AndromedasWake
Member
Recently, I was sent a message by YouTube user thelambreturn and, perhaps foolishly, believed it to be a sincere astronomy related question. As a result, I responded but having seen a comment from him on my channel mentioning the bacterial flagellum, realised what I was dealing with. Still, his first response seemed genuine, so I continued. After one more he got himself quite wound up and started preaching. See for yourself.
Messages begin.
Then, shortly afterwards....
Messages end.
On reflection, I made a couple of mistakes that could cause potential confusion. Most notably, I told him the solar disk changes in apparent size throughout the year, but not from one day to the next, which is contradictory. It is merely not noticeable from day to day, and to the unaided eye will always appear about 0.5 degrees. This is what I meant to imply, but could have phrased it better. I am still considering how to respond, and will update the post (after this paragraph) with any further messages.
Messages begin.
thelambreturn said:ok explain me why,the sun his always a different size?
AndromedasWake said:I'm not quite sure what you're asking. The apparent size of the solar disk changes periodically over the course of a year, because our orbit around the Sun brings us closer to it during the Northern Hemisphere Winter. We are closer to the Sun now and will be furthest from it in 6 months. Although the change is not very great, it is the reason we see annular eclipses (like the one recently seen in Northern Africa and India). When our orbit brings us closest to the Sun, and the Moon's orbit takes it furthest from the Earth (remember, neither of these orbits is perfectly circular), the disk of the New Moon cannot cover the disk of the Sun at totality. The correct word is annularity, because we still see the Sun's limb and some of its face as an annular shape.
You may be alluding to the periodicity of the Sun's diameter. This is a pretty controversial topic, since previous measurement's have been shown to be wrought with experimental error giving us a very poor historical record of the variations, but we expect the variation nonetheless because the Sun, like all stars, varies periodically in its luminosity. We expect the more active Sun to inflate somewhat, because the increased radiation pressure slightly outmuscles the gravity holding the star together. Of course, over long periods the two are effectively balanced, but on short periods they are continuously fighting. This leads to a small variation in size, though it is difficult to measure precisely. Sofia et al. published an interesting summary of the problem in 2005, which can be found here: http://is.gd/6J89n
Hope that helps!
-TK
thelambreturn said:my question his,if we roll on a space time continium,around the sun,like hellicentrism say,why then the sun his not the same size at each time of the day,why we have a sun 3 time bigger one day at 3 ,the day after 3 time smaller,and why they say that at the speed of light time stop,and in the same theory they say it take 8,2 minutes to light to travel sun to earth!
Then, shortly afterwards....
thelambreturn said:hmmm maybe its 8,3,but what do we know since WE,i mean you and me,never been to space,and test all this,they (THEY) can say waterver what they want to say,how could WE be sure.
AndromedasWake said:I have formal scientific training in astrophysics, which is the study of the motions of celestial bodies and the forces which govern those motions. In that sense, I am one of "them". You do not need to go into space to calculate the distance to the Sun, the mathematical proof is very simple. The ancient Greeks were the first to make decent estimates by calculating firstly the distance to the Moon in terms of Earth radii (they found the Earth's radius by measuring its curvature using shadows and assuming it to be spherical). Once you have the distance to the Moon you can construct a trigonometric problem when the Moon is half-lit, but you have to estimate the size of the Sun. For a long time, most people believed the Sun to be about 20 times further away than the Moon. The true figure is around 400 times further away, but how did we determine that?
Well, the Europeans and Islamic astronomers raced to pin down the answer, but Europe won when Kepler published his laws of planetary motion, which accurately described the paths all the planets took around the Sun. By observing Mercury and Venus, the two inferior planets, astronomers like Kepler were able to calculate how close they were to the Sun, and how close we are relative to them. His earliest estimates put the distance at around 250 times, much closer to the actual value of 400. Further refinements came with better observations, and the figure of about 150,000,000 km was well established by the 20th Century. Today, we can use RADAR to accurately measure the distance to the other planets and we can trace the periods of their orbits extremely accurately, so we have a very good picture of the Solar System. And it's just as well, because knowing the distance to the Sun and other planets has allowed us to send spacecraft all over the Solar System. In fact, there is a future mission planned which will actually go to the Sun!
Now, your question seems to be about the apparent size of the Sun. I can assure you (because I'm an astronomer, and the Sun is one of my favourite things to study through a solar-filtered telescope) that the Sun is not bigger or smaller from one day to the next. It always subtends an angle of 0.5 degrees on the sky (that's about half the width of your little finger).
It may look bigger or smaller because of the weather. If you see the Sun through thick cloud, much of the glaring light (which is scattered off the sky) is stripped away and you see less of it, whereas on a clear day if you look at the Sun you'll see a big white disc, because the light is scattering all over the place. But the Sun's disk is always the same size. It may also look bigger at sunrise/sunset, because the Sun and the Moon look bigger when they're near the horizon. This is purely an optical illusion caused by our brains to make things look bigger when they're low enough to be compared with the ground, and smaller when they're high overhead.
Hope this helps.
P.S. NEVER EVER look at the Sun through a telescope without getting help from an astronomer. You need a special filter to take away over 99.9% of its light, including 100% of the UV light or you will blind yourself!
thelambreturn said:you dont answer,you tuen around and say totaly irrlevant things,you know nothing,all you supposed wisdom his fake,bla bla bla,my question his simple,WHY you say time stop at light speed,and it take 8,3 minutes to light to travel sun to earth,and why the sun his not always the same size if we are rolling on a space time continium,it should be the same size no,let me guess your answer,gaz effects,ok then,why the moon when its out in the day,his not full,if shes full at night because of supposed gravity bend light,why when shes in direct contact with light of the sun its not full,you know it would help you to read the bible,cause the time his near.
Messages end.
On reflection, I made a couple of mistakes that could cause potential confusion. Most notably, I told him the solar disk changes in apparent size throughout the year, but not from one day to the next, which is contradictory. It is merely not noticeable from day to day, and to the unaided eye will always appear about 0.5 degrees. This is what I meant to imply, but could have phrased it better. I am still considering how to respond, and will update the post (after this paragraph) with any further messages.