World Science Scholars

### 2.4 Speed

Discussion
• What direct evidence do we have that the Earth is spinning? After all, much as in the example from the lecture in which George and Gracie are floating in space, we don’t seem to feel the Earth’s motion. (Hint: Is the rising/setting of the sun convincing evidence? Have you ever encountered a Foucault Pendulum?)

• stars changed position cause the earth rotates

• Foucault pendulum or the rotation of high/low pressure systems.

• The shifting of the shadows show the world we live in is as much a shadow world as a world of light.

• Day and Night due to rotation of Earth

• Day and Night, Foucault pendulum

• Day and night and Foucault pendulum. I would like to add perspective. Physics tells us that the earth is in constant motion, so now when I think of stillness, I remember this. This is kind of cool for me as an elderly woman coming back to physics. So much I have forgotten..

• Position of stars change in the sky due to rotation of Earth.

• the changes in position of stars

• The Foucault pendulum proves the earth is rotating. The day night cycles shows us that the earth is rotating and the changing of shadows length also adds to this conclusion.

• gnomon shadow changes, Coriolis Force, Faucoult Pendulum, movement of the stars,

• day and night

• so in the case of earth, the sun is moving for us means from our perspective, so this is same as car example the car is moving but from our perspective the world is moving, so in this earth case from our perspective the sun is moving but actually the earth is moving similar to the car example actually the car was moving

• I would come to this by thinking like Copernicus in the 16th Century. It wouldn’t have been possible for the regular tilts/shifts in position in the movement of Sun and other Planets and Constellation throughout the year if it would have been “Geocentrism”. And by observing the motion of nearby planets we can tell about the movement of Earth as well. And once we step into the concept of “Heliocentrism” from the previous one, we can prove day/night, seasons, revolution, etc.

• And then, of course, we have Foucault Pendulum, Coriolis Effect, etc.

• Polaris, the North Star, appears to be stationary and all other stars appear to spin around this star, indicating that the Earth spins on this axis.

• No comment

• we can say we are not in inertial frame because we feel a force on us , either sitting we have presure from the seat, walking we have presure on feet, We do not feel any lateral force on us if we are not moving. Then since we feel forces on us we are not in inertial frame.

• We know we are not in an inertial frame because we know we are moving due to earth’s spinning and orbiting around sun. So our velocity is changing. But your argument doesn’t apply.There is no net force on us if we sit in a chair. If we sat on a chair on a non-spinning earth floating in space we would still feel pressure from the seat, yet would be in an inertial frame.

• Changing of season…simple terms earth goes far from sun we encounter the winter season. It comes near the sun we get the summer season

• Saransh Gupta , actually the Earth is closer to the sun in winter and further from it in summer. The seasons don’t have anything to do with our distance from the sun, rather they are caused by the axial tilt of the Earth.

• Observed apparent movement of the sun and stars in the sky, and wobbling of natural pendulums such as church chandeliers.

• How water flows in a vortex and how it is different between north and south of the equator. Note, changing of seasons has to do with the earth’s orbit about the sun and its tilt on its axis in relation to the orbital plane and not with the Earth spinning.

• La posición de las estrellas

• what about the dark holes in all galaxies ever seen?

• The stars looks like they are moving around us, the day and night, and the seasons, are evidence that we are moving.

• Podemos notarlo en la bóveda celeste (es una concepción que se utiliza para representar las estrellas vistas en un domo en el cielo, desde nuestra perspectiva) que las estrellas tienen una dirección particular al oeste. Si tomamos de referencia la estrella polar, que se encuentra aproximada al polo norte celeste y tomamos una secuencia de fotografías a lo largo de la noche veremos que las que están alrededor forman un círculo debido a su rotación, se conocen como star trails.

• We can see apparent movement of the stars, mainly in the north we can see this “drawings” like circles in the sky (If we took some pictures we could see those circles).

• La Física nos dice que la tierra está en continuo movimiento, en este caso rotando. Es interesante demostrar esto con el experimento péndulo de Foucault.

• By observing the apparent movement of the stars in the celestial vault at night. If you’re either in the Northern or Southern hemisphere, especially at high latitudes, you’ll notice that the stars seem to be moving around a certain point in the sky (to the celestial north/ south pole). It becomes more apparent if you take a sequence of photos of this motion; the stars will leave a circular trail.
Another evidence is the experiment with the Foucault pendulum.

• done

• Sun rises every morning and sun sets in the evening. Starry heavens and seasons…

• What direct evidence do we have that the Earth is spinning? we have direct evidence that the earth is spinning because of the sun, moon, and stars. The sun is always moving so as the moon and the stars are always moving due to the rotation of the earth.

• Yay! Another elderly woman! <grin>

• stars changed position cause the earth rotates and also sun rises in the east and sets in east which is also a proof and also the retrograde motion of mars can prove this.

• FOUCAULT pendulum changes its plane with the rotation of earth depending on which latitude it is kept. Moreover,the change of day and night also proves it.

• Certainly stars, sun, moon and all rotating overhead are proof. Yes, Foucault pendulum is also proof. Add to that latitude changes in season, sun angle, hurricane direction all give strong evidence of the earth’s spin.

• yo i love jesus

• yo i love relativity

• I think we can also use the relative trajectory of rockets when they are launched to the space.

• Day and night, stars rising and setting etc., even though they seem like a good evidence of earth’s rotation, in my opinion, aren’t direct evidence, as those can mean that the universe is going around the earth. Foucault Pendulum too I’d say isn’t a direct evidence as it’s not immediately evident that it’s the effect of earth’s rotation. The only evidence which points to earth rotating is all the stars except Polaris rotating.

• A foucault pendulum is a good way to test show the rotation of the earth and on different days we see different maps of the night sky

• self

• The foucault pendulum proves that the earth rotates ,it depends on the latitude at which it is situated as the plane of oscillation of the bob of the pendulum completes a full circle in a day if it is at either geographic pole and the time required to complete a full circle for the plane of oscillation increases as we move towards the equator.
The time required depends on the formula – ω=360° sinφ / day.

• STR is great

• If we were in an inertial frame of reference, the objects we observe – the sun and other stars- on which no external force is acting (/gravity, yes! But no resultant force I guess) would appear to us at rest or uniform velocity motion. Instead we see the sun rising in the east to travel the entire curvature in the sky to set in the west. A clue that it could be us spinning to have us ‘see’ so.