Naked Science Forum
Non Life Sciences => Physics, Astronomy & Cosmology => Topic started by: LetoII on 09/05/2012 22:53:17
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I would like some help with the following:
Is (outer)space more empty than a man made vacuum? If so, does this influence the maximum speed allowed inside this vacuum?
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Mystical response by ksgaur1 moved to New Theories
http://www.thenakedscientists.com/forum/index.php?topic=44098.0
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I would like some help with the following:
Is (outer)space more empty than a man made vacuum? If so, does this influence the maximum speed allowed inside this vacuum?
That depends on the particular equipment used to establish the man made vacuum and whee inn space you're looking at the pressure.
http://en.wikipedia.org/wiki/Vacuum#Outer_space
I'm not sure what you mean by does this influence the maximum speed allowed inside this vacuum? but I assume you're refering to the speed of single particles in otherwise vacuum regions of space. If so then the answer is yes. The density of particles determines the distance a particle travels without crashing into another particle thus limiting its speed. In a near perfect pressure of zero there are still photons movingt around and these photons can keep slaming into, say, electrons. The electrons then scatter off the photons by the process known as Compton scattering. The process might null out the speed of the electrons if the directions of the photos is random and have random energies.
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imatfaal - It' nice to have a forum where new scientific ideas can be discussed. My problem with this person's use of it is that he is misusing it. What he is posting is not science, it's religion. Nothing he said can be considered a topic that is scientific. It simply doesn't fit the definition of science in any shape or form. I'd hate to see this placed misused as a religion forum. That's a good way to destroy it. Please forgive me if this is an inappropriate way to express myself. I wasn't certain if it was best placed here than in the New Theories forum since what I'm addressing is abouty science, not religion. And, in my humble opinion, his topic is not mysticism, it's religion, a respectible area of man's concerns.
Regarding ksgaur1's first post in this forum whose link you gave above -
The author of that post has clearly stated that his aim of life is to prove the existence of God scientifically. Something that cannot be started in a science forum, especially since nothing in his post is scientific in any sense of the word. The author seems to believe that merely tossing words around in the same post where you toss scientific words around that you've somehow created a post whose content is scientific. Nope. Sorry ksgaur1. That's just not the case. In my opinion, what you posted was all Poppycosh! There is nothing in that post that is scientific. There are forums to discuss the kind of thing that you wish to, but this is not the place for it and your books, which you merely mentioned, is of no value unless you wat somene to reada them, not to merely know of their existance. The place for what you're searching for is here
http://www.christianboard.com/board/
Even at lease one of those people will argue that it doesn't belong there either. I know since I'm a faithful Christian who posts there and I will argue what I just said. ;D
Please keep The Naked Scientists forum 100% science! I beg you!!
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wow thanks PMB thats really helpfull.
Indeed i meant to ask for any change in the maximum speed of the particles that move through this vacuum.
as for the other post on vacuum, i agree with imatfaal and say its too much religion based.
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wow thanks PMB thats really helpfull.
You're most welcome. And welcome to the forum! :)
as for the other post on vacuum, i agree with imatfaal and say its too much religion based.
I agree with you. It seems to me that imatfaal thinks its religion and seems to think it's find to let it thrive in the New Theories forum. I wish that wasn't the case didn't. I know how that kind of thing goes when it is left to itself.
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Returning to the original question, there is an article on the interplanetary medium at http://nineplanets.org/medium.html (http://nineplanets.org/medium.html)
and an article on ultra-high vacuum technology at
http://en.wikipedia.org/wiki/Ultra-high_vacuum (http://en.wikipedia.org/wiki/Ultra-high_vacuum)
The article on the interplanetary medium states that the density ranges from about 5 to about 100 particles per cubic centimetre "near the Earth". That is not really what is meant here -- it means "at the Earth's distance from the sun, but a long way from the Earth".
The article on UHV technology defines UHV as referring to pressures (presumably at ambient temperature around 300 K) below 100 nPa.
1 mole of any gas = 6 x 1023 particles occupies about 24000 cubic centimetre at 105 Pa (atmospheric pressure). That means 2.5 x 1019 particles per cubic centimetre.
A man-made vacuum 100 times better than the UHV limit -- 10-9 Pa -- would therefore contain about 250,000 particles per cubic centimetre. It is quite likely that that is not the limit of UHV technology, and a more thorough web search might reveal a pressure or particle density that can be considered the best for a man-made vacuum.
But the flavour that I am getting -- 250,000 as against 5 to 100 -- is that space is much emptier than the best man-made vacuums, especially since the inner solar system (Earth's region of space) is immersed in much more background gas than remote areas of interstellar space.
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Please let us stick to S.I units I know that Astronomers like to use there own selection of units but I believe a science forum should alaways use S.I (no more cc please)
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Please let us stick to S.I units I know that Astronomers like to use there own selection of units but I believe a science forum should alaways use S.I (no more cc please)
Indeed.
"Not correct the smallest black holes observed have a mass of 5-10 solar masses"
from
http://www.thenakedscientists.com/forum/index.php?topic=5915.msg385825#msg385825
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Syhprum, cubic centimetres are indeed SI units -- any power of 10 of the basic unit with a latin prefix milli-, centi-, mega-, etc. counts as a SI unit (if we are using a liberal modern interpretation of SI, as opposed to a pedantic 1960s interpretation). As a chemist, you must surely use L = dm3 without even blinking.
However, for anyone who is challenged by the use of such obscure units as cm3 (= mL), let me revise the original of my posting to
250,000 million particles per cubic metre for a very sophisticated man-made UHV system, as opposed to 5 to 100 million particles per cubic metre for the interplanetary medium at the Earth's distance from the sun.
As far as the use of BTU, feet, miles, pounds, etc., is concerned, then I tend to agree with you that they should not appear in a science forum, except insofar as this forum is intended for the general public, not necessarily science trained, and many US citizens are totally unfamiliar with any sort of metric units, let alone pedantic SI. Posters should be able to post in units that are comfortable to them, and that should take precedence over the strict SI thought police!
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My excuse for being lousy at Thermodynamics is that every time I tried to learn it, the blighters had changed to different units! I grew up using Imperial units, was taught science in CGS which switched half-way through to SI, was taught in a mixture of SI and Imperial in higher ed, then moved to the US and had to unlearn everything and go back to Imperial. It's hardly surprising that I'm really messed up.
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My excuse for being lousy at Thermodynamics is that every time I tried to learn it, the blighters had changed to different units! I grew up using Imperial units, was taught science in CGS which switched half-way through to SI, was taught in a mixture of SI and Imperial in higher ed, then moved to the US and had to unlearn everything and go back to Imperial. It's hardly surprising that I'm really messed up.
With the added problem that, having left the Empire, the US felt obliged to call the unit system something other than "Imperial", and to use outdated "pounds" and "gallons" that did not match the British and Colonial usage.
On second thoughts, it is the British and Colonials who do not call the system "Imperial". Presumably the obviously French term "Avoirdupois" is a cheap shot at Napoleon for instituting the metric system across the channel!
I understand from a specialist colleague that our Australian ceramics technologists have solved their unit problems by casting all their recipes in 'gram per pint'!
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too bad to hear that our vacuum making isnt that good :P
as for SI standards, we should use them. It makes it easier for most students to understand what being said. atleast thats the case for me.
another question from me regarding vacuums:
if space is more empty, does it allow light to travel through it faster? Or is this only bound to the stage / size of our universe as a whole?
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"Not correct the smallest black holes observed have a mass of 5-10 solar masses"
Hoisted by my own petard, astronomers can be forgiven for using their own special units such as Solar masses for out of this world things but I wince when they go on about Ergs or Angstroms when there are proper well understood S.I units.
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Syhprum, I have no real quarrel about the desirability of sticking to SI units.
Without getting too technical and pedantic, erg and ångström do depart from SI units by mere powers of 10, but they do not contain the prefixed main unit.
Erg are unnecessary and unacceptable, and nobody who is not (1) over 50, or (2) trained by an out-of-date teacher, should even know about them. Ångström are a slightly different matter, because IUPAC has given official blessing for their continuing use -- unnecessary in my view.
µJ = 10 erg or nJ = 0.01 erg are acceptable and practically useful SI alternatives, as are nm = 10 Å and pm = 0.01 Å.
cm3 is also quite an acceptable SI unit -- it contains the main unit m with an appropriate prefix -- and it should not make you wince!
By the way, I take it from the last few bits of chat that you are an astronomer. Astronomers seem to have forgotten that distances in the solar system are conveniently expressed in Gm and Tm, and any SI purists among them should immediately start a campaign to express interplanetary and orbital distances in these units --- [;D]