Common misconceptions in Astronomy?

[derekmcd]

"<i>s that proved or even demonstrated?</i><br /><br />Yes.<br /><br />"<i>Have you ever seen a coffer cup, or anything less than a planet, attract something else?</i><br /><br />Yes.<br /><br />"<i>Be careful not to confuse theory with fact. Even if that's what the professionals do.</i>"<br /><br />Pros understand, quite well, the differences of theory and fact. It's the rest of us that confuse the two.<br /><br />"<i>I think the biggest misconception, because even the 'great minds of our time' belive it, is that comets and asteroids are 'dirty snow balls'.</i>"<br /><br />Comets... yes. Atsteroid are a completely different story.<br /><br />"<i>Even after a so called 'snow ball' slammed into a 'gas giant' planet (Jupiter, shoe-maker/levy) and produced a great explosion visible from Earth.</i>"<br /><br />Explosion is a relative term. Some might call it a plume. Even so... A snowball with enough mass will distrupt an atmosphere. Jupiter's atmosphere is quite dense. An object penetrating Jupiter's atmosphere at such velocities (including something with a light desity) will still produce spectacular results.<br /><br />i'll stop here...<br /><br /><br /><br /><br /><br /> <div class="Discussion_UserSignature"> <div> </div><br /><div><span style="color:#0000ff" class="Apple-style-span">"If something's hard to do, then it's not worth doing." - Homer Simpson</span></div> </div>

 

[brellis]

Regarding objects smaller than a planet gravitationally attracting other small objects, don't we have some examples orbiting earth in the population of pieces of manmade space junk? Do larger pieces gravitationally affect the trajectories of smaller ones? <div class="Discussion_UserSignature"> <p><font size="2" color="#ff0000"><em><strong>I'm a recovering optimist - things could be better.</strong></em></font> </p> </div>

 

[heyscottie]

Anything smaller than a planet demonstrating attraction?<br /><br />Well, there is always the Cavendish experiment, which demonstrated attraction between large metallic spheres in a lab and experimentally measured the constant G (though its intent was to measure the density of the earth).<br /><br />Large metallic spheres in a lab are significantly smaller than a planet.<br /><br />And, by the way, Deep Impact did find ice. There was just less ice and more dust than was expected. Not enough of a difference, IIRC, to completely rewrite theories on Comet formation and composition. But, to be fair, analysis of that data is ongoing.

 

[CalliArcale]

<blockquote><font class="small">In reply to:</font><hr /><p>Regarding objects smaller than a planet gravitationally attracting other small objects, don't we have some examples orbiting earth in the population of pieces of manmade space junk? Do larger pieces gravitationally affect the trajectories of smaller ones?<p><hr /></p></p></blockquote><br /><br />One problem there is that such objects are usually also affected by drag from the very thin upper atmosphere. This can (and often does) swamp other effects.<br /><br />However, just as a random geeky factoid, the sci-fi series "Babylon 5" made reference to the gravitational field of the station itself in one episode -- not anything generated technologically, but just a consequence of its mass -- when a bit character was spaced and it was realized that the corpse would have to still be quite close by, orbiting the station. They later received a letter from a scientist who worked out a rough estimation of the station's mass and concluded that they were correct; it had sufficient mass to retain this gruesome satellite. <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>

 

[yevaud]

Smaller than a planet, but in an observable, solar sense?<br /><br />Link <div class="Discussion_UserSignature"> <p><em>Differential Diagnosis:  </em>"<strong><em>I am both amused and annoyed that you think I should be less stubborn than you are</em></strong>."<br /> </p> </div>

 

[CalliArcale]

Some my favorite misconceptions:<br /><br />* You can't see the Moon during the day. I am shocked at this one; obviously a lot of people never even look at the sky.<br /><br />* The stars are fixed. (I was surprised to encounter someone recently who thought that the observations of stars orbiting the center of the Milky Way were odd because they were moving at all. I explained that it was the speed that made them unusual; most stars don't travel that fast. She was quite surprised to learn that other stars do move.)<br /><br />* Constellations would look backwards if seen from the other side.<br /><br />* Hubble's pictures are better because it's closer to the stars and planets.<br /><br />* One that I encountered just once was this one: that the aurora borealis are reflections off ice crystals that can occur very low down, close enough to touch. I think he was just confusing aurora borealis and other phenomena such as parhelia, though. <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>

 

[newmoon]

One common misconception is that all elements heavier than iron arose in supernovae.

 

[yevaud]

True. They arose from three different mechanisms: From Nucleosynthesis during the Big Bang, continual Stellar Nucleosynthesis, and from the periodic SN. <div class="Discussion_UserSignature"> <p><em>Differential Diagnosis:  </em>"<strong><em>I am both amused and annoyed that you think I should be less stubborn than you are</em></strong>."<br /> </p> </div>

 

[MeteorWayne]

Yev,<br />Did you mean to say that elements heavier than Li7 occurred from Nucleosythesis during the big bang? That doesn't match what I think I know <img src="/images/icons/smile.gif" /><br /><br />I was not aware of that.<br /><br />Can ya educate me before the big Noreaster? <div class="Discussion_UserSignature"> <p><font color="#000080"><em><font color="#000000">But the Krell forgot one thing John. Monsters. Monsters from the Id.</font></em> </font></p><p><font color="#000080">I really, really, really, really miss the "first unread post" function</font><font color="#000080"> </font></p> </div>

 

[silylene old]

Actually some elements (in most cases very minor amounts) arose through processes other than nucleosynthesis during the Big Bang, stellar nucleosynthesis or in supernovas. There are three additional mechanisms, described below. (Recopying from the "copper" thread in this forum<br /><br />""In fact everything other than Hydrogen, Helium and Lithium all came from star processing." <br /><br />There are two exceptions to this statement: beryllium and boron, which arose via spallation.""<br /><br />Many other exceptions to this are certain daughter isotopes subsequently formed by decaying of the primary unstable isotope (which were formed within a star which went nova or supernova), long after the supernova was vor and gone. For example, supernovas spread Al-26 isotope widely into space....over the next few hundred thousand years, this decayed to form Mg-26. Mn-53 formed within and spread by supernovas gradually decayed to form the supply of Cr-53. Etc, etc.<br /><br />Spallation, as mentioned above is also an important process which forms elements in interstellar space. From Wikipedia:<br /><blockquote><font class="small">In reply to:</font><hr /><p>When the heavy nuclei components of primary cosmic rays, namely the carbon and oxygen nuclei, collide with interstellar matter, they break up into lighter nuclei (in a process termed cosmic ray spallation), into lithium, beryllium and boron. It is found that the energy spectra of Li, Be and B falls off somewhat steeper than that of carbon or oxygen, indicating that less cosmic ray spallation occurs for the higher energy nuclei presumably due to their escape from the galactic magnetic field. <font color="yellow">Spallation is also responsible for the abundances of Sc, Ti, V and Mn elements</font>in cosmic rays, which are produced by collisions of Fe and Ni nuclei with interstellar matter...<p><hr /></p></p></blockquote><br /><br />Finally, I want to point out yet another mechanism for forming unique isotopes: Cosmic rays inte <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>

 

[yevaud]

Well, I mentioned the big three, but yes, those as well. <div class="Discussion_UserSignature"> <p><em>Differential Diagnosis:  </em>"<strong><em>I am both amused and annoyed that you think I should be less stubborn than you are</em></strong>."<br /> </p> </div>

 

[yevaud]

http://astro.berkeley.edu/~mwhite/darkmatter/bbn.html <br /><br />Curiously, it doesn't state it, but Astrophysicists understand that many elements were created during BB Nucleosynthesis, and thus "frozen in," so to speak. <div class="Discussion_UserSignature"> <p><em>Differential Diagnosis:  </em>"<strong><em>I am both amused and annoyed that you think I should be less stubborn than you are</em></strong>."<br /> </p> </div>

 

[bobw]

<font color="yellow">Have you ever seen a coffer cup, or anything less than a planet, attract something else?<br />Be careful not to confuse theory with fact. Even if that's what the professionals do.</font><br /><br />I have been keeping tabs on gravity experiments which use very small masses at close distances. Masses much smaller than a coffee cup. This picture is from the link below which points to several experiments if anybody is interested, other cool pictures too. Here's what the professionals do.<br /><br />Gravity at the 100 Micron Scale and Below. <br />http://www-conf.slac.stanford.edu/ssi/2005/lec_notes/Long/long.pdf <div class="Discussion_UserSignature"> </div>

 

[alokmohan]

there is also widespread belief that black hole is a region in space empty of matter <br /><br />vanDivX I in fact black holes are very massive.Stellar black holes have at least three solar masses.It contiues upto tens of solar mass.Then starts supermassive black holes which may be million solar masses to billion solar masses.One misconception is that black hole has been seen.The whole matter is speculative and black holes most probably exist.<br />

 

[silylene old]

Another common misperception that a vacuum is empty.<br /><br />It isn't. In fact a vacuum is teeming with virtual particles that constantly wink in and out of existence. Hence the origin of the Casimir effect (which is experimentally verified). <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>

 

[kyle_baron]

<font color="yellow"><br />Another common misperception that a vacuum is empty. <br /><br />It isn't. In fact a vacuum is teeming with virtual particles that constantly wink in and out of existence.</font><br /><br />For all PRACTICLE purposes, the vacuum is empty. Virtual particles can only be seen with the light energy added to the existing empty space. However, on the macro/cosmic level , virtual particles MIGHT act as the dark energy that is accelerating the expansion of the universe. <div class="Discussion_UserSignature"> <p><font size="4"><strong></strong></font></p> </div>

 

[michaelmozina]

For all practical purposes the vacuum is not empty, it is full of plasma, and plasma is an excellent conductor of electricity. <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>

 

[silylene old]

<font color="yellow">For all PRACTICLE purposes, the vacuum is empty. Virtual particles can only be seen with the light energy added to the existing empty space.</font><br /><br />I am correct.<br /><br />Here are some references: 1, 2, <font color="yellow">It is not empty. Even when all matter and heat radiation have been removed from a region of space, the vacuum of classical physics remains filled with a distinctive pattern of electromagnetic fields</font>/a>, <a target="_blank" href="http://www.ldolphin.org/zpe.html">4.<br /><br />I could continue onwards with hundreds more references, and articles by respected phyicists. <br /><br />Even if a volume is devoid of matter, and devoid of heat and light, quantum level fluctaions in electromagnetic fields cause virtual particles to pop in and out of existance. This is the origin of the Casimir effect, which has been demonstrated experimentally several times. Some of these experiments are very cool. <br /><br />The Casimir effect can be measured in the absence of light, showing that it is possible to observe the effects of these virtual particles without having to add light energy.</a> <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>

 

[silylene old]

<font color="yellow">For all practical purposes the vacuum is not empty, it is full of plasma, and plasma is an excellent conductor of electricity. </font><br /><br />Plasma is ionized gas, a form of matter. Plasmas can have a measurable pressure, even if they are rarified. I work with plasmas, and we measure the pressure of them all the time. A plasma is not a vacuum. <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]

My point however (maybe we're talking about different issues by the way) is that "space" as we understand it, is filled with what Birkeland described in this way:<br /><br /><blockquote><font class="small">In reply to:</font><hr /><p>"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. We have assumed that each stellar system in evolutions throws off electric corpuscles into space. It does not seem unreasonable therefore to think that the greater part of the material masses in the universe is found, not in the solar systems or nebulae, but in "empty" space.<p><hr /></p></p></blockquote><br /><br />Today it is believed that normal (visible) matter only makes up approximately 4% of the mass/energy of the universe, so it would seem that he was correct in that assessment of the makeup of "space". <br /><br />Space and "vacuums" here on earth are of course filled with neutrinos and subatomic energy galore. There is no such thing as "empty" space. What we understand as "space" is really not anything like a pure (empty) vacuum. <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>

 

[SpeedFreek]

The problem here is that a vacuum is defined as being empty. Physicists often use this definition which is in fact really a <i> perfect </i> vacuum, when discussing the ideal test results that would be obtained in a vacuum.<br /><br />The vacuum of space or the best vacuum we can make in a laboratory are both defined as <i> partial </i> vacuum.<br /><br />So, a vacuum <i> is </i> empty, but doesn't ever actually occur. <div class="Discussion_UserSignature"> <p><font color="#ff0000">_______________________________________________<br /></font><font size="2"><em>SpeedFreek</em></font> </p> </div>

 

[michaelmozina]

I think we're both on the same page now.<br /><br />The key point from my perspective is that our universe is filled with all sorts of things, including plasma, neutrinos, photons, etc. The plasma in particular plays a highly significant role in plasma cosmology theory. <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>

 

[silylene old]

<font color="yellow">The problem here is that a vacuum is defined as being empty. Physicists often use this definition which is in fact really a perfect vacuum, when discussing the ideal test results that would be obtained in a vacuum. </font><br /><br />In fact, you are mistaken and mired in old terminology. You are using the 19th century definition of a vacuum, back before quantum mechanics was understood, and back before the Casimir effect was predicted, and then verified. (an analogy is that you are defining motion according to Newton's understanding, before the refinements and complexity of relativity were understood).<br /><br />Physicists now understand that a vacuum is not empty, but contains virtual particles which pop in and out of existance. <br /><br />Perhaps the word you are looking for is a "void", a mythical volume of space-time entirely free of matter, energy, dark matter, dark energy and any kind of virtual particle produced by random fluctuations in electromagnetic fields. Entirely mythical, sadly. <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>

 

[silylene old]

<font color="yellow">My point however (maybe we're talking about different issues by the way) is that "space" as we understand it, is filled with what Birkeland described in this way: </font><br /><br />Actually I am not talking about space, or the vacuum of space, or dark matter, or dark energy. I am not talking about electrons and "flying electric ions", which are a form of matter.<br /><br />I am talking about the modern definition of a "vacuum", period. Modern physics now understands that a vacuum is filled with virtual particles popping in and out of existance. <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>

 

[vandivx]

vacuum is a vacuum is a vacuum... if its filled with something than you should stop talking about vacuum<br /><br />but that's 'modern physics' for you<br /><br />vanDivX <div class="Discussion_UserSignature"> </div>