If you want to get your mind around the research that won three astronomers the Nobel Prize in physics last week, it helps to think of the universe as a lump of dough - raisin-bread dough, to be precise - mixed, kneaded and ready to rise. Hold that thought.

Now consider Albert Einstein - not the wild-haired, elderly, absent-minded professor he became in his later years but a young, dashing scientist in his 30s. It's 1916, and he's just published his revolutionary general theory of relativity. It's not necessary to understand the theory (thank goodness). You just have to accept that it gave scientists the mathematical tools they needed to forge a better understanding of the cosmos than they'd ever had.

There was just one problem. Relativity told physicists that the universe was restless. It couldn't just sit there. It either had to be expanding or contracting. But astronomers looked, and as far as they could tell, it was doing neither. The lump of dough wasn't rising, and it wasn't shrinking.

The only way that was possible, Einstein realized, was if some mysterious force was propping up the universe, a sort of antigravity that pushed outward just hard enough to balance the gravity that was trying to pull it inward. Einstein hated this idea. An extra force meant he had to tinker with the equations of general relativity, but the equations seemed so perfect just as they were. Changing them in any way would tarnish their mathematical beauty.

Einstein did it anyway. The universe ought to behave according to the laws he had set out, but it simply wasn't cooperating. The "cosmological constant" - his name for the new antigravity force - became part of the theory.

Then, a decade or so later, the great astronomer Edwin Hubble went up to the Mount Wilson Observatory above Pasadena and used the world's most powerful telescope to peer deeper into the universe than anyone had before. Making excruciatingly careful measurements of the galaxies he could see beyond the Milky Way, Hubble was astonished to learn that they weren't stationary at all. The galaxies - the raisins in the bread dough - were in motion, each moving apart from the other. The dough was rising in all directions, and the raisins were going along for the ride.

This discovery ultimately lead to the Big Bang theory, which says that the cosmos was once tiny, with all matter packed tightly together, and that it's been expanding every since. When Hubble first announced his results, however, Einstein was more concerned with its consequences for general relativity. If the universe was expanding, the cosmological constant wasn't needed. His beautiful equations had been right to begin with. In 1931, Einstein came to Mount Wilson to shake Hubble's hand and thank him for saving relativity from the cosmological constant, whose invention Einstein denounced as "the greatest blunder of my life."

But this year's Nobel suggests that it was Einstein's statement, not the cosmological constant, that may have been the true blunder. Once astronomers accepted that the universe was expanding, they began to wonder if it would expand at the same rate forever. Or maybe, if there was enough gravity from all of those billions of galaxies pulling on each other, it would slow down, and or even slow to a stop someday and fall back on itself.

In the mid-1990s two independent teams of astronomers, one based at the Lawrence Berkeley National Laboratory and the other at observatories in Baltimore and Australia, decided to find out. Armed with telescopes far more powerful than anything available in Hubble's day, they began using supernovas - titanic explosions in which a single dying star briefly outshines an entire galaxy - as markers to measure the expansion speed at different times in the history of the universe. They could do it because telescopes are really time machines. The light from a distant supernova has taken so long to get here that when we finally see it, we're seeing a snapshot from billions of years in the past. If the supernova is relatively nearby, the snapshot is relatively recent.

By measuring the speed and distance of many different supernovas, from many different eras, you can see whether anything has changed over the billions of years of cosmic history. And when the astronomers looked, things had changed, but in a way nobody expected. The expansion of the universe wasn't slowing down. It was speeding up. The dough was, and still is, rising faster now than it was in the beginning. A baker would be astonished by this bizarre behavior. So were the astronomers. The only explanation that made sense: Einstein's "greatest blunder" was actually one of his greatest predictions. There really is a mysterious antigravity force. Einstein's only mistake was in rejecting it.

The 1998 discovery of the accelerating universe earned the Lawrence Berkeley Lab's Saul Perlmutter half of this year's Nobel. His competition - Brian Schmidt of the Australian National University and Adam Riess of the Space Telescope Science Institute, split the other half.

Only two questions remain. First, why did it take the Nobel committee so long to recognize such an important discovery? The answer is that they wanted to be really, really sure it was true.

The other question: What is this antigravity force, anyway? Theoretical physicists call it dark energy, but do they have ideas about what it actually is, how it works? Plenty, but are they convincing? "Well, no," Riess said in a telephone interview last week. "They really aren't."

Another Nobel awaits whoever figures that one out.

**Explore further:**
Astronomers Gravitate Toward Einstein's Telescope

**More information:**
Michael D. Lemonick is a senior writer for the nonprofit journalism organization Climate Central and is a contributor to Time, where he was a senior writer for 21 years. He wrote this for the Los Angeles Times.

## voltaire96

the infamous E=Mc2

his special theory of relativity has no such restrictions on the universe expanding. its simply Energy=Mass.

Einstein knew exactly what he was doing, we are moving from his general theory of relativity to his special theory of relativity, he anticipated this shift in 1905!!

he was the greatest. please no denigrate his memory like that.

## Silverhill

Both theories are still applicable, still relevant; they do not represent any kind of transition of understanding.

SR is not simply E=mc^2. It also shows the (observed) changes in mass, length, and time that a fast object undergoes.

There is no black hole "beneath" the Earth, not even if by "beneath" you mean "at the center". The local spacetime is not being contracted; it simply has the curvature expected from the planet's size and density.

Now, maybe if neutron repulsion were at work.... ;-)

## Callippo

Later it turned out, the Universe is really expanding and his constant became redundant for ever - so Einstein was never wrong about being wrong.

You cannot make Universe steady state (which was original model) and expanding with increasing speed (which is current model) with using of single constant.

## Callippo

## dtyarbrough

## Seeker2

So are we in some airtight bottle? Are there walls out there? Maybe just more spacetime. Which means visible space is expanding into an infinite universe. The visible universe, they say, is flat within 1 or 2%, which means parallel lines go on forever and ever in every direction. This doesn't sound consistent with the raisin bread analogy as I see it.

## PinkElephant

## hard2grep

## Vendicar_Decarian

Meaningless Claptrap. Chronic from people calling themselves Voltaire.

## Vendicar_Decarian

I have noticed that there are a lot of jabbering apes jabbring idiocy in this thread.

## Mr Bill

## Vendicar_Decarian

You don't have a clue to what causes pressure do you?

## Vendicar_Decarian

Integration Constant.

## Vendicar_Decarian

Observation doesn't mesh with your personal ideology. And that is why you will always be a religionist and never a scientist.

## Skepticus

## SR71BlackBird

## Daleg

The real issue is not Einstein right or wrong it is why a term which seemed necessary then redundant, and now necessary again leads by any way of calculation to a 10 to 120 power error in calculated contribution to the curvature of space as opposed to observation. Since the Cosmological term fits naturally into the equations why do physicists' have to so finely tune it by setting it to almost zero to make space flat, that is the real issue?

## Daleg

## Husky

## Callippo

If Einstein used some constant to adjust his theory to steady state model, then we cannot the same constant to fit the same theory to expanding universe. So Einstein wasn't wrong about being wrong - he simply remained wrong, until you believe in model of expanding Universe.

## Callippo

## Callippo

## Callippo

R_{\mu v} - \frac{1}{2} R g_{\mu v} \Lambda g_{\mu v} = \frac{8 \pi G}{c^4} T_{\mu v}

Where \Lambda is the original cosmological term.

The original cosmological term could not meaningfully balance gravitation, because the two forces operate on different principles: one is a constant repulsive force without regard to distance, the other is an apparent force proportional to to r-2. The present use of a cosmological constant makes more sense, because the Universe isn't expected to remain in equilibrium. So IF YOU BELIEVE in expanding Universe, then the Einstein was right about being wrong, but from different reason, than he thought. So he was actually double wrong from perspective of contemporary L-CDM model.

## Callippo

http://www.google...Einstein was wrong about being wrong

One such catchy title simply creates a new virtual reality, which some people will believe for ever. This is insane.

## sherriffwoody

Imagine, We are a bubble, in curved space, but bouncing among an infinite multitude of other bubble universes. Each bump into a bubble is a big bang, the lumpyness we see in background radiation is the result of the collision, its an expanding shock wave, not the extremity of our universe. It also means certain things can be older than the collision. e.g some cosmologists and astrophysicists have claimed certain things in our universe must be older that the current estimate. Somtimes our universe may expand, sometimes contract, it depends on the pressure our universe is surrounded by

## Callippo

## Noumenon

If the cosmological constant is "vacuum energy" density, than the more space there is the more negative pressure, since it would be intrinsic to space itself rather than an additional "substance",... but no one knows for sure.

## Aliensarethere

## kaasinees

Show me evidence of observations that conclude expansion.

## Noumenon

## PinkElephant

Or perhaps you are unfamiliar with the concept of magnitude. You want to change a constant-value positive expansive force from exactly counterbalancing gravitational contraction to creating accelerating expansion? Increase its magnitude.

Yes, it's that elementary, my dear Calippo.

## Seeker2

Well maybe because it really is flat, within experimental error.

... Hubble explained red shift with tired light theory from many good reasons, which are completely ignored by now

Strange. Now light is given a free pass through spacetime. Everything else seems to have to pay the piper.

... whereas now the same constant is interpreted like the force, which accelerates it. Can anybody else spot the paradox here?

Well maybe the value of the constant is different.

## kaasinees

http://en.wikiped...ed_light

## Noumenon

Zwicky wasn't entirely respected because never showed his ideas had to be correct rather than only might be.

## Callippo

Your attitude just unwittingly illustrates the degree of freedom, in which the modern physicists are dealing with predictions of their proclamativelly "mathematically exact" theories.

Who cares, if they're actually predicting opposite effects of different magnitude, until they're backed with equations...? Important is, the publications are out and money are still going.

## Callippo

http://coldfusion...bologna/

It's comparable to the evidence of Higgs boson with 1 MW heatings effects in collider detectors (which are working in picoWattt range during Higgs boson detection). Do you see the difference in standards in application of reliability criterion?

## Seeker2

I should qualify my ideas about a free pass through spacetime - it should be a free pass with no (apparent)scattering.

## Daleg

The question was rhetorical, of course space is flat, the point was to emphasize that the addition of the cosmoligical constant or "Dark Energy" is necesary to make it so. The issue about setting it to almost zero is that scientist's are unhappy with any term derived "naturally" that requires such exacting fine tuning, because it smacks of intervention with the initial parameters to explain it.

## Daleg

ideas about what they might be. He knew there was dark matter way back in the 1930's, but hey it only took the rest of the Astronomers 50 yrs. to take his ideas sesriously, and prove he was right.

## Daleg

## Daleg

## hush1

Isaac wanted this Absolute to be space and time.

Albert&Co. corrected this (to the best of their abilities)and forced space and time to be curved. To no avail. Locally, all was to remain euclidean in the limit.

Only two catches to this Absolute Curvature:

All Euclidean geometries are curved.

Euclidean geometries no longer have physical meaning.

In the beginning, everything was "non"-euclidean. And in the end, everything remains and retains intrinsic curvature.

With only one assumed constraint:

The Continuum exists.

I will leave you to argue about beginnings and endings - don't want to spoil all your fun. :)

Why post this here? It's the perfect place to hid a breakthrough in progress - breakthroughs are declared here daily under the guise of crackpot. lol I lose nothing.

## hush1

Da riemannsche Mannigfaltigkeiten im Allgemeinen in keinen Raum eingebettet sind, wird in diesem Teilgebiet der Differentialgeometrie eine KrÃ¼mmungsgrÃ¶ÃŸe gebraucht, die unabhÃ¤ngig von einem umgebenden Raum ist. Dazu wurde der riemannsche KrÃ¼mmmungstensor eingefÃ¼hrt. Dieser misst, inwieweit die lokale Geometrie der Mannigfaltigkeit von den Gesetzen der euklidischen Geometrie abweicht.

Only one itsy bitsy problem with this:

When you want a curvature that is independent from the space it is to be embedded in, you can not introduce a Riemann curvature tensor that measures the deviation of the local manifold geometry to that of the laws proscribed by Euclidean geometry.

Why?

Because the Euclidean geometry itself has intrinsic curvature.

The Riemann curvature tensor produces gibberish. Of course, that is what I will be accuse of, because for centuries the Laws of Euclid are assumed to be locally valid.

## hush1

## Noumenon

Differential geometry does not require an embedding space to function as the mechanics of non-Euclidean geometry. And what do you mean "Euclidean geometry is curved"?! Also there's no "laws of Euclid",.. not physical laws,.. just flat mathematical geometry. You'll need to explain what you mean.

## Isaacsname

Thankfully expansion prevents all the nuts in the mix from aggregating too.

Take that how you want to :P

## Callippo

Now we can ask, how these tiny fluctuations would affect the spreading of light in seemingly flat space-time? Again, we can use a water surface analogy for qualitative prediction of this dispersive geometry.

http://www.carden...ples.jpg

We can see, just because of dispersion of waves at the tiny density fluctuations, the spreading of ripples is not linear and it exhibits the characteristic curvature of space-time

## Callippo

But it means too, all these artifacts are product of dispersive nature of wave spreading in particle environment forming the vacuum and they've nothing to do with its actual geometry or topology. The existence of red shift and dark energy doesn't mean, the Universe is curved as such.

## Callippo

But at the water surface the way, in which surface ripples are dispersing depends on their initial wavelength and for ripples larger than the density fluctuations the character of their dispersion is reversed. Such long wavelength ripples are increasing their wavelength and the water surface appears expanding instead of collapsing with increasing distance from observer.

http://www.aether...ples.jpg

So, if the dense aether model is correct, we should observe the same wavelength dependence even for space-time expansion in vacuum. If we wouldn't observe it, then the L-CDM model is correct instead.

## hush1

A commentary on a website will not be the place this realization enfolds or takes hold. I know this.

It is like the time when the world was declared round.

Only worst. There is no advantage to making myself a target for the sake of advancing all of science. I will never again state this or I'll wait to see if someone else has the same realization and submit to that person or those persons

my work in support.

Your statement is absolute correct. That was not addressed. Addressed were all the physical models of cosmology and/or GR/SR.

The curvature of euclidean geometry is not zero. That has consequences for all other derivatives derived from the assumption that the curvature of euclidean geometry is zero.

This is too big for me to impress that on the world and too big for you to understand. I expect this. You never read this.

## hush1

If

Then, you know the constant of curvature for the universe.

What is it and what is the unit of measure, besides euclidean metric did you used? Or. What do you arrive at for the euclidean measure of curvature? This must be non zero for your models to have intrinsic curvature.

## hush1

Perfectly understandable. The world is changing fast enough, isn't it? - Without changing the foundations of the last two hundreds years again.

## Noumenon

Guy, you're not making sense. By mathematical DEFINITION, Euclidean geometry is flat. Riemannian geometry is a generalization of Euclidean geometry to incorporate the notion of curvature.

Is this a joke? LOL

## hush1

## hush1

## hush1

The measure of curvature comes from Euclidean geometry. Only 'flat' doesn't exist in Nature. 'Flat' is an axiom of math, not Nature. The curvature for Riemannian Geometry is arbitrary. No geometry will ever describe or model Nature, as long as curvature is derived arbitrarily.

## Noumenon

How does this make Euclidean geometry "itself has intrinsic curvature"?

## Callippo

http://www.techno...v/26333/

But it would be nice to derive the current size of observable Universe from first principles. IMO Heim's theory can derive the smallest and largest curvature of Universe from values of gravity constant and speed of light.

## Noumenon

You're not making sense. You say above that Euclidean geometry has "intrinsic curvature" then now you say "Euclidean geometry is flat". The measure of curvature does not "comes from Euclidean geometry",... it comes from derivitives between tagent spaces via a (levi-civita) connection. It is calculus. That (co)tangent spaces are flat in the limit by definition, does not equate to saying "measure of curvature comes from Euclidean geometry".

## Callippo

## Noumenon

What do you mean is "derived arbitrarily"? The metric (which determines curvature) is derived from the pretense of mass-energy, an observational fact.

## Noumenon

Oct 16, 2011## hush1

What makes Euclidean geometry flat? You say the definition.

"That (co)tangent spaces are flat in the limit by definition"

The curvature is arbitrary.

What does not make the curvature of Riemannian Geometry arbitrary?

What makes the curvature stop at Riemannian Geometry curvature and no other curvature?

The curvature for Riemannian Geometry is arbitrary. No geometry will ever describe or model Nature, as long as curvature is derived arbitrarily.

## Callippo

## hush1

You start with 'flat'. And 'bend' 'flat' to your heart's content. What stops the 'bending' at the curvature called Riemannian Geometry?

## Noumenon

## hush1

All forms or shapes without a hole is a sphere.

This is true for all manifolds with finite or infinite dimensions.

What geometry lies beyond all manifolds with one or infinite dimensions? Name one.

## hush1

## Callippo

So I presume, from sufficiently distant perspective both intrinsic, both extrinsic models of Universe will converge together. The intrinsic model says, the speed of light is constant and Universe is evolving. The extrinsic model says, the speed of light is variable and the Universe is steady-state. But in dense aether model is no apparent reason to support one model over another one, it just predicts the convergence of both models together.

## Callippo

For example, people are divided in matter of creation/evolution by now. But maybe - I repeat maybe - it's possible, the origin of life has evolved outside of Earth, maybe even outside of Milky Way galaxy in some previous generation of it - thus mimicking the creation event in at least limited extent. So it may be possible, from sufficiently distant perspective both these interpretations are indistinguishable each other in random model of Universe. Maybe the proponents of both evolution, both creation still have their bit of truth from their own perspectives.

## Noumenon

Einsteins field equations can either be solved for the stress-energy tensor or for the metric, both of which rely on observational input, not know a-prior. It is a physical theory, not purely mathematics.

## Callippo

## Seeker2

So unscattered photons do lose energy on their path through spacetime. This would put the expansion of the universe and the big bang question back on the burner.

I like your position on Zwicky and I definitely go for plausability.

## Callippo

http://www.srnr.a...logy.pdf

## hush1

Euclidean Geometry is flat. Einsteins 'geometry is a Continuum.

'Flat' is any form or shape, regardless of infinite dis-/contortions

All forms and shapes without a hole is a sphere.

## hush1

Yep. Make that curvature disappear. Anyway you can. Includes magic wand.

"In physics, they represent vacuum solutions to the analogues of Einstein's equations for Riemannian manifolds of any dimension, with vanishing cosmological constant. Ricci-flat manifolds are special cases of Einstein manifolds, where the cosmological constant need not vanish."

## Noumenon

All tensors are NOT matrices. In physics tensors are a physical entity that transcend any particular matrix representation, any basis, which is why Christoffel symbols are not matrices.

Topologically equivalent to a sphere only.

## Noumenon

## hush1

There will be other articles to discussed.

## Noumenon

## Noumenon

Yes, good call,... you wouldn't want anyone to find out you're "really" making sense, better to hide behind a wall of word-spaghetti.

Spacetime curvature as formulated in GR does not imply an absolute space.

## Noumenon

## Grizzled

Didn't you know thar beneath the Earth there are only the three elephants and the giant turtle?

Seriously though, as soon as people start talking about up, down, above or beneath - you can safely ignore everything else they have to say on the subject of relativity.

## thewhitebear

## Isaacsname

Nothing, lots of nothing.

## hush1

Every new era's beginning makes little sense for most. I am describing human reactions to the new. Reactions such as Isaac's reaction is to be expected (see above comments).

Cloaking events with gaps in time is other example. Invisible cloaks were science fiction at best not long ago.

Yes, Nounmenon, you are correct. Einstein physics implies just the opposite. Space is relative, not absolute. Time is relative, not absolute.

Newton can see where his physics falls short. For all the Newtons of the world, a few days is all that is needed to accept new physics and to stop describing words as spaghetti.

Einstein can see where his physics falls short. For all the Einsteins of the world, a few day is all that is needed to accept new physics...and so forth. The drift.

## hush1

I like this very much. The most logical answer to what you quoted. Kudos

## hush1

Oct 16, 2011## hush1

## paintingfrom

## Daleg

You have no valid point, Euclid made Euclidean Geometry Flat, his premise is based on the angles you will measure on a flat surface, which is dictated by the definition "Flat", any Geometrical angle which measures contrary to this indicates surface curvature, by which measurements of angles based on Euclidean geometry will fail. That is the very definition of Curvature any angular measurement which deviates from flat Euclidean Geometry. As for stopping with Reimann, that is because he catalogued all curved spaces.

## merelogic

## hush1

I'm quoting Poincare. His conjecture. Superseding Euclid.

A Catalogue? Of curves? All curves? From Riemann? Where?

lol merelogic

Loses something when translated in English, don't cha think?

## Daleg

## rawa1

## Noumenon

## Flyboypuppy

## rawa1

It's strange coincidence, which is unexplainable with L-CDM cosmology, but it's still easy to explain with dense aether model. In recent observations it seems, the actual size of Universe is really much larger (and as such older), than the L-CDM model is assuming.

http://www.techno...v/26333/

## rawa1

The exception of neutrinos consist of the fact, they're very weak and subtle solitons, so that accidental fluctuations of underwater can occasionally wipe out the effect of surface deformation. Under such a situation, the neutrino propagates like underwater sound wave exclusively, i.e. much higher speed, than the surface ripples. During these rare moments the spreading of neutrino is literally detached from water surface, so it can propagate higher speed. This situation is the more probable, the higher speed the neutrino is - whereas low energy neutrinos would propagate in normal subluminal speed.

## rawa1

This model is slightly complicated with fact, the space-time is not completely flat due the presence of CMBR fluctuations, so that the low energy neutrinos can still propagate with subliminal speed, until their energy is not higher, than the energy of CMBR photons. And the photons can spread with slightly superluminal speed, until their energy (i.e. frequency) is not higher, than the energy/frequency of CMBR photons.

## hush1

You have to free yourself from your classical traditional maths. All Geometry is shape or form.

Poincare's Conjecture:

All shapes and forms without a hole is a sphere.

When you realize what this means for all Geometry, you will find Euclid insufficient, unnecessary, and incomplete.

You can not use the physical to defend your stance or math.

The new paradigm is:

All Geometry is Poincarian, not Euclidean. And when one does this, n-body problems are no longer intractable. Field equations have exact solutions, and protein folding problem is solved.

## Deesky

Brilliant! Why are you keeping this a secret? Stupid scientists - why didn't they think of this before! /facepalm

## hush1

"Completion of the Proof of the Geometrization Conjecture" on 24 September 2008.

So three years might be eternity to some. I regard three years as insufficient for the scientific community to adapt and evolve.

## Deesky

Thurston's geometrization conjecture was first proposed back in 1982. And while it may have remained a conjecture until a proof was found, it would not have stopped other researchers from assuming its correctness and thus pursuing potentially valuable fields of applied research anyway (such as the ones you mention: n-body, field equations, protein folding).

What evidence do you have that any of those fields will be 'solved' on the basis of this mathematical proof? Is it just wishful thinking?

## hush1

My "evidence" is math. Inadmissible for the physical sciences.

For some, math is wishful thinking - until it's application in research proves and solves physical obstacles.

## Deesky

So you don't have any basis for your grand claims. I thought so. Merely pointing to some piece of mathematical esoterica and assertively claiming that it WILL solve various hard problems is simply a matter of faith without supporting evidence.

## hush1

Your mirror - You see yourself and there is nothing to add.

Enlighten us. Tell us the correct way to do research.

## pauldentler

In dark flow galaxies are moving at a rate far in excess of the "cosmological constant", and "colliding galaxies" should never occur according to the original prognostications of the "cosmological constant" back in the 19 There are too many things we observe that contradict the hypotheses of steady state expansion including the laws of thermodynamics of energy conservation which require a "closed system" in which to function in which a lot of so-called cosmologists want a Universe which operates outside these principles.

## Noumenon

As I asked you in this and the other thread, it is up to you to show how this Poincare conjecture proof can be put to use for physics. Your vagary suggest to me you don't know. I have been unable to find anything more concrete than sweepingly vague claims that Pereman's work may have implications for relativity. That's not good enough to be meaningful.

## hush1

Perelman is a tool maker. I am a tool maker. Use the free tools however you like. The tools work. For the nonphysical.

If the nonphysical has no meaning, then you are correct.

## mpc755

Aether is continuously being emitted into the Universal jet.

The pressure gradient associated with the aether emitted into and propagating through the Universal jet is dark energy.

## Seeker2

...what does the universe eat!?

Dark Energy - likely comes from inflation where matter and spacetime are created, spacetime in a very compressed form, the energy of this compression now being what we observe as dark energy. A sort of similar attempt is made by mpc755:

...The pressure gradient associated with the aether emitted into and propagating through the Universal jet is dark energy.

## Seeker2

## hush1

Parody on: "Only in America";

Only on earth. The only life form in the Universe that exists and lives on a curve and manages to construct the only non applicable not-even-wrong expression to describe Nature:

A line. A 'flat' line without curvature. The source and birth of all manifolds.

lol

## hush1

You missed the curve.

The line is fine. Replace it when you are ready.