tombombodil wrote:Another thing I thought of (in terms of theories and skepticism etc) is that something can be far from "set in stone" (the way I would consider Newtonian physics or the Pythagorean theorem to be "set in stone") can still be experimentally valid and more importantly, practically useful. For example non-real numbers are pretty esoteric to most people and didn't even get accepted as worth consideration by academics until a few hundred years ago, but mechanical and civil engineers use them all the time to allow them to build physical things that we walk on/in.
It could follow that a theory/model that later proves to be off the mark, could in the present be somewhat useful for a number of practical applications, not to mention being a necessary stepping stone to a more accurate theory.
Magmoo wrote:One the great gaps between the scientifically literate and those who are less so is the proper understanding and use of terms. The whole "theory" issue for example. Are there any fundamental terms and concepts that you experience people miss using that you would like to clear up?
Burning wrote:Magmoo wrote:One the great gaps between the scientifically literate and those who are less so is the proper understanding and use of terms. The whole "theory" issue for example. Are there any fundamental terms and concepts that you experience people miss using that you would like to clear up?
I'm going to broaden this a bit to misconceptions that bother me. There is a bit of an element of misuse or misunderstanding of terms to what I'm going to talk about, but I'm going to be going beyond just the meaning of words. Just wanted to be out in the open about that.
Anyway, there were two things that particularly sprung to mind with this question.
1. "Uncertainty" is not a bad thing
There seems to be an expectation among a lot of people that science will give absolute answers. That's not actually possible, even in principle.
There is no measurement technique that is perfect. Measuring the same thing twice can result in two different answers. The better the technique, the smaller the difference will be, but you can't eliminate the possibility of discrepancy completely. Furthermore, there can be outside influences that can introduce a variation. When we talk about repeating a measurement, we mean that we do our best to have everything the same the second time as it was the first. There's still going to be stuff beyond our control, however.
"Uncertainty" is our estimate of how large our assorted variations might be. No measurement is really complete without an uncertainty. The measurement result is the scientist's best estimate of the real value. The uncertainty gives the range of values that the scientist is reasonably confident contains the real value.
Of course everyone wants small uncertainties. But a large, realistic uncertainty communicates important information. A small but unrealistic uncertainty is worse than no uncertainty at all.
2. Science does not require "experiments," and experiments do not require "controls."
OK, this is really two misconceptions, but they are extremely similar. Both are based on a true principle, but have the problem that they're too specific.
I'm a bit sensitive to the first one, having a background in astrophysics. I have actually been told by people that astrophysics is not a science because you can't you can't perform experiments on stars, planets, etc.
To be clear, science requires objective observations. If you have those, you can evaluate the predictions of the scientific theories. Experiments are observations where you have some control over what happens, not just what you look at. That control makes it easier to get the data you need. I'm sure there are astrophysicists that would like to have a star-in-a-jar that they could fiddle with. But it's not necessary to have that control, and it doesn't make your observations more objective.
Similarly, in all observations whether they are part of experiments or not, you need to be able to isolate the factors you are interested in from all the others that might be present. The control subject or control group method that you learned about in grade-school science is one technique for this. It is excellent when you are trying to understand how person/animal/system responds to outside stimula or influences. It's not much use if you are trying to study the intrinsic properties of something. Furthermore, in experiments where a control is appropriate, it is not necessarily adequate.
Too many people have been taught the importance of a control without really understanding its role properly. So they judge results based on whether there is something that they recognize as a control, without considering whether or not there's something that doesn't really look like a control but that serves the same purpose.
Burning wrote:Lord Foul wrote:What I don't get about gravity, and weight, is how far does it reach? I mean, everything that has mass has gravity, and the greater the mass the greater the gravity. And gravity acts upon stuff with mass to give it weight, presumably after you've subtracted the gravity effect of the mass itself.
So... if the total mass of stuff in the universe is BRIAN BLESSED (a very large space number tending to infinity), why isn't the weight of everything absolutely ENORMOUS?
Or, put another way, how far does gravity reach?
You are on the edge of deep waters. The short version is:
(a) Gravity reaches forever, but gets very weak as you get far away.
(b) However, the main reason that the force of gravity on you from a huge universe is so small is that you're surrounded by the stuff so the pull from the stuff on one side gets cancelled by the pull of the stuff on the other.
(c) "Weight" doesn't actually have a good scientific definition for complicated reasons. However, our every day experience of weight is the force of gravity from Earth alone.
EDIT: If you're interested I can give a longer answer in my Physics AMA thread.
Lord Foul wrote:So, is gravity a function of both mass and distance, then?
Also, does a fat person fall faster than a thin person because their mass is higher and therefore their gravitational pull on the planet is slightly greater?
At what point do you stop falling towards Earth and start falling towards Mars, relative to the distance between them?
tombombodil wrote:I thought the modern consensus was that gravity isn't actually a force that acts on anything. It's just a distortion of space-time caused by massive bodies [yo mama joke placeholder] that simulates a force. Things in orbit around other things are travelling in a straight line as far as they're concerned, but since space is curved around massive bodies [another yo mama joke placeholder] they appear to be travelling in an oval of some kind.
Lord Foul wrote:If he's right and they are not moving, then that must mean the world is moving up at them, which is all very well except that the same thing happens wherever you are around the globe, and it can't be moving in every direction at once.
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