Common misconceptions in Astronomy?

[weeman]

Anyone have any common misconceptions that most people have when it comes to Astronomy?<br /><br />One thing that I learned in my most recent Astronomy class are the dynamics of achieving orbit. When the astronauts are in orbit around Earth, they are not weightless due to lack of gravity. The astronauts appear weightless because they are in a state of free-fall; basically, the astronauts (and space shuttle), are falling around the planet. The Shuttle typically has a orbital velocity of about 17,000-18,000mph. <br /><br />Picture this, you are standing on a platform that extends from the surface of Earth all the way up into space to the point of orbit (the Shuttle's average distance from Earth's surface). If you ran off this platform you would land farther from the base depending on how fast you ran off the top. So, you run a little bit faster off the top of the platform each time you make a jump. With greater speed each time, you land farther and farther from the platform's base. Hypothetically, if you could run fast enough off the platform, you would fall around the Earth, and land right back on top of the platform, after making a full orbit around Earth. <br /><br />So, the astronauts aren't weightless due to lack of gravity, they are just going for a VERY expensive skydiving trip <img src="/images/icons/wink.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>

 

[alokmohan]

Another misconception is 4th dimesion.And infinite gravity of black hole.We should know that time is the 4th dimension.And there is nothing called hyperspce.AT least we three dimesioners cannot perceive it.Singularity is talked of ,very few know it.

 

[5billionyearslater]

Probably the biggest misconception of all is the Big Bang. Some imagine this big explosion at a specific place in "space".<br /><br />I also think distance and time are often mis-interpreted. Everyone knows the universe is big, but few can really understand just how big it is. Time is a big issue too which is why it occupies a dimension. 100 years to us human is more than a lifetime, but in cosmology (and/or astronomy) It's little more than a billion billionth of a second.<br /><br />Another misconception that really hack me off is people who think looking for life in the universe means looking for other humans/intellegent beings. Life means anything from microbial all the way upto intellegent lifeforms. SETI of course looks for the intellegent stuff and that's all it can do. Microbial life, which is certainly going to be very common in the universe and certainly won't be transmitting radio waves. So, you non-believers, there is tons more lie in the universe, we just haven't found it yet (for numerous reasons) but remember the universe is inconciveably big (see second misconception).<br /><br />....another?.... Ok, why not: Practical Astronomy. Practical Astronomy is just that - practical and not everything you will see in the night sky through a telescope will look as amazing as Saturn or Jupiter! But, do they? The main difference between the casual observer and the astronomer (amateur or otherwise) is the passion for the sky. Sure plantetary oberving is fun and is an awe-inspiring sight but there is so much more to observing than looking at and studying planets. That faint patch of light you can see is a nebula where new stars are being born billions and billions of miles away - and YOU CAN SEE IT! with just a light-gathering device (no electronics or complex technology) Just optics - bloddy hell, that is amazing don't you think!<br /><br />I really could go on forever, but let's see what others' say.

 

[arkady]

The one I encounter the most is thinking of a light-year as a timespan, and not a distance. <div class="Discussion_UserSignature"> "<font color="#0000ff"><em>The choice is the Universe, or nothing</em> ... </font>" - H.G Wells </div>

 

[logicize]

Hmmm, I thought a light year was a year in which you weighed less. <img src="/images/icons/smile.gif" />

 

[heyscottie]

1) Many people seem to think that Polaris is the brightest star in the sky, when it is in fact an unremarkable 2nd magnitude star.<br /><br />2) Black holes as "sucking machines". Ask people what would happen if the sun was replaced by a black hole with the same mass, and they'll tell you that the planets will get sucked in.<br /><br />3) The Earth is closer to the Sun in the summer, which is what causes seasons. Or, alternatively, seasons are caused by the tilt, but it is cold in the winter because that hemisphere is tilted AWAY from the sun, and is therefore farther away from it.

 

[derekmcd]

Double post. <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>

 

[derekmcd]

Spaceships are heated up during re-entry due to friction with the atmosphere. <br /><br />What actually happens is the leading edges of the craft is compressing the air in front creating high pressure which, in-turn, heats the air.<br /><br />The "no gravity in space" misconception is my favorite, though. Amazing how often you can catch people on that one. <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>

 

[silylene old]

That people would "explode" if they encountered a vacuum without a pressure suit.<br /><br />That candles can't burn in "zero gravity".<br /><br />That you could hear sounds or explosions in a vacuum.<br /><br />That a moving mass has inertia in a weightless enivronment.<br /><br />That the surface of Pluto is dark because the sun is so far away.<br /><br />That comets and asteroids approaching the Earth on a collision path could be diverted at the last moment by a nuke or two.<br /><br /> <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>

 

[derekmcd]

The moon is, in fact, not cheese. <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>

 

[halcyondays]

People who think that the moon has a dark side.

 

[weeman]

The Moon isn't made of cheese!? But Wallace and Gromit went to the moon and it was most definitely made of cheese <img src="/images/icons/wink.gif" /> <br /><br /> <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>

 

[space_coops]

You always hear people ask what happened before the Big Bang. Well, nothing did. Time/space started with the Big Bang. An explosion OF space.

 

[vogon13]

Many people buy into the time zone hoax.<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>

 

[vandivx]

<font color="orange">That a moving mass has inertia in a weightless enivronment. </font><br /><br />I guess I am dense, can you explain that to me how it is not so, maybe that wine I drank is taking fatal effect <img src="/images/icons/wink.gif" /><br /><br />my personal and private favorite is not from astronomy field but physics, it when physicists talk about electron being charged and they wonder how can it hold together when negative charges repel and with serious face they talk about bootstrap forces... <br /><br />mind you, its not ordinary folk that fall prey to this misconception but professional physicists none the less, that makes it all the more piquant <br /><br />vanDivX <div class="Discussion_UserSignature"> </div>

 

[l3p3r]

Yeah that one stood out at me too, can you explain further? <div class="Discussion_UserSignature"> </div>

 

[qso1]

Excellent explanation.<br /><br />I recall trying to figure out what the 4th dimension should look like at one time. Gave that up when I found out it was a description of space time more or less. <div class="Discussion_UserSignature"> <p><strong>My borrowed quote for the time being:</strong></p><p><em>There are three kinds of people in life. Those who make it happen, those who watch it happen...and those who do not know what happened.</em></p> </div>

 

[qso1]

logicize:<br />Hmmm, I thought a light year was a year in which you weighed less.<br /><br />Me:<br />I thought it was light beer, now I'm really confused LOL. <div class="Discussion_UserSignature"> <p><strong>My borrowed quote for the time being:</strong></p><p><em>There are three kinds of people in life. Those who make it happen, those who watch it happen...and those who do not know what happened.</em></p> </div>

 

[heyscottie]

I think silylene meant to say "That a moving mass has NO inertia in a weightless environment".<br /><br />Another one: That Bode's law is a law.<br />

 

[alokmohan]

Poor Bode.You are remembered even today.Uranus was disovered by your grace. In 1766, a German mathematician named Johann D. Titius developed an arithmetical relationship between the approximate distances of the planets from the Sun. Although it wasn't until 1772, when it was published by a man known as Johann E. Bode that it attracted attention. Today it carries his name and it's known as Bodes' Law. <br /><br /> The law states the relationship between the planets can be expressed by adding 0.4 to each term in the progression - 0 , 0.3 , 0.6 , 1.2 , 2.4 , 4.8 , 9.6 , etc. ( in which each number is double the preceding one). Each term in the sequence is given in astronomical units, or A.U. ( 1 A.U. = 93 million miles, the mean radius of Earths distance from the Sun).9 <br /><br /> This is shown in the table below. <br /><br /><br />Table 1 Distance Mercury Venus Earth Mars Asteroid Belt Jupiter Saturn Uranus Neptune Pluto <br />Predicted 0.4<br /> 0.7<br /> 1<br /> 1.6<br /> 2.8<br /> 5.2<br /> 10<br /> 19.6<br /> 38.8<br /> 78<br /> <br />Actual 0.39<br /> 0.72<br /> 1<br /> 1.52<br /> 2.1-3.5<br /> 5.2<br /> 9.5<br /> 19.2<br /> 30.1<br /> 39.6<br /> <br /><br /><br /> At the time of the discovery of Bodes' Law, only six planets were known and the numbers closely fitted the observable facts with over 95% accuracy. However, as you can tell, with the discovery of the planets Neptune and Pluto, it seemed to bring the fatal blow to this theory and today is generally regarded as being merely a coincidence. <br /><br /> However, if you select the last planet that fits this law, Uranus discovered in 1781 with its mean radius from the sun at 19.2 A.U. or approximately 1,785,600,000 miles. Followed by the planet Neptune at 30.1 A.U. ( 2,799,300,000 miles ) and Pluto at 39.6 A.U. ( 3,682,800,000- miles). You can tell there is still an arithmetical ( harmonic ) series at work. Each planet starting from Saturn, with a mean distance from the Sun of 9.5 A.U. ( 886,2

 

[silylene old]

<font color="yellow">I think silylene meant to say "That a moving mass has NO inertia in a weightless environment". </font><br /><br />I meant exactly what I said: "That a moving mass has inertia in a weightless environment".<br /><br />Most people do know that a stationary mass has inertia (which is the point you were making). So I cannot say this is a common misperception.<br /><br />Definition: Inertia is the tendency of an object to resist a change in motion; stated another way, the tendency of a body to resist acceleration; stated another way, the tendency of a body at rest to remain at rest or of a body in straight line motion to stay in motion <font color="yellow">in a straight line</font>unless acted on by an outside force. The meaning of a body's inertia therefore is altered from the original meaning as "a tendency to maintain momentum" to a description of the measure of how difficult it is to change the momentum of a body.<br /><br />A moving body still resists additional acceleration along it's vector of travel; and a moving body still resists acceleration in a vector that is at any other angle to its motion (to either turn it, or to slow it). Hence a moving body still has inertia! That inertia hasn't "disappeared" is the common misperception...most people think a moving body has no inertia, but it does have inertia to any re-application of a force. <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]

clearly you know what you talk about as far as inertia goes but still that sentence should have included the 'NO' in it, read again the thread, those sentences were meant to state people's 'wrong beliefs' and not 'what they do not know'<br /><br />what must also confuse people is when they hear about that anomalous acceleration of the Pioneers, even newpaper and magazine articles for laymen talk about acceleration and rarely they mention what is really meant - that the probes are really slowing down or in laymen logic - they are decelerating, I believe that outside academic journals one shouldn't use the term acceleration in that way<br /><br />there is also widespread belief that black hole is a region in space empty of matter<br /><br />vanDivX <div class="Discussion_UserSignature"> </div>

 

[vandivx]

<font color="orange">Picture this, you are standing on a platform...</font><br /><br />you know that the first man to realize and describe it in similar fashion was Newton?<br /><br />I think the problem is that people who had some basic physics education didn't give it much thought, they just learned it by rot because it was required of them at some point, those without such education today still don't even know that things around us gravitate among themselves, that is they imagine that it is only the Earth which attracts these things but they themselves do not attract, test it on somebody and you will see how many think that or at least are unsure if things like coffee cups gravitationally attract other things <br /><br />vanDivX <div class="Discussion_UserSignature"> </div>

 

[nevyn]

Is that proved or even demonstrated? Have you ever seen a coffer cup, or anything less than a planet, attract something else?<br /><br />Be careful not to confuse theory with fact. Even if that's what the professionals do.<br /><br />I think the biggest misconception, because even the 'great minds of our time' belive it, is that comets and asteroids are 'dirty snow balls'. 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.<br /><br />Even after we smashed a lump of copper into one and nothing happened the way their models thought it would (and other models had predicted exactly what happened, before the event). They didn't find any water or ice and still they think of a snow ball.<br /><br />Even after comets have lit up again while travelling away from the sun. They still stick to their snow ball models.<br /><br />"The biggest misconceptions are those being stated as fact!"

 

[ianke]

Read the "asteroid: 90 antiope" thread here in SS&A.<br /><br />It shows 2 asteroids orbiting each other. That is smaller than planets. <div class="Discussion_UserSignature"> </div>