Energy = mass * (speed of light) squared This equation tells us how much energy we get from reactions that destroy mass, Now, if you want light in the past to travel, say, 6 billion (current) light years in the space of 6000 years, you need to speed it up one million times. In other words, you increase the amount of energy released by nuclear reactions by one trillion.
nice try;-p, but there's a flavor flaw. E=mc^2 is no fundamental law, but is derivable if, and depends critically on the assumption (observation/whatever) that, c is constant. if c is variable, E!=mc^2.
Path of a photon from stellar centre to surface
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Star In A Jar
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· Score: 1
The radiative energy transport *can* be described by a random walk process. Photons are repeatedly absorbed and re-emitted in random directions. Consider random walk in plane:
If theta_i is the re-emitting angle at step i,
after N steps the coordinates of a photon are:
x = sum_over_N{ d cos(theta_i) }
y = sum_over_N{ d cos(theta_i) }
since he directions are randomly distributed and independent:
r = sqrt(x^2 + y^2) = sqrt(d^2 * [(sum...)^2 + (sum_y...)^2]
-> r = d*sqrt(N)
photon mean free path: d = 1/(kappa * density) = 10^-4 m.
r ~ 10^9 m
number of steps: N = (r/d)^2 = 10^26
total path travelled: s = Nd = 10^22
total time: t = s / c = 10^6 year.
although my feeling is that this actually should be a little bit higher.
conclusion: 10^7 years is just fine.
Mundie is right... about Edison
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Mundie Responds
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· Score: 1
Mundie teaches us why leading inventors as... Thomas Edison succeeded... insight... unique... blabla.
Let me tell you all a story I know about Thomas Edison and Nikola Tesla you might find interesting. Both were amazing inventors and it can be argued that we owe to them the way we use electricity today. To them?
In 1882 Thomas Alva Edison had been the manufacturer up until that point in history of the system that carried the current to the households of America: direct current.
Direct current was not practical for traveling long distances to houses, and required transformers to boost the signal several times along the path from the generating plant to a person's house or to a building because of
the resistance of the direct signal through the copper wires they used. This required costly and bulky equipment to have to be installed along the path to one's house, and caused electricity to be expensive and therefore rare.
Edison was the leader in the production and maintenance of the equipment that his transmission system required; he designed and was responsible for the building of the system.
Tesla offered the idea of a rotating magnetic to produce AC (altenative current). This meant that the voltage could be changed without serious loss of energy, using transformators, which are
not costly, and quite small.
So really, Tesla's method was much more efficient. And Edison knew it. But... Edison was earning nice sums from his direct current power plants, which he had a few patents for (really a monopol), and he didn't want Tesla to fiddle with his money.
So... at West Orange, New Jersey, Edison and his men began paying schoolboys to kidnap small animals off the streets. Edison used them in live demonstrations about the dangers of AC. He would have the small animal tied to a large metal slab, and electrocuted in deliberately crude experiments. There were posters up all around the
city that said, "Warning!" at the top and in smaller print went on to warn residents about being "Westinghoused," as electrocution was called by Edison's men.
So really, Edison was not a very nice person.
Tesla was humilated by him, and because of him, Tesla's genious was not recognized by the public. In contrast to Edison he died as a poor man.
Today, thanks to Tesla, we use AC, and it saves the electrical companies milliards of dollars every year.
Mundie teaches us that "the creativity and inventiveness needed to deliver their products was comparable to that needed for the underlying theory or discovery that made their business possible in the first place."
Arguably he is actually talking about how to best electrocute furry animals...
This is not 'just' combining telescope light. This is an interferometer. It enables the system to measure the difference in arrival time of a (plane) wave front, from a distant object. This translates into a measurement of position on the sky.
This is general practice in the radio regime, but it is damn hard in the optical. Not only because of the seeing, the distortion introduced by the atmosphere, but also because the phase information in lightwaves at visible wavelengts generally tends to get destroyed when you tamper with it. In an radio-interferometer one tampers a lot with the signal before combining.
The only solution is to build optics of so-called 'interferometric quality' which means that contact surfaces have to be smooth on the scale of a fraction of the wavelenght (!).
As usual, most ppl claiming the economical viabily of space mining just multiply the rough guess of the total abundance with the current market price. Geez.
Hello, extraction costs? Hello distance? Hello concentration? Yeah right, 'making rocket fuel from icy asteroids' in orbit at 3 AU (a couple of years of travel time). Lets factor in how much fuel you loose just transporting it about;-p
This is of course a bit too subtle for a PR. So you are probably right in accusing us of presenting one aspect of this work in an overly dramatic fashion, and perhaps all of this is not sufficiently exciting for/.
I understand. Thanx for taking the time to explain this and that. This type of stuff should have been modded +plenty informative in the ideal/.
For now i'll spare my breath fo yet another round of replies to anyone who will post that this is yet another proof that there are infinite universes/big bangs/klingons.
I shall ignore the rant - send me email to my IfA address if you want to know what I think of this kind of comment
I assume you understand what initiated my response. If you have been following slashdot lately and take interest in the way astronomy is reported, you should get annoyed by the total lack of depth. This message just topped me over.
Finding MASSIVE clusters at z>0.3 is a rather enormous deal though. Observationally, that is. I admire the Virgo Consortiums pretty pictures as much as the next guy but in the end all theories (or numerical simulations as it were) have to be tested against reality. And that's where the problem lies.
The only distant clusters out to z = 0.4 I am aware of are all fairly heavy. My feeling is that this is because they are X-ray selected. I agree that that Virgo's prediction stand untested, but thats exactly what they are asking (begging) observers. Their predictions are so detailed that it must be possible in the near future to refute or confirm certain aspects. However it remains a problem that they are living in physical quantities, they appearantly have a hard time converting this to observational tests.
The clusters at z=1.2 and beyond that you mention are all very interesting but firstly, there's about 3 or so of them at the moment that have been confirmed in X-ray observations. Not exactly the kind of sample one would want to draw representative conclusions from. Secondly, these very distant clusters are PUNY. They are easily a factor of ten less X-ray luminous than the average MACS cluster. Hence they provide very little leverage for cosmological studies.
I did not intend to suggest that these clusters (altho very interesting) would be represtative. But they are all caught in puberty, which in itself is very interesting. Even a few very hi-z clusters could tell more about how they form than many 'nearby' clusters. I'm not sure I agree that they are puny. They are not X-ray luminous, but converting this to mass in a cluster that is not in equilibrium is tricky.
Ideally we would want MASSIVE clusters at z~1 or beyond but so far only one has been found. MACS provides the best sample we can come up with given the existing data: the most massive clusters at (on your scale) intermediate redshifts.
I am not disputing the MACS survey, surely the science harvest from this project will be impressive. However to again explain the background of my rant: I was getting sick and tired of the way/. handled science reports. I was not attacking the original authors.
If you want to take your cosmology from SN and CMB observations, fine by me. The constraints from clusters run pretty much orthogonal to those from the other techniques and since we're trying to constrain three cosmological parameters I'd say it's very useful to have the clusters too. You can drop any of the three and still get a reasonable idea of what values are most consistent with the observations. But that's not the idea. We want independent measurements from completely different realms to make sure we're getting the right answer.
I am completely aware of the fact that different measurements contrain parameter space in different ways. Ideally each observation-type would have sufficient resolution to provide overal agreement and smaller scale disagreements, and hopefully provide clues about the details of the theoretical predictions or more importantly observational biases. I did not suggest that one should prefer one observation over the other (altho i think that CMB has the best case sofar concerning cosmological parameters), rather to attack the suggestion in the article that this result challenges our view. I was under the impression that this study provided agreement.
Please note that my critique was on the reporters, and the lassez-faire science culture in this tech-ezine.
I find it difficult to consider this a shortcoming of our work. But of course you are free to find this boring...
Shortcoming? I never said it would be. Boring? hardly. I'd wish there were more posts like this. Usually i'm replying to star trek zealots.
If something is moving away from us at nearly the speed of light (say.9c), then the light from that object still moves towards us at c, rather than.1c as you might expect.
...unless it is space itself that expands faster than c. '> c expansion' occured in the inflationary period in the beginning of the universe. Observational 'prove' is the homogeneity of causally disconnected areas in the cosmic microwave background and the overal homogeneity of the observed universe. Only an inflationary 'faster than light' expansion explains this feature in a natural way.
It's funny how little cosmologists confidence in already knowing everything (like age & size of universe) was shaken by the fact that their most fundamental prediction of the behaviour of the universe was completely wrong. (The fact that distance galaxies are accelerating away from us as opposed to decelarating)
Actually, supernovae results indicate that the universe switched to acceleration only in recent epochs z=1. De/accelaration is notoriously hard to measure at some distance and no cosmologist would have claimed now or in the past that testing universe models is a precision job. De/Accelaration in itself not a fundamental prediction, it is a measurement then to be used to justify different models. And there are a lot of tricky stuff involved with supernova measurements. Oh, and last but not least. SNe do not provide any clues at really high redshifts z>2.
The universe is the largest gravitationally bound structure in the universe...
Recent distant supernova measurements indicate that the expansion of the universe is accelerating in recent epochs: thus the universe is not gravitationally bound.
but it is feasible that as these distant structures are studied in more detail gravitational effects which indicate some other very large masses outside the bounds of what we can detect as the edge of our universe are discovered.
Interesting idea but some major problems. Outside the bounds of our observable Universe, would mean way back in time when the universe was so hot that ionized gas made it opague (because we look back in time). I cannot mean spatially 'outside',whatever that means in curved 4d Riemann space. If it did, our universe model would be incorrect (which is conceivable but not observed) but remember that both gravitational lensing and our cosmology are derived from the same set of equations: general relativity. Using one to disprove/change the other is impossible.
Furthermore lensing signal is only detectable against background sources in specific configurations, because they are the ones that are distorted. If you go to really high-z you're are rapidly running out of sources, apart from the fact that they are incredibly faint and small. (ie better test this in the nearby universe: since the responsible mass is 'outside' our universe there is no need to go distant). Besides this, there's an argument against large mass concentrations influencing our Universe, the gravitational shear this would introduce would be VERY observable as the first superstructures were forming, biased by the influence of this mysterious matter. But the universe is amazingly smooth at large scales. (btw if the gravitational waves from the 'other universe' can travel to us, why not matter and electro-magenetic radiation)
For all you cosmo-zealots: the 'edge' of our detectable universe is one in time not in space. It is called the Cosmic Microwave Background, and it's a wall of plasma redshift by about 1500 to the microwave regime. You see it in every direction you look, we are surrounded by it.
Euclidian style thinking wont get you very far in cosmology.
[RANT] I become increasingly frustrated with the way science (especially astronomy) is portrayed on/. Although I'm happy that ppl take interest in this field, I feel that creating hypes or suggesting breakthroughs in every little article is just not the way to go. It may be the american way... I dunno. For NASA, pumped PR is essential for its survival. I'm also amazed that whereas/. readers are in general critical and sceptical, when the subjects changes to science they believe everything without actually trying to understand what is being said.[/RANT]
Finding clusters @ z = 0.3 is no big deal and wont challenge our current understanding of how quickly the Universe evolved into its current hierarchical structure of stars, galaxies and clusters. The current theoretical (numerical) view of the deep universe comes from the Virgo Consortium and predicts the existence of clusters on much higher redshifts. Wat is interesting is that it appears to be relatively easy to image large amounts of cluster. Clusters have been found out to a redshift of 1.2 (universe 40% of current age) and protoclusters at z = 2.2 (universe 25% of current age). CAVEAT: this MACS sample are selected on basis of their X-RAY properties; they were snatched from the ROSAT source list. Only heavy clusters with lots of infalling gas will produce much X-RAY emission, therefore biasing against smaller/less gass rich clusters. It is completely unclear if the study of high density regions (ie clusters) is representative of global picture galaxy and cluster evolution.
There is also a program underway called the Sloan Digital Sky Survey; a huge project where they (amongst other things) try to find clusters by optical selection in an automated way.
Finally, the article states "The analysis is not yet complete, but it is already clear that our observations are in conflict with a high value of omega."
Translation: this does not mean that our current picture is challenged. To the contrary: this study very crudely confirms other analysis (spatial structure in cosmic microwave background) and arguments for low omega_matter. Low Omega_matter is the currently favoured model. Trying to present this study as a breakthrough in this respect is false.
there is no proof that black holes exist! They are still entirely theoretical constructs,
All ideas are theoretical constructs. Numbers are theoretical constructs, Quantum Theory is a beautiful theoretical construct. However i do not see you getting skeptical of the number on your bankaccount, nor violently disagreeing with QT (oh wait my processor is operating according to an entirely theoretical construct). Now i now that space-time singularities freak ppl out and that the observational evidence is necessarely indirect, but you completely misjudge physicists and astronomers (who actually understand the theoretical framework), if you assume that this is an issue painfully overlooked.
and whilst standard general relativity seems to demand their existance other formulations of general relativity don't
G.R. does not demand, but rather allows their existence. Other formulations either are abstractions of GR (and therefor embed it) or have a different behaviour and are disqualified time and again by observations (for example the gravitational lensing effects).
and we can't even say what a unified theory will predict once they finally get from being airy speculation to a solid theory.
*sigh* To get the record straight: it is general relativity that has an excellent record and firm and elegant theoretical basis (and it is a bitch to disprove). Are you suggesting throwing it away for a unfinished unified theory that is speculative, in flux and extremely hard tot test?. If the US doesnt wanna build Large Hadron Colliders you might never find out the connection between metrics and the other interactions.
It is still a very real possibility that astronomers and astrophysics alike have simply seized on a theoretical result without any thought of whether it is valid and used it to justify all kinds of celestial phenomena which have nothing to do with black holes at all. There's no excuse for such slipshod science, and it's all too likely that future scientists will look back and laugh.
The only person flirting with slipshod science is you my friend. And you're general argument that astronomers are just plain wrong might be true, but they are certainly a heck of lot more informed than you. And history learns that the future scientist will most likely look back in wonder and respect. The development of human knowledge and understanding is a cumulative affair. Research done by one is used as a basis for those who follow, one generation gives knowledge and a treatise from which to live to the next.
Bernard de Chartres (12th century) said: "In comparison with the ancients we stand like dwarves on the shoulders of giants". This might well be said of scientists in this age.
Wheeler has a lot to answer for with his glib coining of the phrase "black hole". Do you think people would be so ready to assume their existance if they had been called "dark stars" as they once were? This smacks more of faith than reason.
Black hole is a term that stuck because the general public (ie you) thought that it was more catchy (people also like and misunderstand 'Big Bang'). Before this they were referred to by the community as "frozen stars" (or "dark stars", thought up by Laplace), but scientists who are working with it in da math, couldnt care less whatchacall it.
Maybe it's time to catch up on the literature before posting. It is not hard: try "black" "hole" "faq" keywords.
Doesn't this undermine some parts of the 'big bang' theory? According to this theory the universe started in one central area and exploded. There was no material to consume.
To keep it short and simple: no. Big Bang theory is actually some kind of misnomer because it appeals to the idea of a 3d explosion which is not the correct metaphore to describe the evolution of a Friedman-Lemaitre universe, let alone inflation theory. Also, the existence if black holes in this (galaxy-evolution) context isnt even remotely connected to subject.
When are we going to get to the stage when we can actually launch human-piloted (or not) craft and physically go out and explore these things and prove them right or wrong?
I see you fail to grasp the size of even the local universe. Galaxies are FAR away. Not as in 'it-must-be-expensive-to-get-there' away. I mean 'it-takes-multiple-millions-of-years-at-the-speed- of-light' away. For several (non-technical but rather physical) reasons it is impossible for humans to travel at more than a fraction of c. Please factor in above.
Saying that black hole jets help trigger star formation is very different from suggesting that these two phenomena are linked in a single set of evolutionary processes.
For example; it is widely believed that most stars in galaxies are being formed in relatively short powerful bursts. These bursts are triggered by the hierarchical clustering of subgalactic components. In many of these 'merging' galaxies spectral analysis does not show the black hole fingerprint (strong forbidden lines). These lines are hardly attenuated by dust, so if you dont see them it is unlike that the galaxy hosts an active BH.
Actually, in the merging scenario, which is favoured by theoreticians and observers (as opposed to the unlikely single monolithical collapse), the hardest part is to cool down star formation! Read: we have a hard time understanding what processes actually inhibit SF, let alone promote it.
Altho this research sheds new light on how complex the live and birth of galaxies is and how we lack in detailed understanding of the physical processes and interactions, to claim on the basis of a study of 14 Seyfert galaxies that this amounts to a breakthrough in this field is tentative.
If you read these type of articles precisely, you must be sensitive to the words ['may', 'might','help','possibly','suggest'] and give credit to the researchers effort to be cautious.
It must be pointed out that that if you really want to find out what the relation between BH and SF is you need to go to the high redshift universe. The problem is that hi-z sources are just to damned faint to study spectroscopically (no... hubble is useless here).
I used to live in a geek house some 4-5 years ago. It was one of the most fucked up years in my live I have to say, heh. Installed my first Linux (Kernel 1.2.18, Slackware 3.1?) in a hot summer vacation: yeah it took me two weeks to get it all running. Non supported soundcards, non supported video drivers, and a monitor that burned out after 3 days;-p
There were three of us in a house of five, all installing Linux connecting with token ring thin ethernet, so we could play MUD over a shared modem 8 hours a day *sigh*. We also tended to play lots of DOOM I, hehehe. Ennieweez, one of the geeks was a girl, and a gorgeous one I might say. So it was pretty inevitable that we ended up together for a while.
But allas, I moved out of there a long time ago and I'm having a 'real' life since, without that particular girl, sadly. Nevertheless, Geek houses rule!
As with all comets, they are pristine samples of a time at which our solar system was assembled. They are cosmic fossiles in our own backyard if you wish. If one knows how they break up, you might say something sensible about how they were made in the first place, and therefore about the earliest conditions in our solar system.
Um, if you think that scifi=real life, you need help. Remember, alot of things in scifi books aren't real. Just because it's not said in a scifi book, doesn't mean it can't be true.
I advise you to read the original article, and the try to understand wat is said thereafter, instead of sharing this redundant wisdom with us.
Um, deflector shields as used in Star Trek, yeah. Believe it or not -- and I know this is heresy -- but there is science fiction other than Star Trek. An unconfirmed rumor even says that science fiction existed before Star Trek
No kiddin. My point was the lack of depth in the space.com stories. Your comment does not alter this, and since you seem to have knowledge about the use of deflector shield fiction in other/pre Star trek scifi, please do not hesitate to give me examples. I'm not aware of the use plasma? for this purpose.
Deflector shields as used in any science fiction starship warp space-time in order to deflect. Therefore EM fields or plasmas have nothing to do with it. Deflectors are more connected to the warp drive. Actually they are the same.
Besides this, did anyone read the article and follow the links to see if the story checks out? "Plasmas are capable of shielding satellites": my ass, where's the link to the scientific background?
"plasma" links to a story about plasma propulsion, nice but irrelevant. "energy systems like the deflector shields" link to a crap story about a medical doctor (!) working on a new Big Bang theory. "Cold plasma's......are ambient-temperature, ionized gasses related to those found deep withing the suns core": geez, this is unbelievable. Can someone explain to me what has been found in the suns CORE, and by whom and when?
Please keep on posting this high quality space.com stories.
Although the prospect of such a exciting new approach to gravity and the dark (or rather 'transparent' since it does not absorp light) matter problem, it needs to be stressed that lack of theories and ideas is not the problem.
The actual limit on progress in this field is lack of relevant data, obtained either from super colliders or from deep cosmological observations. Currently it is possible to make many models consistent with the observational constraints because it is these constraints themself which are so loose.
Everybody knows the US killed the giant supercollider program, and the state of affairs in observational cosmology learns that it is very difficult to calibrate measurements of (dark) matter.
To so something more about the last point, since I've researched this last year, it is far from trivial to yield reliably answers on galactic cluster potentials via dynamic or gravitational lens measurements, especially because you need to go into the Infrared to observe (optical) light emitted by stars in the deep universe. Only recently with instruments like ISAAC on one of the VLT telescopes we are able to obtain high quality near-infrared data. For the far infrared imaging space based missions like the NGST are required, because of the polluting thermal radiation from the earths atmosphere. The NGST is still under study and not expected to be launched until 2010!
Until then we can only speculate aboute the nature of dark matter.
The article implies that, to first order, the H3 is nicely dispersed over the entire surface of the moon. En lets suppose it's fairly close to the surface (since created by solar wind interaction) up to 1 meter depth. So, how concentrated is this stuff anyway? Concentration will dominate the extraction costs, right?
Moon surface = 3.6 * 10^13 m^2
Concentration = 1 million tons/(surface*depth)
Lemme see, thats barely 0.03 g/m^3. Extracting and shipping a 10 ton load of H3 to earth would require mining an area of 360 km^2(!).
And all this for a lousy $40 billion dollar revenu? If I recall correctly, solely putting a couple of people on the moon cost about $24 billion dollar 30 years ago.
With typical interatomic scales of Angstroms (1/10 nanometer), circuitry at least ten times bigger and current technology at.somewhat microns, the LA times reports that the difference is a factor of millions. I say errrrr... hundred
One thing that I've noticed over the years is that people who think they're analyzing the industry are judging where it is at by what's at the forefront.
In general this argument holds, but if the industry dramatically lowers the threshold to 'upgrade' (because of gaining market share in this 'new' communication economy for instance) that changes it quite a bit. For example in Holland I've witnessed two revolutions the last couple of years. 1) The advent of the mobile phone. Sure it was around for some time, but the consumer market exploded last year, growing in the order of 1000%. This was mainly due to the telephone market opening up and startup companies investing heavily in order to gain market share. 2) Internet use was always lagging over here, but since the introduction of 'free' Internet (no subscription costs) over a year ago we also saw a tenfold increase.
Since the combination of small embedded mobile systems (did anyone mention Crusoe?) and hi-bandwidth radio packet data transfer (like GPRS) is not just merely another CPU or upgrade but something which offers a range of possibilities, it is difficult to predict how it will evolve.
Slashdot Mirror
I havent read the article, shoot me ;-) But my guess is that they just look for the most massive star in the solar neighbourhood. The reasoning is:
1) a star can only use about 10% of the available hydrogen, before more rapid evolutionary mechanisms set is (ie before some of them go boom)
2) only 0.7% of the rest mass energy is turned into energy
3) the relation between luminosity (L) and mass (M) is:
- M proportional to L^4 (for massive stars)
Thus nuclear time scale (tn):
tn = 0.007*0.1*Mc^2/L ( = 10^10 year for the Sun)
for other massive stars:
tn = (M/Msun)/(L/Lsun) * 10^10 yr
= (M/Msun)/(M^4/Msun) *10^10yr
= M^-3 * 10^10 yr
so if one would find a 10 Msun star nearby, you could expect it to go boom in 10 million years. In other words, a cosmic 'blink of the eye'.
Energy = mass * (speed of light) squared This equation tells us how much energy we get from reactions that destroy mass, Now, if you want light in the past to travel, say, 6 billion (current) light years in the space of 6000 years, you need to speed it up one million times. In other words, you increase the amount of energy released by nuclear reactions by one trillion.
;-p, but there's a flavor flaw. E=mc^2 is no fundamental law, but is derivable if, and depends critically on the assumption (observation/whatever) that, c is constant. if c is variable, E!=mc^2.
nice try
The radiative energy transport *can* be described by a random walk process. Photons are repeatedly absorbed and re-emitted in random directions.
Consider random walk in plane:
If theta_i is the re-emitting angle at step i, after N steps the coordinates of a photon are:
x = sum_over_N{ d cos(theta_i) }
y = sum_over_N{ d cos(theta_i) }
since he directions are randomly distributed and independent:
r = sqrt(x^2 + y^2) = sqrt(d^2 * [(sum...)^2 + (sum_y...)^2]
-> r = d*sqrt(N)
photon mean free path: d = 1/(kappa * density) = 10^-4 m.
r ~ 10^9 m
number of steps: N = (r/d)^2 = 10^26
total path travelled: s = Nd = 10^22
total time: t = s / c = 10^6 year.
although my feeling is that this actually should be a little bit higher.
conclusion: 10^7 years is just fine.
Mundie teaches us why leading inventors as... Thomas Edison succeeded... insight... unique... blabla.
Let me tell you all a story I know about Thomas Edison and Nikola Tesla you might find interesting. Both were amazing inventors and it can be argued that we owe to them the way we use electricity today. To them?
In 1882 Thomas Alva Edison had been the manufacturer up until that point in history of the system that carried the current to the households of America: direct current.
Direct current was not practical for traveling long distances to houses, and required transformers to boost the signal several times along the path from the generating plant to a person's house or to a building because of the resistance of the direct signal through the copper wires they used. This required costly and bulky equipment to have to be installed along the path to one's house, and caused electricity to be expensive and therefore rare.
Edison was the leader in the production and maintenance of the equipment that his transmission system required; he designed and was responsible for the building of the system.
Tesla offered the idea of a rotating magnetic to produce AC (altenative current). This meant that the voltage could be changed without serious loss of energy, using transformators, which are not costly, and quite small.
So really, Tesla's method was much more efficient. And Edison knew it. But... Edison was earning nice sums from his direct current power plants, which he had a few patents for (really a monopol), and he didn't want Tesla to fiddle with his money.
So... at West Orange, New Jersey, Edison and his men began paying schoolboys to kidnap small animals off the streets. Edison used them in live demonstrations about the dangers of AC. He would have the small animal tied to a large metal slab, and electrocuted in deliberately crude experiments. There were posters up all around the city that said, "Warning!" at the top and in smaller print went on to warn residents about being "Westinghoused," as electrocution was called by Edison's men.
So really, Edison was not a very nice person.
Tesla was humilated by him, and because of him, Tesla's genious was not recognized by the public. In contrast to Edison he died as a poor man.
Today, thanks to Tesla, we use AC, and it saves the electrical companies milliards of dollars every year.
Mundie teaches us that "the creativity and inventiveness needed to deliver their products was comparable to that needed for the underlying theory or discovery that made their business possible in the first place."
Arguably he is actually talking about how to best electrocute furry animals...
This is not 'just' combining telescope light. This is an interferometer. It enables the system to measure the difference in arrival time of a (plane) wave front, from a distant object. This translates into a measurement of position on the sky.
This is general practice in the radio regime, but it is damn hard in the optical. Not only because of the seeing, the distortion introduced by the atmosphere, but also because the phase information in lightwaves at visible wavelengts generally tends to get destroyed when you tamper with it. In an radio-interferometer one tampers a lot with the signal before combining.
The only solution is to build optics of so-called 'interferometric quality' which means that contact surfaces have to be smooth on the scale of a fraction of the wavelenght (!).
...only one baseline. The visibility of their interferometric signal is limited, they are only sensitive to certain spatial frequencies.
Damn, we need an array of these things. O wait, VLTI.
As usual, most ppl claiming the economical viabily of space mining just multiply the rough guess of the total abundance with the current market price. Geez.
;-p
Hello, extraction costs? Hello distance? Hello concentration? Yeah right, 'making rocket fuel from icy asteroids' in orbit at 3 AU (a couple of years of travel time). Lets factor in how much fuel you loose just transporting it about
This is so naive.
This is of course a bit too subtle for a PR. So you are probably right in accusing us of presenting one aspect of this work in an overly dramatic fashion, and perhaps all of this is not sufficiently exciting for /.
/.
I understand. Thanx for taking the time to explain this and that. This type of stuff should have been modded +plenty informative in the ideal
For now i'll spare my breath fo yet another round of replies to anyone who will post that this is yet another proof that there are infinite universes/big bangs/klingons.
PR author speaking again.
/. handled science reports. I was not attacking the original authors.
ello
I shall ignore the rant - send me email to my IfA address if you want to know what I think of this kind of comment
I assume you understand what initiated my response. If you have been following slashdot lately and take interest in the way astronomy is reported, you should get annoyed by the total lack of depth. This message just topped me over.
Finding MASSIVE clusters at z>0.3 is a rather enormous deal though. Observationally, that is. I admire the Virgo Consortiums pretty pictures as much as the next guy but in the end all theories (or numerical simulations as it were) have to be tested against reality. And that's where the problem lies.
The only distant clusters out to z = 0.4 I am aware of are all fairly heavy. My feeling is that this is because they are X-ray selected. I agree that that Virgo's prediction stand untested, but thats exactly what they are asking (begging) observers. Their predictions are so detailed that it must be possible in the near future to refute or confirm certain aspects. However it remains a problem that they are living in physical quantities, they appearantly have a hard time converting this to observational tests.
The clusters at z=1.2 and beyond that you mention are all very interesting but firstly, there's about 3 or so of them at the moment that have been confirmed in X-ray observations. Not exactly the kind of sample one would want to draw representative conclusions from. Secondly, these very distant clusters are PUNY. They are easily a factor of ten less X-ray luminous than the average MACS cluster. Hence they provide very little leverage for cosmological studies.
I did not intend to suggest that these clusters (altho very interesting) would be represtative. But they are all caught in puberty, which in itself is very interesting. Even a few very hi-z clusters could tell more about how they form than many 'nearby' clusters. I'm not sure I agree that they are puny. They are not X-ray luminous, but converting this to mass in a cluster that is not in equilibrium is tricky.
Ideally we would want MASSIVE clusters at z~1 or beyond but so far only one has been found. MACS provides the best sample we can come up with given the existing data: the most massive clusters at (on your scale) intermediate redshifts.
I am not disputing the MACS survey, surely the science harvest from this project will be impressive. However to again explain the background of my rant: I was getting sick and tired of the way
If you want to take your cosmology from SN and CMB observations, fine by me. The constraints from clusters run pretty much orthogonal to those from the other techniques and since we're trying to constrain three cosmological parameters I'd say it's very useful to have the clusters too. You can drop any of the three and still get a reasonable idea of what values are most consistent with the observations. But that's not the idea. We want independent measurements from completely different realms to make sure we're getting the right answer.
I am completely aware of the fact that different measurements contrain parameter space in different ways. Ideally each observation-type would have sufficient resolution to provide overal agreement and smaller scale disagreements, and hopefully provide clues about the details of the theoretical predictions or more importantly observational biases. I did not suggest that one should prefer one observation over the other (altho i think that CMB has the best case sofar concerning cosmological parameters), rather to attack the suggestion in the article that this result challenges our view. I was under the impression that this study provided agreement.
Please note that my critique was on the reporters, and the lassez-faire science culture in this tech-ezine.
I find it difficult to consider this a shortcoming of our work. But of course you are free to find this boring...
Shortcoming? I never said it would be. Boring? hardly. I'd wish there were more posts like this. Usually i'm replying to star trek zealots.
If something is moving away from us at nearly the speed of light (say .9c), then the light from that object still moves towards us at c, rather than .1c as you might expect.
...unless it is space itself that expands faster than c. '> c expansion' occured in the inflationary period in the beginning of the universe. Observational 'prove' is the homogeneity of causally disconnected areas in the cosmic microwave background and the overal homogeneity of the observed universe. Only an inflationary 'faster than light' expansion explains this feature in a natural way.
It's funny how little cosmologists confidence in already knowing everything (like age & size of universe) was shaken by the fact that their most fundamental prediction of the behaviour of the universe was completely wrong. (The fact that distance galaxies are accelerating away from us as opposed to decelarating)
Actually, supernovae results indicate that the universe switched to acceleration only in recent epochs z=1. De/accelaration is notoriously hard to measure at some distance and no cosmologist would have claimed now or in the past that testing universe models is a precision job. De/Accelaration in itself not a fundamental prediction, it is a measurement then to be used to justify different models. And there are a lot of tricky stuff involved with supernova measurements. Oh, and last but not least. SNe do not provide any clues at really high redshifts z>2.
The universe is the largest gravitationally bound structure in the universe...
,whatever that means in curved 4d Riemann space. If it did, our universe model would be incorrect (which is conceivable but not observed) but remember that both gravitational lensing and our cosmology are derived from the same set of equations: general relativity. Using one to disprove/change the other is impossible.
Recent distant supernova measurements indicate that the expansion of the universe is accelerating in recent epochs: thus the universe is not gravitationally bound.
but it is feasible that as these distant structures are studied in more detail gravitational effects which indicate some other very large masses outside the bounds of what we can detect as the edge of our universe are discovered.
Interesting idea but some major problems. Outside the bounds of our observable Universe, would mean way back in time when the universe was so hot that ionized gas made it opague (because we look back in time). I cannot mean spatially 'outside'
Furthermore lensing signal is only detectable against background sources in specific configurations, because they are the ones that are distorted. If you go to really high-z you're are rapidly running out of sources, apart from the fact that they are incredibly faint and small. (ie better test this in the nearby universe: since the responsible mass is 'outside' our universe there is no need to go distant). Besides this, there's an argument against large mass concentrations influencing our Universe, the gravitational shear this would introduce would be VERY observable as the first superstructures were forming, biased by the influence of this mysterious matter. But the universe is amazingly smooth at large scales. (btw if the gravitational waves from the 'other universe' can travel to us, why not matter and electro-magenetic radiation)
For all you cosmo-zealots: the 'edge' of our detectable universe is one in time not in space. It is called the Cosmic Microwave Background, and it's a wall of plasma redshift by about 1500 to the microwave regime. You see it in every direction you look, we are surrounded by it.
Euclidian style thinking wont get you very far in cosmology.
[RANT] I become increasingly frustrated with the way science (especially astronomy) is portrayed on /. Although I'm happy that ppl take interest in this field, I feel that creating hypes or suggesting breakthroughs in every little article is just not the way to go. It may be the american way... I dunno. For NASA, pumped PR is essential for its survival. I'm also amazed that whereas /. readers are in general critical and sceptical, when the subjects changes to science they believe everything without actually trying to understand what is being said.[/RANT]
Finding clusters @ z = 0.3 is no big deal and wont challenge our current understanding of how quickly the Universe evolved into its current hierarchical structure of stars, galaxies and clusters. The current theoretical (numerical) view of the deep universe comes from the Virgo Consortium and predicts the existence of clusters on much higher redshifts. Wat is interesting is that it appears to be relatively easy to image large amounts of cluster. Clusters have been found out to a redshift of 1.2 (universe 40% of current age) and protoclusters at z = 2.2 (universe 25% of current age). CAVEAT: this MACS sample are selected on basis of their X-RAY properties; they were snatched from the ROSAT source list. Only heavy clusters with lots of infalling gas will produce much X-RAY emission, therefore biasing against smaller/less gass rich clusters. It is completely unclear if the study of high density regions (ie clusters) is representative of global picture galaxy and cluster evolution.
There is also a program underway called the Sloan Digital Sky Survey; a huge project where they (amongst other things) try to find clusters by optical selection in an automated way.
Finally, the article states "The analysis is not yet complete, but it is already clear that our observations are in conflict with a high value of omega."
Translation: this does not mean that our current picture is challenged. To the contrary: this study very crudely confirms other analysis (spatial structure in cosmic microwave background) and arguments for low omega_matter. Low Omega_matter is the currently favoured model. Trying to present this study as a breakthrough in this respect is false.
there is no proof that black holes exist! They are still entirely theoretical constructs,
All ideas are theoretical constructs. Numbers are theoretical constructs, Quantum Theory is a beautiful theoretical construct. However i do not see you getting skeptical of the number on your bankaccount, nor violently disagreeing with QT (oh wait my processor is operating according to an entirely theoretical construct). Now i now that space-time singularities freak ppl out and that the observational evidence is necessarely indirect, but you completely misjudge physicists and astronomers (who actually understand the theoretical framework), if you assume that this is an issue painfully overlooked.
and whilst standard general relativity seems to demand their existance other formulations of general relativity don't
G.R. does not demand, but rather allows their existence. Other formulations either are abstractions of GR (and therefor embed it) or have a different behaviour and are disqualified time and again by observations (for example the gravitational lensing effects).
and we can't even say what a unified theory will predict once they finally get from being airy speculation to a solid theory.
*sigh* To get the record straight: it is general relativity that has an excellent record and firm and elegant theoretical basis (and it is a bitch to disprove). Are you suggesting throwing it away for a unfinished unified theory that is speculative, in flux and extremely hard tot test?. If the US doesnt wanna build Large Hadron Colliders you might never find out the connection between metrics and the other interactions.
It is still a very real possibility that astronomers and astrophysics alike have simply seized on a theoretical result without any thought of whether it is valid and used it to justify all kinds of celestial phenomena which have nothing to do with black holes at all. There's no excuse for such slipshod science, and it's all too likely that future scientists will look back and laugh.
The only person flirting with slipshod science is you my friend. And you're general argument that astronomers are just plain wrong might be true, but they are certainly a heck of lot more informed than you. And history learns that the future scientist will most likely look back in wonder and respect. The development of human knowledge and understanding is a cumulative affair. Research done by one is used as a basis for those who follow, one generation gives knowledge and a treatise from which to live to the next.
Bernard de Chartres (12th century) said: "In comparison with the ancients we stand like dwarves on the shoulders of giants". This might well be said of scientists in this age.
Wheeler has a lot to answer for with his glib coining of the phrase "black hole". Do you think people would be so ready to assume their existance if they had been called "dark stars" as they once were? This smacks more of faith than reason.
Black hole is a term that stuck because the general public (ie you) thought that it was more catchy (people also like and misunderstand 'Big Bang'). Before this they were referred to by the community as "frozen stars" (or "dark stars", thought up by Laplace), but scientists who are working with it in da math, couldnt care less whatchacall it.
Maybe it's time to catch up on the literature before posting. It is not hard: try "black" "hole" "faq" keywords.
Doesn't this undermine some parts of the 'big bang' theory? According to this theory the universe started in one central area and exploded. There was no material to consume.
To keep it short and simple: no. Big Bang theory is actually some kind of misnomer because it appeals to the idea of a 3d explosion which is not the correct metaphore to describe the evolution of a Friedman-Lemaitre universe, let alone inflation theory. Also, the existence if black holes in this (galaxy-evolution) context isnt even remotely connected to subject.
When are we going to get to the stage when we can actually launch human-piloted (or not) craft and physically go out and explore these things and prove them right or wrong?
- of-light' away. For several (non-technical but rather physical) reasons it is impossible for humans to travel at more than a fraction of c. Please factor in above.
I see you fail to grasp the size of even the local universe. Galaxies are FAR away. Not as in 'it-must-be-expensive-to-get-there' away. I mean 'it-takes-multiple-millions-of-years-at-the-speed
Saying that black hole jets help trigger star formation is very different from suggesting that these two phenomena are linked in a single set of evolutionary processes.
For example; it is widely believed that most stars in galaxies are being formed in relatively short powerful bursts. These bursts are triggered by the hierarchical clustering of subgalactic components. In many of these 'merging' galaxies spectral analysis does not show the black hole fingerprint (strong forbidden lines). These lines are hardly attenuated by dust, so if you dont see them it is unlike that the galaxy hosts an active BH.
Actually, in the merging scenario, which is favoured by theoreticians and observers (as opposed to the unlikely single monolithical collapse), the hardest part is to cool down star formation! Read: we have a hard time understanding what processes actually inhibit SF, let alone promote it.
Altho this research sheds new light on how complex the live and birth of galaxies is and how we lack in detailed understanding of the physical processes and interactions, to claim on the basis of a study of 14 Seyfert galaxies that this amounts to a breakthrough in this field is tentative.
If you read these type of articles precisely, you must be sensitive to the words ['may', 'might','help','possibly','suggest'] and give credit to the researchers effort to be cautious.
It must be pointed out that that if you really want to find out what the relation between BH and SF is you need to go to the high redshift universe. The problem is that hi-z sources are just to damned faint to study spectroscopically (no... hubble is useless here).
I used to live in a geek house some 4-5 years ago. It was one of the most fucked up years in my live I have to say, heh. Installed my first Linux (Kernel 1.2.18, Slackware 3.1?) in a hot summer vacation: yeah it took me two weeks to get it all running. Non supported soundcards, non supported video drivers, and a monitor that burned out after 3 days ;-p
There were three of us in a house of five, all installing Linux connecting with token ring thin ethernet, so we could play MUD over a shared modem 8 hours a day *sigh*. We also tended to play lots of DOOM I, hehehe. Ennieweez, one of the geeks was a girl, and a gorgeous one I might say. So it was pretty inevitable that we ended up together for a while.
But allas, I moved out of there a long time ago and I'm having a 'real' life since, without that particular girl, sadly. Nevertheless, Geek houses rule!
As with all comets, they are pristine samples of a time at which our solar system was assembled. They are cosmic fossiles in our own backyard if you wish. If one knows how they break up, you might say something sensible about how they were made in the first place, and therefore about the earliest conditions in our solar system.
Um, if you think that scifi=real life, you need help. Remember, alot of things in scifi books aren't real. Just because it's not said in a scifi book, doesn't mean it can't be true.
I advise you to read the original article, and the try to understand wat is said thereafter, instead of sharing this redundant wisdom with us.
Um, deflector shields as used in Star Trek, yeah. Believe it or not -- and I know this is heresy -- but there is science fiction other than Star Trek. An unconfirmed rumor even says that science fiction existed before Star Trek
No kiddin. My point was the lack of depth in the space.com stories. Your comment does not alter this, and since you seem to have knowledge about the use of deflector shield fiction in other/pre Star trek scifi, please do not hesitate to give me examples. I'm not aware of the use plasma? for this purpose.
The story is still crap.
Deflector shields as used in any science fiction starship warp space-time in order to deflect. Therefore EM fields or plasmas have nothing to do with it. Deflectors are more connected to the warp drive. Actually they are the same.
...are ambient-temperature, ionized gasses related to those found deep withing the suns core": geez, this is unbelievable. Can someone explain to me what has been found in the suns CORE, and by whom and when?
Besides this, did anyone read the article and follow the links to see if the story checks out? "Plasmas are capable of shielding satellites": my ass, where's the link to the scientific background?
"plasma" links to a story about plasma propulsion, nice but irrelevant.
"energy systems like the deflector shields" link to a crap story about a medical doctor (!) working on a new Big Bang theory.
"Cold plasma's...
Please keep on posting this high quality space.com stories.
Although the prospect of such a exciting new approach to gravity and the dark (or rather 'transparent' since it does not absorp light) matter problem, it needs to be stressed that lack of theories and ideas is not the problem.
The actual limit on progress in this field is lack of relevant data, obtained either from super colliders or from deep cosmological observations. Currently it is possible to make many models consistent with the observational constraints because it is these constraints themself which are so loose.
Everybody knows the US killed the giant supercollider program, and the state of affairs in observational cosmology learns that it is very difficult to calibrate measurements of (dark) matter.
To so something more about the last point, since I've researched this last year, it is far from trivial to yield reliably answers on galactic cluster potentials via dynamic or gravitational lens measurements, especially because you need to go into the Infrared to observe (optical) light emitted by stars in the deep universe. Only recently with instruments like ISAAC on one of the VLT telescopes we are able to obtain high quality near-infrared data. For the far infrared imaging space based missions like the NGST are required, because of the polluting thermal radiation from the earths atmosphere. The NGST is still under study and not expected to be launched until 2010!
Until then we can only speculate aboute the nature of dark matter.
Ivo
Fun.
The article implies that, to first order, the H3 is nicely dispersed over the entire surface of the moon. En lets suppose it's fairly close to the surface (since created by solar wind interaction) up to 1 meter depth. So, how concentrated is this stuff anyway? Concentration will dominate the extraction costs, right?
Moon surface = 3.6 * 10^13 m^2
Concentration = 1 million tons/(surface*depth)
Lemme see, thats barely 0.03 g/m^3. Extracting and shipping a 10 ton load of H3 to earth would require mining an area of 360 km^2(!).
And all this for a lousy $40 billion dollar revenu? If I recall correctly, solely putting a couple of people on the moon cost about $24 billion dollar 30 years ago.
Dream on.
Ivo
With typical interatomic scales of Angstroms (1/10 nanometer), circuitry at least ten times bigger and current technology at .somewhat microns, the LA times reports that the difference is a factor of millions. I say errrrr... hundred
Geez, if they can't even get that right.
One thing that I've noticed over the years is that people who think they're analyzing the industry are judging where it is at by what's at the forefront.
In general this argument holds, but if the industry dramatically lowers the threshold to 'upgrade' (because of gaining market share in this 'new' communication economy for instance) that changes it quite a bit. For example in Holland I've witnessed two revolutions the last couple of years. 1) The advent of the mobile phone. Sure it was around for some time, but the consumer market exploded last year, growing in the order of 1000%. This was mainly due to the telephone market opening up and startup companies investing heavily in order to gain market share. 2) Internet use was always lagging over here, but since the introduction of 'free' Internet (no subscription costs) over a year ago we also saw a tenfold increase.
Since the combination of small embedded mobile systems (did anyone mention Crusoe?) and hi-bandwidth radio packet data transfer (like GPRS) is not just merely another CPU or upgrade but something which offers a range of possibilities, it is difficult to predict how it will evolve.
Something tells me it's going to be ***BIG***.