Measuring the Hubble Constant Better

eldavojohn writes "The Hubble Constant is used for many things in astrophysics: from determining how fast things are moving away from us, to the total volume of the universe, to predicting how our universe will end. The current best value for the Hubble Constant is 74.2 ± 3.6 (km/s)/Mpc according to recent conventional methods and the recently restored Hubble Telescope. Most astronomers agree that that's within 10% of its actual value. Researchers now claim that they might be able to get to 3% using water molecules in galactic disks to act as masers that amplify radio waves, to analyze galaxies seven times as far away as the current measurements. The further away the 'standard candle' is, the more assured they can be that local effects are not skewing the measurements. From one of the researchers: 'We measured a direct, geometric distance to the galaxy, independent of the complications and assumptions inherent in other techniques. The measurement highlights a valuable method that can be used to determine the local expansion rate of the universe, which is essential in our quest to find the nature of dark energy.' Once the Square Kilometer Array is completed, they hope to get even closer to the actual value."

Comments

Hubble constant now a misnomer

[Omnifarious]

From what I know, it's been discovered in the past decade or so to not be a constant. The expansion of the universe is accelerating. This is a minor nitpick, I know. :-)

Re:Hubble constant now a misnomer

[American Expat]

It's just obeying the first rule of computer science: Constants aren't
(second rule: Variables won't)

Re:Hubble constant now a misnomer

[OeLeWaPpErKe]

Doesn't this constant place an additional limit on the size of the universe (or at least the part of the universe we're ever going to see) ?

c / 74.2 km/s * Mpc = 300000 / 74.2 * 3 261 636.26 lightyear (1 Mpc = 3 261 636.26) or about 1.31872075 Ã-- 10^10 lightyear, about 13 billion lightyear.

Because at that distance, the stars would be moving away from us at light speed, so in reality there's an event horizon between us and stars at that distance. Light from stars further away would never reach us, due to it having unlimited redshift.

As you can see, if the hubble constant becomes bigger, the universe shrinks. If it lowers, the universe becomes bigger.

Re:Hubble constant now a misnomer

[cheftw]

And how come it's measured in some stupid space unit? It's a frequency so it wants hertz!

http://www19.wolframalpha.com/input/?i=hubble+constant+in+hertz

It's called SI. Get with the program dudes.

Re:Hubble constant now a misnomer

[selven]

Technically, the only way the Hubble constant can be a constant is if the universe is expanding exponentially.

Re:Hubble constant now a misnomer

[Anonymous Coward]

And how come it's measured in some stupid space unit? It's a frequency so it wants hertz!

The Hubble constant tells you the speed that astronomic objects move away from us (or from any point in the universe, cf. Galilei invariance) depending on how far it already is, hence (km/s)/Mpc. An object at the distance of 1 Mpc moves away at approximately 74 km/s.

Now what exactly does the value in Hz tell you? Nothing.

Re:Hubble constant now a misnomer

[Daniel Dvorkin]

It's measured in "stupid space units" because it's used in astronomy, of course. "Kilometers per second per megaparsec" has a much more intuitive interpretation, when considering the speed at which distant galaxies are moving away from us, than does "cycles per second."

Re:Hubble constant now a misnomer

[Khashishi]

The value in Hz gives you the scaling frequency of the universe. It makes sense to talk about the inverse of this frequency, which is in seconds, which is the time it takes for the universe to grow to e times its former size.

Re:Hubble constant now a misnomer

[Celestial Avatar]

Hubble's constant is a measure of how the expansion velocity (in units of kilometers per second) of the universe changes with an object's distance from us (in units of megaparsecs), yielding units of km/s/Mpc. It is improper to simply cancel the distance units which would leave you with units of frequency (i.e., inverse seconds).

Another example in astronomy is the unit given to monochromatic flux, which typically has units of Joules/meter^2/second/Hertz. Note that the unit has both seconds and Hertz. Now, one may naively simply cancel Hertz and seconds, leaving the unit as Joules/meter^2, but this is wrong. Monochromatic flux measures the energy (in Joules) passing through an area (in square meters) in a given time interval (in seconds) of light of a specific frequency (in Hertz). Seconds and Hertz are measuring different quantities and cannot be cancelled when dealing with monochromatic flux.

Re:Hubble constant now a misnomer

[electrostatic]

Just the opposite. "Hubble Constant" generally refers to Ho, which is the current rate of expansion.

After the Big Bang, mutual gravitation of mass in the Universe slowed the rate such that expansion went at about t^(2/3) -- see http://en.wikipedia.org/wiki/Friedmann_equations for the scale factor (rate of change of expansion) in a matter-dominated universe.

Einstein's General Relativity says that space contains energy -- called dark energy or vacuum energy, which has the effect of causing inflation. After about 10 billion years of expansion, the amount of dark energy became greater than the total amount of mass of normal and dark matter (which does not change). Now it's about 70+% of the total mass. Consequently the rate of expansion has increased to become exponential. IOW, the scale factor is now going as e^t.

In any event, the Hubble "constant" is a measure of how fast the Universe is expanding. This rate has never been constant when considered over a period of, say, a billion years. It is slowly changing. Currently -- and forever more -- the Hubble parameter is increasing due to the exponential rate of creation of new space, ie, dark energy.

Re:Hubble constant now a misnomer

[davester666]

Didn't they already figure out how they screwed up creating the Hubble telescopes main mirror? Or is the mirror warping now?

And didn't they just do the last fix on it just last month?

Re:Hubble constant now a misnomer

[selven]

I was talking about the km/sec/megaparsec value. If the rate of change (speed they're flying away from us, aka derivative) is directly proportional to the current value (the distance, if this was a graph it would be the y coordinate), it's an exponential function.

Re:Hubble constant now a misnomer

[cheftw]

I have no wish to start an internet argument, nor is astrophysics my department, but I would bet you a shiny penny that if you did cancel them nothing bad would happen. Life would go on and all your calculations would be correct. (Assuming you got them right in the first place).

Counterexamples welcome.

Re:Hubble constant now a misnomer

[cheftw]

It tells you everything. Multiply it by a distance - you get a speed. Way more useful than the other one IMHO.

Re:Hubble constant now a misnomer

[Anonymous Coward]

The Hubble *parameter* has never been a constant, even in the ''classical'' models. The Hubble *constant* usually means the rate of expansion as it is measured *now*. What has been discovered in 1998 is that the expansion is accelerating in stead of decelerating as they expected.

Re:Hubble constant now a misnomer

[Betelgeuse]

Is something "bad" going to happen? No. Does it make interpretation of the quantity more confusing? Absolutely.

Re:Hubble constant now a misnomer

[Artifakt]

Some of the inflationary models also suggest the universe is very, very much bigger than the part we could theoretically see, a factor of about 10e30 times or more. (We could theoretically look back close to the total age of the universe, and because of expansion, the total distance would actually be at least a bit more than 2x larger than that roughly 12 Billion years would seem to allow, say 26-30 Billion LY radius.).
        For those models where the total size of the universe is so much bigger than the observable part, theory predicts there could be many zones, each with differing Hubble constants as well as other variant properties. So even if it turns out the local expansion isn't really accelerating, 'The' Hubble constant may still be just one of many.

Re:Hubble constant now a misnomer

[Artifakt]

Think of Gauss's formula: e to the i x pi power +1 = 0.
This usually gets taught as part of second semester calculus or so. It gives some students headaches, because it emphasizes so strongly how raising a number to a power isn't really best understood as self multiplication once we get beyond the integers (It's fairly simple to see e to the 4th as e x e x e x e, but harder to imagine what e to the i or pi power involves). Just doing one of the simplest possible operations to the equation, making it read: e to the i x pi = -1, shouldn't do anything bad, should it? Some students rush to do this, after all, it makes the equation 1 term smaller.

      But the 'point' of the equation, the thing the student needs to understand so he or she sees why knowledge of e lets that student integrate and derive for a whole bunch of functions that the student couldn't deal with at all the prior semester, is that e is that number which is the base of a function that maps sums onto products, and whose rate of change is identical to itself. The actual value of e can be determined by a limit:

Lim (as delta x goes to 0) of (e to the power delta x)-1 / delta x = 1.

What's the derivitive of a constant (such as 1)? Zero! And just doing an operation most of us learned in first grade obscures the relationship and makes it harder for the student to understand.

Re:Hubble constant now a misnomer

[Anonymous Coward]

The expansion of the universe is expanding because the universe is expanding...

The hubble constant is kind of like compound interest - the more money you have the more in interest you get. The "interest" rate itself is a fixed constant value but the money increases over time.

Think of the distance between most gravitationally unbound galaxies as money and the hubble constant is the interest rate (Amount of new space created between galaxies)

There is more and more space so galaxies expand faster and faster but at any point in time the expansion rate given any current distance is goverened by the hubble constant.

Now there are plenty of "theories" out there that play with the hubble constant (interest rate) over time... None of which have ever predicted anything useful :)

Re:Hubble constant now a misnomer

[Anonymous Coward]

Your correct in that the hubble constant implies a limit on the observable universe from each observer (In some sense we are each the "center" of the universe)

We are however able to view distant galaxies receeding at faster than the speed of light (from our perspective!!) due to metric expansion of space itself.

Obviously at some point light from outside our verse pointing twoard our verse will never reach us because at extremely large distances space between expands faster than information can travel.

I don't think its correct that red-shifting causes objects in the observable universe to disappear. The CMB is the most distant thing we can observe and yet we can still detect it at Microwave energies.

Re:Hubble constant now a misnomer

[cheftw]

I think you need haskell to determine e that way :)

But where would you differentiate a constant? Like 2 is a constant, but d/dx(2^x)=(ln2)(2^x)!=0

Re:Hubble constant now a misnomer

[michaelwv]

The expansion rate of the Universe at the present time is called the Hubble constant. Astronomers more generally refer to the Hubble parameter to describe the expansion rate as a function of cosmic time. We have known that the Hubble parameter changes with time for at least 60 years, but, as you note, we've only known that the rate is currently accelerating for the past decade.

Re:Hubble constant now a misnomer

[electrostatic]

You are correct. Currently the scale factor, a(t), goes as e^kt. The Hubble parameter can be defined defined H(t) = (da/dt)/a.

Therefore we take the derivative of e^kt and get k*e^kt. Substituting, H(t) = k * e^kt / e^kt = k.

Thus H(t) is constant in an exponentially expanding universe.

Re:Hubble constant now a misnomer

[Anonymous Coward]

Einstein's General Relativity says that space contains energy -- called dark energy or vacuum energy, which has the effect of causing inflation.

Nearly right. In GR, if free space is energetic, then that energy will have a gravitational effect, i.e., it will slow down the ticking rate of clocks from the perspective of an observer at a large distance, at rest with respect to the slice of free space, and in a region of space that is less energetic (i.e., with a lower vacuum energy).

GR itself says nothing about the vacuum energy, although the cosmological constant was intended to offset it with a negative pressure term that allows for the metric expansion of space in the presence of a nonzero energy of free space, since otherwise because space is large, an energetic vacuum could not accord with observation of large structures (galaxies, galactic clusters) because the clock-tick differences between free space and large structure centres of mass would wreck the observed rotation rates of substructures at varying distances from the centres of mass. Also, a sufficiently large vacuum energy would likely lead to a contracting rather than expanding universe.

The interpretation of the cosmological constant is awkward. For example, in Lambda-CDM, the cosmological constant Lambda is defined in the ratio 8 pi : Lambda = 8 pi rho_vac where rho_vac is the intrinsic energy of free space, and fits into the cosmological constant version of EFE, and serves to offset the vacuum energy. Awkwardness arises in the requirement for the vacuum energy to increase in proportion to the increase in volume of space, and there is no widely accepted candidate for the source of this "dark energy". The Lambda-CDM dark energy must be locally tiny (equivalent to a mass of less than 1e-26 kg/m^3) to accord with large scale structure observation, but that value does not agree with quantum mechanical explanations for things like the Casimir effect which expects vacuum energies more than 100 orders of magnitude larger. Although one can think of this in terms of offsetting a huge postiive rho_vac with an opposite-signed huge cosmological constant, any kind of tiny local variation in vacuum energy density in the early universe would be expected to have dramatic observable effects on the layout of the universe at the largest scales (much larger supervoids than we see so far; much tighter clusterings than we see so far). Tiny variations in vacuum energy in a model with a small rho_vac fits well with what we actually do see, since small inhomogeneities are negligible in a very weak field model. (It also makes it easier to model cosmic inflation in a QFT way as a scalar field of inflatons rolling down a total (global) vacuum potential energy hill, where the rate of metric expansion is inversely related to the speed of the roll of the inflaton field. At the top of the hill the roll is slow, further down the hill the roll is faster, and the implication is that the local vacuum potential energy is lower. This line of thinking falls apart very quickly if the present local vacuum energy is still large. Measuring H0 allows comparisons with plausible Mexican Hat potentials, which may require a rejection of this type of model of inflation (or lend it evidentiary support, depending on findings)).

*Checks the Hubble Constant*

[Alzheimers]

Yep, he's still dead.

Re:*Checks the Hubble Constant*

[Red Flayer]

So is the value 0 or 1?

I'd assume the dead state is 0, and the live state is 1 -- except Hubble was living while he calculated the value, so he may have assigned 0 to the live state, and 1 to the dead state. Or he might have foreseen my current problem and switched the values just to trick me.

Speaking of which (my current problem), it appears my doomsday machine has entered into a positive feedback loop, and I'll only know how to fix it and save the planet if I have the correct value. I'd appreciate an accurate (and swift) answer if you can kindly help me.

Re:*Checks the Hubble Constant*

[Anonymous Coward]

The doomsday machine output should have a value with a lower limit of 0 and an upper limit of 1. Fractional parts should be rounded to the nearest integer.

Re:*Checks the Hubble Constant*

[Red Flayer]

The doomsday machine output should have a value with a lower limit of 0 and an upper limit of 1. Fractional parts should be rounded to the nearest integer.

Poppycock.

The outcome of my doomsday machine is DEATH. And SUFFERING. Also, some Mountain Dew. But mostly DEATH.

Re:*Checks the Hubble Constant*

[Chris Burke]

Yep, he's still dead.

But that measurement is only accurate to within 10%.

Re:*Checks the Hubble Constant*

[Hurricane78]

'E's not dead! 'E's pinin' for the nebulas!

Re:*Checks the Hubble Constant*

[Hurricane78]

Our two outcomes are DEATH. And SUFFERING... And Mountain Dew..
Our three outcomes are...

On another note: What's the difference from Mountain Dew and DEATH?

Volume of universe?

[ubergeek65536]

How can something of infinite size have a volume?

Re:Volume of universe?

[Anonymous Coward]

I think you just answered yourself

Re:Volume of universe?

[Yokaze]

AFAIK, the universe is not infinite in size, it is just infinite. The very same way a circle is infinite, but has a length, or a ball or torus a surface.

Re:Volume of universe?

[Anonymous Coward]

Wait, infinite volume!?!? ... and here my amp only goes up to 11!

Re:Volume of universe?

[harryandthehenderson]

Whoever said the universe had an infinite size?

Re:Volume of universe?

[Anonymous Coward]

If you've accepted that universe started in Big Bang and expanded ever since, how difficult it is to accept it expanded to a some finite point?

Re:Volume of universe?

[Anonymous Coward]

How can something of infinite size have a volume?

The universe is finite.

Re:Volume of universe?

[JohnFluxx]

When people talk about whether the universe is infinite or not, they are referring to the whole thing.

When people talk about the volume, they are referring to the observable universe. The observable universe is about 93 light years across

Re:Volume of universe?

[rm999]

The size of the Universe is entirely an unknown. As such, scientists don't talk about it much.

Re:Volume of universe?

[east coast]

I think you forgot a few digits... it's about 93 billion light years across.

Re:Volume of universe?

[JustSee12]

What are you talking about? The Milky Way alone has a diameter of around 100,000 light years.

Re:Volume of universe?

[Khashishi]

That makes no sense. Thank you for playing. Maybe you mean a circle has an infinite number of points?

Re:Volume of universe?

[Celestial Avatar]

The observable universe is about 93 light years across

So you're one of those reeeally young earth creationists...

Re:Volume of universe?

[Khashishi]

There are some WMAP data in which the low quadrupole moment of the CMB patterns suggests that the universe might, in fact, be finite. But it's REALLY iffy in my opinion, and other than that, there's no evidence (AFAIK) for a finite universe, despite ubiquitous claim.

Re:Volume of universe?

[djp928]

It isn't infinite in size. The size is approaching infinity, though. The universe is finite, but unbounded--meaning it is finite in volume at any given time, but is constantly increasing in size as space expands.

We may never know exactly "how big" the universe really is, since we are effectively cut off from whatever is beyond the edge of the observable universe. Anything that might be beyond that is expanding "away" from us faster than light--so we can never see it from here, and can likely never go there (barring discovery of true FTL travel).

Re:Volume of universe?

[JohnFluxx]

Good grief, I'm off by a factor of a billion and people complain. So picky :P

Re:Volume of universe?

[JustinOpinion]

We have to be more careful with what we mean by 'size' and 'volume' and such.

The observable universe is the region of space we can see. The universe has a finite age, so there is a finite distance over which we can see. Any further than that, and light literally hasn't had enough time to reach us. So there is indeed a boundary beyond which we cannot observe. This boundary recedes as time goes on. The universe is ~13.5 billion years old, but because the universe was expanding during all that time, the observable universe is bigger than just 13.5 billion light-years (see comoving distance)... in fact it is 46.5 billion light-years in radius.

Now there is every indication that the universe extends beyond the cosmological horizon. So as the universe ages, we see more and more of the full universe, which is much larger than our observation volume. So how big is the universe as a whole? Our best understanding right now is based on the curvature of spacetime. If spacetime at large scales is curved, then the universe can loop back upon itself and thus the universe is finite. If spacetime is perfectly flat on cosmological scales, then in fact the universe as a whole is infinite in size.

Our best measurements indicate the universe is flat, within error. Our best theories of the origin of the universe, coupled with available data, generically predict that the universe is infinite. So our current best answer is that the universe is infinite in size/volume. A strange result, perhaps, but that's our best understanding of the current data. Now there are indeed errors on our measurements, so our universe could be smaller. But the curvature is so small that it implies our universe contains at least 1000 Hubble volumes (the Hubble volume is the surrounding space beyond which nothing is accessible since matter is receding faster than light). Others have analyzed the night-sky looking for 'repeat patterns' that would be expected for smaller closed universes, and no such patterns have been found.

So the observable universe is finite (but ever-expanding), and the full universe is considerably larger (infinite according to our current best data and theories).

Re:Volume of universe?

[vlm]

Maybe you mean a circle has an infinite number of points?

Getting closer ... infinite number of tangents at a constant radius from one central point.

Infinite number of points is just any ole line or squiggle.

Re:Volume of universe?

[dmartin]

The size of the Universe is entirely an unknown. As such, scientists don't talk about it much.

Not entirely unknown. We have some pretty good lower bounds on what it can be =).

Re:Volume of universe?

[Jarjarthejedi]

Who modded "a circle is infinite" as insightful? A circle with a finite radius has a finite area, only a circle with infinite radius has infinite area. As the other responses to this say a circle does have some qualities which are infinite, but that doesn't make it infinite (anymore than 1 is infinite because it belongs to the natural numbers which are infinite is a good argument).

Re:Volume of universe?

[ubergeek65536]

Who says the universe has a finite age? The observable universe might have an age if defined in such a way as creation by some large scale event (aka big bang) What we know of the universe is just one "big bang event" out of a possible infinite number of others over an infinite amount of time. I think the problems begin when astrophysicists make the assumption that universe was created in the first place.

Re:Volume of universe?

[david_thornley]

Finite means limited; infinite means unlimited.

Now, take a circle. Put a pencil tip on one point and start moving it along the circumference (clockwise or counterclockwise, it doesn't matter). Now, get back to me when you've reached the end and can't go any further. You can continue infinitely far along a curve of finite length.

The ideas I've seen about an infinite but not infinitely-sized Universe tend to be more complicated, but it's the same general principle.

Re:Volume of universe?

[Betelgeuse]

I know what you're saying, but I think you're just confusing it.

The standard way to say this is that the universe is "finite but unbounded," in the same way that the [i]surface[/i] of a sphere is.

Re:Volume of universe?

[Anonymous Coward]

>It isn't infinite in size. The size is approaching infinity, though.

Umm, that's an odd thing to say. Do you mean the size is simply getting larger? "My dog's age is approaching infinity, although it's likely to cease in a few years..."

Or do you mean that it's nearly AT infinity? If so - and if your initial (unproven) assertion is correct - then I'm afraid it's a long long way off infinite size. When every cubic nanometer of the current finite universe is represented, once for every nanosecond of its life, by a volume the current size of the universe, then we will only just have started counting! Infinity is big.

Re:Volume of universe?

[djp928]

I mean it in the same sense as when you're talking about limits in calculus. The size of the universe is tending towards infinity--meaning it is growing without limits.

FYI: A maser is...

[Anonymous Coward]

A microwave aser.

How big?

[T Murphy]

Once the Square Kilometer Array is completed

The name sounds impressive, but how big will it be?

Re:How big?

[JustOK]

about 298997.51157527 square fathoms. HTH.

Re:How big?

[Zerth]

Around pi * 318,309.886 m^2

Re:How big?

[meringuoid]

The name sounds impressive, but how big will it be?

One square kilometre to begin with, although the rate at which it will be expanding is yet to be measured to sufficient accuracy.

Award for finding the Hubble Constant

[Anonymous Coward]

Jeremy Mould talks about it here

Great Experimental Idea

[Colonel Korn]

1 - Distance measurements are currently kludged together very carefully using bridging. We use one measurement, for instance parallax based on the Earth's movement over 6 months, to show us the distance to a star that has some particular properties and which our models say should always be a certain luminosity. The parallax measurement has error bars.

2- Then we find a much more distant star of that same type that is near a particular type of supernova, and measure its brightness, comparing that to the brightness of our first star to give the distance to the distant star, and thus the supernova as well. That has bigger error bars.

3- Then we look for that type of supernova in very very distant galaxies. Supernovae are brighter than the rest of their galaxy put together while they're burning hot, so we can see them at tremendous distances. We use the measured brightness of that supernova to determine the distance to its galaxy.

4- Then we pair the knowledge of its distance with its velocity with respect to us, which we can determine through redshifting of something with a familiar spectrum. More error bars. That becomes a single point for the determination of the Hubble Constant (and yes, the "constant" is changing).

With only a cursory glance at TFA, it looks to me like this is a way to skip to step 3 or 4, thereby avoiding the need to bridge these length-scales using several techniques.

Re:Great Experimental Idea

[JohnFluxx]

More details here: http://en.wikipedia.org/wiki/Cosmic_distance_ladder

Re:Great Experimental Idea

[anarchyboy]

Yes it looks like they are measuring the distance by paralax using the fact that galaxies are in fact quite wide really. From the article it looks like this has been done before for galaxies close by which is not very usefull for measuing hubbles constant but that they have found way of amplifying the signal from distant galaxies. What the article doesn't say is how they measure both the linear and angular size of the gallaxy which is required to gauge the distance it just says that they did. If so then this is indeed very good news for narrowing down hubbles so called constant.

As a side note using standard candles is as you said very hard and requires bridging as you put it, one method used is I believe to assume that distant galaxies have a maximum size / brightness which puts a bound on the distance to them. The measurement of velocity is actually very acurate and easy and while it may contribute to the error bars of the estimate in hubbles constant I think the contribution would be tiny compared to the problems in measuring distance.

Re:Great Experimental Idea

[Betelgeuse]

The trouble is that these galaxies aren't that far away (despite the article summary says). They're quite a bit further away than the previous measurements of water masers, but you still need to use Type Ia supernovae to actually get to the distances where this discussion gets interesting. The cool thing about the water masers is that they might allow us to get out a bit further without using another "rung" on the distance ladder, but there is no way that they are going to replace the (much, much more distant) Type Ia supernovae.

Um, no. Hubble's assistant says its not a constant

[UnknownSoldier]

Halton C. Arp, a professional astronomer was Edwin Hubble's assistant, says otherwise ...

http://www.electric-cosmos.org/arp.htm

Good enough?

[dandart]

Presumably "Erm, around 100" isn't good enough then?

Re:Good Enough?

[John Hasler]

> When I was doing university physics with a slide rule, three significant figures ( 74.2
> ± 3.6 (km/s)/Mpc) was good enough for anything.

When I was doing university chemistry with a book of log tables four significant figures was barely good enough for my homework.

Re:Good Enough?

[Prof.Phreak]

Indeed. This constant may not be a constant. It may not be the same everywhere in the universe. So by observing things very far away (distance and time), we may actually end up with a less accurate number for a `local' variable.

Good Enough?

[Kozar_The_Malignant]

When I was doing university physics with a slide rule, three significant figures ( 74.2 ± 3.6 (km/s)/Mpc) was good enough for anything. Is our next probe going to miss M31? Oh yeah, get off my lawn too. :-)

Electric Universe?

[Chris Daniel]

Maybe you should present a more credible source, if you wish to be taken seriously.

Re:Electric Universe?

[UnknownSoldier]

Edwin Hubble's assistant isn't credible enough?!

lol !

--

William A. Tiller, Materials Sciences Department, Stanford University wrote: "The present scientific establishment has grown somewhat fossilized by its current world picture and is locked into a view of reality that has outlived its usefulness. It has begun to limit mankind's growth and has so increased its sense of specialization, separateness, materiality, and mechanical computer-like functioning that it is in real danger of self-extermination."

Re:Electric Universe?

[Anonymous Coward]

Just a hint, science is not about who you are, it is (at least stated simplistically) about what you can say and defend with evidence. Asserting that someone is credible because they were Edwin Hubble's assistant is a logical fallacy known as an appeal to authority. The only credibility that should ever be recognized in science is that which comes from theory, built from testable hypotheses, and supported by all available evidence. Anything else is, quite frankly, madness.

Re:Electric Universe?

[Chris Daniel]

The website is what I was questioning, really, although another reply hits on the fact that simply being an assistant to Hubble does not necessarily make a person credible. electric-cosmos.org is a proponent of the "electric universe" "theory" -- which has been thoroughly rejected over and over, but remains a favourite of the conspiracy theorist type.

Re:Electric Universe?

[UnknownSoldier]

> electric-cosmos.org is a proponent of the "electric universe" "theory" -- which has been thoroughly rejected over and over

NASA begs to differ...

The TSS-1R electrodynamic tether experiment: Scientific and technological results

N. H. Stonea, W. J. Raittb and K. H. Wright, Jr. c
a Space Sciences Laboratory, NASA Marshall Space Flight Center, Huntsville, AL 35812, USA
b Center for Atmospheric and Space Science, Utah State University, Logan, UT 84322, USA
c Center for Space Plasma and Aeronomic Research, University of Alabama in Huntsville, AL 35899, USA

Available online 25 July 2003.

Abstract

The Tethered Satellite System program was designed to provide the opportunity to explore certain space plasma-electrodynamic processes (associated with high-voltage bodies and electrical currents in space) and the orbital mechanics of a gravity-gradient stabilized system of two satellites linked by a long conducting tether. A unique data set was obtained during the TSS-1R mission in which the tether electromotive force and current reached values in excess of 3500 volts and 1 amp, respectively. The insight this has allowed into the current collection process and the physics of high-voltage plasma sheaths is significant. Previous theoretical models of current collection were electrostatic--assuming that the orbital motion of the system, which is highly subsonic with respect to electron thermal motion, was unimportant. This may still be acceptable for the case of relatively slow-moving sounding rockets. However, the TSS-1R results show that motion relative to the plasma does affect current collection and must be accounted for in orbiting systems.

But I guess its easier to believe in scientific dogma, then keep an open mind.

Re:Electric Universe?

[Chris Daniel]

I am disappointed that this was the best you could come up with to support your theory. The existence of cosmic plasmas such as those encountered by the TSS-1R mission is quite widely accepted. Proving that they have the effects claimed by the theory you apparently advocate is quite another matter.

I read the first chapter of the book on electric-cosmos.org, and it mostly seems to be jeering at the complexity and unintuitive nature of current theories, while also heavily emphasizing the "unprovability" of any type of astrophysical theory. How convenient. Perhaps it's a bit tough on the underdog supporters, but when it comes to scientific inquiry, the burden of proof is very much upon the challenging theory. So far, the "electric universe" crowd has produced absolutely nothing compelling, other than cries of "help help, I'm being repressed!"

It's easier for me to believe the majority of scientists ("scientific dogma" if you prefer) than an ostracized minority. There is a large difference between keeping an open mind and pouring my uneducated (I'm not an astrophysicist) efforts into supporting a currently unacceptable theory.

Re:Electric Universe?

[UnknownSoldier]

Maybe you can explain why these PhD's are so gullible for "buying" into a "currently unacceptable theory":

http://members.cox.net/dascott3/Endorsements.htm

"I really love this book. It is causing me to rethink a great deal of my own work. I am convinced that The Electric Sky deserves the widest possible readership.... I felt genuine excitement while reading and felt I was delving into a delicious feast of new ideas."
- Gerrit L. Verschuur, PhD, University of Manchester. A well-known radio astronomer and writer, presently at the Physics Department, University of Memphis. He is the author of "Interstellar matters : essays on curiosity and astronomical discovery", and "The invisible universe - The Story of Radio Astronomy" as well as many other books and scientific papers.

"You don't have to be an astronomer to enjoy this book. It's an exciting story about how a small group of physicists, engineers and other scientists have challenged the 'establishment' - the 'big science' astronomers who are reluctant to listen to anyone outside their own elite circle."
- Lewis E. Franks, PhD, Stanford University, Fellow of the IEEE (1977), Professor Emeritus and Head of the Department of Electrical & Computer Engineering, University of Massachusetts (Retired).

"Gravity was the focus of 20th century astronomy. For the 21st century, it will be electromagnetism and plasmas in addition. This forthcoming scientific revolution is presaged by the rapid pace of discoveries about our own star, the Sun, and its total plasma environment, and discoveries about the nature of the interstellar medium."
- Timothy E. Eastman, PhD, Head of Raytheon's space physics and astrophysics groups. He is well known for his work on magnetospheric boundary layers and the initial discovery of the Low Latitude Boundary Layer.

"It is gratifying to see the work of my mentor, Nobel Laureate Hannes Alfvén enumerated with such clarity. I am also pleased to see that Dr. Scott has given general readers such a lucid and understandable summary of my own work."
- Anthony L. Peratt, PhD, USC, Fellow of the IEEE (1999), former scientific advisor to the U.S. Department of Energy and member of the Associate Laboratory Directorate of the Los Alamos National Laboratory. He is the author of Physics of the Plasma Universe and numerous published papers.

--

I find a hard time placing faith in any pseudo-religious Science that can't even understand the importance of consciousness by simply ignoring it from their equations.

no, that's not right

[Khashishi]

Universe expansion will create causal separation in the future, but not the past. It doesn't limit how far away you can see something, because you are looking at something in the past, but it does prevent you from going there. Because looking backward in time, the universe is shrinking, and you can see more and more of the universe going back. Looking forward in time, everything is getting more separated, and, for far regions of space, the rate of separation is higher than light can catch up to.

In the scenario of big rip, the acceleration of the expansion continues to increase until the future light cone of every particle is separated from the future light cone of every other particle. The past light cones still intersect.

Re:no, that's not right

[BizzyM]

Universe expansion will create causal separation in the future, but not the past. It doesn't limit how far away you can see something, because you are looking at something in the past, but it does prevent you from going there. Because looking backward in time, the universe is shrinking, and you can see more and more of the universe going back. Looking forward in time, everything is getting more separated, and, for far regions of space, the rate of separation is higher than light can catch up to.

You just blew my mind

Re:no, that's not right

[naam00]

ing back. Looking forward in time, everything is getting more separated, and, for far regions of space, the rate of separation is higher than light can catch up to.

This can only be if there are (massive) regions of space moving faster than light, relative to us.

That an entire galaxy would get accelerated to even a small percentage of light speed is hard enough to believe, but even something like 50% light speed cannot be the speed of a galaxy. Just think of the energy required to accelerate it. FTL is supposed to be impossible, and no respectable scientist can seriously believe that there are so many galaxies moving faster than light, right ?

It's somewhat more subtle than that. The galaxy isn't 'racing through space', space itself is expanding -- between us and the galaxy mostly, since galaxies tends to stick together due to gravitation.

This can be, over long distances, percieved to happen at a FTL rate, though nothing is actually moving at that rate. And relatively speaking, that FTL galaxy is unmeasurable, since you will never see it racing away from you.

10% Might have mattered in the Princess Bride

[Anonymous Coward]

Miracle Max: He probably owes you money huh? I'll ask him.
Inigo Montoya: He's dead. He can't talk.
Miracle Max: Whoo-hoo-hoo, look who knows so much. It just so happens that your friend here is only MOSTLY dead. There's a big difference between mostly dead and all dead. Mostly dead is slightly alive. With all dead, well, with all dead there's usually only one thing you can do.
Inigo Montoya: What's that?
Miracle Max: Go through his clothes and look for loose change.

Bad Labrador

[Bad Labrador]

I've been following Alexander F Mayers work on Minkowski's (Einsteins Maths Teacher) space time mathematics which Einstein, who didn't understand them, called "superfluous erudition'. Mayer derives a model for the universe that does not require the universe to be expanding, let alone accelerating expansion, does not require "Dark matter" nor "Dark energy", that makes a damn sight more cosmological sense than the "Big Bang" and fits the current observations, much, much better, with no free variables like "quintessence". He makes a prediction for the LRO mission as well. http://www.jaypritzker.org/index.html

Re:Bad Labrador

[anarchyboy]

Well since Minkowski latter came to be a major contributor to the development of the theory of relativity he clearly decided that they weren't worth the effort either. Any model the does not require the universe to be expanding must really take some work to avoid the fact that it clearly is. The fact the dark matter has nothing to do with the universe's expansion well that is to say the evidence for dark matter does not rely on it. Proposing that dark matter does not exist would require rethinking not just relativity but newtons gravitational laws. Also what makes more sense than the big bang? I assume since it makes more sense you could explain it for me?

Re:Bad Labrador

[Bad Labrador]

The only evidence for expansion is that the further away a galaxy is from us, the more red shifted it is. Mayer/Minkowskis equations show that the red shift may be an artifact of curved space time and not a radial recessionary velocity at all. His equations appear to fit the observed data much better and explain such things as the Pioneer anomaly much better. If Mayer is correct, the Hubble constant measurements are merely measuring the change of timelines due to the curvature of spacetime. Needless to say, Mayer is not a popular man.

Re:Bad Labrador

[anarchyboy]

Why not? If he's theory is right surely that would be a good thing? interestingly I read the book you linked to and found it quite hard going, there was little explanation of the ideas presented and seemed to have many descriptive quotes from people like minkowski that were then interpruted, woryingly these 'sound bites' were offered as support of the theory presented.

The multi-dimensional description of time was woefully under explained, probably due to a lack of a concise mathematical description but was instead given a more general description. As a physicist I have a precise understanding of what the space time of general relativity is mathematicaly the physical interperation can be tricky at times and the mathematics hard but it is very well defined and unfortunatly the link you gave did not furnish me with the similar well defined mathematical description of the Mayer's theory.

I would be interested to see a derivation of some known results from GR or newtonian gravity and from cosmology, reproduced in Mayer's frame work as this would provide a good starting point from which to understand the theory. Just in case you are interested I would like to see how the theory reproduces orbital trajectories (ie keplers laws), The equivalent description of the CMB would also be usefull. I may just me being lazy but as you've probably guessed I'm not overly impressed so far.

What really ticked the 'crackpot' box for me though was the single publication, proclaimed as a revolution of great importance. I would like to include a quote but it appears i can't copy and paste it so just read the last paragraph on page 136. Such a statement really has no place in a scientific document and is really indicative of the entire document

Within 10%???

[Anonymous Coward]

I just don't understand this.

FTA:
1) The current best value for the Hubble Constant is 74.2 ± 3.6 (km/s)/Mpc
2) Most astronomers agree that that's within 10% of its actual value

But shouldn't everyone, even astronomers, agree that value is within 5% of 74.2?
If the actual value is, say 80, then why say ± 3.6?

cave man measure hubble constant

[Anonymous Coward]

cave man measure it good

So their measurement of the Hubble constant is 69

[boot_img]

According to the article "the astronomers determined that the galaxy UGC 3789 is 160 million light-years from Earth". This translates to 49 Mpc. According to NED, the velocity (in the Cosmic Microwave Background frame) is 3385 km/s.

Therefore this measurement of the Hubble parameter is then 3385/49 = 69 km/s/Mpc.

(Unfortunately the article does not quote an uncertainty on the 49 Mpc measurement. Because of peculiar velocities, I would estimate that there is at least a 300 km/s uncertainty on the 3385 km/s velocity. )

Anonymous Coward

[Anonymous Coward]

The actual value is 42 nmi/sec/MPC. It would be in nautical miles because the Earth was designed to calculate the answer.

Re:So their measurement of the Hubble constant is

[Betelgeuse]

It's also possible that this galaxy is not totally in the Hubble Flow. In other words, it might be pulled around by other nearby galaxies/galaxy clusters. All galaxies are affected by this to some extent, but with nearby galaxies (like this one), these gravitationally-caused velocities can be significant compared to the Hubble expansion-caused velocities.

10%? I should hope so

[jandersen]

The current best value for the Hubble Constant is 74.2 ± 3.6 (km/s)/Mpc according to recent conventional methods and the recently restored Hubble Telescope. Most astronomers agree that that's within 10% of its actual value.

10% of 74 is 7.4, corresponding to ± 3.7; meaning that in the very worst case, where the true value is at one end of the interval, we can only get about 10% away. What the astronomers agree on is that the estimate of the uncertainty on the measurements is something like ± 3.6. This is not as trivial a matter as it would seem - it can be quite complex to calculate and is a source of many of the more embarrasing errors in science.

ahh thats not exactly right

[Anonymous Coward]

This thread is now about,
Alexander F. Mayer.

The Perimeter Institute recently gave a lecture...

[NoseyNick]

The Perimeter Institute recently gave a lecture on this, by Brian Schmidt, Australian National University - "The Universe From Beginning to End". I understand they will EVENTUALLY make these lectures available on their website, after they've made a bit of money by showing them on Discovery etc: https://www.perimeterinstitute.ca/en/Outreach/Public_Lectures/Public_Lectures/