Space and The wonders/mysteries of The Universe

I think if they don't tune everything to the preset schedule they have to massively recalculate everything, which doesn't work so well with a 9 minute transmission delay. So in the acceleration and deceleration burns they carefully tweak things until it fits. Not total precision from the moment of liftoff.

I remember Az had posted a shot of what it would look like if the moon were the size of saturn (can't find it now), and I thought it looked small.  The shot here looks better to me, but I realized looking out my window that the moon does look awfully small when away from the horizon, and that previous shot had saturn away from the horizon.  So maybe so.

https://www.theatlantic.com/technology/archive/2013/06/what-the-night-sky-would-look-like-if-the-other-planets-were-as-close-as-the-moon/277247/

Um....speed?

If you're talking about free projectile type motion, then sand or water clocks would be fairly inadequate to get dynamical variables like acceleration.  This is why Galileo slid things down a long ramp to slow things down, then extrapolated what would happen if straight up and down.  He had success because he was measuring a constant acceleration, but if acceleration is changing you need more advanced instrumentation.  

The reason you want acceleration is to relate it to force, which may indeed change with the properties of your object.  Larger mass/surface area ratio would tell you something about air resistance, for example.

There's some confusion here if balls are being rolled because kinetic energy goes into rotation motion as well as translational motion.  But if not rolling then friction looms large.  There's a reason why everyone accepted Aristotelian physics for nearly 2 millenia, even though we can point out obvious problems with it from simple observation. Pulling numbers out of observations is hard! That's why math was used in astronomy first: everything happens on the order of days as opposed to seconds.

What you are actually measuring is angular change per time. Since distance = radius x angle, this is equivalent to speed, but objects that are further away are travelling a longer distance across the same angle, so are moving faster if doing it in the same amount of time.

BUT we are on a rotating earth, so everything has this built-in angular speed, or I should say velocity because it depends on what direction you are looking. So all that I say above depends on you subtracting out this fixed angular velocity, which is not as hard as it sounds because the stars are so far away that even though they may be moving very fast, they are covering such small angles that you can treat them as fixed points in the rotating sky. So all you have to do is see how objects are moving relative to the stars. Your fixed obelix ends up not being all that useful except to help mark where the earth is in its complex self rotation plus orbit around the sun.

But let's go back to that planet you are observing. From how long it takes to cross a particular part of the star field (best measured in days rather than hours) you can figure out how much time the total orbit will take (though it's more complicated because the earth keeps changing position making the planet sometimes appear to be moving in retrograde). Once you have the orbital period figured out, you can figure out it's distance from the sun relative to the earth's distance to the sun.

Figuring out the earth's distance from the sun is no easy feat, but Aristarchus of Samos figured out a method, and though he was off by a factor of 60 his reasoning was totally valid, it was the measurements to a fraction of a degree that were off.

Yeah, just saw that - it's very exciting!  Will probably take a couple decades to sort out, at least.

though the 'standard' physics isn't making sense to me either right now. They are claiming a B meson (which contains quarks from the first and third family) should decay into electrons and muons - but muons are associated with the second family of quarks. So either the B meson statement is wrong or I have no idea how this is supposed to work.

Update on the Mars rover, things be moving slow.

https://www.yahoo.com/nasa-mars-flight-test-030634860.html

Hmm - does the same thing to me. I looked back in my history to see if I didn't copy the whole thing, but it disappeared from there too. Link must have broken somehow.

All it's saying is that in the past two weeks the rover dropped off the helicopter, backed away, and did a slow rotation test of the propellers. A high rotation test is scheduled for next week.

Seems like anything they do has to go through six committee meetings before it's put on the schedule. Which way to navigate around a basketball sized rock, etc.

They can't do anything in real time and they don't want to get stuck. But it seems they might have done better if they programming some simple intelligence into it. When you send a dog to chase a ball, it will dither around, sniff a rock that needs sniffing, perform a simple search pattern and eventually find the ball. Piddle on the way back. It's just doing things dogs know how to do, it doesn't need to be micromanaged.

But they've got limited power and a very expensive dog. I suppose careful planning makes sense.

So they flew the helicopter this morning.  Too data intensive to send video from Mars, so what you have is the control crew reacting to images and telemetry data.  What strikes me about this is how young the crew is: I don't see a face that looks older than 35.  I can see how the helicopter was seen as a non-essential training mission for young engineers.  Look how excited they are!  Cute.

Looking forward to those, Lance.

Figgy - I agree with Lance about taking such statements with a good dose of salt.  Reporters tend to take anything that looks interesting that happens to be published anywhere and file it under "scientists say" instead of "there are some untested theories out there that speculate".

The "infinite universe" is already debatable.  The other bubble universes even more so.

https://phys.org/news/2015-03-universe-finite-infinite.html

https://www.forbes.com/sites/startswithabang/2017/10/14/ask-ethan-is-the-universe-finite-or-infinite/

Speaking of which:

Mrs Figg wrote:https://www.theguardian.com/science/2021/mar/23/large-hadron-collider-scientists-particle-physics

new physics yikes!

I think this is the best explanation I've seen of why it may NOT be new physics, but calculational disagreement.

https://medium.com/starts-with-a-bang/why-you-should-doubt-new-physics-from-the-latest-muon-g-2-results-fda1ffc159e6

to summarize: Experiments are measuring something called the magnetic moment of the muon.  Exactly what that is doesn't matter, but it needs to be compared to an extremely difficult theoretical calculation.  Parts of this calculation are so difficult that traditionally people borrow parts of it from experimental measurements made of electrons: essentially "why should we calculate this hard part when we already measured it somewhere else?".   This blended experimental/theory calculation does not agree with the new measurements.

But some theoretical physicists have done the entire calculation using supercomputers, and came up with an answer that matched the new experiment.  They claim the old way of doing the calculation was flawed because the experimental measurement of the electron can not be used for the muon. (I've read elsewhere that this is related to treating the electron as a point particle, but this doesn't work for the much larger muon).  Until the discrepancies between the two ways of doing the calculation are hammered out it's premature to declare new physics.