By that definition it could be said that the Sun and Jupiter orbit each other as Jupiter’s barycenter with the Sun lies outside the Sun.
The thing is, all observations are relative. It is entirely possible, that the sun and its orbiting collection of satellites (“planets”) as a whole circle our motionless earth…
The thing is, then you would have to claim mysterious forces that allow a whole solar system to orbit a smaller body (let’s call it “deificational force”) in addition to the existing laws of physics.
the point is… and this is one of Newton’s claims to fame… the simplest explanation that works - works best. You and Newton and Galileo can measure the gravity that causes apples to rain onto our heads and derive the gravitational constant. You can show its charcteristics. If you don’t believe the published measurement of the size of the Earth, you can repeat the measurements of the Greek philosophers, trek from Luxor to Athens and check the angle of the sun at noon on a particular day. (You can even verify the solar calendar if you’ve got a few decades). You and a buddy can do parallax measurements of the moon against the stars from different locations to get distances. An so on… you can do experiments that replicate the footsteps of the giants.
This was Newton’s biggest discovery, to prove the same gravity that drops apples can and must move planets. If you choose to believe a “god force” rearranges the universe so as to keep earth stationary in the face of newtonian 9and Einstein) physics, then you may be right. The question is - what would you do to prove the existence of such a diversion from Newtonian physics? What experiment would you perform to show it does or does not exist?
This is the crux of science and the experimental method. If a universe where Newton was right is physically indistinguishable from one where everything follows Newton, except the mighty spaghetti monster wobbles absolutely everything else in a 1 year cycle and keeps the earth still using a magical made-up force - then that theory is irrelevant. If it can’t be experimented with, it basically ain’t science.
Afterlife falls in the same category. There is no experiment to prove God, or afterlife, or giant turtles all the way down - therefore it has nothing to do with science.
The letter writer is simply confusing “established” with “unproveable”. We believe the earth orbits, or there are subatomic particles, because the best minds in the world have done the investigation and proofs for us and haven’t found any holes in the theory* . Thousands of people have done the proofs at one time or another, then based further works and further science and further proofs on the correctness of those proofs, until we have jet aircraft, colour TV, and canned beer.
This is very different from believing without any proof being shown anywhere.
( *Except, for example - Relativity - here’s where Newton’s work was a little fuzzy at the edges, and Einstein showed that was because it was an approximation at uch-less-than-light speeds. The greatest minds then just refined the model - and experimentally, have proven it works).
I didn’t want to nitpick this same point, as it’s more esoteric than illuminating, but you’re right.
The better definition would be that one of the foci of the orbit is centered on a body.
The Earth’s core is at one focus of moon’s orbit. The sun lies on a focus for all the planet’s orbiting about it. And so on. Ellipses rather than circles.
Accepting a fact that can be readily observed, even if you haven’t done so yourself, isn’t faith. Actually, personal observation is a pretty unreliable way to nail down the truth of existence.
There are concepts you can prove to yourself if you really want to, but most people just go along because it works. Like math proofs.
There are other things you can’t practically find out unless you’re rich or know some guys. Like exotic particle physics. Don’t have a particle accelerator or a satellite? Too bad. You’ll have to trust peer review.
OK, that’s an excellent point.
I think the dedicated layman can convince themselves that the earth orbits the sun, though.
Granted. But it is still a proof. Just a cockamamie one. The OP didn’t ask for truth. Darth Vader murdered your father is true, from a certain point of view. You will find that the truth depends a lot on your point of view.
How would you do that, exactly (without expensive equipment and a lot of appeal to other astronomical theories and complex mathematics)? :dubious:
This was known for millennia and never led anyone to remotely suspect that the Earth orbits the Sun rather than vice-versa. It was fully accounted for in the Ptolemaic system (albeit in a rather arbitrary way).
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Probably the nearest thing to an empirical demonstration that you can get with fairly simple equipment (a fairly low power telescope) is to observe the phases of Venus over the course of a year. It should then be possible to convince yourself, with the aid of some some simple diagrams, that the pattern of phase changes (and changes in apparent size) that you see are inconsistent with geocentrism and consistent with heliocentrism. Galileo was the first to make these observations and draw this conclusion from them.
A more rigorous proof will require copious, detailed and accurate measurements of the movements of the planets across the night sky, and a lot of quite complex mathematics, by which it can be shown that a heliocentric scheme with Kepler’s laws (elliptical orbits, etc.) describes the planetary behavior more accurately than any version of Ptolemaic theory (geocentric, with circular “orbits”, eccentric points, epicycles, and equants).
However, even all this can be reconciled with a theoretical system such as Tycho Brahe’s wherein the Sun (and Moon) orbit the Earth, and all the other planets orbit the Sun. It is an inelegant theory (especially when you bring in the elliptical shape of orbits), but consistent with the observable facts about the observable motions of the heavenly bodies (at least, what you could observe at home with equipment that would not cost millions). To show this model is unworkable really requires you to get into other physical mechanisms of the solar system, gravitational theory and Newtonian mechanics. You can’t make the Tychonic system consistent with that.
With a powerful telescope and very accurate measuring equipment you could observe stellar parallax, but its not something you could do for yourself, at home.
I think we ought to stop calling trust “faith”. Faith is believing something without reason. Trust is having good reasons to believe something without it actually being demonstrated to you.
There are good reasons to believe that there is a steakhouse in Australia, even if you’ve never seen it. Your good friend, who you have no reason to doubt, has been there. If you want, you can look up its address online. But without going there, you can’t be sure your friend isn’t lying to you and spoofing websites just to fool you.
I trust that my wife loves me. She’s never done anything to make me doubt it, she says she loves me, and behaves most of the time as if she really does. Can I look inside her head to verify she isn’t just fucking around? Nope.
All that is based (in my mind) on the faith I have that there is an external reality and the fact that my senses give me a approximately accurate picture of that reality.
I believe most religious faith is along these lines. The hardcore Christians I’ve met have faith that the Bible is true. Everything else, belief in God, Jesus, gays are bad, and Noah’s Ark all stems from that, plus the trust they have in their family, pastor, and church community who tell them it is so.
The difference is that believing in an external reality that my senses can perceive seems to be more fundamental, and it really isn’t possible to live as if that isn’t true. Indeed, even the religious must take that same axiom, they just go an (unjustified, in my opinion) step further. But who am I to argue with someone else’s axioms? We’ve all got at least a few.
Missed edit window.
The proof that bup mentions, that is described at io9, is the stellar parallax method. Because the stars are so far away, this effect is extremely small. It could not be measured at all in the 17th century, despite determined attempts to do so (whose failure many people, not at all unreasonably, took to be excellent observational evidence showing that the Earth was not moving around the Sun). It can be measured today, but it takes expensive and complex equipment. It is not going to convince a skeptical layperson (even an open minded one).
On the other hand, the phases of Venus observations can be done by a layperson using a cheap telescope or binoculars, and their significance is fairly easy to explain and understand (with the aid of simple diagrams - it is not easy to explain just in words). Although there were reasons (not, for the most part, anything to do with religion) why this data failed to convince many of Galileo’s contemporaries, I think it should be plenty enough to convince a modern layperson with an open mind.
Well, I say it only takes simple diagrams, but after ten minutes of Googling I am unable to find a version of the diagrams that do not either contain glaring errors (like not showing the Earth at the center of the geocentric model!) or simply fail to make all the relevant issues clear. :rolleyes: So much for the information age.
I could draw it for you on a blackboard, but on the web I do not seem to be able to show you a correct and adequate diagram.
I’d accept that.
“Extraordinary claims require extraordinary evidence” but the obverse is true also.
I accept that France exists, although I’ve never verified it myself. My acceptance isn’t called “faith.” I have confidence that if I went to the trouble, I could visit France myself, just like I could take the trouble to make the same astronomical observations that people have been doing for hundreds of years to see for themselves that our solar system is heliocentric.
With the telescope, Galileo showed these facts that disagreed with expectations:
- Jupiter’s moons: this was the first clear evidence of anything orbiting something other than Earth
- phases of Venus, as mentioned above. More below
- the moon has craters (it was assumed to be perfectly spherical, as part of the perfect heavens)
- the milky way was mostly stars, not nebulous clouds
Regarding Venus, it could have phases and still conform to Ptolemy’s model of concentric heavenly spheres. If Venus’s sphere was outside the Sun’s, it would only show full and gibbous phases. If it was inside the Sun’s, it would show only crescent and new phases. Galileo showed that it had all phases, shattering the Ptolemaic model completely, and causing astronomers to adopt hybrid theories that allowed both Earth and the Sun to be the centers of revolutions – oddly, ignoring his earlier demonstration of Jupiter’s moons.
In any case, the phases of Venus are pretty good evidence that Venus revolves around the Sun, and Jupiter’s moons show that other bodies can revolve around other bodies. That doesn’t prove that the Earth revolves around the Sun while the Moon revolves around the Earth, but it certainly makes it more plausible.
Can’t, because it not a reproducible experiment. But observational evidence is strong enough to feel safe using it as an assumption, and so far nothing has failed to work when attempted with the assumption that the earth orbits around the sun.
The thing is, you could argue a ptolomeic system - some planets orbit the sun, which then orbits the earth. That, however, relied on magical powers (or perhaps, unknown unspecified forces) that allowed an extremely large mass to circle a smaller one.
Newton’s theory, which can be proven at multiple scales depending on your wallet, demonstrates a simpler model - gravity works the same on all masses, and results in planets circling the sun, moons orbiting planets, and apples falling - all obeying the same law.
Things like star parallax or doppler shift of spectral lines in distant stars are simply gravy that reinforce the vast pramid of established knowledge. But if you feel any particular piece of that pyramid of science knowledge is flawed, you can devise an experiment to check it. If you feel the theory of gravity is incorrect - in which way? “Everything in gravity works except sun orbits earth”? What happens as solar wind particles and meteorites fall onto the earth? Do they magically become “earth” and violate the laws of gravity? or has earth statred to move oh so slightly in recent eons due to the influx of non-earth material? …and so on.
That is the difference.
Science makes predictions that would not work unless the model of how the universe works was accurate.
Religious faith posits things that are unprovable.
Honestly, I’ve never seen that the moons of Jupiter were all that big of a deal. How do we know that the Galilean moons orbit Jupiter? Because they always stay close to it in the sky. But we already have an example of that, differing only in degree, with Mercury and Venus staying close to the Sun. If you’re going to come up with some contrived mechanism to keep Mercury and Venus close to the Sun without actually orbiting it, then you could use the same mechanism to keep Io, Europa, Ganymede, and Callisto close to Jupiter without orbiting it.
You don’t need reproducible experiments to prove something scientifically.