Ask any question you want about Physics

What exactly is the 3-manifold of comoving space...or the shape of our universe?

.hi again reagarding the hipparcos misssion that calculated the many parrallax's that happen i can see what you mean by the distance making the stars look like they orbit with us and i agree it seems rediculous to think this happens, my question is surely the amount the satellite moves in space is tiny compared to the six month movement of earth so why can this satllite see the parallax but we cant on earth(or can we)?. I dont quite understand what you mean by the earths orbit is tilted to the milky way plane if the milkyway plane is not the same as earths tilt in orbit then wont the distance between earth and stars change over 6 months i assume this does happen but once again the distance makes it to hard for us to detect is this right?

apart from measurements from parallax is there any other way we can measure star distances

originally posted by: teamcommander
a reply to: Arbitrageur

I do appreciate your reply. However, this is very close to the same reply I got from a gentleman from NASA in 1963, as he watched my first model jumping up from the floor at my highschool science fair.

I have a little better understanding of what you have from that description. The reason it falls back down is you have no way to keep it going, right? Or do you? From that description it sounds like you don't.

One possibility is to sign up for a local physics course and discuss the idea with your physics teacher, or you may learn some things in the course that could help your idea or explain why it will or won't work. NASA is open to innovative new ideas, but it doesn't sound like your idea is ready for a presentation to NASA yet.

a reply to: RedParrotHead
As far as we can measure, it's flat, but Michio Kaku thinks the flatness measurements don't rule out the possibility of a curved "spherical" geometry, however they do suggest the sphere would have to be of immense proportions.

The example Kaku used for an analogy was that it would be like an ant crawling on the surface of a giant hot air balloon. The balloon is so much larger than the ant it would look like a flat surface to the ant, even though it was curved.

Also as a consequence of this flatness, if Kaku is wrong about the small curvature, and it's actually really flat, then it could be infinite.

originally posted by: edfloaters
.hi again reagarding the hipparcos misssion that calculated the many parrallax's that happen i can see what you mean by the distance making the stars look like they orbit with us and i agree it seems rediculous to think this happens, my question is surely the amount the satellite moves in space is tiny compared to the six month movement of earth so why can this satllite see the parallax but we cant on earth(or can we)?.

Yes we can see the parallax from Earth but there are problems observing from Earth, aside from all the wobbles, the atmosphere creates distortion and by getting above the atmosphere we can avoid atmospheric distortion to make accurate observations. You're right the satellite orbited the Earth but the orbit baseline wasn't large enough, so in fact the satellite did use the Earth's orbit over 6 month intervals as part of the calculation, though it gets a little more complicated as explained here:

Measuring distances to stars via parallax

I dont quite understand what you mean by the earths orbit is tilted to the milky way plane if the milkyway plane is not the same as earths tilt in orbit then wont the distance between earth and stars change over 6 months i assume this does happen but once again the distance makes it to hard for us to detect is this right?

Yes the baseline of Earth's orbit is about 16 light minutes, and the star could be 100 light years away, so what's 16 minutes compared to 100 years? Not much. The distance comparison at the speed of light is analogous to the time comparison.

originally posted by: edfloaters
apart from measurements from parallax is there any other way we can measure star distances

Parallax is the one we understand the best, but there are many others. If you follow the parallax link I posted it goes to an explanation of the cosmic distance ladder which explains all the other measurement methods, or most of them.

originally posted by: hgfbob
Simple fact of SCIENCE: if any of the potential energy from the accelerating mass went to destroying itself, it will lose kinetic energy which requires that the building slow in its fall.......but since it did fall at free-fall acceleration, it wasn't causing itself to collapse.

Is that statement true or false?

a reply to: Mary Rose
This question is related to the parallax question earlier, where I mentioned that current technology can't measure the parallax effect on stars more distant than 1000 light years or so. Why do you suppose this is? Does the parallax effect stop on stars further than 1000 light years away?

Since it's a well-understood function of an isosceles triangle which we all learned about in early math courses, it's reasonable to presume that the parallax effect also occurs on stars greater than 1000 light years away, but the effect is too small to measure.

With that in mind, replace the rungs of a ladder with plastic soda straws. Put a 1 ton weight on the top rung of the ladder and measure the acceleration of the object.

Now measure the acceleration of the object in free-fall without any soda straws slowing it down. If you don't measure any difference, it's probably not because the soda straws aren't slowing it down, it's probably because the difference is beyond your measurement capability.

Therefore from one perspective it's true, but from another perspective it can be perceived as "false" or at least unsupported by measurable evidence, if the effect is too small to measure.

The example I like to use is dropping a paper clip. In theory, as the paper clip falls toward the Earth, the Earth also falls toward the paper clip. However I will never be able to prove the latter with experiments, just as you're unlikely to show soda straws slow down the fall of a 1 ton object versus free fall.

originally posted by: Mary Rose

originally posted by: hgfbob
Simple fact of SCIENCE: if any of the potential energy from the accelerating mass went to destroying itself, it will lose kinetic energy which requires that the building slow in its fall.......but since it did fall at free-fall acceleration, it wasn't causing itself to collapse.

Is that statement true or false?

False its impossible for a building to collapse at free fall.

a reply to: Arbitrageur

Currently with Hubble distances can be determined up to 10000 light years! not bad huh? Eventually i see that distance getting much further.

a reply to: dragonridr

False its impossible for a building to collapse at free fall.

yet here we are.....

NCSTAR 1A 3.6] "This free fall drop continues for approximately 8 stories, the distance traveled between t=1.75s and t=4.0s...constant, downward acceleration during this time interval. This acceleration was *9.8m/s^2*, equivalent to the acceleration of gravity."

NICSTAR 1A 4.3.4] Global Collapse..."The entire building above the buckled column region moved downward in a single unit, as observed, completing the global collapse"

NCSTAR1A p.39/130
"the damage from the debris from WTC 1 had little effect on initiating the collapse of WTC 7."

seems an interval of global unified acceleration equal to g. occurred in WTC7 for 1/3 of it's 6.5 second collapse.

if ya need it broken down further.....

constant acceleration equal to gravity occurred in WTC7 for 2.3 seconds.

WHEN did it occur.....1.75 seconds, to 4.0 seconds...

WHAT does it encompass???.....the ENTIRE building.......moving as ONE, there is NO part doing anything different than any other part DURING the interval of found FFA.

what does ALL agreed science tell us about mass accelerating equal to g.?.....that NONE of the gravitational energy is available to destroy the supporting structures, ALL converted to MOTION!

meaning, any bending, crushing, breaking connections, REMOVAL of structural RESISTANCE, BELOW the mass ACCELERATING, is occurring WITHOUT the assistance of energy from the mass accelerating. Zero resistance.

now where else ON EARTH do we see those SAME numbers????
open ANY science/physics text of your choosing, turn to the section of Gravitational Acceleration...."rate of acceleration seen by ALL mass REGARDLESS of weight toward the earth, at sea level, *~**WITHIN a VACUUM**~* is *9.8m/s^2*.

hmm.....the SAME numbers we see under 'CONTROLLED conditions, WE SEE occurring globally and UNIFIED in a 47 story steel frame @ 1.75 SECONDS, when kink forms, to 4.0s of the collapse....2.5 seconds later, it's done....6.5 second building collapse from FIRE we can't really see from the windows.

NCSTAR1A-3.2]"It is likely that much of the burning took place beyond the views of the windows"

now, you said this is IMPOSSIBLE, then we are in agreement...it is impossible as a natural occurrence....till 9-11 that is..and here it is, a NEW phenomenon of science called LOW TEMP thermal expansion...a new phenomenon they refuse to prove ACTUALLY occurred, through science.

"the phenomenon that we saw on 9/11 that brought this particular building down was really thermal expansion, which occurs at lower temperatures."

now can ya see why I ask the physics question to explain HOW this new phenomenon REMOVED the required resistance to allow the global unified acceleration found.

a reply to: dragonridr
Yes they are using a technique called spatial scanning in conjunction with the parallax measurement:

NASA's Hubble Extends Stellar Tape Measure 10 Times Farther Into Space

Astronomers have developed yet another novel way to use the 24-year-old space telescope by employing a technique called spatial scanning, which dramatically improves Hubble's accuracy for making angular measurements. The technique, when applied to the age-old method for gauging distances called astronomical parallax, extends Hubble's tape measure 10 times farther into space.

Also that only mentions using the technique on Cepheid variables and doesn't say if it works with ordinary stars.

The European Space Agency's Gaia mission should have even better capabilities.

a reply to: hgfbob
9/11 posts are off-topic in this thread

a reply to: Arbitrageur

With that in mind, replace the rungs of a ladder with plastic soda straws. Put a 1 ton weight on the top rung of the ladder and measure the acceleration of the object.

why do we even need to REDUCE the strength of your example BEFORE we start??????

oh yea, YOU need ALL the advantage ya can get!!!!!!

and we are talking 'LIKE' objects smashing into each other...or did ya FORGET that also.....

. If you don't measure any difference, it's probably not because the soda straws aren't slowing it down,

because the 'straws' are being REMOVED AHEAD of the collapse wave!!!!lmao.

dude.....get use to it...this is NOT going away.

The example I like to use is dropping a paper clip. In theory, as the paper clip falls toward the Earth, the Earth also falls toward the paper clip.

where is the 'dropping of ANYTHING'??????

there are NO dynamics UNTIL the vertical support ALLOW it to occur, the reason we are all here.....NOT the other way around.....lol....uhm...mr rocket scientist, do you actually have degrees in anything, or do ya just read Marvel comics to come up with this stuff?

a reply to: Arbitrageur

9/11 posts are off-topic in this thread

that is why I asked a PHYSICS QUESTION!!!!!


and as dragonridr already posted


"False its impossible for a building to collapse at free fall."


so YOU tell me all about this NEW physics of LOW TEMP thermal expansion and HOW it removed the necessary structural RESISTANCE to allow global unified ACCELERATION equal to g. to occur for 105 vertical feet for 1/3 of the 6.5 second collapse.

AGREED upon science states......."NONE of the gravitational energy was available to destroy the supporting structures, ALL converted to MOTION!"


tell me how this NEW science created conditions for the global unified acceleration BEFORE 1.74 seconds.

"the phenomenon that we saw on 9/11 that brought this particular building down was really thermal expansion, which occurs at lower temperatures."

please tell us all HOW this new phenomenon, that ONLY seemed to occur on ONE day.....never to be seen before or since......removed the...
105 vertical feet of LOAD BEARING continuous vertical support....
8 floors of truss assemblies with carrier beams...
lateral, cross, and diagonal bracing throughout...
tens of thousands of bolts and welds...
Interior partitions...
office contents...
utilities....

all before 1.74 seconds or at the VERY LEAST, globally and unified AHEAD of the collapse wave.

a reply to: dragonridr

It happens all the time with controlled demolition, does it not?

originally posted by: hgfbob
a NEW phenomenon of science called LOW TEMP thermal expansion...

Is that a true statement?

Is there a phenomenon called low temperature thermal expansion in physics, or not?

If there is, does it make sense scientifically in the government report being referenced?

a reply to: hgfbob


Tell you what stop spamming the thread and i promise you you caan email me the data you believe to be correct and ill show you the math.

originally posted by: Mary Rose
a reply to: dragonridr

It happens all the time with controlled demolition, does it not?

originally posted by: hgfbob
a NEW phenomenon of science called LOW TEMP thermal expansion...

Is that a true statement?

Is there a phenomenon called low temperature thermal expansion in physics, or not?

If there is, does it make sense scientifically in the government report being referenced?

No if a building falls on its own or demolished does not increase the speed it can fall this is set by gravity and unaffected by anything other than its original momentum. As far as low temperature thermal expansion i gave you the formula for steel if we have a formula obviously we are aware it occurs.

a reply to: dragonridr

This is a public forum and the member you are addressing has been patiently giving input to the whole wide world concerning serious questions of scientific import that ultimately affect everyone.

The use of the word "spam" in this context is uncalled for.

a reply to: Mary Rose

The title of the thread is "Ask any question you want about Physics". The poster in question has repeatedly spammed (yes, spammed) a bunch of 9/11 conspiracy rants repeatedly. Answers have been given but the commentor does not appear to be interested in any answers that do not conform to their conspiratorial beliefs around 9/11. Not only that, but the information spammed is nothing new. There's a whole forum for people to argue over 9/11 and the only reason the commentor is spamming this thread is because the last thread they were spamming about 9/11 was locked in part due to "constant regurgitation of material that has been posted ad-nausea". And here we are, the same material being spammed ad nauseum.

a reply to: Arbitrageur

What is, in your opinion, the ultimate goal of Physics?

Omniscience?

a reply to: hgfbob

Stop being a Clown

read up on structural loads!!!.

S&F Arbitrageur

originally posted by: Mary Rose
a reply to: dragonridr

This is a public forum and the member you are addressing has been patiently giving input to the whole wide world concerning serious questions of scientific import that ultimately affect everyone.

The use of the word "spam" in this context is uncalled for.

I suggest you check his 9/11 posts before saying that!