I read about solar and sidereal day several times but never understood. So couldnt remember. After watching this video i feel like i will never forget the difference. Really Helpful. Thank you so much.
Sidereal day applications involve the Earth's angular velocity = (360 degrees)/(period), where "period" is the time it takes the Earth to turn through 360 degrees, which is 1 sidereal day = 23 hr 56 min 4.09 sec, not 1 solar day = 24 hr. The easiest way for a telescope to track a star is to use an equatorial mount (see Wikipedia) and rotate it at the Earth's angular velocity. As another application, the Coriolis force on the wind and ocean involves the Earth's angular velocity. In other words, if you want clear time-lapse photographs of galaxies and nebulae from Earth or if you want accurate weather forecasts, you have to use the sidereal day.
I love your content! I’m learning a lot, especially the life and death of stars, I devoured those. Just one thing, it’s pronounced “sai·dee.ree.uhl”. Thank you on behalf of my OCD.
The word "mean" is defined as "average", which suggest correctly that the solar day is not constant but varies over the year. Thus the second was defined as 1/86400 of a mean solar day. (the average length of a solar day).
Hello, this made me wonder, doesnt the fact that the sun rises and sets at different times each day contradict the matter discussed in this video? BTW thank you very much for your tutorials, love them all
Okay, I think Im beginning to understand better. I still have one last question. Did you set the axis of rotation at 0 degrees for some reason, and not 23.5 as in different videos? Because Im struggling with this idea because I think it conflicts with the solar analemma. Again, thank you very much
Earth is also tilted and rotating in elliptical orbit around sun so time of Noon varies round the year and we have the Equation of time in this regard. But I have failed to understand why the sidereal time of rotation of earth remains the same round the year? Because the earth must be displaced a bit from it's position from the stars during it's orbital movement around the sun round the year. How this displacement does not effect on the sidereal time? Can anyone put some light please.
First of all, isn't sidereal pronounced sai·dee·ree·uhl, and not side·reel ? Secondly, isn't a sidereal day 23 hours, 56 minutes, 4.09 seconds and not 9.5 seconds?
Most sources do indeed indicate that the sidereal day is about 23 hours 56 minutes and 4 seconds (some show less than 4 seconds and some show more than 4 seconds)
How many days in solar year. You may say 365.2425 as per gregorian, 365.25 as per julian and 365.24218 as per scientific community or astronomers and astrophysicists, they called it tropical year and calculated that sidereal year (alignment to fixed star) is lessen by about 20 minutes every year. This difference in tropical and sidereal year led to idea of precession of equinox or say gyroscopical motion of earth, the precession rate calculated as about 50" (seconds in angle) per year. These precession cause shifting of season relative to fixed constellations of ecliptic. But you might wonder that this is not correct. A year consists of 359 synodic days (from sunrise to next sunrise) or days. As we know from science and observation if one want that a sidereal day (position of a star to next rise or day) is 4 minutes less than a synodic or day. So a day is 24 hours of average, while a sidereal day is 23 hours and 56 minutes. We are not assuming that whether earth is rotating or sidereal day is of 1 degree. That makes calculation lot easier but that takes assumptions. The difference of 4 minutes cause sun to rise further eastward from that star. So to again align for that star with its initial position took one complete sidereal rotation or one sidereal day. So mathematics is, no. of days per minute of sidereal recession = 1/4 days per minute. For a complete sidereal circle of 23 hours and 56 minutes or 1,436 minutes is = 1/4 × 1,436 = 359 days. Now this 359 days or 360⁰ is duration of a sidereal year in terms of synodic days. Here we don't take assumption that 1 sidereal day is 1⁰ on ecliptic, so loss of time for 360⁰ is = 360 × 4 = 1,440 minutes or 1 day. Subtract this from 360 days (assuming 1⁰ on ecliptic is 1 synodic day) is 359 days. Here both tropical and sidereal year aligns after 359 days, so there is no precession of equinox or shifting of seasons. Question is why scientific community still persists on a year of 365.24218 days, which was modified version of ancient egyptian by greeks or romans. Their own calculation says that sidereal year is 20 minutes more, which comes naturally as 5 more days than 360 days and each day is 4 minutes less. They reversed the result by saying tropical year is shorter.
@@wirito : But then you disregard the etymology. The plain order of characters does not make a word. "Sidereal" comes from latin "sidus" [see-dus], the star. The suffix "al" is "concerning the ...", and the "sidus" is put into the accusative. So it's "sid [noun]-ere [acc.]-al [concerning]". Only you english speakers make this "ai" sound out of an "i", which is more like "ee". So maybe try "seed-ee-ree-al".
I've understood this but have never been able to articulate it. This is an amazing direct tutorial that has me extremely excited because you also explained something I was not expecting. THE CAUSE OF CLIMATE CHANGE! My bad..I'm on my phone and didn't realize the next video started..this comment was for your elliptical orbit video..thanks for posting these videos
Hi. Does the Sidereal day account for Axial Tilt, Axial Precession & Apsidal Precession too? What about the solar system moving through space at staggering speeds? Thanks in advance for any information you can share.
I am totally confused, you say that a Solar day is 24 hours but If we have to wait another 4 minutes (approximately)does that mean a Solar day is 24 hr's and 4 mins(approximately) and a sideral day is the same. or does it mean that the star signs never change. Sorry I don't undsrstand it. If the Earth rotates an extra one degree a day (adding an extra 4 mins a day) then after 180 days the Earth will be facing the Sun at 12 noon but It will be 12 midnight according to my clock, because 4mins*180=720mins/60 = 12hours. If you don't add that extra one degree a day to the Earths rotation it will match with my clock but the Earth would now be facing the Sun at 12 Midnight.
@@MichelvanBiezen At 12 noon the Earth would be facing the Sun. After 180 days the Earth will be facing away from the Sun at 12 noon. So the Earth is Flat.
@@MichelvanBiezen If after one spin of the Earth around the Sun as portrayed on your board(24 hours). If the Earth has started its spin facing Eastwards towards the Sun, then finishes its first spin facing Eastwards (having moved counter clockwise about one degree on the Sun) so after 180 days it will have travelled 180 degrees on the Sun(now still facing Eastwards with its back to the Sun). The whole science of global movements is full of abouts. the Moon orbits the Earth about every 27.3 days to 29.9 or something like that, nothing is black or white. I am sorry to say that the flat Earth makes so much more sense to me at this moment in time.
@@Peterpan2355 - if we used a sidereal day, that would be the case, but that is why we wait for the same point on earth to be pointed to the center of the sun again, and base clocks on the solar day.
This then is because sunrise to sunrise is 24 exact hours (as our watches and clocks have verified for hundreds of years and sundials for longer). Star rise to star rise is 23:56. How can these two speeds be relevant when the earth’s rotation is what causes the stars and sun to appear to move at all through our sky. Two separate heavenly body speeds and one earth speed does not work and therefore requires another earth/star model. If experimentation thwarts a theory, the theory goes, the science stays.
The Earth makes one rotation every 23 hours, 56 minutes, 4.1 seconds. But since the Earth revolves around the Sun, it has to rotate a little longer (235.9 seconds) for the Sun to appear in the exact same spot as the previous day. That is why a solar day is 24 hours.
@@MichelvanBiezen what you’re seeming to say is that we have to wait another 239.5 seconds each day to see the sun rise verses when we see the stars rise (based on whatever our marker star might be) The issue I’m seeing (which I will attempt to word differently), is that the earth is rotating at one speed. The sun, which is infinitely closer to us (in this model) than the stars should have the same, if not faster- for distance sake -rotational view than the stars. Those luminaries in the sky (based on our observation of earth’s cycles) aren’t expanding fast enough with the galaxy to upset our use of them as a perfect clock, which consistency implies that their regularity to the earth should be exactly the same, not 4 minutes off. The earths rotation and orbit should effect our view of the stars exactly the same as our view of the sun. These objects are lights in our sky and the earth’s rotation is causing all of their movement. This absolutely requires the same view in movement. A theory that could help us move forward would be: possibly the solar model we rely on needs tweaking because we can repeatedly observe that the sun and stars move at different speeds.
To keep it simple. The stars are essentially fixed in position relative to us. Therefore the stars give us the true rotational period of the Earth (23 hours 56 minutes 4.1 seconds). After each period the stars will appear in the exact same place. But when we use the solar day instead, the stars will appear in a differnt location after 24 hours.
Sorry. The math just does not add up...it WOULD have to be in a perfect circle orbit. But it is not. It is an elliptical orbit like you have explained before and changes speed constantly (speeds up and slows down) so the math is all messed up. Not only that, but the moon also orbits in an elliptical orbit around the earth...so the math there is messed up too. And for anyone who does not believe in God, how is the sun and moon the same size during an eclipse?...seems to be very coincidental that the moon is both 400 times smaller than the sun and 400 times less far from the earth at the same time. Too perfect without a God.
@@rday710 no it isn't you muppet, but you're right about the coincidences, and the Moon is only ever full during the hours of darkness wherever you are in the World, it does make me wonder if there was indeed an invisible hand behind the creation of the Universe,
I have a hard time believing this because if each solar day is 23hour and 56 mins and today the sun is high up at noon, that means that in 20 days noon will be 10am, which is not what I experience over the past 30 years of my life.
You're the best night sky teacher.
He is a all rounder. Am also a fan of his mathematics lectures as well.. 💯💓
I read about solar and sidereal day several times but never understood. So couldnt remember. After watching this video i feel like i will never forget the difference. Really Helpful. Thank you so much.
What a load of rubbish this video is. The Earth spins four minutes short of twenty four hours, yet on my phone it is exactly twenty four hours
Sidereal day applications involve the Earth's angular velocity = (360 degrees)/(period), where "period" is the time it takes the Earth to turn through 360 degrees, which is 1 sidereal day = 23 hr 56 min 4.09 sec, not 1 solar day = 24 hr. The easiest way for a telescope to track a star is to use an equatorial mount (see Wikipedia) and rotate it at the Earth's angular velocity. As another application, the Coriolis force on the wind and ocean involves the Earth's angular velocity. In other words, if you want clear time-lapse photographs of galaxies and nebulae from Earth or if you want accurate weather forecasts, you have to use the sidereal day.
Nice descrtiption. 🙂
Thank you! Very positive, upbeat and well versed explanation.
Very very helpful. This sort of material is quite difficult coming from a textbook, but very simple when presented in the right format.
Glad it was helpful!
you explain these concepts so clearly thank you
Thank you so much! I have a quiz tomorrow and I was a bit lost on the definitions of these two :)
Beautiful explanation. 👍
Glad you think so!
Thankyou so much :)That was most lucid explanation of this concept that I've come across .
thank you. Glad it was helpful! 🙂
You are amazing sir. All respect.
Thank you! Beautifully explained.
You're very welcome! 🙂
Great illustration !!
Glad you liked it.
Glad you liked it.
Great tutorial sir.Helped me alot
Great explanation! Thanks!
It is fun to explore the night sky once we learn how.
I love your content! I’m learning a lot, especially the life and death of stars, I devoured those. Just one thing, it’s pronounced “sai·dee.ree.uhl”. Thank you on behalf of my OCD.
Thank you. This is how the dictionary tells us we shoud pronounce that: sīˈdirēəl
thank you...very explanative video..
Best explanation ever!!
Glad it was helpful!
You are a great teacher, thanks a lot
Very helpful, thank you! :)
Thank you so much for the video. And one more question , Is Sideral day and one mean solar day is same?
The word "mean" is defined as "average", which suggest correctly that the solar day is not constant but varies over the year. Thus the second was defined as 1/86400 of a mean solar day. (the average length of a solar day).
Finally! I understand!
Very well explained
Thank you. Glad you liked it.
Amazing teacher
Excellent!
Thank you. Glad you liked it. 🙂
Very nice explanation! thanks :)
Glad you liked it
Thank you very much sir, that was very good.
Very welcome
Hello, this made me wonder, doesnt the fact that the sun rises and sets at different times each day contradict the matter discussed in this video?
BTW thank you very much for your tutorials, love them all
No, the principle here depends on the rotation of the Earth, not when the Sun rises or sets.
Okay, I think Im beginning to understand better. I still have one last question. Did you set the axis of rotation at 0 degrees for some reason, and not 23.5 as in different videos? Because Im struggling with this idea because I think it conflicts with the solar analemma.
Again, thank you very much
Yes, for simplicity, but you are correct, it should be 23.5 degrees.
Earth is also tilted and rotating in elliptical orbit around sun so time of Noon varies round the year and we have the Equation of time in this regard. But I have failed to understand why the sidereal time of rotation of earth remains the same round the year? Because the earth must be displaced a bit from it's position from the stars during it's orbital movement around the sun round the year. How this displacement does not effect on the sidereal time? Can anyone put some light please.
The stars ar e so far away, that any motion (including revolving around the Sun) of the Earth is insignificant.
First of all, isn't sidereal pronounced sai·dee·ree·uhl, and not side·reel ? Secondly, isn't a sidereal day 23 hours, 56 minutes, 4.09 seconds and not 9.5 seconds?
Most sources do indeed indicate that the sidereal day is about 23 hours 56 minutes and 4 seconds (some show less than 4 seconds and some show more than 4 seconds)
@@MichelvanBiezen - thanks, but in this video, you were showing 9.5 seconds - where did the 9.5 seconds come from? a different source?
That is an old number that I remember. Over time these constants are remeasured or recalculated.
Excellent
Thank you. Glad you liked it. 🙂
Sir, did sidereal cause leap year happened?
Tq
Thanks sir
How many days in solar year. You may say 365.2425 as per gregorian, 365.25 as per julian and 365.24218 as per scientific community or astronomers and astrophysicists, they called it tropical year and calculated that sidereal year (alignment to fixed star) is lessen by about 20 minutes every year.
This difference in tropical and sidereal year led to idea of precession of equinox or say gyroscopical motion of earth, the precession rate calculated as about 50" (seconds in angle) per year. These precession cause shifting of season relative to fixed constellations of ecliptic.
But you might wonder that this is not correct. A year consists of 359 synodic days (from sunrise to next sunrise) or days. As we know from science and observation if one want that a sidereal day (position of a star to next rise or day) is 4 minutes less than a synodic or day. So a day is 24 hours of average, while a sidereal day is 23 hours and 56 minutes.
We are not assuming that whether earth is rotating or sidereal day is of 1 degree. That makes calculation lot easier but that takes assumptions. The difference of 4 minutes cause sun to rise further eastward from that star. So to again align for that star with its initial position took one complete sidereal rotation or one sidereal day.
So mathematics is, no. of days per minute of sidereal recession = 1/4 days per minute.
For a complete sidereal circle of 23 hours and 56 minutes or 1,436 minutes is = 1/4 × 1,436 = 359 days.
Now this 359 days or 360⁰ is duration of a sidereal year in terms of synodic days. Here we don't take assumption that 1 sidereal day is 1⁰ on ecliptic, so loss of time for 360⁰ is = 360 × 4 = 1,440 minutes or 1 day. Subtract this from 360 days (assuming 1⁰ on ecliptic is 1 synodic day) is 359 days.
Here both tropical and sidereal year aligns after 359 days, so there is no precession of equinox or shifting of seasons. Question is why scientific community still persists on a year of 365.24218 days, which was modified version of ancient egyptian by greeks or romans.
Their own calculation says that sidereal year is 20 minutes more, which comes naturally as 5 more days than 360 days and each day is 4 minutes less. They reversed the result by saying tropical year is shorter.
Very nice input. Thank you.
Thank you help me a lot
Thank you.
Thankyou so much
Thank you
You're welcome
Thank you!
Perfect
Isn't "sidereal" pronounced 'sai-de-re-al'? Instead of 'side-real'?
You're right!
I couldn’t believe it but it’s true. Pronouncing it as sahy - deer - ee- uh l is weird. I prefer side-real!
@@wirito : But then you disregard the etymology. The plain order of characters does not make a word. "Sidereal" comes from latin "sidus" [see-dus], the star. The suffix "al" is "concerning the ...", and the "sidus" is put into the accusative. So it's "sid [noun]-ere [acc.]-al [concerning]". Only you english speakers make this "ai" sound out of an "i", which is more like "ee". So maybe try "seed-ee-ree-al".
I've understood this but have never been able to articulate it. This is an amazing direct tutorial that has me extremely excited because you also explained something I was not expecting. THE CAUSE OF CLIMATE CHANGE! My bad..I'm on my phone and didn't realize the next video started..this comment was for your elliptical orbit video..thanks for posting these videos
Isn't it 23h 56m 4.09s since the difference of side and solar is 3m 55.909s ?
There are indeed more accurate measurements of the solar day.
Thnx!
Thank u !
Hi. Does the Sidereal day account for Axial Tilt, Axial Precession & Apsidal Precession too? What about the solar system moving through space at staggering speeds? Thanks in advance for any information you can share.
The sidereal day is a measured value.
Thank u
You're welcome!
Such a good video
I am totally confused, you say that a Solar day is 24 hours but If we have to wait another 4 minutes (approximately)does that mean a Solar day is 24 hr's and 4 mins(approximately) and a sideral day is the same. or does it mean that the star signs never change. Sorry I don't undsrstand it. If the Earth rotates an extra one degree a day (adding an extra 4 mins a day) then after 180 days the Earth will be facing the Sun at 12 noon but It will be 12 midnight according to my clock, because 4mins*180=720mins/60 = 12hours. If you don't add that extra one degree a day to the Earths rotation it will match with my clock but the Earth would now be facing the Sun at 12 Midnight.
The sidereal day is about 23 hours and 56 minutes. A solar day is 24 hours long.
@@MichelvanBiezen At 12 noon the Earth would be facing the Sun. After 180 days the Earth will be facing away from the Sun at 12 noon. So the Earth is Flat.
I don't follow your logic. (If A then B?)
@@MichelvanBiezen If after one spin of the Earth around the Sun as portrayed on your board(24 hours). If the Earth has started its spin facing Eastwards towards the Sun, then finishes its first spin facing Eastwards (having moved counter clockwise about one degree on the Sun) so after 180 days it will have travelled 180 degrees on the Sun(now still facing Eastwards with its back to the Sun). The whole science of global movements is full of abouts. the Moon orbits the Earth about every 27.3 days to 29.9 or something like that, nothing is black or white. I am sorry to say that the flat Earth makes so much more sense to me at this moment in time.
@@Peterpan2355 - if we used a sidereal day, that would be the case, but that is why we wait for the same point on earth to be pointed to the center of the sun again, and base clocks on the solar day.
This then is because sunrise to sunrise is 24 exact hours (as our watches and clocks have verified for hundreds of years and sundials for longer). Star rise to star rise is 23:56. How can these two speeds be relevant when the earth’s rotation is what causes the stars and sun to appear to move at all through our sky. Two separate heavenly body speeds and one earth speed does not work and therefore requires another earth/star model. If experimentation thwarts a theory, the theory goes, the science stays.
The Earth makes one rotation every 23 hours, 56 minutes, 4.1 seconds. But since the Earth revolves around the Sun, it has to rotate a little longer (235.9 seconds) for the Sun to appear in the exact same spot as the previous day. That is why a solar day is 24 hours.
@@MichelvanBiezen what you’re seeming to say is that we have to wait another 239.5 seconds each day to see the sun rise verses when we see the stars rise (based on whatever our marker star might be)
The issue I’m seeing (which I will attempt to word differently), is that the earth is rotating at one speed. The sun, which is infinitely closer to us (in this model) than the stars should have the same, if not faster- for distance sake -rotational view than the stars.
Those luminaries in the sky (based on our observation of earth’s cycles) aren’t expanding fast enough with the galaxy to upset our use of them as a perfect clock, which consistency implies that their regularity to the earth should be exactly the same, not 4 minutes off.
The earths rotation and orbit should effect our view of the stars exactly the same as our view of the sun. These objects are lights in our sky and the earth’s rotation is causing all of their movement. This absolutely requires the same view in movement.
A theory that could help us move forward would be: possibly the solar model we rely on needs tweaking because we can repeatedly observe that the sun and stars move at different speeds.
To keep it simple. The stars are essentially fixed in position relative to us. Therefore the stars give us the true rotational period of the Earth (23 hours 56 minutes 4.1 seconds). After each period the stars will appear in the exact same place. But when we use the solar day instead, the stars will appear in a differnt location after 24 hours.
Yes but wouldn't the earth have to be orbiting the sun in a perfect circle orbit. Or else the world clocks would get all out of whack?
No, the orbit does not need to be perfectly circular.
Sorry. The math just does not add up...it WOULD have to be in a perfect circle orbit. But it is not. It is an elliptical orbit like you have explained before and changes speed constantly (speeds up and slows down) so the math is all messed up. Not only that, but the moon also orbits in an elliptical orbit around the earth...so the math there is messed up too. And for anyone who does not believe in God, how is the sun and moon the same size during an eclipse?...seems to be very coincidental that the moon is both 400 times smaller than the sun and 400 times less far from the earth at the same time. Too perfect without a God.
@@rday710 Because the Earth is Flat.
Exactly!
@@rday710 no it isn't you muppet, but you're right about the coincidences, and the Moon is only ever full during the hours of darkness wherever you are in the World, it does make me wonder if there was indeed an invisible hand behind the creation of the Universe,
I have a hard time believing this because if each solar day is 23hour and 56 mins and today the sun is high up at noon, that means that in 20 days noon will be 10am, which is not what I experience over the past 30 years of my life.
Each sidereal day is 23 hours and 56 minutes, and each solar day is 24 hours.
@@MichelvanBiezen oh wow thanks I dunno how I got that switched around sorry.
Thank you!