How Does Newton’S First Law Of Motion Relate To Galileo’S Concept Of Inertia?
- Marvin Harvey
Home Science Physics Alternate titles: Newton’s first law law of inertia, also called Newton’s first law, postulate in physics that, if a body is at rest or moving at a constant speed in a straight line, it will remain at rest or keep moving in a straight line at constant speed unless it is acted upon by a force,
- The law of inertia was first formulated by Galileo Galilei for horizontal motion on Earth and was later generalized by René Descartes,
- Before Galileo it had been thought that all horizontal motion required a direct cause, but Galileo deduced from his experiments that a body in motion would remain in motion unless a force (such as friction ) caused it to come to rest.
This law is also the first of Isaac Newton’s three laws of motion, Although the principle of inertia is the starting point and the fundamental assumption of classical mechanics, it is less than intuitively obvious to the untrained eye. In Aristotelian mechanics, and in ordinary experience, objects that are not being pushed tend to come to rest.
The law of inertia was deduced by Galileo from his experiments with balls rolling down inclined planes. For Galileo, the principle of inertia was fundamental to his central scientific task: he had to explain how it is possible that, if Earth is really spinning on its axis and orbiting the Sun, we do not sense that motion.
The principle of inertia helps to provide the answer: since we are in motion together with Earth, and our natural tendency is to retain that motion, Earth appears to us to be at rest. Thus, the principle of inertia, far from being a statement of the obvious, was once a central issue of scientific contention,
- By the time Newton had sorted out all the details, it was possible to accurately account for the small deviations from this picture caused by the fact that the motion of Earth’s surface is not uniform motion in a straight line.
- In the Newtonian formulation, the common observation that bodies that are not pushed tend to come to rest is attributed to the fact that they have unbalanced forces acting on them, such as friction and air resistance.
In classical Newtonian mechanics, there is no important distinction between rest and uniform motion in a straight line: they may be regarded as the same state of motion seen by different observers, one moving at the same velocity as the particle and the other moving at constant velocity with respect to the particle.
What is the relationship between Newton and Galileo?
It was a development of Galileo’s ideas that led Isaac Newton to lay down his famous three laws of motion. These, plus Newton’s own ‘law of gravity’, would provide the ultimate explanation for Kepler’s elliptical orbits and really tell us what was going on.
What is Galileo’s concept of inertia?
Galileo and the Concept of Inertia – Perhaps Galileo’s greatest contribution to physics was his formulation of the concept of inertia : an object in a state of motion possesses an “inertia” that causes it to remain in that state of motion unless an external force acts on it.
- Most objects in a state of motion do NOT remain in that state of motion.
- For example, a block of wood pushed at constant speed across a table quickly comes to rest when we stop pushing.
- Thus, Aristotle held that objects at rest remained at rest unless a force acted on them, but that objects in motion did not remain in motion unless a force acted constantly on them.
Galileo, by virtue of a series of experiments (many with objects sliding down inclined planes), realized that the analysis of Aristotle was incorrect because it failed to account properly for a hidden force: the frictional force between the surface and the object. Thus, as we push the block of wood across the table, there are two opposing forces that act: the force associated with the push, and a force that is associated with the friction and that acts in the opposite direction. Galileo realized that as the frictional forces were decreased (for example, by placing oil on the table) the object would move further and further before stopping.
How does the law of inertia support Galileo’s idea?
T he law of inertia states that: – A body will preserve its velocity and direction so long as no force in its motion’s direction acts on it. For example : a package thrown out of an airplane will continue to move at the speed of the airplane on the horizontal axis (in the direction of the airplane’s movement). The law of inertia is the basis of the new physics of the seventeenth century. This law is also true according to modern physics. Galileo discovered the law during the first decade of the seventeenth century, but in fact he did not understand the law in the general way we have formulated it here. Up to the time of Galileo, it was thought that one must exert force in order to cause and preserve motion, as claimed by the physics of Aristotle, Indeed, when we look at the world surrounding us, we see that in order to continue movement we must exert force.
Thus, for example, in order to conserve the speed of a car, the engine must work. Objects on which no force is exerted to preserve their movement eventually come to a stop. Galileo understood that one can explain the stopping of bodies by the common experience that we always encounter a force of friction which resists the motion of bodies.
However, without such resistance force, the bodies would continue to move at their previous speed. The law of inertia is also important for Galileo’s astronomy. He used this law to explain why we do not feel the earth’s motion, and especially why objects falling on the surface of the earth move together with the earth.
- This explanation is related to the law of relativity, which is also based on the constant acceleration of bodies.
- In this way, Galileo succeeded in refuting the claims of his opponents, as in the example of the boat in which Galileo proves the law of inertia.
- Galileo suggested a number of additional proofs for this law with the help of the inclined plane,
You will find an additional explanation next to the globe in the exhibition room. Laboratory – THE LAW OF INERTIA
Why Newton’s first law is called Galileo?
Newton’s first law of motion is also called Galileo’s law of:A. Conservation of momentumB. InertiaC. FrictionD. Conservation of mass Answer Verified Hint: Consider a body at rest and another body in motion with constant velocity. Compared with the situation where in one situation we apply an external force and in the other condition we don’t have any external force on them.
Define their state. We will get Newton’s first law from the second condition.Complete step-by-step answer:Newton’s first law of motion can be defined as if the net external force on a body is zero, its acceleration will be zero. If there is an external force applied, then only we can get an acceleration.We can simply state the above law as every body which is in a state of rest will continue to be in the state of rest or every body which is in motion in a straight line will continue to be in this state of motion unless we apply any external force on it.Galileo gave the concept of motion as the state of rest and the state of uniform linear motion are equivalent.
According to him, if the net external force on an object is zero, an object’s rest continues to be at rest and a body in motion continues to move with uniform velocity. This property of the body is called the inertia. A body does not change its state of rest or state of motion unless we apply an external force on it.
This is Galileo’s law of inertia.So, we can say that Newton’s first law of motion is also called the Galileo’s law of inertia.The correct option is (B).Note: Newton’s laws are built on Galileo’s laws and Galileo’s law of inertia was the starting point of Newton’s first law of motion.We always experience many forces like gravitational force, frictional force etc acting on a body.
But then also we get a state of rest or state of uniform motion on earth because all the forces acting on a body cancels out to give zero total external force. : Newton’s first law of motion is also called Galileo’s law of:A. Conservation of momentumB.
What is the difference between Newton’s law of inertia and Galileo’s concept of inertia?
A. READINGS – Objective – At the end of the lesson, you should be able to explain the subtle distinction between Newton’s 1st law of motion (or Law of Inertia) and Galileo’s assertion that force is not necessary to sustain horizontal motion. Who was Galileo Galilei? What were his contributions to the concept of inertia? The concept of inertia was first formulated by Galileo Galilei for horizontal motion on Earth.
- Before Galileo it had been thought that all horizontal motion required a direct cause (this idea came from Aristotle), but Galileo deduced from his experiments that a body in motion would remain in motion unless a force (such as friction) caused it to come to rest.
- Galileo Galilei was an Italian scientist who first explained the concept of inertia.
He observed that when a ball rolls down an inclined plane, its speed increases; and when it rolls upwards, its speed decreases. This change in speed was due to gravity. When the ball rolled down the inclined plane, it was pulled by gravity, so its speed increased.
The opposite happened when the ball rolled up the inclined plane. He then asked himself what would happen to the ball if it was rolling on a horizontal plane such as the floor. A ball rolling on the floor is not moving with or against gravity, so what would happen to its speed? Galileo thought that the ball rolling on a floor would remain moving with constant velocity if the friction between the floor and ball would be removed.
Galileo tested his theory in an experiment using two inclined planes. When the ball was rolled from one inclined plane to the next, it almost reached the height from which it was released as shown in Figure A, If the steepness of the second inclined plane is decreased, the ball would still reach the same height from the point it was released as shown in Figure B,
Finally, he then removed the second inclined plane and watched the ball as shown in Figure C, He observed the ball and made his conclusion: the ball would continue to move in a straight line with constant speed. Galileo asserted that if friction was absent, the ball would continue to move with constant velocity,
It would continue its state of motion unless a push or a pull compels it to change that state. Galileo called this tendency of materials to resist change in their state of motion as inertia, His assertion was the inspiration for Newton’s 1st law of motion.
They both implied that no force is needed to keep the motion of an object and the object’s inertia would keep it from changing its state of motion. ISAAC NEWTON’S FIRST LAW OF MOTION (LAW OF INERTIA) and the CONCEPT OF FORCE Isaac Newton (1643 – 1727) is an English mathematician, physicist and astronomer and was one of the most recognized and influential scientists of his time.
He is famous for formulating the three laws of motion which explain why objects move or don’t move. Newton’s first law is often stated as: an object at rest stays at rest and an object in motion stays in motion with the same speed and in the same direction unless acted upon by an unbalanced force.
This postulate is also known as the law of inertia ****. The behavior of all objects can be described by saying that objects tend to “keep on doing what they’re doing” (unless acted upon by an unbalanced force). If at rest, they will continue in this same state of rest. If in motion with an eastward velocity of 5 m/s, they will continue in this same state of motion (5 m/s, East).
If in motion with a leftward velocity of 2 m/s, they will continue in this same state of motion (2 m/s, left). The state of motion of an object is maintained as long as the object is not acted upon by an unbalanced force. All objects resist changes in their state of motion – they tend to “keep on doing what they’re doing.” There is an important condition that must be met in order for the first law to be applicable to any given motion.
The condition is described by the phrase “. unless acted upon by an unbalanced force.” As long as the forces are balanced – the first law of motion applies. For instance, a book placed on top of a table would stay at rest because the forces acting on it are balanced. The force of gravity is pulling the book down and the force of the table is pushing the book up.
The forces are therefore balanced. The state of motion of the book is at rest. However, if an unbalanced force is acted upon on the book, say for example a child will push the book leftward, then the book is no longer at rest but on the state of motion because of the unbalanced force (push) caused by the child.
- A ball is pushed on a plain.
- It would stay in motion on the same direction with the same speed indefinitely if the friction is absent and there is no outside force on the ball.
- However, if an unbalanced force is acted upon on the ball, such as an object that would block the ball or the force of friction is present between the ball and the floor, then it would change its speed and would eventually stop.
The ability of an object to resist change in its state of motion is called inertia. Heavier objects have greater inertia. They are more able to resist the force acted on them. If a heavy object is at rest, it cannot be moved easily because it has a great inertia.
If a heavy object is moving, it is harder for it to be stopped because it has greater inertia. For example, a refrigerator is pushed sideward, because the refrigerator has a great inertia, it is able to resist the force acted on it, and would not be moved easily especially if the force acted on it is not great.
Or if a very big, fat man is running on a field, it is hard for him to stop immediately because of the great inertia. Lighter objects have lesser inertia. If a light object is at rest, it is moved easily and if it is moving, it is easier for it to be stopped because of its lesser inertia.
Is there a difference between Galileo’s assertion and Newton’s first law of motion? There is a subtle difference. The difference lies in the concept of force. Galileo knew about friction but did not know about the concept of force. He used the term ‘push and pull’ to signify forces. It was Sir Isaac Newton who defined the concept of force (balanced and unbalanced forces) and their relation to motion.
The concept of inertia was a result of Galileo’s studies of motion. Inertia refers to the tendency of any material to resist change in its state of motion. Galileo asserted that if a rolling ball was ‘left alone’ it will continue to move with constant velocity. The only difference between Galileo’s assertion and Newton’s first law of motion is the concept of force, Galileo did not know yet the concept of force, and it was Newton who finally explains the nature of forces.
_8. Which scientist first elaborated more on the concept of force and motion? a. Aristotle c. Isaac Newton b. Galileo Galilei d. Albert Einstein _9. Why do you lean towards the left when a car turns right? a. Because of gravity c. Because of velocity b. Because of buoyancy d.
- Because of inertia _ 10.
- What is the difference between Galileo’s assertion of force and Newton’s first law of motion? a.
- Galileo did not know about friction while Newton did and used that in his law of inertia b.
- Galileo knew about friction but only used ‘push and pull’ to signify force.
- It was Newton who really studied the concept of force and its relation to motion.c.
Newton knew about friction but only used ‘push and pull’ to signify force. It was Galileo who really studied the concept of force and its relation to motion.d. Galileo’s assumption of force was used by Newton to develop his first law of motion.
Was it Galileo or Newton who first proposed the concept of inertia?
Galileo Galilei first proposed the concept of inertia.
Which of Newton’s laws is a restatement of Galileo’s law of inertia?
Newton’s first law states that every object continues in a state of rest, or of uniform speed in a straight line, unless acted on by a nonzero net force. Newton’s first law, usually called the law of inertia, is a restatement of Galileo’s idea that a force is not needed to keep an object moving.
What is the similar and different ideas about motion by Galileo and Newton?
Summary – Sir Isaac Newton’s work was the capstone of the Scientific Revolution, utilizing the advances made before him in mathematics, astronomy, and physics to derive a comprehensive understanding of the physical world. Johannes Kepler enunciated his laws of planetary motion in 1618.
Galileo determined the laws of gravity and explored the laws of motion on earth. Newton first conclusively affirmed the laws of motion and linked them with Kepler’s laws of planetary motion. Before Newton, no one had demonstrated conclusively that the movements of heavenly bodies were related to terrestrial physics.
Galileo had suggested this, but was censored by the Church before he was able to do further work to prove his theories. The first step in Newton’s work was to solidify the laws of motion that Galieo had studied and hinted at without clearly expressing.
- The first law states that a body at rest tends to stay at rest; a body in motion tends to stay in motion unless compelled to change by an applied force.
- The second law states that the change in motion is proportional to the applied force and takes place in the straight line by which that force is applied.
The final law states that for every action there is an equal and opposite reaction. Armed with these solidified theories of dynamics, Newton proved that the force that acted on planets and moons was the same force that caused a stone to fall to the ground: gravity.
He first demonstrated this by calculating that if one extended the same gravitational force that acted on objects on the surface of the Earth to the distance of the moon, it predicted nearly exactly the same orbit that was observed. The concept of universal gravitation-that every particle of matter attracts every other particle with a force proportional to the product of the two masses and inversely proportional to the square of the distance between them-is Newton’s major contribution to science and the centerpiece of his work.
The observed structure of the solar system was perfectly explained by assuming that the major organizing force among heavenly bodies was gravity. In order to apply the theory of universal gravitation to heavenly bodies with curved paths through space, Newton built upon the contributions of the mathematicians of the age and developed calculus.
- Using this tool he discovered that the attraction exerted by a spherical body on an external point could be calculated by assuming the mass of the body was concentrated at its precise center.
- This theory was the final step in producing accurate calculations, and soon the mechanisms of organization in the universe became clear to him.
In 1687, Newton set forth his findings in the most respected scientific work of all time, Philosphia Naturalis Principia Mathematica, better known as the Principia. This work established a model of the structure and functions of the universe based on universal gravitation which remains in use today, confirmed generation after generation by observation and calculation.
The scientific community immediately recognized Newton’s findings as revolutionary and proven with such clarity and logic as to be nearly indisputable by rational argument. Gradually, his mechanical analysis of the heavens became widely known, and accepted as the basis for all future astronomy. Newton is quoted as saying, “if I have seen farther than others, it is because I was standing on the shoulders of giants,” by way of thanking his predecessors for the contributions to science which made his Principia possible.
Indeed, Newton’s work represents the finale in a long chain of theory and discovery that evolved throughout the Scientific Revolution. The beginnings of progress had come in the sixteenth century. Nicolas Copernicus suggested that perhaps the ancient concept of the Earth’s position in the universe was flawed.
- Giordano Bruno went one step further to claim that the universe itself was far different than the ancients and the Church perceived, and that it stretched out infinitely.
- Next, Kepler reduced the motions of the planets to intelligible mathematical rules.
- Galileo developed the system of earthly mechanics that he hinted might be applied to the heavens.
Newton’s work was the culmination of this chain of science, inspired by the ideas of these men and the methods and tools developed by them and others of his predecessors. The Principia linked the last two remaining pieces of the puzzle-Galileo’s physics and Kepler’s astronomy-and emerged with the ‘grand design’ so many before him had sought.
- The design seemed not to have been established by any planning or simple geography, but rather by the interaction of the forces of nature, principally gravitation, on an enormous scale.
- At first, the full revolutionary extent of Newton’s work was not recognized by even Newton himself.
- But during the coming century it became evident.
The essence of Newton’s revolution was that he had conceived not only a plausible, but demonstrable model for the workings of the universe, solely relying on mechanics and completely separate of any spiritual influence. When this became clear, it was obvious that the Principia marked the most profound break from the grip of the Middle Ages.
- One of the reasons that Newton’s theories gained only gradual acceptance is that he wrote for mathematicians, and the full significance of his work was not accessible to any but those who were most highly trained in mathematics.
- He needed the aid of interpreters to bring the concepts of the Principia to the masses.
One of the most effective of these interpreters was Voltaire, who invented the well known story of Newton and the falling apple, and explained the Newtonian philosophy in a 1737 work, whose publication can be seen as the end of Aristotelianism, the pop of the final bubble of breath from lips already cold.
What can be infer about the relationship of Galileo’s concept of motion to that of Newton’s law of inertia?
Inertia is associated with an object’s mass. The larger the mass the larger the inertia. Both Galileo and Newton inferred that because of inertia, objects which are not being pushed or pulled, if initially motionless, will remain motionless.
Is Galileo law of inertia?
Galileo’s law of inertia is as stated below: ‘ An object, if once set in motion, moves with uniform velocity if no force acts on it.’
How did Galileo discover Newton’s first law in a limited way?
Written By Insha_S Last Modified 30-06-2022
Galileo’s Experiment: Galileo Galilei was an Italian philosopher, astronomer, and mathematician who produced significant advances in the fields of astronomy, material strength and motion, as well as various new scientific techniques. Galileo Galilei was a major influence in the development of science.
- A number of scientific ideas from Galileo Galilei laid the foundation for later scientists.
- Galileo discovered that objects move at a constant speed in the absence of force by observing how they move on an inclined surface.
- He made an assumption that a stone rolling down an inclined plane accelerates as it descends.
Continue reading the article to know more details regarding Galileo’s experiment.
What is the difference of Newton and Galileo?
Galileo made major contributions to the fields of physics, astronomy, cosmology, mathematics and philosophy while Newton is best known for his contribution to physics. Unfortunately, the two were never able to work together as Issac Newton was born the same year Galileo died, 1642.
Is inertia the same as Newton’s first law of motion?
The property of a body to remain at rest or to remain in motion with constant velocity is called inertia. Newton’s first law is often called the law of inertia.
Who proposed inertia in the first law of motion?
An object at rest remains at rest, and an object in motion remains in motion at constant speed and in a straight line unless acted on by an unbalanced force. – Newton’s first law states that every object will remain at rest or in uniform motion in a straight line unless compelled to change its state by the action of an external force.
Who developed the concept of inertia and made it his first law of motion?
In a previous chapter of study, the variety of ways by which motion can be described (words, graphs, diagrams, numbers, etc.) was discussed. In this unit (Newton’s Laws of Motion), the ways in which motion can be explained will be discussed. Isaac Newton (a 17th century scientist) put forth a variety of laws that explain why objects move (or don’t move) as they do.
Which law of Newton is known as law of inertia?
Newton’s 1st law describes the property of the inertia and is therefore also called the ‘Law of Inertia’.
What is the difference between Galileo and Newton’s views on gravity?
Galileo found that gravity affects objects with the same force, while Newton saw that gravity depends on the mass of an object.
Was Galileo before or after Newton?
Isaac Newton was born on Christmas Day, 1642, the same year Galileo died.2.
Did Galileo and Newton live at the same time?
Newton’s Life – In 1642, the year Galileo died, Isaac Newton was born in Woolsthorpe, Lincolnshire, England on Christmas Day. His father had died three months earlier, and baby Isaac, very premature, was also not expected to survive. It was said he could be fitted into a quart pot.
When Isaac was three, his mother married a wealthy elderly clergyman from the next village, and went to live there, leaving Isaac behind with his grandmother. The clergyman died, and Isaac’s mother came back, after eight years, bringing with her three small children. Two years later, Newton went away to the Grammar School in Grantham, where he lodged with the local apothecary, and was fascinated by the chemicals.
The plan was that at age seventeen he would come home and look after the farm. He turned out to be a total failure as a farmer. His mother’s brother, a clergyman who had been an undergraduate at Cambridge, persuaded his mother that it would be better for Isaac to go to university, so in 1661 he went up to Trinity College, Cambridge.
- Isaac paid his way through college for the first three years by waiting tables and cleaning rooms for the fellows (faculty) and the wealthier students.
- In 1664, he was elected a scholar, guaranteeing four years of financial support.
- Unfortunately, at that time the plague was spreading across Europe, and reached Cambridge in the summer of 1665.
The university closed, and Newton returned home, where he spent two years concentrating on problems in mathematics and physics. He wrote later that during this time he first understood the theory of gravitation, which we shall discuss below, and the theory of optics (he was the first to realize that white light is made up of the colors of the rainbow), and much mathematics, both integral and differential calculus and infinite series.
However, he was always reluctant to publish anything, at least until it appeared someone else might get credit for what he had found earlier. On returning to Cambridge in 1667, he began to work on alchemy, but then in 1668 Nicolas Mercator published a book containing some methods for dealing with infinite series.
Newton immediately wrote a treatise, De Analysi, expounding his own wider ranging results. His friend and mentor Isaac Barrow communicated these discoveries to a London mathematician, but only after some weeks would Newton allow his name to be given.
This brought his work to the attention of the mathematics community for the first time. Shortly afterwards, Barrow resigned his Lucasian Professorship (which had been established only in 1663, with Barrow the first incumbent) at Cambridge so that Newton could have the Chair. Newton’s first major public scientific achievement was the invention, design and construction of a reflecting telescope.
He ground the mirror, built the tube, and even made his own tools for the job. This was a real advance in telescope technology, and ensured his election to membership in the Royal Society. The mirror gave a sharper image than was possible with a large lens because a lens focusses different colors at slightly different distances, an effect called chromatic aberration,
This problem is minimized nowadays by using compound lenses, two lenses of different kinds of glass stuck together, that err in opposite directions, and thus tend to cancel each other’s shortcomings, but mirrors are still used in large telescopes. Later in the 1670’s, Newton became very interested in theology.
He studied Hebrew scholarship and ancient and modern theologians at great length, and became convinced that Christianity had departed from the original teachings of Christ. He felt unable to accept the current beliefs of the Church of England, which was unfortunate because he was required as a Fellow of Trinity College to take holy orders.
Happily, the Church of England was more flexible than Galileo had found the Catholic Church in these matters, and King Charles II issued a royal decree excusing Newton from the necessity of taking holy orders! Actually, to prevent this being a wide precedent, the decree specified that, in perpetuity, the Lucasian professor need not take holy orders.
(The current Lucasian professor is Stephen Hawking.) In 1684, three members of the Royal Society, Sir Christopher Wren, Robert Hooke and Edmond Halley, argued as to whether the elliptical orbits of the planets could result from a gravitational force towards the sun proportional to the inverse square of the distance.
- Halley writes: Mr.
- Hook said he had had it, but that he would conceal it for some time so that others, triing and failing might know how to value it, when he should make it publick.
- Halley went up to Cambridge, and put the problem to Newton, who said he had solved it four years earlier, but couldn’t find the proof among his papers.
Three months later, he sent an improved version of the proof to Halley, and devoted himself full time to developing these ideas, culminating in the publication of the Principia in 1686. This was the book that really did change man’s view of the universe, as we shall shortly discuss, and its importance was fully appreciated very quickly.
Newton became a public figure. He left Cambridge for London, where he was appointed Master of the Mint, a role he pursued energetically, as always, including prosecuting counterfeiters. He was knighted by Queen Anne. He argued with Hooke about who deserved credit for discovering the connection between elliptical orbits and the inverse square law until Hooke died in 1703, and he argued with a German mathematician and philosopher, Leibniz, about which of them invented calculus.
Newton died in 1727, and was buried with much pomp and circumstance in Westminster Abbey, despite his well-known reservations about the Anglican faith. An excellent, readable book is The Life of Isaac Newton, by Richard Westfall, Cambridge 1993, which I used in writing the above summary of Newton’s life.
What relationship is there between Galileo and the heliocentric theory?
Portrait of Galileo Galilei by Justus Sustermans The year was 1608 and the first telescope had just been invented, intended to be used to see far away objects across land. But when word of this invention reached the Italian scientist Galileo Galilei, he thought to use it to look at the skies.
- Galileo was quick to master the art of making his own telescope, which could magnify objects by up to 20 times.
- The general consensus at this time was that the Sun orbited around the Earth, but with the help of Galileo’s observations, our cosmic perspective changed forever.
- The idea that the Sun and other cosmic bodies orbited around the Earth was called the geocentric model,
Many of the ideas behind the geocentric model came from the ancient philosopher Aristotle and ancient astronomer Ptolemy. Aristotle believed all of the heavenly bodies were perfect spheres, with perfectly smooth surfaces and without blemishes. This made them different to the Earth, which he believed was imperfect as it had mountains, valleys and ridges.