Prove that the earth goes around the sun

rattis

I find it obvious, as did many previous people, that the sun goes aroudn the earth. I of course know htis to be untrue as it has been drummed into me again and again for the past 16 years.

Can someone please prove to me (so that i can prove to others as well) that the earth goes around the sun. Do not be afraid to explain using mathematics, as i see that as the only way of undeniable proof.

selfAdjoint

The first person who had experimental evidence for this was the astronomer F.W. Bessel who in 1838 was able to measure the parallax of a nearby star. This showed that the earth was at a different place, relative to the star, in June than it was in January. And geometry showed that the two places were on opposite sides of the sun. More parallax measurements since his time have confirmed that the earth follows a closed path around the sun.

Phobos

Welcome to Physics Forums, rattis.

It certainly looks like it, doesn't it? But looks can be deceiving.

The "aberration of starlight" was the definitive proof of the heliocentric solar system.
http://www.encyclopedia.com/html/a1/aberstrlt.asp

And then there's all the spacecraft we send around the solar system which (1) successfully reach their destinations based on a heliocentric model of the solar system and (2) take photographs showing the sun at the center.

If you accept the values for the mass of the Earth and Sun, then the laws of gravity & planetary motion show you that the orbit around the common center of mass is near the center of the sun, not the Earth.

There are other evidences too...

Zero

You can start with basic gravitational theory, throw in a little bit of ballistics and orbital mechanics, and of course our successful navigation of craft through the solar system, all of which show conclusively that the earth orbits the sun.

Canute

I thought the doctrine of Galilean relativity asserted that we couldn't know which orbited which. The maths is a lot easier in a heliocentric solar system, but that doesn't in itself entail that it is one. Surely all we know is that a heliocentric solar system is a very useful assumption? Or is this nonsense?

Zero

Just because it is a useful assumption, that does not mean it is nonsense. If both views are assumptions, but one is more useful and practical, guess which one we should go with?

Plus, of course, I'm not sure if Galilean relativity even applies?

rattis

well yes, but i dont know if the spacecarft have every acctually gone into space or if it is just a con by government (worse case sinario).

Can i see some mathematical proof that the earth does infact go around the sun?. Like i say the only proof i have at the moment is that i can see the sun move around the earth everyday, but this is not the case as everyone says.

I am not an astronomer but mathematician, so im not sure if this whould be in the maths section


just edited to fix quote tag - Phobos

Zero

You may as well give up, if you have to try to account for people who think the entire space program is a lie...

Canute

I didn't suggest that the assumption was nonsense. I was wondering if what I said was nonsense.

No argument - but it's not really relevant.

No I'm not either, that's what I'm checking. But I can't immediately see why not, it's relative motion after all.

Phobos

At the time of/preceding Galileo, you could model it (the motion of the planets, etc.) very well either way. But the aberration of starlight nailed the sun down in the center with the Earth going around it. (that required very precise telescope measurements...something not available at the time of Galileo)

Phobos

Diehard skeptic, eh? Check the math on parallax & aberration of starlight. (Google search or wait for some helpful PF member to present it here.)

Canute

Thanks. Can you explain that aberration a bit?

Nereid

rattis,

If you want a mathematical proof, completely disconnected from any observation or experiment, then you'll be disappointed - without any observations at all, you can't even know of the existance of the Sun, Moon, or even the Earth!

If you distrust everything that you read, and need proof of your own, you can do the stellar aberration experiment yourself. You could buy the equipment, probably for less than the cost of an average US house, or make it all yourself, from scratch. You may find an interested physics teacher at a nearby high school, who would welcome the chance to have her class take part in some real, 'hands-on' physics, so you could have the benefit of a critical audience.

Canute (and rattis) -> A one page, mathematical introduction to stellar aberration.

Canute

Thanks, I'll try to understand it. However I'm not sure it proves anything other than that if one assumes that the sun is going around the earth then one must also assume that the stars are as well. [:D]

selfAdjoint

How do you feel about the earth's rotation on its axis? Skeptical there too? Look up Foucalt's pendulum and coriolis force. If you can accept the earth's rotation then it affects you candidate idea that the stars go around the earth.

The point is that it's your responsibility, denying the common wisdom, to come up with a self consistent alternative. If you can't find one, that in itself is an argument for the orbiting earth.

Incidentally, parallax shows that the stars move relative to the earth in an annual cycle, and abberation shows that light moves relative to the earth in an annual cycle (90^o out of phase with the first one). If you assume the earth stationary, then these are two curious unexplained facts, but if you assume it orbits, then it is explained, the earth is moving relative to the stars and as it moves its speed causes the abberation of light. Even the phases are in sync.

Canute

Not at all. Spin is a different case. (BTW I'm not skeptical about
the fact the the earth goes around the sun, just wondering about whether it is the only way of interpreting the facts. I understood that with enough Ptolemaic circles you could model a stationary earth).

That's the possibility I'm exploring.

Surely some fancy maths could sort that out, based on a stationary earth and an orbiting universe? I agree that it would a peverse way of looking at it, but it seems possible.

Adam

I'm not going to read the whole thread, so I apologise if someone has already properly answered this.

Rattis, the Earth and Sun both spin around the common centre of mass, called the barycentre, or baricentre. Exactly the same as if you hold hands with someone and both spin around each other, leaning out.