Sixty Symbols - 2020-12-20
Professor Mike Merrifield discusses the stellar aberration and the acceleration of the Sun. More links and info below ↓ ↓ ↓ More with Professor Merrifield: http://bit.ly/Merrifield_Playlist Gaia Early Data Release 3: https://www.cosmos.esa.int/web/gaia/early-data-release-3 Visit our website at http://www.sixtysymbols.com/ We're on Facebook at http://www.facebook.com/sixtysymbols And Twitter at http://twitter.com/sixtysymbols This project features scientists from The University of Nottingham http://bit.ly/NottsPhysics Patreon: https://www.patreon.com/sixtysymbols Sixty Symbols videos by Brady Haran http://www.bradyharanblog.com Email list: http://eepurl.com/YdjL9
It is mind-blowing! The sun travels with 220 km/s and we can measure an acceleration of 1cm/s in a year!
@Eidetic Ex Sure, if your telescope is GAIA's astrometry instrument, your ruler is its radial velocity spectrometer, and your camera is 1 gigapixel. (You can't measure the Sun's acceleration from home.)
The velocity of Sun rotating about the center of the galaxy should reverse completely in half a turn which takes 440000/0.01 years. So the sun completes one revolution around the center of the galaxy in 88 million years. If the orbit is a circle its diameter would be 2x10^17 km!
Our psyche is part of nature, and its enigma is as limitless. Thus we cannot define either the psyche or nature.
@Dolphin Man You've only chosen your limit.
@Hayden Travis "There are, moreover, unconscious aspects of our perception of reality. The first is the fact that even when our senses react to real phenomena, sights, and sounds, they are somehow translated from the realm of reality into that of the mind. Within the mind they become psychic events, whose ultimate nature is unknowable (for the psyche cannot know its own psychical substance). Thus every experience contains an indefinite number of unknown factors, not to speak of the fact that every concrete object is always unknown in certain respects, because we cannot know the ultimate nature of matter itself."
GAIA is so underrated in popular science.
Why isn't it visible in the night sky
@Prateek Gupta You mean the spacecraft? It's 1.5 million km away.
Dr Merrifield is just what i needed on a rainy day like today ❤️
rainy rainy frog goes go croak the bee go bzzzzzzz
Its Professor Merrifield
Very exciting to have the 3rd data release from Gaia; this will help with photometry a lot, especially with the Milky Way's satellites.
Awesome content as usual
Thank you - you're very kind.
WOAH 😳, I spent many hours in my younger days pondering this very thing, ie , if your moving then should the source of light appear to change position .
It turned out to be a question I never asked, I assumed that if I was thinking about it then many a greater mind than mine had already thought about and solved this ‘problem’ .
It’s so nice to hear you guys speaking about the thoughts I had when I was in my youth , and of course I was right , a far greater mind than mine had pondered this and proved it to be true .
It's incredible how we take knowing the position or movement of stars for granted, seeing how many factors there are in calculating it. Really interesting video.
Its not that incredible when you think about the timelines. We were still debating whether our galaxy was the entire universe less than a century ago, and even once we'd sorted that out we still were pretty clueless until that famous Hubble Deep Field in 1995. Its only been 25 years since we finally realized the true scale of the (visible) universe.
That's not anywhere near enough time to change the existing conceptions of the entire population, many of whom still think the course of their life is determined by the motion of the the nearest few hundred stars relative to only six of our solar system's eight planets.
To those of us who actually follow cosmology, even in a fairly casual context, it seems like this stuff has been known "forever", especially when much of the foundational stuff we're taught in the introductory and high school courses was worked out by folks during the enlightenment. But in some ways our modern understanding of cosmology is newer than things like gene splicing or even the internet where most of us learn about it these days.
Just to be clear, obviously some people believed the universe was bigger than we knew about prior to 1995 - otherwise nobody would have bothered wasting a large amount of Hubble's time pointing at an "empty" patch of space in the first place.. but prior to the Deep Field image, we had no real evidence either way and there wasn't a general consensus at the time that we'd find anything in those "empty" patches.
This i really great stuff. And I agree with my former commentators in two thing: Gaia is a heavily underrated mission and the sound spectrum steals way too much attention for no reason :)
Just for fun, I calculated how much mass is contained within the Sun's orbit around the Milky Way, based on those numbers. That comes up to approximately 102.8 billion solar masses, assuming a perfect, or near perfect circular orbit.
Well, considering the milky way has 100 billion stars and most of them weigh a little bit less than 1 solar mass this seems about right.
@Thror251 - The exact number is "billions and billions".
Love this channel!
Love this comment.
@Sixty Symbols love this reply!
Oh get a room, you two. ;-)
Regarding the question where the energy for the measured acceleration comes from: NOWHERE. No energy needs to be transferred to keep an object in circular motion. You need the gravitational _force_, but that force doesn't need to do any work because it's perpendicular to the velocity of the solar system. That also means that the acceleration in this video doesn't correspond to a change in speed, just in direction.
Thank you for the clarification. I wasn't sure what was meant.
Does the sun not also decelerate from the highest point in its orbit and accelerate from its lowest point?
@VatticTV I looked into it a little and found that the current models indeed suggest that the Sun's orbit in the galaxy has some eccentricity, so that would mean there's some change in speed, as you said. But the video points out that the main effect measured in the GAIA paper is a centripetal acceleration that appears to agree with what one expects from a circular orbit. When gravity speeds up or slows down the Sun, this change in kinetic energy comes at the expense of a change in gravitational potential energy. But there is no such tradeoff required when only the direction of the motion changes.
@jursamaj I agree in principle, but the video specifically mentions that the main effect that accounts for the measured acceleration is the centripetal acceleration. That's where I took issue with the suggestion that energy transfer is responsible for the observed effect.
@Jens Nöckel Thank you for the reply.
I realised the acceleration spoken of in the video was not the same as in my question. Well I did once I read your initial comment. It wasn't so clear in the video.
@Teacher Hayes I think the explanation needed to use velocity which as a vector quantity not speed that at least in general use is not a vector quantity. Road speed limits would be quite interesting if they showed the maximum velocity in the three orthogonal directions rather than the 'speed' in the direction the road is curving.
Interesting interview, always a fan of Prof. Mike Merrifield. Not a fan of the bar waveform effect at the bottom of the screen when the both of you are on screen lol
@Jean Bigboute - Yes, he literally just posted on this thread, and you replied to him. Some people complained about the paper being brown and textured, instead of plain white.
The waveform (not an equaliser; an equaliser is a very different thing) is there basically to add some "texture" to an otherwise empty area of the screen (same as the brown paper texture). I didn't find it particularly distracting, but I do think it looked kind of "cheap" (low res, blurry, etc.). A coloured spectrogram could / would probably look nicer.
@RFC3514 Please - no. Higher resolution distracting noise in color is in no way an improvement over lower res distracting noise in black and white.
@Ni999 - By that logic, every presenter should be filmed in front of a plain white background instead of going outdoors and standing in front of sunsets or busy streets or trees waving in the breeze. Where would that leave Brian Cox?
@RFC3514 I understand completely. You're able to conflate a background that might impart mood, atmosphere, or context with meaningless noise from a spectrometer and criticize me for having a problem with logic. Brilliant.
@Ni999 - As long as you understand.
The rain graphic was excellent and instantly made the concept click (at least a little) thanks Dr Brady and Professor Merrifield!
This kind of science I love so much, it's way more convincing than biology (the field in which I worked). :)
Not more convincing, but just more understandable, surely?
The complexities of biological systems seem at the moment to far outstrip things we seem to know about the astronomical universe in terms of complexity; I agree with that.
But that doesn't mean any conclusion in one is any more convincing than the other.
The two do seem in some ways to be converging. Wouldn't it be ironic if the knowledge we gained from studying biology ultimately explained gaps in astronomical understanding?
There have already been connections hinted at (shown?) between biological systems and quantum theory.
Personally, I think it's only a matter of time before everything becomes holistic and we can all just go down the pub and relax. (Assuming lockdown has ended by then.)
@Vark Ster Our psyche is part of nature, and it's enigma is just as limitless. Thus we cannot define either the psyche or nature.
Brilliant as usual. Thanks
Thank you - glad you liked it.
If parallax can be measured by acceleration, wouldn’t an observatory in a highly elliptical orbit around the earth (where it speeds up towards the focal point and slows down towards the apogee), be much better for measuring the parallax of stars?
Incredible story of understanding our place in the galaxy.
The anxiety of watching Prof. Merrifield swinging his precious head towards that beam... Careful - we need you to keep using that!
this was the first channel i subscribed to and it was the only one for a looong time. :}
thank you again for the great content, everyone involved
Incredible data from Gaia.
Gaia is my favourite spaceship now but when I first heardve what it was going to do I thought eh ok I guess but I just never imagined what ppl could do w that data. but soooo many cool papers keep coming from Gaia data all different stuff that we understand now that we had no clue before
We measured 1% of our galaxy with Gaia. That probably doesn't seem like a lot to some people but if you can even just attempt to think about how big of a leap that is from not even knowing there was more than 1 galaxy out there, it's hard not to find our world incredible!
Totally missed the fact that the result wasn't quite what we've expected. Sun is apparently closer to the centre as previously thought
With conflicts between the Hubble constant, the accelerating expansion of the Universe from dark energy, influences of dark matter, and on and on I'm surprised they can measure anything to this accuracy.
That's simple: neither the Hubble constant nor the scale factor enter this equation. Also, any tiny acceleration part from dark matter is just that: a small fraction of the measured value. Note that the measured value has only 2 significant digits, so it's fair to say it is not "accurate" at all. We can measure everyday distances to 4 digits accuracy with household items, e.g. your height in mm. Don't confuse accuracy with absolute value. This is not to say GAIA isn't an outstanding mission!
With GAIA data can they calculate the fine structure constant at a million points?
Lovely bit of production work as James Bradly and John Herschel "comes into focus". :)
Thanks for the video. Wonderful.
You are welcome.
This channel only for legends❤✔
holy moly I just learned about this luminar paralax stuff and its amazing!
Like whaat we see sth in a different place when we move perpendicular to the light it produces?? this sounds crazy!
How did they separate the motion of the Milky Way relative to the quasars?
The angle of light coming from the quasars is tilted in the Sun's reference frame compared to the Milky Way's reference frame. The direction of this tilt also changes as the Sun orbits the Milky Way.
been a while since I was in school but shouldn't most of the instances where the professor uses the term "speed" be replaced with "velocity" instead since there is a directional component?
Not if he only cares about the magnitude of the vectors. Otherwise you would be right.
Shouldn't measured acceleration be greater than calculated due to dark matter?
Wouldn't placing GAIA in the first Lagrange Point of Jupiter render more precise results? Baseline would be larger and thus paralax would be larger.
It would take 12 years (Jupiter's orbital period) to get a complete data set. By the time you designed, launched, traveled, and got your first data set it would be 20+ years. Given the lifetime of a RTG (which you'd need) you would get about 4 or 5 datasets before the satellite's life was over. We can get a 3 cm/sec sq accuracy from an Earth based satellite. How much more accuracy do you really need? Is 20+ years worth it?
@Steven Griffin Thx for your insight. Long cycle time is indeed a downer. Don't think you'd need RTG (Juno doesn't need one) and don't think anybody would complain about too precise measurements, but it's probably simply not worth the effort.
This is so confusing after reading so much that gravity is an illusion and orbiting bodies don't actually experience any acceleration, but follow a straight path in curved spacetime
Always nice to see Prof. Merrifield... BUT IT WILL NEVER BE ENOUGH!!! MAKE MORE!!!!1!!! MOAAARRRR!"!!!!!111!!!!!1!one!"!!!1!!
What's the acceleration of the Sun relative to the local standard of rest?
probably a bit slower than the stuff closer to the middle of the galaxy and a bit faster to the outside stuff lol but in all seriousness it would probably differ by a few percent at most
Would anybody else like Prof MM to tackle Halton Arp and intrinsic red shift?
Interesting video. But I hated the audio waveform effect on the screen.
Same here, weird eh?
So science finally tamed the sun and installed a speedometer on it.
waiting for people to realize we can build telescopes that are 1km^2, space based, adjustable full parabolic, metallized foil, fault tolerant, <1/100th exposure time, super-resolution (gigapixel+), sectorable, full-spectrum IR-UV, and lightweight ... we're paying to see the stars quickly, and with high resolution, yet we're fiddling our thumbs for the foreseeable future.
Man is clever but not wise
Isn't the acceleration like g on Earth? Constant for every object orbiting the black hole of our galaxy. (same distance of course)
It's great they got Murray from Flight of the Concords to run the interview.
measuring 0.2 nano meter per second acceleration on a speed of 220 000 meter per second. thats some sensitivity of several order of magnitude
Me at start of video: It's going to be a small number. Er, 2X10-10m/s2. OK, that is small..
How much more parallax would you get from putting 2 telescopes in orbit out past Pluto, on opposite sides of the solar system from each other?
It has almost been done — do a search for “NASA’s New Horizons Conducts the First Interstellar Parallax Experiment.”
Something like a 35~50 x longer baseline to measure from.
all right, time to watch it a second time to understand what this is about.
I vaguely remember learning about centripetal acceleration in school. For the first time Physics no longer seemed intuitive. (in that an orbiting body could be accelerating without changing its apparent velocity)
But since you are on the Earth (which is rotating), you are accelerating without seeming to change velocity! It's pretty weird, right?
And when you go around corner in a car? Yeah; same.
None of those things seem like what we initially feel like what 'acceleraction' is. But acceleration is just a term. Which is defined as that exact thing!
I can't define 'love' or 'art' or 'wealth' or 'happiness'. But I can define acceleration. Maybe that's what why some people are interested in physics, and some are not.
Dunno. Just putting it out there.
@Vark Ster Yes my mistaken assumption as a kid was that acceleration meant getting faster not that a constant force was being applied.
What can we deduce about dark matter from that data?
This should have come out before my Gaia essay....
This is confirmation of what we already know, is it not? I mean it is kind of an obvious fact that the sun goes around the milky way and therefore has to be accelerating?
Juan Valdez - 2020-12-20
I've been watching this channel for years and had no idea that was THE Mike Merrifield from Astronomy textbook fame. I've been reading them for my studies for ages and now have a much greater appreciation for them! Thanks for such informative videos Brady and Professor Merrifield!