"You are not here merely to make a living. You are here in order to enable the world to live more amply, with greater vision, with a finer spirit of hope and achievement. You are here to enrich the world, and you impoverish yourself if you forget the errand." -Woodrow Wilson
It's been another fantastic week here at Starts With A Bang, and I've got to laud all of you for doing your best to make it a good one! Let's get right into what this past week held:
- Is there any such thing as pure energy? (for Ask Ethan),
- More than stars: the Milky Way's dust mapped in 3D for the first time ever (for Mostly Mute Monday),
- Hey Shaq? Here's how you can figure out the Earth is round for yourself,
- Why doesn't antimatter anti-gravitate? (from Sabine Hossenfelder),
- 5 vital lessons scientists learn that can better everyone's life, and
- Finding Earth's twin in space may be impossible.
I'm sure you've caught our new Starts With A Bang podcast, on why Pluto isn’t a planet anymore, like 1,000 other people. What you may not know is, thanks to our generous Patreon supporters, we're going to be constructing a history-of-the-Universe poster unlike anything you've ever seen before! Can't wait!
I also wanted to thank everyone for keeping it more civil and adult in the comments than we've had it here in a long time. Keep it up, and nobody will need the banhammer any time soon. With that out of the way, let's get right on into our comments of the week!
Global sea level rise since 1992 hits past the 8 centimeter mark in the AVISO altimetric graph. Image source: AVISO.
From Denier on, you guessed it, denying that global warming and its consequences are a concern: "First of all, the ocean has been rising for the past 22,000 years. You’re not going to stop it no matter what you do. It is currently rising at around 1.8 mm per year. Some places go a little faster and some go slower but 1.8 mm / year is the average. That comes to around 3.5 inches of rise in 50 years. Sooo Scary! Let’s destroy the economy immediately."
Yes, melting ice and warming temperatures will cause the ocean level to rise. The current rate of rising is about double what you state, as you are giving a centuries-long average for the rise; it is rising faster now. Why? Due to the increased temperatures caused by humans. Yes, we have "only" increased by about 1 degree Celsius in the past 130 years or so, but about 0.8 degrees of that have come in the past 50 years.
Hotter temperatures melt ice faster; warmer oceans experience thermal expansion; melting ice adds to the mean ocean volume. But the biggest effect will happen in jumps, when ice sheets calve, fall into the ocean or otherwise cause a discontinuous jump in sea level. You talk about 8 meters in over ten thousand years, and I'm more worried about that first meter -- or even a half meter -- happening within centuries. Your lack of concern comes from a point of ignorance, either willful or not; I can't say, that's up to you. But your data is out-of-date. At least revise and resubmit.
From Ragtag Media on Judith Curry: "@ Dingaling dean. Sooo when Judith Curry was a globull Nut Job climate change is real you loved her. Now that she has come to her senses for the climate scam going on you despise her."
So I know it's unlikely you've been following Curry in the level of detail I have, so let me give you a recap: in the mid-2000s, Curry, a hitherto respectable climate scientist, invested heavily in her "stadium wave" theory of climate models. She claimed there was an undiscovered natural variation in the climate, and that a periodic "waving" up-and-down was going to be discovered, as a flat and then cooling period would happen. Of course, the Earth continues to warm unabated, and her model has been thoroughly discredited.
She has since engaged in blatantly inappropriate data analysis -- known as lying or fraud in a scientific field -- and continues to argue her discredited case over and over, changing nothing even as the data continues to not support her claims. So there is fraud going on, but "the scam" has not been correctly identified by you.
Heat-trapping emissions (greenhouse gases) far outweigh the effects of other drivers acting on Earth’s climate. Source: Hansen et al. 2005, Figure adapted by Union of Concerned Scientists.
From eric on a number in much more agreement with actual sea level rise: "Here is the current Goddard satellite data, which shows that that old estimate was about half of what we are experiencing – instead of 1.7mm/yr, the observed rate is more like 3.4mm/year."
Thank you. And there's an important add-on to this, because temperatures continue to rise, driven by increased CO2 concentration, which also continues to rise. It's 3.4 mm/year. And accelerating.
From Ragtag... "So I guess you are correct in me not finding any wisdom or common sense in that grey matter of yours no matter how hard I look because it simply does not exist."
and Wow... "Just your average blithering idiot.
That WAS what you were waiting for, right, ragbag?"
This has not gone unnoticed. Knock it off. You were doing so well, and I like to think this is part of the backsliding behavior that you can't help yourself about. But help yourself. This is the ban-worthy stuff I'm trying to eliminate.
And now, enough commenting about comments. Let's get into the science!
Empty space with no matter, energy, curvature, gravitational energy, etc. Image credit: Amber Stuver of http://www.livingligo.org/.
From John on dark energy and the other forms: "This distinction between Dark Energy and the other forms energy assumes is intriguing."
I absolutely agree with this. When it comes to all the other known forms of energy, they are particle-dependent. Gravitational, electrical, nuclear, etc., all rely on fundamental interactions. Chemical energy relies on more derived combinations of electromagnetic interactions and discrete quantum states. But dark energy appears to be tied to a fundamental field itself, with no particle equivalent. Is dark energy tied to a particle at some level? Is it related to the inflaton field? Is it changeable over time, depending on the Universe's conditions?
I still hope that the 21st century will reveal some answers here.
Visualization of a quantum field theory calculation showing virtual particles in the quantum vacuum. Image credit: Derek Leinweber.
From Patrice Ayme on dark energy and energy creation/destruction: "If energy can be created ex-nihilo, independently of wave-particle transfers, as apparently observed, why couldn’t energy be DESTROYED during, because of, and AS the usual wave-particle transfer?"
It is important to recognize that only in the strictest sense -- where energy is not defined in General Relativity -- is the conservation of energy violated. If one imposes the work/energy theorem on the expanding Universe, then energy is conserved even in the case of dark energy; it's just that we have no right to impose it in General Relativity.
Image credit: Sean Carroll via Steve Hsu of http://infoproc.blogspot.com/.
From CFT on how dark energy affects particles... without interacting with them: "It is silly to speculate that actual particles of our universe can not access/interact with imagined dark energy, while at the same time proposing that the dark energy is having an affect on those same said particles by accelerating them."
I don't understand where the silliness comes in here. If you're on a trampoline and I don't touch you, but I do touch the trampoline, can you see where I affect you, even though you and I never interact? Dark energy affects the fabric of the Universe where the particles reside; the particles are affected by the Universe's fabric, but not by dark energy directly. It's pretty straightforward.
From PJ on cosmic dust's redshift, quantified: "How much of the red shift in distant galaxies, etc., will this account for after calibration?"
It depends on where you look, but the amount of "redness" versus what's expected otherwise can be very severe if you look in the galactic plane itself. One of the potential problems with looking at an object is that you only see the photons that reach you, and so if you see a red color in an object, you won't know why it's red: is there dust or is it redshifted?
But Wow's comment, "PJ Dust doesn’t cause redshift, it blocks blue. The light curve is totally different." is germane and relevant. It causes an effective reddening, but not a red shift. If you use spectroscopy, you will see no additional shift; the ambiguity comes when you take photometric measurements only. If you know what the intrinsic light from your star/galaxy looks like, you can measure and quantify the dust present, which is what Pan-STARRS did.
From Michael Kesley on tired light: "You may be interested in reading the Wikipedia article on “tired light”, which was one of the desperate attempts to explain away the observed cosmological expansion. The last second, “specific falsified models,” has useful details on dust reddening vs. proper redshift."
Two of my favorite facts about tired light are that it would cause a non-blackbody CMB (above), grotesquely ruled out by the observations, and that it was proposed in 1929 by Fritz Zwicky, who then spent the rest of the paper trying to discredit the idea. It was an awesome way to propose a cosmological alternative: to throw it out there, make the case for it, and then talk about how to rule it out.
When you're at the optimal distance to measure the Earth's curvature, a buoy's bottom will be visible right on the horizon line. For a human at sea level, that will never be as much as six kilometers from the buoy. Image credit: mark_az of Pixabay.
From Wow on why Americans call it 'boo-ee' instead of 'boy': "Is this why americans pronounce it “booey”?"
Apparently, there once were two ways of pronouncing the word in England, one of which took hold in the colonies and one of which took over in England. In the book A Practical Grammar of English Pronunciation by Benjamin Humphrey Smart (London, 1810), he writes:
Bw, in the words
(9) Buoy, buoyance
is represented by bu. They should never be pronounced boy, boyance.
Unfortunately, it seems that Shaq has not taken my challenge.
The two ways Earth could cast a circular shadow on the Moon: by being a spherical object (bottom) or a disk-like object (top). Image credit: Windows to the Universe Original (Randy Russell), under a c.c.a.-s.a.-3.0 unported license.
From Michael Mooney on special relativity and a pancake Earth: "The science of relativistic observational differences and “equal validity for all frames of reference” (SR) insists that a pancaked Earth is an “equally valid” description. Maybe it’s time to address length contraction as applied to Earth, Ethan."
I am afraid that there is no amount of rational thought that will get you to change your mind on this. If you move fast enough to contract Earth, then you effectively contract all the other spherical objects and the distances between them as well, and all the physics will work out equally well in that reference frame as it does in this one.
You have been all over the internet for a long time, if I've pegged you correctly, telling the tales of your misinterpretation of special relativity and "paradoxes" that are easily resolved.
After all, this is you, isn't it?
From Frank on negative gravitational masses: "As far as I know creating particles with negative mass requires negative energy. Also negative energy known to exist but it is unknown if it can be created artificially."
If you want to create a particle with negative mass, according to the presently accepted physics we have, you need negative energy. Antimatter is known to require a positive energy to create it, and to release positive energy when destroyed. However, that is a measure of its inertial mass, and it is only an assumption of the equivalence principle that inertial mass and gravitational mass must always be the same. This is true -- as demonstrated experimentally -- for matter, but not necessarily for antimatter. We still have work to do to know for certain.
From Denier on a possible explanation for dark matter: "CERN Physicist Dragan Hajdukovic theorized that anti-gravity explained the MOND effect on galactic rotation curves. In one aspect at least it absolutely does explain an effect attributed to dark matter."
I can't blame you for misinterpreting this study too much, because it's pretty deep into the weeds. What he's claiming is that if you run standard quantum field theory but attribute a negative gravitational mass to antimatter, then creating particle/antiparticle pairs will create a "gravitational dielectric," where the vacuum can be gravitationally polarized. This is similar to electromagnetic polarization, where a "medium" in between two parallel plates in a capacitor will increase the capacitance of the space in there, by effectively changing the permittivity and permeability of free space.
One of the thing that's long been noted about MOND is that if you changed Newton's laws by adding a non-zero dielectric medium throughout space, a minimum acceleration in galactic rotation is an emergent phenomenon. Hajdukovic's paper basically puts these two effects together. A measurement of the gravitational mass of antimatter would kill this.
The gravitational behavior of the Earth around the Sun is not due to an invisible gravitational pull, but is better described by the Earth falling freely through curved space dominated by the Sun. Image credit: LIGO / T. Pyle.
From Michael Mooney on curved space and orbits: "Why is there no discussion in physics about the mechanics of “curved space” as a medium which guides planets in their orbits, applying force to keep them from flying off out of the solar system?"
Because when physicists do discuss these things, we discuss the mathematics governing them and the observational consequences. Those are physically interesting things to discuss. "Ontological interpretations of relativity" aren't typically interesting to physicists, since they don't teach us anything about our Universe, but rather our intuitive preconceptions. We must work to overcome those, not give into them.
You claim to challenge the assumptions of the math associated with relativity... but if you don't understand the math itself, what makes you think you understand the underlying assumptions and their implications? Philosophy is useful for a tremendous number of things, but can you point me to even one scientific advance that happened because of a philosophical contribution?
Kepler's Platonic solid model of the Solar system from Mysterium Cosmographicum (1596). Image credit: Johannes Kepler.
From Denier on five flamebait comments designed to troll scientists: "Scientists highly value being right. Their self-worth is often tied up in their knowledge and being seen as wrong translates in their mind to devaluing them personally. It is human nature to fill in the unknown parts of other people with your own traits, but that isn’t reality. Although every likes to be correct, it isn’t nearly the driving motivation in society that it is to academics."
I would argue that this is highly contrary to... let's say, 97% of the evidence. The overwhelming majority of scientists will change their mind on any issue when presented with persuasive, robust evidence. This happened in astrophysics with dark matter and dark energy; this happened in climate science with global warming; this happened in gravitational wave astronomy with the first LIGO detection; this happened in particle physics with the discovery of the Higgs boson at 126 GeV. Your psychological evaluation of scientists is suspect, and your comparison with scientists to the rest of a society that has been proven to Dunning-Kruger themselves at every turn is... well, let's say lacking in evidence.
On the plus side, the UK just did the very thing you told me would be legally indefensible and highly unconstitutional in the USA.
From Wow, earlier today, crossing the line: "OK, so since you seem to think that compassion against you is insulting, I won’t bother, mooney. Or you”re just a whiney little asshole.
No, that is an apt description. Not an insult.
So, absent that whining, you still have nothing about proving your claim that science has nothing but contempt for psychology?
Because that’s an insult too.
Oh, I get it, you only care about people not being super special nice to you, amirite?
Aw, snowflake, nobody gives a rats ass. Either put up or shut up."
This comment literally happened after I began writing this article today.
Enjoy your week off, Wow. See you next Sunday.
A Minkowski diagram of the contracted ladder from the relativistic "ladder paradox" problem. Image credit: Wikimedia Commons user Life of Riley.
From the not-very-blameless Michael Mooney: "Same goes for length contraction if Ethan continues to refuse to address his distinction between contracted physical objects (not physical shrinking) and contracted distances between stars (“real.”)"
Did you seriously the Comments of the Week from two weeks ago where I addressed this at length and gave you a link to the Wikipedia page that discusses that exact paradox in depth, complete with resolution?
And finally, from Frank on searching for non-carbon-based forms of life: "Few years ago I had read that hundreds of famous scientists sent a signed letter to NASA to not just search for carbon-based life, search for other kinds of life too.
But I don’t if they suggested any practical way how exactly such a search can be done."
The life we're searching for is the life we know how -- or have conceived of how -- to search for. This includes not only direct biological/biochemical signatures, but signals from all over the electromagnetic (and now gravitational wave) spectrum. If we find something promising, you'll hear about it. If not from the entire world, then surely from me.
Have a great week, everyone, and I'll see you back here tomorrow!
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Do you realize you just made my point? Scientists want to be right. If you show them something else is right, they'll change.
In larger society tribalism is the stronger motivation. People wont be as harsh towards the unacceptable behavior of an athlete on their favorite team. People don't care that fake news is fake so long as it reinforces the tribe.
My point is that academic scientists sometimes act differently from the general public and scientists don't realize the atmosphere is different inside their bubble. Your previous statement conjured it, and your latest statement only reinforces it.
I'm not saying Scientists are bad for being wishy-washy intellectually as new information comes in. I myself am that way. I'm also not saying society is bad for being so tribal as it evolved for a reason. I just find it amusing when academics don't realize they've incorrectly projected a trait where it doesn't belong.
Yup. Couldn't do it here. Canada also passed M-103. Couldn't do that here either.
Ethan's dismissal of my comments (my replies interjected):
" From Michael Mooney on special relativity and a pancake Earth: "The science of relativistic observational differences and “equal validity for all frames of reference” (SR) insists that a pancaked Earth is an “equally valid” description. Maybe it’s time to address length contraction as applied to Earth, Ethan."
"I am afraid that there is no amount of rational thought that will get you to change your mind on this. If you move fast enough to contract Earth, then you effectively contract all the other spherical objects and the distances between them as well, and all the physics will work out equally well in that reference frame as it does in this one."
You invoke "rational thought?!" Moving fast as you observe and measure Earth does not change Earth's shape. That is rational!
You forget again that a contracted Earth is only "apparent," i,e., that fast moving frames of reference do not change the physical shape of planets and stars. There is no physics to support shrinking planets and stars. Nobody (or "frame of reference") "effectively contracts" physical bodies or cosmic distances. That is based on Einstein's philosophy that there is no "real world" independent of "observation," measurement, geometric models and, of course... the bottom line and end of discussion, Math.
You have quoted me correctly. Being "pegged' and "telling tales" is your own insulting spin on my longstanding contribution to the ubiquitous body of criticism of relativity's *doctrines,* now "established" beyond criticism... except for scholars like Ross... Who's cogent argument you will not address. (Too busy, I suppose.)
" From Michael Mooney on special relativity and a pancake Earth: "The science of relativistic observational differences and “equal validity for all frames of reference” (SR) insists that a pancaked Earth is an “equally valid” description. Maybe it’s time to address length contraction as applied to Earth, Ethan."
"I am afraid that there is no amount of rational thought that will get you to change your mind on this. If you move fast enough to contract Earth, then you effectively contract all the other spherical objects and the distances between them as well, and all the physics will work out equally well in that reference frame as it does in this one."
Focus on this if you will: ' If you move fast enough to contract Earth, then you effectively contract all the other spherical objects and the distances between them as well, and all the physics will work out equally well in that reference frame as it does in this one."
This needs editing, but I'm out of time.
I found "more time." Sorry I can't edit out the repeated quote.
The focus I intended to emphasize was that no matter how fast anything moves it will not "contract Earth" or shrink the distance between stars in "the real world," assuming a real world as objective realism does, contrary to the assumptions of "instrumentalism."
I still hold out hope we will find life on the Jovian moons.
"... we’re going to be constructing a history-of-the-Universe poster unlike anything you’ve ever seen before!"
Sign me up!
Sinisia has explained this to you: the frame of reference doesn't change the Earth's spacetime interval. That's what remains constant. That's the 'reality' which every measurement confirms, every person in every frame of reference agrees on and sees as identical, etc., etc. That's the objective reality you're looking for.
You forget again that a contracted Earth is only “apparent,” i,e., that fast moving frames of reference do not change the physical shape of planets and stars. There is no physics to support shrinking planets and stars.
Frame of reference doesn't change their shape or movement in spacetime. They don't shrink in spacetime. But individual space dimensions and the time dimension aren't separately conserved.
Incorrect; see above. Einstein theories posit a real world independent of observation. The description of objects in that real world is given by its spacetime interval.
However, to try and move us out of the never-ending cycle of your repeating the same complaint over and over again and us repeatedly trying to explain to you what's going on with relativity, how about we try a different approach. How about you tell us something observationally different between your idea and Einstein's? If Einstein is wrong and you are right, what should we see that you get right and he gets wrong? Got any ideas?
I'll keep this short because my posts don't seem tobe going through and so I may be repeating myself. Sinisia explained this to you quite clearly. An object's spacetime interval is independent of observation and measurement and even frame of reference. But it's x, y, z, and t are not separately independent of frame of reference...no matter how much you want them to be...
For the record, I missed Ethan’s reply to my challenge above… reminded by his recent weekly replies. (I’m not good at navigating here.):
” From Michael Mooney on special relativity and length contraction: “So the distance between stars depends on the speed of the traveler (no objective cosmos independent of frame of reference), but spherical bodies in space don’t flatten out (contract in diameter) depending on speed of the observing point of view. (“We don’t think so” anyway.) So what is the difference here? Please explain.”
“There is a big difference between what different observers see; that’s the key point of special relativity, and one of the biggest sources of confusion for those trying to learn it and wrap their minds around it.”
I have never challenged the “big difference between what people see” in SR. I (and many other SR critics) only challenge the claim that those differences reflect actual physical variations in objects and distances. Yet no SR theorist will admit, “Yes, the differences are only apparent.”
That is my whole point. Nuff said.
(I transcribed this from the referenced comment page.)
Thank you for explaining your repeated refusal to understand the science of climate change - you prefer to believe the fake stories about the gloom and doom that you believe would result from addressing it rather than the mountains of evidence that support the scientists.
Try not to be so sanctimonious and learn more about WHY many scientists don't agree with the idea of carbon dioxide as being the climatic bogey man some have made it out to be. The Earth's climate has always changed, and will continue to do so even if you screw people over with high energy costs (such as in the EU and the UK). Scary computer models that diverge rapidly from reality even with hand tuning are not 'mountains of evidence' of anything, scientific or otherwise.
I also understand the theory of carbon dioxide being the primary driver of climate change just fine, and I reject the theory because it is proven false by geological observations alone. We know for a fact that CO2 in the atmosphere has been over five times what it is now in the distant past, yet the earth didn't spiral into a runaway greenhouse effect of any kind. Water vapor is also a far more powerful greenhouse gas than CO2, the planet is over seventy percent covered with it, and yet... the world manages not to roast because of it. Most climate models are also treating CO2 influences as linear when they are logarithmic.
The fact that global warming rhetoric is also in complete alignment with leftist ideology and political control over people and money than an actual scientific remedy that would have any predictable or measurable effect on the climate at all should be a big red flag. Almost all global warming initiatives/fantasies revolve around immense mandatory economic redistribution schemes managed by some centrally controlled world government that has the power to determine pretty much everything under an enlightened technocratic elite.
cft, linking to watts' site demonstrates you chose not to understand. It is no different than a vaccine denier linking to natural news.
The Universe is expanding. Scientists have attributed this expansion to Dark Energy, an energy inherent to space itself that effectively pushes outward with enough force to overcome gravitational collapse. Among scientists this idea is widely accepted today.
Early in the 1900’s as Einstein was forming the idea that became General Relativity he recognized a problem with his bowling ball on a bedsheet theory of gravity. It would unerringly collapse everything in the universe into a black hole. That didn’t match observations. To get his theory to match observations he needed a force that effectively pushed outward with enough force to overcome gravitational collapse and he called it the ‘cosmological constant’.
Was Einstein right? Did he invent the idea of Dark Energy? If you ask scientists or Einstein later in his life the answer is no, and no. Ethan even wrote a piece on how it really was a blunder of Einstein’s.
The Earth may be warming. That doesn’t mean scientists predicting global warming are right. As the Einstein example demonstrates, simply getting the direction right isn’t good enough to be correct. That isn’t how science works. The theory makes a very specific prediction that is supposed to be the ‘fingerprint’ of human induced warming. It is called the Tropospheric or Tropical Hot Spot (IPCC AR4, Bengtsson 2009, Trenberth 2006, Ramaswamy 2006), and it isn’t there. It doesn’t exist. Satellite measurements are corroborated by weather balloon collected data. It isn’t bad data. It is a failed prediction. It is wrong.
I could go on and on about failed models only to receive in return a list of failed models made by ‘denier’ scientists. Nobody has it right yet. No one has a model that perfectly predicts Earth’s atmosphere. They’re ALL wrong to varying degrees. I’m not the one whistling past the graveyard here. Einstein was wrong with his cosmological constant and for the same reason anthropogenic global warming theory is wrong today.
The problem with your argument is how do you know what the reality actually is? If we can't trust measurements to determine true reality, and you've rejected measurement as a test for true reality, how do we find true reality?
Suppose we wish to determine the true shape of the earth. How do we go about doing so? We can measure the radius of the earth in different direction from the center. We find that these radii agree to a very high degree of accuracy (they actually are a bit different depending on whether they are equatorial or polar radii, but I'm ignoring this). We can then conclude that the earth is spherical (or nearly so).
You would stop there and say that the earth really is spherical. However, the postulates of relativity state that there are no preferred reference frames. The reference frame of a rocket ship moving at 0.8c with respect to the earth is equally valid as one not moving at all. If the moving observer makes the same measurements he will find that the earth is NOT spherical. The radii measured in the direction of travel will be much shorter than the radii measured in a perpendicular direction.
You would conclude that the observer in the rocket is wrong and that the true shape is spherical. What is your basis for this conclusion? You cannot point to the observation that gravity causes objects that are sufficiently large to be round as that basis. That statement is in fact not true. The true statement is that an object that forms under the influence of a force that is radially symmetric will be round. In the Newtonian approximation, it is true that gravity is radially symmetric, ie. the gravitational force depends only on the distance between the attracting bodies, not on the direction of action. In the reference frame of the rocket, gravity is no longer radially symmetric; it acts more strongly in the direction of the velocity vector.
If you fully consider the effect of length contraction, you see that this must be so. Consider a mass element on the surface of the earth. The distance between the center of gravity and that mass element will depend on the location of that mass element. If it is located in a direction parallel to the velocity vector, then that distance will be length contracted, hence shorter. Since gravity depends on the inverse square of the distance, the force acting on that mass element is greater than the force acting on a similar mass element located in a direction perpendicular to the velocity.
Now think clearly about what this all means. The first postulate of relativity, which is an inherently reasonable one, states that the laws of physics are the same for all observers. Let's test this WRT the above situation. The commoving observer sees that the force acting on a mass element on the surface of the earth is the same regardless of direction. He therefore concludes that the mass elements are all located equidistant from the center; i.e. the earth is spherical. The moving observer sees that the mass elements located in the direction of travel are closer to the center than those located perpendicularly. Therefore, these mass elements must be closer to the center; i.e. the earth is not spherical, but rather is flattened in the direction of travel.
What basis do you have to say that the commoving observer is right and the moving observer is incorrect? Both are applying the laws of physics and find that those laws hold as expected. Why is the rocket observer wrong?
I brought up a perhaps unfortunately named concept in a post I addressed to you some time ago, namely the concept of a proper measurement. That is simply defined as the measured value of a quantity in a commoving reference frame. It would be true that the proper shape of the earth is (nearly) spherical. That term is unfortunate, however, in that it implies that the measurement in a commoving frame is somehow more real or valid than one in any other frame. That is not the case.
Just to try one last thing to get the point across: please tell me your true velocity right now, not just an apparent one. The whole point of relativity is that lengths and times behave in the same way as velocities, not differently as was previously believed. Newton though of time and space as absolutes. Relativity rejects this and concludes that the space-time interval is the absolute, not time or space individually. All of the rest of the conclusions of relativity: length contraction, time dilation, etc., follow directly from this.
" I’m not the one whistling past the graveyard here. Einstein was wrong with his cosmological constant and for the same reason anthropogenic global warming theory is wrong today."
wow - such a foolish statement, based on the foolish critique that "no model perfectly predicts climate".
If you base all of your conclusions on things that can never happen, as you do, you'll never be disappointed. Of course, just like you, you'll never be correct.
Sean T (#14):
" However, the postulates of relativity state that there are no preferred reference frames. The reference frame of a rocket ship moving at 0.8c with respect to the earth is equally valid as one not moving at all."
The postulates of relativity are not universally accepted as absolutely, indisputably true. (See objective realism and a huge body of scholarly criticism of those *assumptions*, most recently my link to Kelley Ross on the ontology of "curved space.")
The argument is that those differences are only *apparent* not actual physical differences.... that there is no physical force changing physical shapes and lengths. The force of gravity does in fact form the 'raw materials of' planets and stars into near spheres in spite of your argument (citing the limits of Newtonian physics) to the contrary.
Images, upon which appearances are based, are carried by light. We might reasonably expect distortion in those images as an "observer" (frame of reference) approaches the speed of light. The reason that "proper length" from a co-moving frame is actually a "preferred frame" is that it need not depend on an image carried by light. A long enough ruler laid against an object (or through it for spherical bodies) by a blind man will give the "proper length" of an object without distortion of *images.*
I'll have to leave it there for now.
Ps: Clearly all velocities are relative. I have previously belabored that point myself.
A philosophy article written in 1996 for a non-peer-reviewed journal the author appears to have created themselves is hardly the sort of disagreement that is going to shake the physics community. That's pretty much identical to a vanity press publication. If you want to claim relativity is receiving credible and serious criticisim, you'll have to do better than that.
Are you trying to claim here that light would be traveling slowly for them? That light would not appear to be moving at c in their reference frame? That's wrong. It's empirically shown to be wrong.
Go look at Sinisia's video again with the train and the tunnel. The tunnel is not a light beam - agreed? Its built of matter and can be used as a measuring stick, agreed? Specifically, if we want to measure the length of the train while moving, we can ask if it fits in the tunnel such that neither ends sticks out. Yes? So if a stationary observer measured a train to be longer than the tunnel when it wasn't moving, but then when the train is moving at near c it fits in the tunnel, by your own logic that would mean the contraction is real and not just an image, correct? Because that's what will happen.
it's Sinisa not Sinisia ;) but ok
"he postulates of relativity are not universally accepted as absolutely, indisputably true. "
True, there will always be some crank or another who disagrees.
"Images, upon which appearances are based, are carried by light."
Are you saying that light is solely a vessel for carrying images, and not a thing on its own?
No my good man. The word you are looking for is 'faith'. I believe in people. I believe they can do great harm, but they can also accomplish amazing things.
Back in the mid-1600's England's Charles II married Portugal's Catherine of Braganz and got 7 crappy islands as a wedding present. There was nothing there except some fishing villages and even those often flooded.
A little over a hundred years later the East India Trading Company had installed a Brit by the name of William Hornby as Governor, and he came up with a plan now known as the Hornby Vellard for the 7 islands.
Keep in mind this is 1782. In the US we were still fighting the American Revolutionary War. On the other side of the world Governor Hornby was joining the islands. With that era's technology and tools they essentially custom created what they felt would be the perfect sea port.
The project was wildly successful and what once was some fishing villages that routinely flooded is now known as Mumbai, the 9th most populous city in the world, and by far the most prosperous city on that part of the planet.
We've learned a trick or two since then. I have faith in our ability to engineer the environment. I have more faith in that than in the economically displaced remaining civil. In weighing one against the other I know which way I lean.
You do not speak for science, or have a monopoly on the truth, so get off your high horse. Ethan already does enough science PR and parroting, so that job is already taken.
In addition, calling someone a denier is purely an insult not a counter argument you little tool. It is also the language of zealous religious persecution, or an offhanded insult in reference to being anti-semetic or 'holocaust denial', neither of which is relevant to the discussion or to me - and in addition to the fact you do not know my personal beliefs, quite a stupid thing to accuse me of. You do however prove my point made about how the issue of carbon climate change policy is purely political, not scientific, as you are using Alinksy's 'Rules for radicals' and not the scientific method to make your case.
No, sorry, you are again basing arguments on opinions, not what I or the science says.
Flatly saying the science is wrong is denying what the evidence shows - hence, you are a denier of the science. There is no link to holocaust denial in it, despite your comments.
"Alinksy’s ‘Rules for radicals"
It is always amusing to see that the people who refer to that bit of crap are the folks who hold an incorrect position, so they think that having the facts pointed out to them is based on some antiquated and never used in practice guidelines from a third-rate rabble rouser.
Whether you don't want to understand, or can't understand, the science, or the statistics, is not my problem - it's yours. The same can be said for your faux butt-hurt and false attempts to claim that somehow I'm linking you to Holocaust denial.
Note: the second sentence in the second paragraph of my 22 should be "There is no link to Holocaust denial in it, despite your comments."
"Are you trying to claim here that light would be traveling slowly for them?"
No. We all know that light speed is constant through space.
"...for them" is the subjective basis of SR, regardless of any possible objective world "as it is independent of observation," a concept denied by SR.
Dean: Opening with the standard SR insult (no criticism of the doctrine allowed!):
"True, there will always be some crank or another who disagrees."
Science transcends personal opinions and insults... when it is objective.
" Are you saying that light is solely a vessel for carrying images, and not a thing on its own?"
No. And I have no idea why you thought I "am saying" that.
Simply that images are carried by light (at 'c') and that images can be distorted while physical objects and distances in "the real world" can not ... by differences in observed images.
Then stop using religious language for those who disagree with your views, we aren't discussing religion. If you can't accommodate differing views without using the language that cults and zealots use to silence dissent, you should put a sock in it.
Try to understand. Saying you are a science denier is not religious language. Nobody buys your complaint.
@Ethan, and by Ethan, I mean Ethan and not Wow or dean or some other cheerleader who also wants to chime in.
"I don’t understand where the silliness comes in here. If you’re on a trampoline and I don’t touch you, but I do touch the trampoline, can you see where I affect you, even though you and I never interact? Dark energy affects the fabric of the Universe where the particles reside; the particles are affected by the Universe’s fabric, but not by dark energy directly. It’s pretty straightforward."
The silliness was brought in the front door entirely by you Ethan, What an utter load of bullshit. Fabric of the universe? That sure explains things...How about 'and then a miracle occurred'? Vacuous euphemisms and poetic license are not scientific or explanatory, quite the opposite, and there was nothing straightforward about your logistical bait and switch.
First, We aren't on a trampoline at all, BUT If we were, the trampoline is made of something called matter, you are made of matter, I am made of matter, and we are both interacting with the trampoline's matter directly (kinetically), and each other only somewhat indirectly by bouncing around on the trampoline causing it to move beneath each other when we are in contact with it. So, In your first trampoline analogy, everything is made of matter. This really is no different (sans the stupid gridded rubber sheet analogies) with putting you in box and shaking it about until some sense gets drummed into you, or hitting you with a whiffle bat several times over the head until you quit talking like you actually have some profound insight demonstrated by making bad analogies and making meaningless comparisons. In both of my intentionally absurd analogies I could also say I wasn't DIRECTLY interacting with you, the box and the wiffle bat was, but that isn't exactly true either because in effect the box and the wiffle bat are still direct extensions of me kinetically interacting with you. If I were to wear boxing gloves when I punch your face, I can't say I'm not directly influencing you, and you would most definitely say so in such a situation and hold me directly accountable.
From the trampoline nonsense, you then elide to the dark matter/energy nonsense, and espouse it somehow is interacting with me and with you, and yet not influenced by us...or particles...derp....say what? If I am causing your dark matter trampoline to move about in a way that effects you and vice versa, then yes particles are interacting with the dark energy/matter bullshit stuff, but that isn't what you meant is it? You very dishonestly elided from a comparison of classic kinetic interactions (of things bouncing off one another) to one where you withdraw your kinetically mediating 'trampoline' into an utterly non-physical/corporeal entity that you really can't explain interactions, identify, locate, or measure, and yet claim 'straightforward' understanding of. Yeah, straightforward as Lombard street.
That you don't apparently know why Dr. Judith Curry suddenly abandoned support of GCMs and doomsday carbon forcing scenarios shows your ability to seriously research your topics of discussion borderlines on vapid or just plain incompetent. Please stop phoning it in. If you had done some actual legwork and digging, instead of libeling her, you would have known better.
@dean, and for the last time,
I wasn't talking to 'Nobody' buying a complaint, I was actually talking to 'just you' and how I find you and your misuse of terminology offensive.
Please run along and go play with Wow, you both would appear to be much alike and have a lot in common, large male egos, speak fluent sarcasm, enjoy insulting others outside your group, and you can both agree with each other all day long about whatever you wish. Much unlike you, I actually do like to examine ideas I often don't agree with, research, and learn about them. As you do not like doing this, and seem to spend so much time trying to find ways to exclude others from your private country 'club' of true belief, consider me happily excluded from your little click.
I do not recommend ever trying to engage in conversation with me again unless you can learn how to hold a debate about ideas and disagree with people politely, or say something remotely new and interesting besides calling me a 'science denier' or playing the part of Wow's second fiddle.
CFT, I believe you actually try to understand the science as much as I believe in garden gnomes coming to life.
If you and other denialists don't like the term don't flatly deny science, whether it is climate science, the safety of vaccines, relativity, evolution, or anything else.
It's not that hard to understand. The strong nuclear force stabilizes every nucleus in my body, yet the structure that is me has little or no impact on it as a force. The EM force dictates the structure of my molecules and cells, yet I can walk through a pulse induction scanner and not cause a current flow. The Earth's gravitational field holds me on the planet, yet it is negligibly impacted by my existence. Likewise it is easy (or should be easy) to understand that there is another force or field type, acting on us but not significantly influenced by us.
Fine, put up or shut up. Which postulate of relativity is wrong, and what is your experimental evidence for concluding this?
Sean T, I would quit repeating if SR advocates would quit demanding that I answer after not addressing my answers already given.
I countered the assumption/ postulate that there is no preferred frame of reference in #16, based on the difference between images, which can be distorted, and physical objects/ distances which can not (via observational differences.)
Regarding the claim that "all frames of reference are equally valid": If one says that Earth's diameter is about 4000 miles (as he approaches at .86 c,) and another says it's about 8000 miles (as he orbits), they can't both be correct/ valid unless one assumes that there is no "real world" independent of observation/measurement.
The the empirical evidence for a nearly spherical (oblate spheroid) Earth is ubiquitous general scientific *knowledge* while that for a flattened earth is non existent. The latter, "for observer B" is, in the most general sense subjective and theoretical, while the former is physical, factual knowledge.
Last time I will "put up" on why the "equally valid flat earth" is *wrong.*
That is just silly. I don't think you realize how big the ocean is. All of the ice coming off Greenland amount to roughly 220 cubic kilometers of ice per year and still only adds 0.2mm/year. The ice shelf you are so worried about on the West Antarctic Peninsula is already floating. Ice isn't going to cause 'discontinuous jumps'. What we are seeing now is mostly thermal expansion and it will remain nice and gentle.
Actually you talked about 8 meters. I just added in the timescale you neglected to include. Time is important and it is not free.
Let's forget about your 'centuries' and keep it at the shorter 50 years for the sake of steel manning your argument in demonstrating how bad the math is on this.
Imagine you were purchasing a house. You have a good down payment but needed to finance $460k over 50 years at 4.9% (avg of the Treasury Bond over the past century). What you get is $774k of interest owed for a total debt of $1.234 million dollars.
A couple weeks ago I ran through how the proposed changes could cost our economy $4.6 Trillion dollars in yearly damage (>45 Katrina disasters). You conceded that we aren't going to get hit with that next year and pushed the disaster down the line. The 50 year cost on that single year $4.6 Trillion is $12.34 Trillion.
That is just one year, but the below trend damage is annual. Even ignoring economic growth, you'd throw in another $4.6 Trillion next year with 49 years of interest. The year after that you get another $4.6 Trillion with 48 years of interest.
We are not going to get hit with 45 Katrina storms next year. We are not going to get yet with 92 Katrina storms the year after next. The farther you push out the doom, the worse your argument gets.
Remember we aren't talking about a Hollywood disaster. The 50 year doom you are worried about, even at eric's numbers, consist of less than 7 inches of water. Being that the sea level has been rising for 22,000 years the 7 inches of doom is going to happen anyway. The best we can do is to prevent nutballs from trying to torpedo the economy so we have the resources to accommodate the inevitable change.
So who's frame of reference is preferred, then? In which frame of reference is light observed to act differently/move slower than the rest?
As far as I know, your claim that there is a preferred frame has been shown to be wrong by many people, even since Michelson and Morely did their first test of it 130 years ago. There is no frame in which light behaves differently than the rest.
Yes, they can, and the reason is because there is no absolute simultaneity (of measurement) between the two of them. Each one would see the other 'measuring' a different way, with time behaving differently for that other person, and it is these differences that lead to the difference in result But the spacetime intervals the two different people measure will agree, and assuming they both knew relativistic physics, both could say "I understand why the other guy got the answer that he did."
@ #32 Michael Mooney,
To counter the postulate that there is no preferred frame of reference is to assert there is a preferred frame of reference.
eric's question @ #33, "In which frame of reference is light observed to act differently/move slower than the rest? " is to the point.
I'm unaware of experiments returning measurements or observations indicating a preferred frame of reference. That doesn't mean there are none, but when there is evidence corroborating one physical theory and that is at odds with another, the theory supported by evidence is commonly considered better than the other.
You still haven't countered the postulate that there is no preferred frame of reference. That postulate really entails that the laws of physics are the same in all reference frames. In which reference frame are the laws of physics different?
You are begging the question when you state that two different diameter measurements cannot both be right. That is precisely the type of thing that is at question. You don't get to simply state that this is incorrect and then use this as a basis for your argument that relativity is incorrect. If the laws of physics are the same in all reference frames, the speed of light is constant for all reference frames, and interactions cannot take place at speeds faster than c, then it logically and mathematically follows that the earth's diameter really is different depending on the reference frame of the observer.
I have gone over it with you in past posts. An observer moving rapidly relative to the earth would measure the distance between the center of the earth and its surface to be smaller in one direction. That observer would therefore measure the gravitational force to be larger in that direction, and would therefore expect the equilibrium shape of the earth to be flattened in that direction. The laws of physics are obeyed in that reference frame, so you have failed to counter the postulate.
That's the fundamental contribution of relativity to physics: time and space behave in a manner similar to velocity. Answer me this: what's your velocity right now? I don't mean what velocity would you appear to have to someone stationary with respect to the center of the earth, or someone stationary with respect to the sun, or someone stationary with respect to the center of the galaxy, but what is your TRUE velocity?
I'll save you the trouble: you cannot answer that question. There is no such thing as a TRUE velocity. Your velocity is whatever another observer measures it to be. You would measure your proper velocity to be zero (by definition since "proper" means a measurement made in a reference frame that is not moving with respect to the thing being measured), but any other value for your velocity is just as valid. You are moving somewhere between 0 and 24000 miles per day with respect to the center of the earth. You are moving at much faster speeds with respect to the sun or the galactic center. All these are valid measurements of your velocity. All relativity says is that time and space behave in like manner.
More simply, which reference frame is the preferred one? If one observer finds that the earth's diameter is 6000 miles and another finds it's 8000, which is right? It's not good enough to just say both cannot be right; that's just begging the question. You have to be able to say which of the two is correct. You also have to justify your choice and say why the other is incorrect.
Eric, John and Sean T,
Please re-read my #32, so I don't have to keep repeating the same answers to your repeated challenges.
I ask you all again, do you believe that a flattened Earth is an equally valid description? (Seriously, scientifically speaking!) Does the theoretical high speed traveler "really" change the shape of Earth, or would it just *appear* to have a flattened diameter in the direction of his approach? (Rhetorical question.)
You keep repeating the SR doctrine that " laws of physics are the same in all reference frames," as if different reference frames actually changed physical objects (and distances) rather than just seeing contracted images of a stable, unchanging object (say Earth.) I have commented repeatedly on the difference between images of objects and the actual physical objects themselves.
Ps, Regarding Sean T, #16, last paragraph:
How many times must I repeat? ( #16) " Clearly all velocities are relative."
Finally, " the laws of physics are the same"...* for all physical objects.* They do not shrink without application of compressive force. Differences in frames of reference do not apply such force. The images change, not the physical objects. Does anyone here understand that?
Edit: Regarding Sean T, #36, last paragraph:...
Yes. Seriously. Scientifically speaking. I already pointed out to you that if a relativistic traveler were to use a sphericaly shaped Earth to calculate things like their trajectory, they'd get it wrong. In their frame of reference, pancake-Earth is not merely 'equally valid' as sphere-Earth, it's the more valid for any prediction or calculation you care to make.
The traveler does not change the 'spacetime interval' of the planet. That is what remains constant. However the traveler's motion does change the Earth's apparent x, y, z, and t properties, just the same way that being on a train zipping past a baseball pitcher may change the apparent v of the ball. This was Sean T's point to you: time and space behave in a like manner as velocity.
Now, please answer my question: in which frame of reference is light moving at a different speed than all the others? IOW, which frame, according to you, is preferred?
Eric: " However the traveler’s motion does change the Earth’s apparent x, y, z, and t properties."
"Apparent" is the key word. Ask Ethan.
The train (or ladder) is only shorter " as it *appears* to the relatively moving observer," not physically. How one sees it at very high speed will have relativistic distortion, precisely described by the Lorentz transform equation.
Ps: Eric, I forgot to answer your last question (#40).
I have agreed often and repeatedly that light speed is constant through space... regardless of frame of reference.
It reminds me of the old saw, "Have you stopped beating your wife? Yes or no!
And one more time, the at rest, co-moving frame is preferred among objective scientists, because one can measure an object directly without depending on differences in the arrival of images carried by light over various distances.
You a reading too much into my word choice. A ball tossed from a nearby pitcher at a person on the train will have a momentum determined by the ball's "apparent" velocity and mass to that train passenger. This will have real world consequences - he will either get hit much harder, or much softer. It's not an illusion, and he won't experience the ball's momentum that a person standing in the pitcher's frame of reference would experience. Likewise, for the relativistic passenger, the x, y, z, and t of pancake Earth will be experienced by them in even physical way. It will have real world consequences, and is not an illusion.
In hindsight I probably should have chosen different wording. To the man on the train, the pitcher's ball is moving faster or slower. To the relativistic traveler, the Earth's shape is foreshortened.
The relativistic stuff you object to derives directly, mathematically from this statement. You simply can't have "yes c is constant in all reference frames" and "yes there is a preferred reference frame" at the same time. At least not for what physics means by 'perferred reference frame.' If c is the same in all refreence frames, then time must dilate, and distance must foreshorten.
When you say 'preferred,' do you simply mean used because it is easier'? That is not what physicists talk about when they use the word preferred. Yes it is mostly true that scientists will use the proper reference frame of themselves and surrounding objects when doing calculations, because it's easier. However, even that practice isn't followed 100% of the time. Most scientists who deal with particle physics and nuclear reactions will calculate reaction dynamics using the center of momentum or center of mass frame of the reaction - which is often moving with respect to the experimenter - rather than the 'at rest' frame of the experiment. Because the former is easier. What you are talking about is a convention that is useful most of the time, but is certainly not a preferred reference frame in the way physicists mean that phrase.
I think one problem we have in communication is that science uses words in a very precise manner. Often the meaning of these words is quite different from what the ordinary meaning of them is.
In our case, the term is "preferred", as in preferred frame of reference. In the scientific usage, this term preferred is used to mean that the laws of physics can only be formulated in the preferred frame of reference and no others.
Relativity makes the postulate that there is no preferred frame of reference. You can apply the laws of physics in ALL reference frames. Of course, that doesn't mean that there isn't one reference frame in which calculating solutions to the equations is easier; typically there is such a reference frame. This reference frame is "preferred" in the colloquial sense of the word, but it's not preferred in the scientific usage of the word since all other possible reference frames could be used if we so wished.
Just to answer some of your other objections, I did deal with your objection about physical forces. Physical forces also are relative (more precisely the notion of "force" ceases to be useful in a relativistic description). In the case of the flattened earth, the moving observer does measure an increased gravitational force in the direction of travel vs. the perpendicular direction. Given that the force of gravity exerted by the earth on a mass element at the surface is greater in the travel direction than in the perpendicular direction, the laws of physics state that the equilibrium shape of the earth should be such that the distance between the center and the surface in the travel direction should be less than that distance in the perpendicular direction. That is precisely what an observer on the ship measures. The laws of physics hold true for the spaceship observer, just as they hold true for the commoving observer.
The laws of physics hold for all observers, but that does not necessarily mean that all observers will measure the same times, distances, velocities (other that that of light), forces, etc. Only the spacetime interval between two events is a constant for all observers.
I am aware that this seems odd and can understand your objection that this undermines the idea of an objective reality. As I have been explaining, though, the idea of changing distances and times between observers is no more damaging to the idea of an objective reality than is the fact that different observers will measure different velocities, an idea you, of course, can accept because you've been able to see the consequences of it without any real difficulty. If light speed were much lower, you would see the consequences of relativity WRT times and distances in your daily life and you would likely object as little as you do to the relativity of velocities.
Eric (#43): " If c is the same in all refreence frames, then time must dilate, and distance must foreshorten."
If "frames of reference" do not change physical objects (they don't) and if "time" is the variable ticking of clocks at different speeds and gravity fields, and if lengths/ distances of "real world objects" do not actually change, as observed from high speed frames...
Then length is actually invariant, time is an artifact of variable "timekeeping" instruments, ... and 'c' remains constant, conveying images to different observers at different distances and "local clock times"... not to be mistaken for the actual physical objects and distances themselves.
Sean T (#36): "... then it logically and mathematically follows that the earth’s diameter really is different depending on the reference frame of the observer."
This nails the fallacy of SR theory very succinctly. It clearly states the belief that math trumps (denies) the physical science of relatively rigid /solid objects.
The fact of the matter is, in spite of SR's insistence to the contrary, that Earth's diameter does not physically change "depending on the reference frame of the observer." That would require a crushing force which would disintegrate Earth "in the real world." Reference my last paragraph in #38. The bottom line there remains unanswered
Ethan once agreed that physical objects don't actually, physically contract, but he refuses to follow up on my length contraction challenge or clarify it for this forum. ...Because it would get him in trouble with "mainstream SR," I think. Nobody criticizes SR without losing credibility in that community.
Mm, nobody buys a crackpot who believes in a cabal of relativity overseers who punish people for asking questions either. Legitimate questions are always valid. Try some once in a while. But until you can back your whining up with calculations you don't have a case.
All your handwaving and question begging still has not come up with an answer to the fundamental question regarding your assertions. How do you determine that a measured value is only apparent and not real? You state that the earth is a rigid body, but this cannot be strictly true. The earth is round, not because the bits of dust, rock, etc. that collided to form it did so in such a way as to make it round, but rather because even though they collided in random orientations, gravity shaped the earth to a spherical shape. If the earth were a rigid body, gravity would have been unable to change its shape.
We now cannot use the rigidity of the earth as a way to determine true reality (Relativity states that there is really no such thing as a "rigid body" anyway). What else do you have to tell us that a measured result is only apparent and not real? That's really the key to all of your assertion.
Sean T (#49): "...gravity shaped the earth to a spherical shape.."
Exactly. I have described the gravitational "formative period" of stars and planets and specified that they are "relatively rigid." ... "Apparently" you missed it or ignored it as you continue to argue a moot point from your SR lecture mode.
You can't have it both ways: "Earth is pancaked" ("frame of reference" doctrine of "reality")... and, "Earth is spherical" (as originally formed.)
It is one or the other, not both... as in "depending on the observer."
Also, I have repeated that "a measured result" can either be "apparent," as carried by light to instruments (or the eye)... variable with the distance to the object and relative speed of the observer... or by direct contact with the object by a measuring device at rest (co-moving) with the object. The latter will be the *valid* description. Last repetition for that too, whether you "hear" it or not.
Ps: I have often acknowledged that the "valid description" above ("proper length") can be found from a fast moving frame by applying the Lorentz transform. It adjusts mathematically for *distortion of images* in that case.
Assume a ping-pong ball is moving at 0.76C. It's diameter (at rest) is 38mm. It's going to hit the Moon.
Now consider an observer on the Moon, filming the impact. If it didn't contract "in reality", the back side of the ball would hit the Moon 6ns after the front side hit. If it actually does contract, it will hit 4ns after.
That seems like a very easy "gedankenexperiment." So which is it, 6ns or 4ns?
You are still question begging. How do you know that the earth's shape in the commoving frame is its "real" shape, and that its shape in any other frame is only "apparent"? How do you determine that the earth isn't "really" pancake shaped and that it is we who see its "apparent" shape as round only because we happen to be stationary with respect to the earth?