Common misconceptions in Astronomy?

[tdamskov]

"Space is full of plasma" seems to me to be a vast overstatement. Interstellar vacuum may contain a few ionized atoms per cubic centimeter on average..

 

[CalliArcale]

It's full of plasma -- like a gas, it expands to fill the available space. It's just an exceedingly thin plasma. <img src="/images/icons/wink.gif" /> (Okay, so that was semantics. But you know what I mean.)<br /><br />It is a common misconception that space is a void, and even a lot of modern sci-fi books and movies will use the word "void" to refer to space. It does sound a lot better that way, after all -- spookier. <img src="/images/icons/wink.gif" /> But it's inaccurate. The technical definitions of space (for the purpose of aerospace records) vary, but usually pick a spot about 50 miles up. So anything above 50 miles altitude is space, even though there's a significant amount of atmosphere up there (just not enough for control surfaces to grab onto).<br /><br />One of my pet peeve misconceptions is this one: continuous velocity in space requires continuous thrust. In fact, with very little matter in space, one can travel along quite fast without any thrust at all after one has accelerated to the desired velocity. <div class="Discussion_UserSignature"> <p> </p><p><font color="#666699"><em>"People assume that time is a strict progression of cause to effect, but actually from a non-linear, non-subjective viewpoint it's more like a big ball of wibbly wobbly . . . timey wimey . . . stuff."</em>  -- The Tenth Doctor, "Blink"</font></p> </div>

 

[michaelmozina]

FYI the whole "virtual particles popping in and out of existence" is a misnomer IMO. When virtual particles were first proposed, we did not know about neutrinos having mass. We do not know if these are simply interactions between preexisting particles in the system. It is highly unlikely that any type of energy is actually being created or destroyed in such events, we are simply seeing the "near collisions" between particles like neutrinos that constantly flow through the system. <div class="Discussion_UserSignature"> It seems to be a natural consequence of our points of view to assume that the whole of space is filled with electrons and flying electric ions of all kinds. - Kristian Birkeland </div>

 

[michaelmozina]

<blockquote><font class="small">In reply to:</font><hr /><p>vacuum is a vacuum is a vacuum... if its filled with something than you should stop talking about vacuum <p><hr /></p></p></blockquote><br /><br />Exactly. I think that the term vacuum ends up being more confusing than it is useful. It tends to give one the impression of something that is completely empty, but nothing in the universe fits that description. This confusion of terms has very negative implications when it comes to plasma cosmology IMO. <div class="Discussion_UserSignature"> It seems to be a natural consequence of our points of view to assume that the whole of space is filled with electrons and flying electric ions of all kinds. - Kristian Birkeland </div>

 

[robnissen]

<font color="yellow"> It is highly unlikely that any type of energy is actually being created or destroyed in such events</font><br /><br />1. Energy is not being created or destroyed, the quantum particles form as pairs with postive and negative energy, therefore, the amount of energy does not change when these pairs of particles pop into existence. <br /><br />2. On a related topic, during inflation, space i.e. vacuum i.e. void was created, but I have never heard a good explanation of how "nothing" is created. Does anyone have any thoughts on this.

 

[silylene old]

As was said in the above post by RobNissen, no energy is created or destroyed by virtual particles. The net gain is exactly zero.<br /><br />Virtual particals exist because fundamentally, quantum mechanics predicts that vacuum energy can never be exactly zero. The lowest possible energy state is called the zero-point energy and consists of a seething mass of virtual particles that have a brief existence. These virtual particles are part of the perturbation theory of quantum field theory, and as you once said before are never directly observable, but their effects are observable.<br /><br />Here is a good discussion from SCIAM:<br /><blockquote><font class="small">In reply to:</font><hr /><p><b>Are virtual particles really constantly popping in and out of existence? Or are they merely a mathematical bookkeeping device for quantum mechanics? </b><br />J. Fleming <br />Madison, Wisc. <br /> <br />Gordon Kane, director of the Michigan Center for Theoretical Physics at the University of Michigan at Ann Arbor, provides this answer. <br />Virtual particles are indeed real particles. Quantum theory predicts that every particle spends some time as a combination of other particles in all possible ways. These predictions are very well understood and tested. <br /> <br />Quantum mechanics allows, and indeed requires, temporary violations of conservation of energy, so one particle can become a pair of heavier particles (the so-called virtual particles), which quickly rejoin into the original particle as if they had never been there. If that were all that occurred we would still be confident that it was a real effect because it is an intrinsic part of quantum mechanics, which is extremely well tested, and is a complete and tightly woven theory--if any part of it were wrong the whole structure would collapse. <br /><br />But while the virtual</p></blockquote> <div class="Discussion_UserSignature"> <div class="Discussion_UserSignature" align="center"><em><font color="#0000ff">- - - - - - - - - - - - - - - - - - - - - -</font></em> </div><div class="Discussion_UserSignature" align="center"><font color="#0000ff"><em>I really, really, really miss the "first unread post" function.</em></font> </div> </div>

 

[weeman]

If a space is completely empty of all matter and all other physical properties (light, magnetic fields, etc.), then it isn't a vacuum, it's void. So, I guess after all this talk about the misconceptions of the term 'vacuum', we could almost conclude that it is a pointless word. The only way it should be used is as a name for the machine that sits in my closet for picking up dirt off of the carpet <img src="/images/icons/smile.gif" /><br /><br />Space being referred to as a vacuum, by many people, is because there is no air pressure in space. When you're in a spaceship and a tiny hole is punctured or a door opens, everything is sucked out of the ship due to the difference in pressure, not the fact that space is a vacuum. <br /><br />Although, this idea makes for some good Hollywood scenes. I don't remember which one it is, but there is a scene in one of the Alien movies where the alien gets sucked out through a tiny hole in a window. Very narly <img src="/images/icons/smile.gif" /> <div class="Discussion_UserSignature"> <p> </p><p><strong><font color="#ff0000">Techies: We do it in the dark. </font></strong></p><p><font color="#0000ff"><strong>"Put your hand on a stove for a minute and it seems like an hour. Sit with that special girl for an hour and it seems like a minute. That's relativity.</strong><strong>" -Albert Einstein </strong></font></p> </div>

 

[silylene old]

Thanks Borman, I learned something new. <div class="Discussion_UserSignature"> <div class="Discussion_UserSignature" align="center"><em><font color="#0000ff">- - - - - - - - - - - - - - - - - - - - - -</font></em> </div><div class="Discussion_UserSignature" align="center"><font color="#0000ff"><em>I really, really, really miss the "first unread post" function.</em></font> </div> </div>

 

[michaelmozina]

<blockquote><font class="small">In reply to:</font><hr /><p>1. Energy is not being created or destroyed, the quantum particles form as pairs with postive and negative energy, therefore, the amount of energy does not change when these pairs of particles pop into existence.<p><hr /></p></p></blockquote><br /><br />The term "pop into existence" is about as metaphysical of an explanation as it gets. That is fine for mythmaking, but not as fine for science. You might as well say a whole universe just goes "pop into existence" just like Guth did. He called it the "ultimate free lunch" in fact. <br /><br />You're talking about energy. It cannot be created or destroyed. It can interact with other things at a quantum level, but it cannot "pop" into existence. <br /><br />These pseudo-mythological ideas predate our understanding of QM and our understanding that neutrinos exist and have mass. Such energy particles flow through our experiments by the billions. They may interact with one another at a quantum level from time to time and for a brief instant it may *seem* like something "popped" into existence, but nothing of the sort occurred. Energy cannot be created or destroyed. It can change forms, but the first law applies to all energy exchanges.<br /><br />There is no "free lunch". That is a myth that violates known laws of physics. <div class="Discussion_UserSignature"> It seems to be a natural consequence of our points of view to assume that the whole of space is filled with electrons and flying electric ions of all kinds. - Kristian Birkeland </div>

 

[kyle_baron]

A common misconception that amature astronomers believe, is that the beautiful nebulas (ie. Great Orion Nebula) that we look at through our telescopes, must be thick patches of interstellar gas. From The Astronomy Cafe p. 112: "At a density of only a few hundred atoms per cubic centimeter, most nebulas are better than the best vacuums we can make on earth." <div class="Discussion_UserSignature"> <p><font size="4"><strong></strong></font></p> </div>

 

[vogon13]

My favorite misconception?<br /><br />That the existence of the universe needs some kind of explanation, or that its' existence contradicts some conservation law.<br /><br /><br />Temporary excursions from 'perfect normality' are allowed. They just become progressively less likely as they become larger. Wait long enough, (which, by the way, is easy to do if you have an infinite duration or two) and something very much like our universe is guaranteed to pop up sooner or later, and sooner or later, it will dissipate back into the primordial void from which it came.<br /><br />On average, (and remember, I am averaging over an infinite eternity of eons) the mass/energy of our universe is not even a micro-blip.<br /><br /><br /> <div class="Discussion_UserSignature"> <p><font color="#ff0000"><strong>TPTB went to Dallas and all I got was Plucked !!</strong></font></p><p><font color="#339966"><strong>So many people, so few recipes !!</strong></font></p><p><font color="#0000ff"><strong>Let's clean up this stinkhole !!</strong></font> </p> </div>

 

[weeman]

<font color="yellow"> That the existence of the universe needs some kind of explanation, or that its' existence contradicts some conservation law. </font><br /><br />Could this be classified as a misconception? Misconceptions are often found with people who are misinformed of our physical, observable universe. A misconception like the Moon being made of cheese can be scientifically proven wrong when we send astronauts there to do so.<br /><br />Although, I can kind of see what you're saying, Vogon. Personally, I wouldn't say that people striving for answers to the Universe's origin is necessarily a misconeption. We are VERY curious creatures, we want to know the answers to all our mysteries, otherwise we might feel like we're lost, or not in control. <div class="Discussion_UserSignature"> <p> </p><p><strong><font color="#ff0000">Techies: We do it in the dark. </font></strong></p><p><font color="#0000ff"><strong>"Put your hand on a stove for a minute and it seems like an hour. Sit with that special girl for an hour and it seems like a minute. That's relativity.</strong><strong>" -Albert Einstein </strong></font></p> </div>

 

[vogon13]

I just see the current mass/energy/existence of our universe as a trivial excursion from the perfect infinite void that existed <i>before</i>, and that will soon (10^1000 years or so) be re-established when the universe completes it's dissipation.<br /><br />Easy come, easy go . . . .<br /><br /><br /> <div class="Discussion_UserSignature"> <p><font color="#ff0000"><strong>TPTB went to Dallas and all I got was Plucked !!</strong></font></p><p><font color="#339966"><strong>So many people, so few recipes !!</strong></font></p><p><font color="#0000ff"><strong>Let's clean up this stinkhole !!</strong></font> </p> </div>

 

[CalliArcale]

<blockquote><font class="small">In reply to:</font><hr /><p>A common misconception that amature astronomers believe, is that the beautiful nebulas (ie. Great Orion Nebula) that we look at through our telescopes, must be thick patches of interstellar gas.<p><hr /></p></p></blockquote><br /><br />Good one! Yes, that's one of the common ones. A variation is that it would look even more beautiful up close, when in fact most nebulas would be harder to spot up close.<br /><br />A related misconception is that nebulas (and other astronomical sights) should look as good in telescopes as they do in the photos published in calendars and posters and things. This is related to the popular myth of "true color images". (There really isn't such a thing.) <div class="Discussion_UserSignature"> <p> </p><p><font color="#666699"><em>"People assume that time is a strict progression of cause to effect, but actually from a non-linear, non-subjective viewpoint it's more like a big ball of wibbly wobbly . . . timey wimey . . . stuff."</em>  -- The Tenth Doctor, "Blink"</font></p> </div>