That is a very good question! We measure the parallax angle based on how much the star appears to move across the sky. What we are actually measuring is TWICE the parallax angle, which you can envision as the arc between the two orange dashed lines I made at 0:57. By the Vertical Angle Theorem, we can equate this to the angle made by the top of the triangle in the video. Half of this is the parallax angle (aka theta). I apologize for not making that explanation very clear in the video! Please let me know if you still have questions.
@@astronaughtpov the explanation is easy to understand but the problem with the explanation and other video's explanation is that they all failed to explain how to obtain the parallax angle. There are three unknowns and we only have one known value (distance form earth to sun). But the parallax angle is still unknown. Unless you mean the parallax angel is the two points from the first view (left) and the second view (right). But it still makes no sense
@@flashmedia8953 I'm not sure I entirely understand your question, but I will try my best to answer. To find the parallax angle to a star, we look at the distance that star appears to shift across the sky at different times of the year (this is the distance between the two points referenced in the video). This distance is found by taking images of the sky and measuring the shift in pixels. These pixels can be converted into an angular unit, like arcseconds, based on the image's plate scale.
Hi, I'm just Curious if you think the speed of Light is constant throughout the Universe or if Universal variables in density could have an effect on the speed of light as compared to here on earth in these specific conditions? Actually, scratch that.... we know that light slows down in water.... So that would mean nobody really has any idea of the true speed of light over large distances in the universe doesn't it?
That is an interesting thought experiment. I have two general thoughts: First (directly to your point of the refraction of light), the universe is not a complete vacuum. Technically, the gas and dust in space will refract light slightly, but the density of matter in space is so low that we can usually approximate it as a vacuum and thus also assume light travels through space at the same speed as it does in a vacuum. On another note, I have also heard an argument critiquing the assumption that light travels at a constant speed in any medium. Basically, the idea behind this argument is that light is measured based on the time it takes to travel in two directions (to a source and then back to us), and we assume that its speed is constant throughout this journey. But what if, instead, light travels at half the speed we expect in one direction and then instantaneously in the other direction? Personally, I think it is more likely that light is constant within a given medium, with the exception of any inconsistencies within the medium itself. But space is weird, so who knows what we'll figure out in the future :)
@@astronaughtpov Thankyou for your reply, I enjoyed reading it. Can I ask you another question.Ancient Indians Believe the number 108 is a universal sacred number representing the number of Chakras in the body.108 is also the ratio of the diameter of the Sun and moon to the distance to the earth. I.E. Distance to earth = 108 x Diameter for both the sun and moon... also the earth is in the perfect position for the moon to perfectly eclipse the sun from our exact viewpoint? And the Speed of light in mph 186,000 x 1.6 to convert to kmph gives 300,000 (allowing for minor rounding at both ends) and when calculated per hour gives almost exactly 1 billion mph.... does this knowledge give you an uneasy feeling that these are rather convenient numbers instead of facts?
I'm afraid I don't quite follow your point on the speed of light. But in general, I would hesitate to put too much meaning into any number with units (because units are defined by humans). Obviously, a ratio is a little different. The fact that the moon and sun appear as roughly the same size in the sky (because the sun’s diameter is about 400 times larger than the moon’s diameter, and the sun is also 400 times farther away than the moon) is an interesting and convenient circumstance, but I don’t necessarily assign additional meaning to it.
Hi, thank you for the explaination.I stumbled upon the same topic while looking at the motion parallax and was wondering how does motion parallax apply to close objects on earth. I am looking into how objects speed is affected by motion parallx. For example, how object moving at speed 2m/s from observer will seems to move farther away. I know that it will be seem to move slower. But how much slower it will be? Are there any formulas to calculate it?
Hi, thanks for the question! Yes, the phenomenon you are referring to is actually the exact same concept on a much smaller scale. A moving observer can be a runner watching the landscape pass by or an astronomer watching the stars as the Earth moves around the sun. The runner will see close objects (like trees) more by much more quickly than distant objects (like mountains) because the angle the runner creates with the trees from one moment to the next is greater than the angle the runner creates with the mountains within this same timeframe. Las Cumbres Observatory created a video that explains this connection really well: ruclips.net/video/iwlMmJs1f5o/видео.html
I linked some resources in the follow-up video to this one (which you can access via the link in the pinned comment), which you may find helpful. However, it seems a lot of people still have this question, so I will work on developing a comprehensive document to further explain how the parallax angle is derived
You can now watch a video specifically regarding how the parallax angle is derived here: ruclips.net/video/W1ocBMOJmW0/видео.html !
Thanks for this explanation of parallax.
Perfect!!
Perfectly done in three minutes
I appreciate the comment!
at 2:30, how do we find parallax angle?
That is a very good question! We measure the parallax angle based on how much the star appears to move across the sky. What we are actually measuring is TWICE the parallax angle, which you can envision as the arc between the two orange dashed lines I made at 0:57. By the Vertical Angle Theorem, we can equate this to the angle made by the top of the triangle in the video. Half of this is the parallax angle (aka theta).
I apologize for not making that explanation very clear in the video! Please let me know if you still have questions.
@@astronaughtpov the explanation is easy to understand but the problem with the explanation and other video's explanation is that they all failed to explain how to obtain the parallax angle. There are three unknowns and we only have one known value (distance form earth to sun). But the parallax angle is still unknown. Unless you mean the parallax angel is the two points from the first view (left) and the second view (right). But it still makes no sense
@@flashmedia8953 I'm not sure I entirely understand your question, but I will try my best to answer. To find the parallax angle to a star, we look at the distance that star appears to shift across the sky at different times of the year (this is the distance between the two points referenced in the video). This distance is found by taking images of the sky and measuring the shift in pixels. These pixels can be converted into an angular unit, like arcseconds, based on the image's plate scale.
Hi, I'm just Curious if you think the speed of Light is constant throughout the Universe or if Universal variables in density could have an effect on the speed of light as compared to here on earth in these specific conditions? Actually, scratch that.... we know that light slows down in water.... So that would mean nobody really has any idea of the true speed of light over large distances in the universe doesn't it?
That is an interesting thought experiment. I have two general thoughts:
First (directly to your point of the refraction of light), the universe is not a complete vacuum. Technically, the gas and dust in space will refract light slightly, but the density of matter in space is so low that we can usually approximate it as a vacuum and thus also assume light travels through space at the same speed as it does in a vacuum.
On another note, I have also heard an argument critiquing the assumption that light travels at a constant speed in any medium. Basically, the idea behind this argument is that light is measured based on the time it takes to travel in two directions (to a source and then back to us), and we assume that its speed is constant throughout this journey. But what if, instead, light travels at half the speed we expect in one direction and then instantaneously in the other direction? Personally, I think it is more likely that light is constant within a given medium, with the exception of any inconsistencies within the medium itself. But space is weird, so who knows what we'll figure out in the future :)
@@astronaughtpov Thankyou for your reply, I enjoyed reading it. Can I ask you another question.Ancient Indians Believe the number 108 is a universal sacred number representing the number of Chakras in the body.108 is also the ratio of the diameter of the Sun and moon to the distance to the earth.
I.E. Distance to earth = 108 x Diameter for both the sun and moon... also the earth is in the perfect position for the moon to perfectly eclipse the sun from our exact viewpoint? And the Speed of light in mph 186,000 x 1.6 to convert to kmph gives 300,000 (allowing for minor rounding at both ends) and when calculated per hour gives almost exactly 1 billion mph.... does this knowledge give you an uneasy feeling that these are rather convenient numbers instead of facts?
I'm afraid I don't quite follow your point on the speed of light. But in general, I would hesitate to put too much meaning into any number with units (because units are defined by humans). Obviously, a ratio is a little different. The fact that the moon and sun appear as roughly the same size in the sky (because the sun’s diameter is about 400 times larger than the moon’s diameter, and the sun is also 400 times farther away than the moon) is an interesting and convenient circumstance, but I don’t necessarily assign additional meaning to it.
@@timothygibbens9796there are lots of convenient numbers when it comes to space… most of it reads more like science fiction than science.
Hi, thank you for the explaination.I stumbled upon the same topic while looking at the motion parallax and was wondering how does motion parallax apply to close objects on earth. I am looking into how objects speed is affected by motion parallx. For example, how object moving at speed 2m/s from observer will seems to move farther away. I know that it will be seem to move slower. But how much slower it will be? Are there any formulas to calculate it?
Hi, thanks for the question! Yes, the phenomenon you are referring to is actually the exact same concept on a much smaller scale. A moving observer can be a runner watching the landscape pass by or an astronomer watching the stars as the Earth moves around the sun. The runner will see close objects (like trees) more by much more quickly than distant objects (like mountains) because the angle the runner creates with the trees from one moment to the next is greater than the angle the runner creates with the mountains within this same timeframe.
Las Cumbres Observatory created a video that explains this connection really well: ruclips.net/video/iwlMmJs1f5o/видео.html
How to measure the angel
I linked some resources in the follow-up video to this one (which you can access via the link in the pinned comment), which you may find helpful. However, it seems a lot of people still have this question, so I will work on developing a comprehensive document to further explain how the parallax angle is derived
The video thumbnail pic is backwards