bertusgeert 1 #1 January 7, 2011 I'm sure, with the use of wide lenses, many of you have encountered similar comments. Upon the posting of a picture of a friend, paragliding at what I would guess is 3000-4000 AGL, someone commented: "wow! you're so high up you can see the curve of the earth!" As I knew, this was due to the camera lens. But it got me thinking, and google doesn't provide a consistent answer either. So, at what point can you begin to see an obvious curve as you leave the globe for space above? I'm not talking about seeing a ship's mast disappear, I'm talking purely "putting a straight edge ruler to the horizon". Can you see it from a commercial airliner? a Blackbird? or do you have to be in a space shuttle? --------------------------------------------- As jy dom is moet jy bloei! Quote Share this post Link to post Share on other sites
nigel99 466 #2 January 7, 2011 QuoteI'm sure, with the use of wide lenses, many of you have encountered similar comments. Upon the posting of a picture of a friend, paragliding at what I would guess is 3000-4000 AGL, someone commented: "wow! you're so high up you can see the curve of the earth!" As I knew, this was due to the camera lens. But it got me thinking, and google doesn't provide a consistent answer either. So, at what point can you begin to see an obvious curve as you leave the globe for space above? I'm not talking about seeing a ship's mast disappear, I'm talking purely "putting a straight edge ruler to the horizon". Can you see it from a commercial airliner? a Blackbird? or do you have to be in a space shuttle? I am convinced that I can see it when I fly commercially so 30-36k. However I have flown at 55-60 000 feet and it is definitely visible then.Experienced jumper - someone who has made mistakes more often than I have and lived. Quote Share this post Link to post Share on other sites
warpedskydiver 0 #3 January 7, 2011 It's really about perception. If we can distinguish a straight line from a curved one, no matter how slight we can then distinguish the curvature of the earth. Quote Share this post Link to post Share on other sites
petejones45 0 #4 January 7, 2011 5000kLook out for the freefly team, Smelly Peppers. Once we get a couple years more experience we will be a force to be reckoned with in the near future! BLUES! Quote Share this post Link to post Share on other sites
bertusgeert 1 #5 January 7, 2011 QuoteIt's really about perception. If we can distinguish a straight line from a curved one, no matter how slight we can then distinguish the curvature of the earth. I guess you're right. The scientific answer, correct me if I'm wrong, is that as soon as you leave sea level, there will be minute differences between a straight line and the horizon. Only from absolute sea level will it be straight. So a man standing up in a boat in the ocean, with really really good eyes, should be able to see it. From there it's just a matter of perspective and judgment whether you actually could distinguish it, or you just think you can. --------------------------------------------- As jy dom is moet jy bloei! Quote Share this post Link to post Share on other sites
Andy9o8 2 #6 January 7, 2011 QuoteIt's really about perception. If we can distinguish a straight line from a curved one, no matter how slight we can then distinguish the curvature of the earth. Good point. For example, Superman, standing on a ladder, looking out over the ocean, could see it. Batman, however, could not. Quote Share this post Link to post Share on other sites
Airviking 0 #7 January 7, 2011 Earth? Curved? Then why don't we fall off?!I believe you have my stapler. Quote Share this post Link to post Share on other sites
nigel99 466 #8 January 7, 2011 Quote It's really about perception. If we can distinguish a straight line from a curved one, no matter how slight we can then distinguish the curvature of the earth. http://www.cs.berkeley.edu/~karthik/pics/2003-10-2-Miami/1-FlightToMiami/web/html/start.html Attached photo is 55 to 60 000 foot. Far more interesting though is the leading edge of the sexiest commercial airliner to ever flyI can't see much difference personally.Experienced jumper - someone who has made mistakes more often than I have and lived. Quote Share this post Link to post Share on other sites
cocheese 0 #9 January 7, 2011 I heard you could see it good from the Concord SST. 50,000 feet? Quote Share this post Link to post Share on other sites
warpedskydiver 0 #10 January 7, 2011 When you are driving, would you notice a curve that has a radius of 30 miles? Yes you would if you were going fast enough. Quote Share this post Link to post Share on other sites
bertusgeert 1 #11 January 7, 2011 QuoteWhen you are driving, would you notice a curve that has a radius of 30 miles? Yes you would if you were going fast enough. I heard somewhere (but who knows if it's true) that a SR-71 flying at top speed will take 15 minutes to make a 360 degree turn. What I do know is true is this: it flew from LA to DC (2300 miles) at a speed of 2,144 mph in 64 minutes, and from St. Louis to Cincinnati in 9 minutes --------------------------------------------- As jy dom is moet jy bloei! Quote Share this post Link to post Share on other sites
brucet7 0 #12 January 7, 2011 A little off topic, but as one flies to Alaska this time of year the light from the other side of the world if visible during the red eye flights. Take off from Seattle in the dark, see a dawn like glow, and land in the dark in Anchorage. Kind of cool.POPS #10623; SOS #1672 Quote Share this post Link to post Share on other sites
theonlyski 8 #13 January 7, 2011 Quote5000k 5 million feet?"I may be a dirty pirate hooker...but I'm not about to go stand on the corner." iluvtofly DPH -7, TDS 578, Muff 5153, SCR 14890 I'm an asshole, and I approve this message Quote Share this post Link to post Share on other sites
nigel99 466 #14 January 7, 2011 Quote Quote 5000k 5 million feet? InchesExperienced jumper - someone who has made mistakes more often than I have and lived. Quote Share this post Link to post Share on other sites
Airviking 0 #15 January 7, 2011 Alright, since this topic is officially hijacked, I need to ask this: One would assume that what we call "Gravitational force" is actually gravitational force minus the centrifugal force caused by the earth's rotation. So how come the pull isn't higher at the poles, where there is no centrifugal force, and lowest at the equator?I believe you have my stapler. Quote Share this post Link to post Share on other sites
billvon 2,989 #16 January 7, 2011 >One would assume that what we call "Gravitational force" is actually >gravitational force minus the centrifugal force caused by the earth's >rotation. So how come the pull isn't higher at the poles, where there is no >centrifugal force, and lowest at the equator? It is. But it's a small effect, less than .5%. So a 200 lb person becomes 199 lbs from that effect alone, not really enough to notice. Also, gravity isn't uniform; mass concentrations make people heavier in some places than others, so the effect may be masked. Probably the biggest effect of the spin is that the planet bulges at the equator since gravity is slightly lower there. A nice side effect of the spin is that it's a lot easier to launch spacecraft from near the equator if you launch them towards the east, since they start with that ~1000 mph from the spin. Quote Share this post Link to post Share on other sites
Airviking 0 #17 January 7, 2011 This forum's better than Google! I believe you have my stapler. Quote Share this post Link to post Share on other sites
nigel99 466 #18 January 7, 2011 http://planetearth.nerc.ac.uk/news/story.aspx?id=763 European Space Agency has a project related to this. It is really cool until 6-12 months ago I didn't realise how much variation there is.Experienced jumper - someone who has made mistakes more often than I have and lived. Quote Share this post Link to post Share on other sites
shropshire 0 #19 January 7, 2011 Quote Quote Quote 5000k 5 million feet? Inches 416,666.667 feet then (.)Y(.) Chivalry is not dead; it only sleeps for want of work to do. - Jerome K Jerome Quote Share this post Link to post Share on other sites
bertusgeert 1 #20 January 7, 2011 Quote This forum's better than Google! That is, in fact, the only thing I use it for. You get much better, higher quality, more concise answers here than google or any wiki, and a bunch of sometimes lame, sometime hilarious jokes inbetween. Better than Google by a 416,666.667 feet --------------------------------------------- As jy dom is moet jy bloei! Quote Share this post Link to post Share on other sites
cocheese 0 #21 January 7, 2011 So like, a Saturn V launch is actually messin with the Earth's mojo? Quote Share this post Link to post Share on other sites
billvon 2,989 #22 January 7, 2011 >So like, a Saturn V launch is actually messin with the Earth's mojo? For the first few minutes, it is actually slowing the Earth down! We can compensate for this by having everyone in the US take an elevator to the bottom floor the instant the launch begins. Quote Share this post Link to post Share on other sites
cocheese 0 #23 January 7, 2011 I heard if everyone in China jumped off their chair at the same time, it would create giant a tidal wave. We better be careful. Quote Share this post Link to post Share on other sites
JohnMitchell 16 #24 January 7, 2011 Quote I heard somewhere (but who knows if it's true) that a SR-71 flying at top speed will take 15 minutes to make a 360 degree turn. I would guess that's about right. I used to work the SR-71's over Idaho, Washington and Oregon. I never saw them do a 360, but even a 60 degree turn took several counties. Quote Share this post Link to post Share on other sites
quade 4 #25 January 7, 2011 QuoteGood point. For example, Superman, standing on a ladder, looking out over the ocean, could see it. Batman, however, could not. Well, few of us are Superman and only slightly fewer of us have the eyesight required to judge that curve until we got much higher up. A batch of us have at least a small amount of astigmatism which means we can't even tell if a line is straight on a good day. Oh, we "think" we can, but the reality of the situation is different, which is why we have a tendency to use things like levels when hanging pictures rather than just eyeballing it. Lastly, our eyes are just terrible at being reliable judges of things like straight lines in general. http://www.123opticalillusions.com/pages/opticalillusions11.phpquade - The World's Most Boring Skydiver Quote Share this post Link to post Share on other sites
