Greatest physical misconceptions

[epoisses]

What about a thread on the greatest fundamental physical misconceptions. They can be historical or present-day. I'll kick off with a real life example.

At home we have a jug with a water filter because the tap water is disgusting. We usually let it in the sink after filling it because filtering is rather slow. My sister-in-law who visited us the other day asked me if there was any technical reason why I put the filter in the sink (which is about 20 cm deep): "Is that to make it filter faster?". I tried to explain the special theory of relativity of height, but it didn't make it easier for her. She finally found peace when I explained it was just laziness to leave it in the sink. (She's not unintelligent otherwise although I must admit she often buys lottery tickets.)

Can anybody top that?

 

[rb1957]

i think they base their claim on the bible saying that the earth is stationary ...

 

[minerk]

Wouldn't it then be blasphemous (sp) to claim that man-made satellites also stand still in space while the universe rotates 'round?

 

[epoisses]

This bunch of catholics has not understood how science works. There is no such thing as "proving" a hypothesis, one can only falsify wrong hypotheses. They would not award $1000 if we only managed to falsify their geocentrism. Somewhere down the article it says that the award is really about: "Can it be proven, by direct and irrefutable scientific evidence, that the Heliocentric system is the ONLY viable system to understand the universe." - Well of course not, as the author wrote just above that, mathematicians are so smart they can model the universe with the earth of, why not, Jupiter as the middle if they felt like. But why would they develop such an ugly, unnecessarily complicated model?

I find it unconceivable that, 5 centuries after the triumph of Copernicus' free intelligent mind over the retarded ideas imposed by the church, some people still write such kind of articles.

Anyway. Can't full moon, new moon, lunar eclipse and solar eclipse falsify geocentrism already? Or does God just hold his hand in front of it to test us...?

 

[rb1957]

i think they have a model of a geo-centric solar system, with the moon and the sun orbiting the earth, and everything else orbiting the sun.

i think they can complicate their model "absurdum" to match the visual record. yes, it results in a very complex model but i don't think science is well served by rubbishing their claims ... i'm not saying that we here have rubbished them, but rather the scientific community in general. i also think that science is not denigrated by proving these models wrong, that this is not "beneath responsible science".

i was thinking that today we can measure the distance to the planets and as the two models (geo- and helio-centric) have very different predictions about the distance between the planets. but then i'd expect them to claim that the "ether" affects laser light in ways we cannot understand.

 

[zeitghost]

Ah.

Epicycles...

Music of the spheres comes next...

As in "la la la what a load of testicles..."?

 

[mechj]

I heard somebody today refer the "speed" of gravity. In the context of interstellar space travel. It was stated that, and I am quoting this, that

"When we have computers that can conquer the speed of gravity we can travel anywhere in the universe because time stops."

Anyone no what the speed of gravity is?

"Education is what remains after one has forgotten everything he learned in school." Albert Einstein

 

[IRstuff]

Does that matter? I'm more curious about "time stops."

TTFN

 

[GregLocock]

/If/ gravity waves are real then they will have a wavespeed associated with them. Probably.

There are several experiments running to detect gravity waves, obviously non have succeeded yet.

Cheers

Greg Locock

Please see FAQ731-376 for tips on how to make the best use of Eng-Tips.

 

[quark]

It is already known fact that the gravitational force is inversely proportional to the square of the distance between two bodies and product of their masses. How fast this change occurs incase of change in the distance between two bodies or masses gives a clue about the speed of gravity. With the tangible time scales available to us, so far, this seems to be instantaneous. It is even thought that gravity propagates at speeds much greater than that of light. Here is a link to one such fascinated idea,

http://www.ldolphin.org/vanFlandern/gravityspeed.html

This link is just to give you an idea about what speed of gravity is. Nothing is guaranteed for the actual technical content. Infact, maximum members of a physics forum, in which I regularly participate, ridiculed this idea, when I posted this link there.

 

[epoisses]

Well this may or may not be a misconception, we'll know as soon as someone manages to falsify the idea (which is not the same as ridiculising it).

 

[GregLocock]

My very vague view is that gravity waves must be very fast, so we probably don't have a good model for them. I'm always amused by how flaky cutting edge physics is, but that's OK, we'll have a working warp drive while the physicists are still arguing about the maths. I hope.

Cheers

Greg Locock

Please see FAQ731-376 for tips on how to make the best use of Eng-Tips.

 

[RDK]

It doesn’t take an engineer to know that whenever someone starts a sentence with “It doesn’t take an engineer to know” that the remainder of the sentence usually has nothing to do with engineering and is wrong.

Rick Kitson MBA P.Eng

Construction Project Management
From conception to completion

http://www.kitsonengineering.com

 

[zdas04]

RDK,
Same with "it's a known fact".

David

 

[quark]

The correction in my post should be 'the gravitational force is inversely proportional to the square of the distance and directly proportional to the product of masses'.

With that, "it is a known fact" actually relates to the universal law of gravitation only or atleast I thought so. I provided the link to give mechj an idea about speed of gravity and not for its numerical value.

Anyhow, I did enjoy the excellent contradiction about saying truth. It is worth remembering.

 

[EnglishMuffin]

quark : VanFlandern is generally regarded as a crank in mainstream physics circles. My understanding is that in General Relativity, gravity waves and gravity both travel at the speed of light, whereas in Newtonian physics, you have to assume that gravity travels at infinite speed, to avoid aberration effects which are known not to occur. In general relativity, for purely circular orbits, the aberration effect which would be produced by assuming a finite speed of gravity is exactly cancelled by the space curvature effect. For elliptical orbits, (which all the planets have) this does not quite happen, so the perihelion of the orbit advances slightly. It is interesting to note that Gerber got the correct answer for the advance of Mercury's perihelion considerably before Einstein did, just by assuming gravity travelled at the speed of light, but Einstein said he had made a number of mistakes and his analysis was "completely wrong". But somehow, Gerber got the right formula, and some have speculated that Einstein mucked about with his own theory until it was consistent with Gerber's result. Gerber was only a humble schoolmaster, and regarded by the mainstream as a bit of an amateur, so who knows - maybe VanFlandern has got something. But personally, I think the odds are against it.

 

[jmw]

Another misconception:
the internet is free, uncensored and unregulated -
and that it should be.
"High minded" people don't ever seem to allow for human nature.

JMW

http://www.ViscoAnalyser.com