World Science Scholars

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    • 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?)

      • of night and day

      • We may not feel the rotation of the earth but are able to observe the effects of its rotation.

      • We can’t exactly say if the Earth is moving around the sun or vise versa. This even makes me question the general relativity because it directly says that lighter objects move around heavier ones. Something should resolve this contradiction. Maybe is just a miss understanding. If anybody could explain, I will appreciate it.

        • It is NOT really true that the lighter object moves around the heavier one. The Sun has such great mass compared to the earth that we can neglect the motion of the sun in many cases, that is true, but every action has an equal and opposite reaction, right? So, if we were the only planet, the Sun would mover in a tiny circle while the earth moves in a much larger circle around the sun, but it’s still true that from the Sun’s perspective, WE appear to be going around it.

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      • I have two answers: one is the effective gravitational acceleration and other one is the Coriolis force acting on the subject, we can detect that we has to be in some rotational motion.

      • You need to define spinning with respect to what? The sun? The stars? You can at the same time spin with respect to (from the viewpoint of) the sun and not spin with respect to (from the viewpoint of) the stars or vice verse. The question is ill defined.

      • I would argue that the rising/setting of the Sun is evidence that either the Sun or the Earth are moving at constant angular velocity- if it was some sort of rocking back and forth effect on Earth you would feel the Earth moving underneath you as it accelerates in another direction. As for the Sun orbiting Earth, this has been disproven by the effects of the suns’ gravity, so by method of deduction I think you can say the Earth is spinning.

      • The direct evidence that the Earth is spinning comes from several sources:
        Foucault Pendulum: A Foucault pendulum is a device that demonstrates the rotation of the Earth. It consists of a long, heavy pendulum that swings back and forth in a fixed plane. As the Earth rotates underneath it, the pendulum appears to change its direction of swing over time. This effect is due to the rotation of the Earth beneath the pendulum and provides direct visual evidence of the Earth’s rotation.
        Coriolis Effect: The Coriolis effect is an apparent deflection of moving objects caused by the rotation of the Earth. It is observed in the movement of air masses, ocean currents, and the trajectory of long-range projectiles. For example, the rotation of the Earth causes winds to curve rather than move in straight lines. The Coriolis effect is a direct consequence of Earth’s rotation.
        Satellite Observations: Satellites in space provide evidence of Earth’s rotation through observations such as the global coverage of weather patterns. Weather satellites orbiting the Earth capture images of cloud movements, which are consistent with the rotation of the planet.
        Celestial Observations: The motion of celestial bodies is consistent with Earth’s rotation. The rising and setting of the Sun, Moon, stars, and other celestial objects can be explained by the rotation of the Earth. These observations align with the Earth’s rotation on its axis.
        While we may not directly feel the Earth’s motion due to its large size and our relative scale, these pieces of evidence, along with others, collectively support the concept of Earth’s rotation.

      • we can take a video of the rotation Earth from the space

      • coriolisis effect

      • Newton’s laws of physics inclusive of the concept of inertia. Also, theoretically speaking, we we would practically be thrown in one direction if the earth were not spinning due to inertia.

    • 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.

      • Logical error here. Logic says that if A implies B it does not necessarily follow that Not A implies Not B. If when you don’t feel a force you continue to move at a constant velocity in a fixed direction you are in an inertial reference frame. It does not necessarily follow that if you do feel a force you are not in an inertial reference 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?

    • nothing to say about this but your explanations are marvelous

    • 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

    • can you please add minkowski 4d ideas

    • 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.
      Don’t know about foucalt pendulum

    • I don’t think we should talk in terms of ‘evidence’. Science does not deal in proofs like math does. All we do in science is construct theories that explain phenomena in the best possible way. With these we work untill some better theory comes along.

    • So the question should rather be: ‘Which phenomena are best explained by assuming the earth rotates about the sun.’

    • not days but seasons as the earth moves in its orbit

    • There is various ways it can be seen such as the star cycle, lunar cycle, 24 hr cycle, shadows, and seasons.

    • As from our prospective its sun moving around the earth and earth is stationary not the sun so rising and setting of sun do not provide any evidence direct. And in ancient time this is a strong evidence for those who believe that Earth is stationary not spinning. But when you start to observe the rising position of sun you would find that its changing throughout the year. And that provide a strong evidence that earth is spinning on its axis and that unusual spin cause it to change the rising and setting position of sun.

    • Basic concept is sun and moon is rotating .

    • We all know that all the stars in the night sky are moving. Since they very far away from us we can’t see its motion, it appears to be at rest. When you take this perspective into account and observe the night sky we could actually see that the stars are moving.so it is obvious that the only explanation that supports our perspective is that the earth is rotating.

    • Great material. Question if one observer in motion relative to another observer is “completely justified in claiming to be stationary and at rest” (course 2.1 at 7:05) what happens to the first observers momentum and kinetic energy if this claim is exercised ?

      • It disappears. Kinetic energy and momentum are reference frame dependent.

    • The coriolis effect is due to the Earth’s angular momentum

    • The Coriolis Effect can be directly explained and also the Foucalts pendulum mentioned is a direct evidence for Earth’s rotation ……. it traces out different paths on the sand below in a way that proves the fact

    • A foucault pendulum is a direct example because it swings in the same plane as the Earth rotates beneath it. Other evidence is the movement of the sky and celestial objects like the sun and moon.

    • Assume, the Earth is not spinning. The only explanation for the change of day and night could be described through Earth orbiting the Sun (at a very large speed, so 24h for one rotation around Sun). Or, of course you can assume that the Sun is orbiting the Earth, again 24h/rotation. If this was the case, we would not experience the change of seasons, because they would be “replaced” by day/night change. Also, the stars at the sky would stand still.

    • 1, Day/night change
      2. Stars and constellations move acrooss the sky
      3. Difference in the steepness of the banks of the rivers flowing from south to north (and vice versa)
      4. Constant ocean flows and winds lie passats.
      5. Foucalt pendulum (at last)

    • Hello Ladies and Gentlemen,

      Justifying the Earth revolves at about 1600 km/hr. breaks the sound barrier. The sound barrier is at 1200 km/hr.

      This is an important ESI-Earth similar inventory item. This allows Jupiter and its speed to possibly use the spin to provide life on Ganymede.

      We may need spin as biologicals surviving both space and its radiation. I do radiation research, as an offshot of polarcusp, polar outflow activity.

      The rising and setting of the sun can be a factor of spin proof. On the moon of the sun called Venus (tidally locked as moons are), we see the now new class of eyeball planets only warm on the face turned to its own star.

      https://education.nationalgeographic.org/resource/coriolis-effect
      The above site talks of the Coriolis effect.

      In polar cusp research, we know the earth spins by visiting the skydisc of circumpolar science. I will try to attatch that file, but it needs work as a doctorate item.

      At polar regions, atmospheres are lower, and the sky is colder. This allows us to see spin when a geyser and the lines from a geyser freeze solid in the sky and proceed to turn.

      I want science credit for the term geyser lines- frozen in the sky.

      Foucault pendulum kinetic energy and momentum also allow for the direct visuals of a wobbling that we nowadays see while computer generated orbits of the 1km long item located at L5 in earth orbit exhibit as it rotates around both L5 and in the lock-on similar to JWST located in L2.

      The procession of the Zodiac is proof of rotation.

      The persecution of science by the church is proof of rotation.

      Tidal differences are proof of rotation.

      The change of day and night (holograms on Orion) occur.

      The position of the rising sun on the horizon- and setting- allows for rotation.

      Shadows & seasons allows for a good catch phrase on this topic – S & S memory cue.

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    • The stars that rotate in the night sky.
      The foucault pendulum such as the one in Londons science museum.

    • effect is due to the Earth’s angular momentum

    • When travelling on sea when you notice a ship far away, it is its sail that appears first.
      A hanging penulums’ movement is also an evidence of the Earth’s spinning.

      • I made a mistake, the ship experience is an evidence of Earth being round.

    • what if we see the motion of the earth from a satellite from the moon? we need not to be in one of those objects right?

    • The Coriolis Effect

    • The proofs are literally all around us, the setting sun’s position moves through the year north to summer solstice then south to winter solstice, etc. etc. etc.

    • The direct evidence that we have that the Earth is spinning is the occurrence of day and night on the Earth, we can clearly see the setting and rising of the sun, dark and sunlight or change in the length of the shadow of an object under the sunlight. And first experimental evidence came from the French physicist Léon Foucault, which shows the coriolis effect (an apparent deflection of the path of an object in motion due to the rotation of the Earth) on a long heavy pendulum.

    • In middle age years, people were convinced that the sun and starts moved around a stationary earth. It needed some genius like Galileo to apply direct observation into the movement of other planets to challenge that belief.

    • Ladies and Gentlemen,

      Antonio’s comment on the genius needs developing. Galileo was also an upstart, an iconoclast, and a rebel.

      In my opinion, as even in Calgary people disbelieve the Earth is round, the Foucault Pendulums need to be built in most cities to retain & justify that memory, and as good art.

      CLG
      🙂
      🍵☕🍵🍵

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    • I saw a Foucault pendulum in a physics research lab. It was quite fascinating.
      I don’t think the rising and setting of sun is convincing evidence for rotation of the earth as the geocentric frame of reference is valid as Dr Greene explained.
      I think convincing direct evidences of spinning of the earth are
      1. Coriolis effect (it’s effect can be observed in hurricanes, tornadoes and air and sea currents)
      2. The way in which distant celestial objects move in the night sky. Polaris in the north pole and Sigma Octantis in the south pole don’t move and as you move away from them the radius of stars’ apparent circular path increases till the equatorial plane and then decreases to zero at the other pole.

    • that is because I think that the rotation of the earth is uniform, and can’t change its rotational speed. If the earth suddenly speeds up or slows down we could detect the change. Yes, I think the day and night changes are evidence for it.

    • that is because I think that the rotation of the earth is uniform, and can’t change its rotational speed. If the earth were suddenly speeds up or slows down we could detected the change. Yes, I think the day and night changes are evidence for it.

    • Weight of a person will be different when he is at equator and at north pole. As earth spins particles on earth surface are in circulation motion and acted upon centrepetal force. Centrepetal force acting on a person is higher at equator than that of at north pole but normal reaction is the same. Hence measured weight at north pole is higher than that of at equator. If earth doesn’t spin weight will be the same at equator and at north pole.

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