What is happening on July 4th that is causing the orbit to change?

Answer 1

Astronomically speaking, nothing unusual 'happens' on July 4th, and there is no

reason to expect the Earth's orbit to 'change' any time soon.

The Earth's orbit around the sun is not a perfect circle. Which is not surprising,

because no natural orbit of anything in the solar system that we're able to see

is a perfect circle. Every gravitational orbit is an "ellipse". Some, like the orbits of

comets, Mercury, and Pluto, are more eccentric. And some, like the orbits of Venus

and Earth, have such small eccentricity that if you saw them drawn on a piece of

paper you'd swear they were circles. The gravitational orbits that are most nearly

circular are the orbits of the artificial 'geostationary' TV satellites. If the orbits aren't

kept very nearly circular, then the birds would appear to drift around their assigned spots

in the sky, and your TV picture might disappear for a while every 23hrs 56min 4sec .

But I'm digressing and losing my focus here. The main point of this paragraph is that

there are no perfectly circular orbits. Every orbit is an ellipse, and the sun is not at

the center, it's at one 'focus' of the ellipse. That's how gravity works.

Since the sun is not at the center of the orbit, there are times when the Earth is

closer to the Sun, and times when the Earth is farther away from it. This has been

going on as long as there have been an Earth and a Sun. The difference between

the nearest and farthest is about 3%. That's why nobody notices it unless they're

interested in science and they measure it or look it up.

The Earth is closest to the sun in January, and farthest from the Sun in July.

In 2012, the dates will be . . . closest on January 5, farthest on July 5.

Now let's go slowly, and consider the shocking implications of what we have learned:

-- On January 5, the Earth is as close to the Sun as it ever gets. That means that

on January 5, the Earth will begin to move farther from the Sun.

-- On July 5, the Earth is as far from the Sun as it ever gets. That means that

on July 5, the Earth will begin to move closer to the Sun.

If the last part was the only thing you heard, you might think that some catastrophe

is about to happen and the world is coming to an end. That's baloney. These things

happen every year. If the last part is the only thing that somebody tells you, then he's

lying to you, trying to scare you, and pulling your chain. Plus, he probably doesn't even

understand what he's talking about, so he is more to be pitied than scorned.

There is no reason known to modern Science why anything should change in the

forseeable future. But of course, as always, there is no water-tight, bullet-proof

guarantee that the Sun will not explode tomorrow. So don't put things off, call

your mother, and what is hateful to you, don't do to others. The rest is commentary.