Cosmic Distance Ladder: Parallax 1
ฝัง
- เผยแพร่เมื่อ 6 ก.พ. 2025
- Introduces the concept of parallax and how our eyes see depth perception. We then explain how this can be applied to astronomy to measure the distances to nearby stars. The first step in the cosmic distance ladder.
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The background stars can be used as reference points to measure the apparent changes in the nearby stars positions, which is easier than trying to find some other absolute reference frame. Think about if you were to take two pictures of a patch of sky at different times, if there were only one star, it could have moved or the camera could have not been aimed exactly right. By overlaying the two pictures and matching up the background stars (unmoving), we get rid of the camera aiming errors.
Absolutely; it wasn't until the mid 1800s that astronomers could even measure the parallax of a few of the very nearest stars. In fact in the 1500s and 1600s the unobserved parallax was considered to be scientific evidence against the Copernican model for the solar system. Parallax angles that small would require distances so great that many people considered implausible. It wasn't until the mid-1900s that we could measure the parallax of more than a few hundred stars.
Thank you for the detailed insight! :) The stars (galaxies) are full of mysteries, and that only adds to to my perspective.
I think the Hipparcos satellite (that has given us most of our best parallax measurements) had more sophisticated ways of stabilizing the cameras and setting up an "extragalactic" reference frame for its measurements, but I'm not as sure about the details of this.
good explained
This was very well and intuitively explained. :) However, getting the measures by ourselves of the actual parallax angle of one particular star could be indeed challenging.
I think its impossible. there are no stars that we can see 90* to the sun. This parallax formula just sounds cool and complicated, designed to scare people from questioning. Not one youtuber astronomer channel, nor website, explains how to get that measurement for yourself.
Very clear explanation, :)
thanks a lot!!! but i didnt quite understand that why star moves in a circle? it doesnt getting further or closer so it should move in a straight line? thanks again
It's not that the star is moving in a circle, but that our reference point (the Earth, which is in orbit around the Sun) is moving in a circle. You can simulate the same effect if you hold up your thumb at arms length and then move your head in a small vertical circle. It will appear as if your thumb is moving in a circle compared to whatever objects are behind it.
Can you please explain a bit more about measuring the angle of parallax according to 8:35 ?
I probably could have explained that better in the video, but in practical terms we use the more distant background stars (that essentially don't show changes in their apparent positions) as reference points and measure the changes in the apparent positions of the more nearby stars. Essentially, if you took pictures of the same region of the sky over the course of a year, most of the stars you could see wouldn't show any relative movements, but the more nearby stars will trace out an oval on the sky. We can measure the angular size of the widest part of that oval and that corresponds with twice the parallax angle.
I know this may sound like an unintelligent question, but is it possible to use the parallax method without waiting a six-month time period? I am madly trying to finish my eighth grade science project that is due in less than a month.... I would choose a simpler project like "why my dog snores" but I found this very interesting. My science teacher hasn't been much help though so any extra advice that could help me would be great. :-D
Right so 4:20 is the geometry part of this method.
Thank you very very much sir!
thanks a ton
thank you very much! :)))
ok... but you know what? how many stars are 90* to the sun? the only stars we can see are away from sun, the night side. Every youtube astronomer channel all, give that same example. Am I missing something, or is this formula complete bullshit?
Four years later, but in case someone else has the same question. As an analogy, stare directly ahead of you, pretending that each eye is earth, half a year apart (the baseline). Can you only see things 90 degrees ahead of you? Of course not. You can look around. You can look left, right, up, down... what would that resemble in astronomical parallax? Taking the two images at different times of the year, perhaps also at different times of the day in different areas of the earth. You could point the camera directly away from the north pole, for example, to get a much different view than on the equator. As long as you know the difference between your pictures, you can calculate your baseline. Right now, I think you're assuming that the picture can be taken only two days a year? In actuality, they just need to be taken half a year apart.... technically, you could take the two pictures the same night as the earth is ALWAYS rotating the earth, but your baseline would be miniscule. Even now, the 2AU baseline is really, really small in the cosmic sense, but it's the best we can do. Taking the photo twice from Neptune in the Neptunian year would be better, as an example!
Looks to me like someone needs a much bigger telescope in say Pluto’s orbit, to better measure those background stars.
If we can measure further with a size baseline, why don't we use it, now we have been using the same baseline of the orbit around the Sun for 100 years, which Hubble was also working on, but we also have a baseline that is 2400 times larger and you can also measure the distances 2400 times further. The fact is, I'll cut it short for the scientists who are not big bang supporters, but as the whole world knows Hubble took many photos 100 years ago, but that position is now at 720,000,000,000 kilometers and can so we now take pictures on a baseline that is 720,000,000,000 kilometers away and so with the 2.5 meter reflecting telescope that Hubble used, we measure the distance of objects up to 480,000 light years away, which is 2400 times further than with the circle around the Sun, if we can now also use the pictures from the Hubble space telescope and the James Webb space telescope, we can measure the distance millions of light years away. Now that that is not used, it seems that the Big Bang supporters, don't want to because they're afraid of losing the sacred big bang. The big bang was consecrated 100 years ago by a pope and science can no longer function properly, because there is no criticism of the big bang and natural laws are twisted to keep the big bang upright. So I'll just give an example, and I'll take the Big Bang remnants, which was 13.4 billion light-years away at 97.5% redshift according to the Hubble Constant, when the radiation we can observe now was emitted. It shows that the light has just come our way at the speed of light and then people forget for a moment that we are in a big bang, where the redshift indicates a removal speed and with the big bang remnants, the big bang supporters assume that those big bang remnants with 97.5% of the speed of light are moving away from us and we don't assume that the light is emitted at 1.975 times the speed of light, because those big bang remnants know that's what we're waiting for. If you take everything a scientist says blindly, then you're pretty wrong if you don't understand what it's about and you get a picture of the universe that really doesn't matter. but they do keep you busy with interesting facts, which are not always correct. Just to be clear, we move with our Solar System at 840,000 kilometers per hour in a circle around the galaxy center.
Als we met een grootte basislijn verder kunnen meten waarom gebruiken we die dan niet, nu gebruiken we al 100 jaar dezelfde basislijn van het rondje om de Zon, waar Hubble ook al mee bezig was, maar we hebben ook een basis lijn die 2400 maal groter is en kan je daar ook 2400 maal verder de afstanden meten. Het is namelijk zo, dat ik het even zal voor kouwen voor de wetenschappers die geen oerknal aanhanger zijn, maar zoals de hele wereld weet heeft Hubble 100 jaar geleden vele foto,s gemaakt, maar staat die positie nu op 720.000.000.000 kilometer en kunnen we dus nu foto,s maken op een basislijn die 720.000.000.000kilometer verder staat en zo met de spiegeltelescoop van 2,5 meter die Hubble gebruikte objecten de afstand meten tot 480.000 lichtjaar ver, dat is 2400 maal verder als met het rondje om de Zon, als we nu ook nog de foto,s van de Hubble ruimte telescoop en de James Webb ruimte telescoop kunnen gebruiken, dan kunnen we miljoenen lichtjaren ver de afstand meten.Nu dat niet gebruikt word, lijkt het er op dat de oerknal aanhangers, dat niet willen, omdat ze bang zijn de heilige oerknal kwijt te raken. De oerknal is 100 jaar geleden ingezegend door een paus en kan de wetenschap niet meer naar behoren functioneren, omdat er geen kritiek op de oerknal mag komen en worden natuur wetten verwrongen om de oerknal overeind te houden. Dan zal ik maar even een voorbeeld geven en dan neem ik de oerknal restanten, die met 97,5% roodverschuiving volgens de Constante van Hubble op 13,4 miljard lichtjaar stond, toen de straling werd uitgezonden die we nu waar kunnen nemen. Daar uit blijkt, dat het licht gewoon met de lichtsnelheid onze kant is opgekomen en gaat men dan maar even vergeten dat we in een oerknal zitten, waar de roodverschuiving een verwijderingssnelheid aan geeft en bij de oerknal restanten gaan de oerknal aanhangers er van uit dat die oerknal restanten met 97,5% van de lichtsnelheid zich van ons verwijderen en we niet aan nemen dat het licht word uitgezonden met 1,975 maal de lichtsnelheid, omdat die oerknal restanten weten dat wij daar op zitten te wachten. Als je alles klakkeloos aan neemt wat een wetenschapper zegt, dan ga je aardig de mist in als je niet begrijpt waar het over gaat en krijg je een beeld van het heelal wat er echt niet toe doet,. maar houden ze je wel bezig met leuke wetenswaardigheden, die toch niet altijd kloppen. Nog even voor alle duidelijkheid wij bewegen met ons Zonnestelsel met 840.000 kilometer per uur in een rondje om het melkweg centrum.
You made a mistake.
tanθ=Perpendicular/Base
So it would be d/1AU not 1AU/d.
+Md. Tunazzin-Ul-Arefin Instead of saying tan(theta) is perpendicular/Base (this is only true if theta is the angle beside the base side) use tan(theta)=opposite/adjacent. From the angle theta that I draw on the diagram, the opposite side is the 1AU length side and the adjacent side to the angle theta is the distance.
Thank you. This really helped.