observer.

Expansion of space only comes into it as a cause of that relative motion.

In the cavity example, the source and observer are not moving relative to one another - they are both pretty much at rest with respect to the resonant cavity (I assume), so no redshift is observed.

 

[KarinsDad]

Huh? So now you're saying they are considering other theories?

Yikes, man. I can't even follow this conversation any more.

The point I was trying to make is that only RECENTLY has there been more interest in non-Dark Matter theories. They have been around for about 30 years out of the 40 years that scientists have been actively trying to pursue DM, but mainstream scientists have called them radical theories for decades. Now, not so radical as more and more scientists are slowly starting to examine them more carefully. Part of the reason for this is lack of results for DM. Part of the reason for this might be because as more elderly / well known scientists who were a bit more rigid in their thinking that DM was the only possible answer have moved on (retired, died, etc.), similar to what happened with the few holdouts of the Static State theory.

Yes, some scientists are slowly getting around to being open minded on this, but for several decades, not so much. Here is just one example of where your claim to open mindedness by scientists doesn't hold much water if it takes three or four decades for them to consider other explanations as maybe not so radical after all. And, many scientists still will not consider anything other than DM.

To be considered open minded, one should examine different possibilities, not just pick the most popular one and stick to it.

This might be what you were not following from what I posted. This is an example of resistance to other ideas that has been happening for decades (since the birth of science actually since science is done by people). It disagrees completely with your claim of how most scientists function.

That said - why do you keep returning to dark matter in particular? It seems to be your point of contention, despite not being the subject of this thread (or even dark energy, which the thread later drifted into) - that you personally feel aggrieved because the majority of tiny number of scientists working on that particular field of research are not focused on a different theory of which you're enamoured? Is that your data set?

I'm not enamored by any specific theory. I was using this as an example. DM is just one of several different theories that didn't seem to have evidence to support it. It never has. Galaxies have observational effects which it tries to fill the hole for, but no evidence. The observations are real (or at least as real as our tools allow us to observe). The theory, maybe, maybe not. And, I don't know if it is Mond or Electromagnetic attraction or something else. All I know is the DM might not be the answer based on what some scientists are now saying. I take what I understand from them. I don't have an agenda (other than discussing it).

It's like Dark Energy. Scientists can state the observational effects that they use it to try to explain, but an explanation for what causes it is still pie in the sky. Until they can explain exactly what it is and what is causing it and they have evidence to illustrate this, there is a fair chance that it might be an incorrect theory.

When one comes up with a theory for science, one has to do experimentation to support or disprove the theory. In both cases here, there is an effect (galaxy rotational speed/lensing and apparent acceleration of universal expansion). But, the explanations for why these are occurring have no real teeth. There is DM. What is it? Don't actually know. There is DE. What is it? Don't actually know. Scientists have tried to come up with the actual answers, but so far, zip, zilch, nada. Some theories. Few real answers.

As an example, NASA scientists have stated that Dark Matter accounts for 23.3 percent of the cosmos, and Dark Energy accounts for 72.1 percent (to within various percentages). Well, NASA scientists don't actually know that, but they stated it. These are percentages presumably based on the "what if" scenario of if DM and DE are correct explanations. But now, this is public information that may or may not be quite accurate, but it has been presented to the public for all intents and purposes as fact. By NASA.

I've seen several "scientific programs" (e.g. Through the Wormhole as one example) where this percentage claim has also been made by people on the show. The public watches the show and many probably considers it fact. Argumentum ad verecundiam is very compelling in our society.


Look at quantum mechanics. All of our evidence for how quarks and other elementary particles work comes from one source. Smashing particles together at high speed. In any other branch of science, having only one basic type of experiment for your theories without other observations or experiments to verify against would be considered shoddy science. But, we have no other way yet to peer into protons, neutrons, and electrons, so science uses what it has. Does it make it correct? Maybe. Maybe not. It's pretty much considered fact in the scientific community and at this point in time, rightfully so. But, there's a fair chance that it is wrong. As Feynman once stated "I think I can safely say that nobody understands quantum mechanics" (granted, he said that over 45 years ago, but it still pretty much holds, we have more knowledge, but it's still a big mystery).

 

[tomBitonti]

Um, neither? Doppler shifting is best modeled by thinking of the wave nature of light, not the particle nature. Then, it the shifting Hubble observed is a result of relative motion between the source and observer.

Expansion of space only comes into it as a cause of that relative motion.

In the cavity example, the source and observer are not moving relative to one another - they are both pretty much at rest with respect to the resonant cavity (I assume), so no redshift is observed.

Isn't the billion mile away emitter technically at rest (more-or-less) relative to us? I thought the passage through the billion light years was what caused the red shift. (This all is confusing because of the seeming difference between everyday velocity and apparent velocity due to space expanding.) Then, the red shift is caused by a curvature along the way. That curvature must not be uniform, otherwise, the light in the resonant cavity should experience a similar red shift. Is the effect imperceptible because it adds non-linearly (in a manner to reduce the effect) in a region already curved due to gravity?

Note: This is all at the edge of my understanding. I'm prepared for any one of these statements to be utterly wrong. What I'm interested in as much as the correct answer (to current levels of understanding) is a correct approach to obtaining the answer.

TomB

 

[Nellisir]

Isn't the billion mile away emitter technically at rest (more-or-less) relative to us? I thought the passage through the billion light years was what caused the red shift. (This all is confusing because of the seeming difference between everyday velocity and apparent velocity due to space expanding.) Then, the red shift is caused by a curvature along the way. That curvature must not be uniform, otherwise, the light in the resonant cavity should experience a similar red shift. Is the effect imperceptible because it adds non-linearly (in a manner to reduce the effect) in a region already curved due to gravity?

Note: This is all at the edge of my understanding. I'm prepared for any one of these statements to be utterly wrong. What I'm interested in as much as the correct answer (to current levels of understanding) is a correct approach to obtaining the answer.

TomB

I think this falls over the edge of my understanding, but here goes. Keep in mind that this is the first time I've ever actually tried to make sense of redshifting and wavelengths, so it's very possible I've gotten something totally wrong or backwards.

Redshift isn't a property of the photon itself. The photon doesn't age or turn red as it travels. Redshifting is a property of one object travelling away from another object, and the wave (not particle) of light between the two. If the two objects are static in relation to each other, there is no redshift, regardless of the time or distance.

In our universe, however, on a intergalactic scale, everything is moving away from everything, in all directions. We are all dots on a balloon, and the balloon is inflating. (If this gets you going about curvature, then it's a flat piece of balloon being pulled from the perimeter). Because the expansion is speeding up, older things are moving faster, and are more redshifted.

Since time = distance, and time = speed, therefore further = older = faster = more redshift.

Light is photons, which are particles, but it is also a wave. The wavelength is the distance over which the wave's shape repeats. Imagine that there's a line between two objects, and that line has a repeating wave pattern. Let's say that there are....30 waves between Object A and Object B. The length between each wave equals X. If the objects are static, X is unchanged. If the objects begin to move together,the waves get tighter and X becomes shorter (X-, aka blueshift). If the objects move apart, X becomes longer (X+, aka redshift). The distance between waves is increasing, but the quantity of waves remains the same. There's still 30 waves, but they have to stretch to accommodate the increasing distance. That's redshift. The wavelength (distance between the same point on two adjoining waves) of light increases as objects move apart.

 

[tomBitonti]

In our universe, however, on a intergalactic scale, everything is moving away from everything, in all directions. We are all dots on a balloon, and the balloon is inflating. (If this gets you going about curvature, then it's a flat piece of balloon being pulled from the perimeter). Because the expansion is speeding up, older things are moving faster, and are more redshifted.

That part I think I get. But, I think this answers my question by building it into the presises of your answer. Why only on an intergalactic scale? Is that because the effect is too small to be measured on a smaller scale (similar to the precession of Mercury, which is barely measurable, compared to the presession of Earth, which I gather is not. Or does the effect not happen at all within a galaxy? Does the wave stay unshifted until it reaches a very flat part of intergalactic space and then start to shift? (With a suitable smoothing in transition?)

If we model this as a set of rigid discs on an elastic surface, say, lots of CDs on a trampoline with sequins sprinkled here and there in-between, then we tighten the trampoline, then the distance between each of the rigid CDs and sequens grows, but the trampoline stretches, sliding, beneath the wide CDs.

But, if that happens, will there be an extra effect applied to light, similar to gravitational lensing, but not accounted for entirely by gravity, as we measure light passing galaxies from distant sources?

TomB

 

[Umbran]

Isn't the billion mile away emitter technically at rest (more-or-less) relative to us? I thought the passage through the billion light years was what caused the red shift.

No, merely having the wave (or photon) travel a long distance won't cause a red shift. The Doppler Effect comes from motion of the source or receiver.

However, I find that at 12:30 AM, I'm not so good at explaining. I will take a stab at it after I've gotten some sleep, if that's okay.

 

[Morrus]

And, many scientists still will not consider anything other than DM.

To be considered open minded, one should examine different possibilities, not just pick the most popular one and stick to it.

This is a good summation of all those paragraphs. I disagree for the following reasons:

1) You are levelling your accusations at "scientists". Those studying dark matter are a tiny, tiny, tiny percentage of scientists.

2) Describing that process as "picking the most popular one and stick to it" is insulting to them and utterly inaccurate.

As far as I can tell your definition of "close minded" is "an expert who doesn't agree with (the non-expert) KarinsDad on how to conduct research of galactic rotation". Which is a definition, I suppose, but not one that I would ever care to use.

It disagrees completely with your claim of how most scientists function.

Okay, okay. How many scientist do you know? Let's have a list of examples. Science is a big, big area - let's have a dozen major theories which are being inadequately and incorrectly researched in your opinion.

It's like Dark Energy. Scientists can state the observational effects that they use it to try to explain, but an explanation for what causes it is still pie in the sky. Until they can explain exactly what it is and what is causing it and they have evidence to illustrate this, there is a fair chance that it might be an incorrect theory.

No scientist has ever claimed to understand dark energy. This is a complete strawman and a misleading line of thought.

In both cases here, there is an effect (galaxy rotational speed/lensing and apparent acceleration of universal expansion). But, the explanations for why these are occurring have no real teeth. There is DM. What is it? Don't actually know. There is DE. What is it? Don't actually know. Scientists have tried to come up with the actual answers, but so far, zip, zilch, nada. Some theories. Few real answers.

This is the OPPOSITE to what you've been saying.

Look at quantum mechanics. All of our evidence for how quarks and other elementary particles work comes from one source. Smashing particles together at high speed. In any other branch of science, having only one basic type of experiment for your theories without other observations or experiments to verify against would be considered shoddy science.

Jeezooos holy mofo, man! So we've progressed from accusations that scientists are narrow-minded, through dishonesty, claims that it is they who are holding scientists back (as opposed to... ice cream salesmen who are progressing it? Who?) to.... now scientists are doing shoddy science?

Really?

Based on your opinion of how they should be conducting this science, you deem it shoddy? You, who admits he doesn't understand it?

Do you really, honestly not see the problem here?