saac
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Posts posted by saac
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18 minutes ago, andrew s said:
In the end I am left with what Einstein's I said "time is what a clock measures "
Regards Andrew
also what we will never have enough of!
Jim
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25 minutes ago, teoria_del_big_bang said:
Well considering it is the one and only post from the OP it has certainly stirred everybody up 🤣
Steve
It's still cloudy here, we can be grateful to the OP for something to occupy the time.
Jim
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Our principal theories do seem to attract tall poppy syndrome style critiques. I think that comes from a fundamental misunderstanding and a lot of misconceptions popularised by pop science. I've never applied GR in anger (would not know how), but I have applied other theories. I've used Euler's theory on stress loading of beams, Prandtl's theory describing laminar flow, both in practical engineering settings. Before you apply a theory you first set about to understand the limits of the theory, the regimes in which the theory provides a reliable description. You also need to define what you mean by reliable - what level of reliability or confidence are you looking for. There's the rub, chase 100% confidence then you are chasing a will-o-the-wisp where you will waste money, time and effort. You will also, and without good reason, discard a perfectly adequate description of nature. So GR , does it have limitations, it goes without saying of course it does. Does it work, is it any good ? Without question of course it is, as has been said already, it has made perfectly sound and verifiable predictions - not only does this thing work it works exceedingly well. If you are trying to apply it outside of its limitation then you don't know what you are doing and your criticism is unfounded. I don't think that is what is happening with modern cosmology with respect to considerations of dark energy/dark matter as examples. Our well tested theories, applied within known limits, are pointing to something we need to better define; this is not blind adherence, this is science at its best, this is how we advance.
Jim
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5 minutes ago, wesdon1 said:
@michael8554 Hi again Mike. Yes the dark matter and dark energy theories are basically scientists admitting " we literally have no clue what it all is!?" Tbh Mike, I have have always wondered about whether the reason scientists can't explain what dark matter and energy is, is because the fundamental Einstein theory of general relativity, which beautifully explains a lot, very precisely, is actually totally wrong, and if scientists worked out a new "Einsteinian type theory of general relativity" that accounted for all the so called unknown mass and energy, then there would be no need for dark matter and energy theories? I feel scientists have stay blindly loyal to Einstein's theories, instead of ripping up the book and starting from scratch, so to speak.
As you rightly say Mike, given time, all will be revealed.
From gravitational lensing to time dilation if I recall it has held up fairly well to testing. What areas about GR do you think need re thinking?
Jim
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22 hours ago, Ags said:
Yes but that 0.0001 s is the bit that counts.
You may be disappointed, maybe nothing of merit happened down there, maybe like us on a Monday morning the universe took a moment before it really got going
Jim
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21 minutes ago, Knighty2112 said:
Hi Jim. I agree. In all honesty I started off my initial post wrong. As such I don’t have an issue with the big bang theory itself. I am OK with that. It is what happened in the before part which science cannot answer that niggles away at me still.
I totally agree, the "what happened before", "what conditions caused this" has to be the logical conclusion to this. I may well be havering here, somebody who actually knows what they are talking about can correct me ! I think I read that to study the conditions closer to t = 0 would need a particle collider with a diameter equivalent to the orbit of Jupiter or the Moon! Most likely wrong but it's the sentiment that counts, "we need a bigger boat" and all that
Here's my parting thought. Isn't it funny that we are not content (and rightly so) with getting to Andrew's 0.0001 s of a 13.8 Gy story. I mean, it's utterly amazing that we have been able to do this right? Most of it hard won, with some serious intellectual capital spent, but also elements of luck (the microwave hiss and the Bell Lab engineers). But we are never content, each new advance always brings more questions. We are constantly asking what is over the other side of that hill
Jim
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8 minutes ago, andrew s said:
0.0001s to 13.8 Gyrs
That is not a bad ratio at all
Jim
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6 minutes ago, Knighty2112 said:
Hi Jim. What I want to know is what’s kicking the can if that’s what we are now calling the universe!
Gus I get that. It's an excellent and entirely natural question and as much as it is unsatisfactory but as others have said "science" is not really equipped to answer that. So that takes us back to what the Big Bang theory sets out to do. It is up front and as honest as can be, it sets out only to describe how the universe evolved (the stages of its evolution), it makes no claim to do anything other than that. In that respect, and given the compelling supporting evidence, it does seem pretty secure, maybe not perfect thankfully - some things still to be reconciled, but pretty solid nonetheless. I don't think we are then kicking the can down the road, not with the Big Bang theory anyway. Maybe what we are doing is looking at an altogether different question and getting frustrated because science can't help out with that one.
Jim
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2 minutes ago, Knighty2112 said:
Great points vlaiv, but still kicking the can down the road!
Sometimes the can has to be kicked down the road, doesn't alter the fact that it is a can though. We know how the can came to be but we don't need to know why in order to kick it.
Jim
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2 hours ago, Nakedgun said:
~
Your post prompted me to dig around in the attic....
Kryptonics also made boards, and this was my second by them. A "carving" board, which worked better at skate parks for me, rather than a "kick-flip" type, which were better for street skating.
Kryptonics wheels, I think the green CX-66 were the hardest compound they offered at the time.
Tracker trucks:
This was my last board before I stopped skating, probably around 1981.
I dare not set foot on it today!
.
Wow that is a lovely board, there is a lot of history on that; did the wheels come coned like that or is that from use? I started skating pretty much in the late to mid 70s when skateboarding really took off here. Of course no internet back then so it was impossible to find out about the wider skateboarding scene and culture, especially if you lived outside the main cities. As kids, we used our boards for getting about town, oh and falling off, which we did a lot
We didn't do tricks, to be honest we never really knew tricks were a thing beyond tic tacking a 360 and jumping kerbs - certainly no ollies. Round about the early 80s following a very long and hard fought campaign by a very special and passionate man, architect Ian Urquhart , we got our first full blown American style skatepark. It was a first for both Scotland and for the UK and would soon make a name for itself on the world skating scene. The Skatepark at Livingston (central belt of Scotland) affectionately known as Livi gained a reputation as a bit of a special place and even attracted a young Tony Hawk to visit and ride in the early 90s. It has gone through both decline and a recent resurgence and now there is a campaign to grant it listed building status, support again coming from key luminaries like Tony Hawk.
Anyway back to Kryptonics, as an 11 year old kid growing up in the central belt of Scotland the very name just imbued those wheels with special powers. That they came from America just added to their authenticity and potency, I was the envy of my pals and I milked it for all it was worth
I got back on a board a few years past; like riding a bike you don't forget the balance of it. To be honest though I was conscious of the effects of falling on my now older and heavier frame so I tried long boarding and wow I was addicted all over again. Lockdown gave me the excuse to really invest some time on the board and I am so grateful for that, it is hard to explain but when I'm on the board it is like a zen like transformation. I guess you will get that experience when you are on your motorbike riding in the desert. Your focus is on one thing only, the moment, it is a brilliant feeling doing big long lazy carving turns and pushing faster than it is really sensible to do! What we do lack here is suitable roads/pathways to skate. I occasionally will push it and skate on the public highway (very quiet neighborhood roads) or take a trip to Dundee or one of our nearby coastal towns to ride on the paved promenades. I have a family member who lives out in San Francisco and if I ever get round to visiting my board will be the first thing that goes into my luggage, I may even by it a seperate seat ticket
ps - tx for sharing the photos of your board - made my day. You need to get it hung on the wall , to remind you of what it was like, and you never know maybe again
https://www.esquire.com/uk/culture/a34617191/livingston-skate-park/
Jim
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Flawless, just stunning, what a joy to see. Take the moment to view the larger image as suggested
Jim
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Hi and welcome to SGL you have found a truly amazing place for help, advice and inspiration.
Jim
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3 minutes ago, DaveS said:
Imaging doesn't have to preclude observing. Once my imaging sequence is up and running I will frequently go out with my 10 X 50s to look around. I have some grab and go kit that I should be making more use of, though it's not the primary focus of my astronomy.
I do similar Dave, once my imaging plan is up and running I turn to my visual set-up. But shhhhh, this kind of loose talk is dangerous, people have been stripped of their eyepieces for suggesting you can do both
Jim
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The happy astronomer is the one that does both, or just does whatever they like without justification or affirmation.
Jim
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Ok, I'm converted, pass me my HB and No 2H pencils.
Jim
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31 minutes ago, paulastro said:
I initially wondered if this was meant to be a serious comment on the issue.
I didn't realise that visual observers were becoming 'unpopular' - I know some visual observers who have quite a few friends.
I suppose visual observers should also be grateful that 'there is a certain charm to visual observing' - I m glad it has something going for it.
On a more serious note though, I am rather concerned that I am ' going to evolve to become more astrophotography than visual'. What does this mean, square eyes to better use monitors, thinner fingers to tap the keyboard keys more effectively?
And 'imaging takes research before going out, planning the night' - and there was me thinking visual observers just rush out at the sign of any clear sky and point the tesescope randomly at any object in the night sky.
Incredible!
Never mind Elon Musk and Mark Zuckerberg cage fighting, these visual v ap astronomy threads always make me giggle. Who would have thought we have such mild mannered seething tension out there under our dark skies. Stand up for original photons, let's hear it for quantum efficiency and something for err EAA whatever that is
Jim
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I have a string of LED white lights that I use once a session is over and I need to tidy up or close the obsy down - without them I find like you the obsy is just too dark. Once up and running I have a single red LED that I'll use as an when needed, it's quite low power.
Jim
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I like the trail shots but my favourite is the last one, the quality of the light and the subject is just glorious. Well done
Jim
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1 hour ago, andrew s said:
Yes, thinking deeply about simple cases is very insightful. Try changing your frame of reference and have the s (normally) stationary balls heading towards the the m (normally) moving ones. Of course the kinetic energy and momentum in the two frames of reference are different.
Regards Andrew
It is so counterintuitive to accept that the natural state of an object is motion, that everything is born into a state of motion. Doors seem to open once you wrap your head around it.
Jim
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Thanks Andrew, I need to spend some time on the maths later today and see if I can follow it through, I'm keen to properly get my head wrapped around this. Re the Newton cradle, if you happen to have one handy (why wouldn't you) and super slo mo on your mobile phone it makes for a lovely video. When you see it in slo mo it just begs the question "how do the balls know when to move and how many". It's a great way to spark curiosity and as an introduction to momentum.
Jim
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Wait a minute, just a further thought, how does that reconcile with conservation of momentum? Or have read into it incorrectly!
Jim
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I've never seen that before, it's fascinating. I love the idea that a ball could sit at the apex for an indeterminate time and then spontaneously, without any external force, roll down the slope, all consistent with the equations of motion. Newton just got cool again
Jim
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1 hour ago, moggi1964 said:
The naivety of youth.
As the great Jay Adams said, "you didn't quit skateboarding because you got old, you got old because you quit skateboarding"
Yep, Kryptonites (Kryptonics), back in the day they were the cool of cool. My first proper skateboard was bought second-hand, a Benjy Board and it came with a set of Red Kryptonites, a set of Green Kryptonites and a set of YoYos. I was in heaven for the best part of 77. You get a pretty price for a decent Benjy board now
Jim
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These little babies were patiently waiting for me when I arrived home - nice postman . My old wheels, well let's say if longboards had MOTs it would be a definite fail. 80 mm of sweet rolling happiness
Jim
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Big Bang theory just does not make sense
in Physics, Space Science and Theories
Posted
Hang on don't go dissing Newtonian dynamics here
Can you tell I am a fan boi - stands up and mutters to the group "I'm Jim and I'm an engineer. It's been 32 days since picked up a slide rule "
We came a long way on the back of Newtonian mechanics - heavier than air flight, split the atom, left the planet, built CERN and found more quantum stuff, put JWST in space to see the beginning. Not so bad for "special cases" - we inhabit that realm. Let's hear it for Newton.
Jim