how can we move through space without feeling inertia?

Question

is there an easy formula that i could see that calculates how fast we could move in a super cluster of galaxies before we would feel inertia? we are moving towards virgo at a speed of 671,080 miles per hour. we are also moving 66,600 mph around the sun. i don't know the speed in which we move around our galaxy.

Answer 1

Inertia is a property of matter. All mater has inertia…..a resistance accelerating.
If given the chance, on object will keep moving in a straight line at a constant speed unless acted on by an outside force (if it was already moving), or will remain at rest unless acted upon by an outside force (if it was initially a rest). <-- From Newton’s 1st Law.

At any instant in time the Earth’s velocity (or any other planet’s velocity) is in a straight line tangent to its orbit, and yet for some reason the Earth keeps going around and around the Sun in a near-circular orbit. The reason is gravity. Gravity acts as the centripetal force which keeps Earth moving around in a circle. Centripetal force acts inward to accelerate the Earth towards the Sun, even though the speed of the Earth is nearly constant at any point around its orbit.

From Newton’s law of Universal gravitation:
F = G * m * M / r^2
Where G is the universal gravitational constant, m and M are the masses of the Earth and the Sun, and r is the radius of the orbit.

The equation of centripetal force,
F = m * v^2 / r
Where m is the mass of the Earth, v is the speed of the Earth, and r is the radius of the orbit.

But since the two forces are actually one in the same in this case, we can set them equal to get an interesting result,
G * m * M / r^2 = m * v^2 / r,
Canceling, rearranging, simplifying,….
r = G * M / v^2
We have just found an equation which relates the radius of Earth’s orbit as a function of Earth’s speed around the sun.
Remember, G is a constant; M (for all intensive purposes) is a constant just equal to the mass of the run. The only variable here is the speed.
If we are given a certain speed of Earth, we can find the radius or its circular orbit. (Or, if we are given the radius of its orbit, we can find the speed required for Earth to maintain this orbit). The two values are linked very closely. As the speed Earth goes around the sun changes, so must its orbital radius.

This same process will work for any other two bodies you want to consider…the Earth and the Sun, the Sun and any one of the other planets, or even the center of the galaxy and the Sun.

For the Sun’s speed around the galaxy, it has some orbital radius. Since the Earth is orbiting around the Sun and has been for some time now (we are moving with the Sun around the galaxy), it is safe to assume that the Earth has pretty close to the same speed as the sun around the galaxy.

If all of a sudden something happened to increase the Sun’s speed around the galaxy, the delicate balance would be disrupted. The sun would start moving relative to the Earth’s normal motion and this would essentially have the same affect as giving the Earth a different speed around the sun (if we narrow our focus in) an the Earth’s orbit around the Sun would change.
If the Earth moves fast enough, it is possible to escape the Sun’s gravitational pull (or if the Sun moves fast enough it can escape the Earth’s gravitational pull). If the Sun’s speed were to change dramatically enough, it would be possible for the sun to loose its pull, so to speak, on the Earth as it moved away.
And this can, similarly be applied to the case of the moon going around the Earth.

Answer 2

Inertia is only felt when your momentum changes. Since we are traveling at a constant velocity there is no inertia.

We would have to start accelerating or decelerating at a fairly high rate to be able to feel it on the galactic scale like that.

Edit: the poster below brings up a good point. I'm actually reading a book dealing with this stuff at the moment. theres a link to a description of Newtons bucket experiment below...its a classic example of what hes talking about.

Answer 3

A tad off topic, but... What would be our standard for zero. Without a point of refrence what would constitute not moving?