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[Edit: Never mind -- I completely misread the quote, as JumpCrisscross points out.]

I stopped reading here:

"But just over a decade ago, astronomers noticed that the most distant galaxies were accelerating away from us much faster than the ones nearby. In fact, the further they looked, the greater the acceleration seemed to be."

This was, in fact, noticed in 1917 by Vesto Slipher, derived from General Relativity by Georges Lemaitre in 1927, and further confirmed by Edwin Hubble in 1929, when it became known as Hubble's Law.

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Hubble's Law said the velocity of distant galaxies was faster than that of nearer ones. It is only in 1998 that we discovered the universe's expansion is accelerating, i.e. that Hubble's "constant" is shifting.

We found this out by very precisely measuring the brightness of a very specific type of supernova, a Type Ia supernova, which has a very consistent intrinsic brightness (about 5 billion times brighter than our Sun) allowing for distance measurements with an uncertainty of just 5%. This was a novel achievement, enough to merit the 2006 Shaw Prize in Astronomy.

somebody needs to update wikipedia then:

>Current evidence suggests the expansion of the universe is accelerating (see Accelerating universe), meaning that for any given galaxy, the recession velocity dD/dt is increasing over time as the galaxy moves to greater and greater distances; however, the Hubble parameter is actually thought to be decreasing with time, meaning that if we were to look at some fixed distance D and watch a series of different galaxies pass that distance, later galaxies would pass that distance at a smaller velocity than earlier ones.[33]

Discovered in 1998, and explained in 2008 using generally accepted equations, at http://finbot.wordpress.com/2008/03/05/dark-energy-obviated/

In short, if you launch a unpowered projectile upward at close to the speed of light, Einstein's prediction of gravitational time dilation (experimentally confirmed) in turn predicts that the projectile accelerates away from you, for as long as its velocity relative to you is close to the speed of light.

(The ivory tower no longer considers ideas that source outside the tower, which explains why this idea is in a blog.)

I can't pretend to understand relativity well enough to verify that blog post's maths, but one of the notes caught my eye:

<quote> 2. Herein, as in most relativity texts, we ignore the travel time of light that prevents a remote event from being seen until after it has occurred. In principle a network of observers can be set up in locally inertial frames that momentarily co-move with the rocket, so that events can be detected by equipment right next to them, and the records subsequently compiled and analyzed. </quote>

I could be reading that wrong, but the author seems to be suggesting that time's inherent inconsistency at relativistic speeds and distances can be mitigated with a "network of observers". I don't know if that's true, but "momentarily co-move with the rocket" sounds like it's ignoring an awful lot of relativistic acceleration of the measuring devices.

The network of observers are moving inertially (i.e. unpowered, freely falling), moving with the rocket for only a moment, so they're not accelerating like the rocket is. That's how those observers can make good measurements, in that moment. For more info search for "momentarily comoving inertial frame" at http://math.ucr.edu/home/baez/physics/Relativity/SR/clock.ht.... Each inertial clock can measure the passage of time accurately.

The math in this post is fine (since, as you note, it's just plugging in numbers to "generally accepted equations"), but it is "solving" the wrong problem:

if you launch a unpowered projectile upward at close to the speed of light, Einstein's prediction of gravitational time dilation (experimentally confirmed) in turn predicts that the projectile accelerates away from you

In other words, the "acceleration profile" produced by this model is: acceleration, then deceleration. But the "acceleration profile" that needs to be explained for our actual universe is deceleration, then acceleration: an apparent slowing down of the universe's expansion, followed by an apparent speeding up. There's no way to get that out of the blog post's model.

To be novel the blog need only show one thing that isn't currently known. Generally accepted physics doesn't recognize that an unpowered projectile launched upward can accelerate away, let alone shown with generally accepted equations. The blog is novel for that alone. The blog explains the acceleration away of supernovae that is currently a mystery, so the blog is novel again for that reason. If we don't accept an advance of physics until it explains a complete set of mysteries (an acceleration profile over the universe's history, in your case), we could be waiting a long time.

The "deceleration, then acceleration" is an implication based on assumptions, not something observed. We haven't actually witnessed any deceleration or acceleration when looking through a telescope. Instead, when we look at various distances from the Earth we see various redshifts (not changes in redshifts), and then, because looking further away is looking back further in the history of the universe (a safe assumption), and based on the assumption that space itself is expanding to cause those redshifts and any changes in those redshifts, we conclude that space itself expanded in a decelerating manner and then, later in the universe's history, in an accelerating manner.

The blog implies that we should rethink those assumptions. It shows that the expanding space paradigm is superfluous. When that paradigm is removed, generally accepted equations can be applied to show that objects sufficiently far away from us (which we can now assume are receding at close to the speed of light, given their high redshifts) accelerate away from us. So when we look close to us we'll see evidence of deceleration, and when we look further from us we'll see evidence of acceleration, but that has nothing to do per se with the history of the universe. Thus the blog does explain the observations that form the acceleration profile you note.

Generally accepted physics doesn't recognize that an unpowered projectile launched upward can accelerate away

Really? What is your source for this extraordinary claim? You yourself said that the equations you used are generally accepted. That means people already understand their consequences. The fact that people don't agree with you about how to apply the equations in a particular scenario doesn't mean people don't believe the equations.

The blog explains the acceleration away of supernovae

No, it doesn't, because its prediction is not the same as what we actually observe.

The "deceleration, then acceleration" is an implication based on assumptions, not something observed

No, the apparent deceleration, then acceleration is what we actually observe. The question is how to interpret these observations. The standard interpretation is that the deceleration, then acceleration are real, not just apparent. Your interpretation is that they are only apparent; but your model can't even reproduce the apparent profile we observe, so your interpretation is not supported by its own model.

So when we look close to us we'll see evidence of deceleration, and when we look further from us we'll see evidence of acceleration

No, you have it backwards. When we look close to us, we see evidence of acceleration (because we're looking at what happened more recently in the universe's history), and when we look farther away, we see evidence of deceleration (because we're looking at what happened earlier in the universe's history). Your model does not reproduce that observation, so it's not a valid explanation.

> Really? What is your source for this extraordinary claim? You yourself said that the equations you used are generally accepted. That means people already understand their consequences.

I'll respond only to this, as I've found here and before that you don't discuss fairly; that's unfortunately common in discussions about physics.

It's logically impossible to provide a source to show that something isn't recognized elsewhere. (This should be obvious to a smart person such as yourself, which is in part why I say you don't discuss fairly.) But you can search all you want to see that the claim cannot be found elsewhere.

That equations are generally accepted doesn't necessarily mean that people already understand their consequences. Understanding their consequences requires also experimenting with the equations in sufficiently various ways. Apparently that wasn't done until the blog author did it, or else I'd likely be able to do a Google search to find elsewhere that acceleration away can be shown by those equations. I'm confident that millions of science students would find "an unpowered projectile launched upward can accelerate away" highly interesting (maybe as well the physicist quoted in the blog post, who is mystified as to how his keys thrown upward could accelerate toward the ceiling). It should be an easy search if it was previously known.

I've found here and before that you don't discuss fairly

You're entitled to your opinion, but I'm also entitled to mine, and since we're being open and honest I'll give it. My opinion is that you are not interested in actually understanding the mainstream theories of physics that you are criticizing (and neither is the author of the blog post you linked to); you are only interested in criticizing them.

But you can't honestly criticize a theory that you don't understand; that means that before you criticize a theory, you must be able to explain what it says (even if you think that what it says is wrong) in a way that its own proponents agree to. I haven't yet seen you do this (and the author of the blog post you linked to doesn't either). See further comments below.

Understanding their consequences requires also experimenting with the equations in sufficiently various ways.

I agree with this in principle, but there aren't enough people or enough time to check all the consequences. So it's not a huge achievement just to calculate a new consequence; you need to show that it's significant. See below.

And for the record, I also agree that the model in the blog post correctly applies the equations (although as you and it are using the term "acceleration", it should more properly be "coordinate acceleration"). I just don't agree that this model can explain our observations of redshifts and apparent brightness of distant objects, since its predictions don't match our actual observations of the universe.

Apparently that wasn't done until the blog author did it, or else I'd likely be able to do a Google search to find elsewhere that acceleration away can be shown by those equations.

Okay, let's assume you're right that nobody has ever done the precise calculations that the blog post's author did, before he did them. If you had said just that--that mainstream physics has never considered the calculation the blog post author did before--I might still have been a bit skeptical, but I probably would have let it pass. Your claim came across as a stronger claim than that; you appeared to be claiming that, if you showed the blog post's calculation to a mainstream physicist, they would say it was wrong--not wrong as in not applicable to the expansion of the universe, but wrong as in incorrectly calculating the consequences of the relativistic rocket equation.

I strongly doubt that is the case, since, as I said above, I agree that the blog post author has calculated the correct numbers using the relativistic rocket equation (even though I don't agree with his application of those numbers to a different scenario). I strongly suspect that if you showed the blog post calculations to a physicist familiar with relativity (such as the author of the relativistic rocket equation page in the Usenet Physics FAQ, which the blog post links to), they would react the way I did: yes, this is a correct calculation using the relativistic rocket equation, but it's not relevant to the expansion of the universe. So saying that "generally accepted physics doesn't recognize that an unpowered projectile launched upward can accelerate away" does not, I think, describe what mainstream physics says in a way that a mainstream physicist would agree to.

the physicist quoted in the blog post, who is mystified as to how his keys thrown upward could accelerate toward the ceiling

This is another way in which the blog post incorrectly describes the mainstream theory. (Trying to arrive at a good description of what a theory says based on a sound bite in a non-technical article is a waste of time anyway; you need to look at the actual technical literature.)

In the blog post's model, the apparent acceleration up towards the ceiling is achieved by launching the keys upward at almost the speed of light. But in the mainstream dark energy model, if our spacetime locally was dark energy dominated, you could release the keys at rest relative to you, and they would accelerate, in the coordinate sense, up towards the ceiling (instead of accelerating, in the coordinate sense, down towards the floor, as you would expect with normal gravity). That's what the physicist quoted in the NatGeo article was actually describing.

when we look at various distances from the Earth we see various redshifts

The redshifts are not the only evidence we look at; we also look at the relationship between apparent brightness of objects and their redshifts. See Ned Wright's cosmology FAQ for a good brief overview:

http://www.astro.ucla.edu/~wright/cosmology_faq.html#CC

Perhaps he meant century?

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