Geocentric And Heliocentric Models

The shape of the universe was refined once again in the 20th century, with the discovery of galaxies beyond the Milky Way and the expansion of the universe . The German astronomer Johann Galle became the first person to observe the planet Neptune in 1846, following calculations made by French mathematician Urbain Le Verrier. The British astronomer William Lassell discovered Neptune’s largest moon Triton two and a half weeks later. This means that there’s no such thing as absolute speed or velocity. A person on a ship may consider themselves to be stationary, with the shore moving away from them, and a person on the shore may consider themselves to be stationary while the ship moves away. No experiment can determine which perspective is correct, and so both views are equally valid.

Brahe had issues with the Copernican model and proposed a Geo-Heliocentric Model where the Moon and Sun orbited Earth but everything else orbited the Sun. He believed Earth was too ‘lazy’ a body to move and his arguments were both religious and based on observation. Later you will learn about parallax – how stars very subtly change apparent position over the course of a year. He said that no parallax was visible – indeed it would be difficult with the naked eye to measure any, Brahe made his observations without aid. Printed on archival quality paper for unrivalled stable artwork permanence and brilliant colour reproduction with accurate colour rendition and smooth tones. Printed on professional 234gsm Fujifilm Crystal Archive DP II paper.

You will discover not the least change in all the effects named, nor could you tell from any of them whether the ship was moving or standing still. The Danish astronomer Tycho Brahe made some of the most accurate ever observations with the naked eye in the late 16th century. He disproved Aristotle’s concept of an unchanging universe when he saw a new star in the constellation of Cassiopeia in 1572. Tycho also proved that Aristotle’s transparent spheres do not exist by showing that comets would have to travel through them. The Catholic Church would not have accepted a realist heliocentric model, and so Copernicus presented his idea as a mathematical model.

If something is moving in a circle, then the direction can be measured in degrees. One full circle is 360°, which is equal to 2π radians, and so something moving at 8 m/s in a full circle, for example, will change velocity (Δv) by 2π × 8 m/s. When objects move in a circle, they change direction, and so can change velocity without changing their speed. This acceleration is known as centripetal acceleration , and it is always directed towards the centre of the circle. In the case of the Earth’s rotation at the equator, the distance is the circumference of the Earth at the equator, which is about 40,030 km, and the time is equal to one day.

People that are moving at a constant velocity are said to be in an inertial frame of reference, and people that are accelerating are said to be in a non-inertial reference frame. Galileo’s relativity is only applicable to objects that are stationary or travelling at constant velocities. You can feel the effect of acceleration , and this means that acceleration is not relative; there are always experiments that can determine if an object is changing velocity and hence accelerating. Despite this, Galileo’s observations were verified within a year by the Italian astronomer Antonio Santini. Galileo’s claims were accepted within a year, even though he didn’t give enough information for others to replicate his results. Galileo was concerned that if others knew how to build a telescope like his, then they would beat him to all the potential new discoveries.