Although we may not feel motion, the Earth is currently moving 67,000 mph (link) around the sun, the solar system is moving 514,000 mph around the center of the Milky Way Galaxy (link), and the Milky Way is moving a staggering 1.3 million mph (link) around the gravitational field of a supercluster. Therefore, it is fair to say that our galaxy is in constant motion, being pushed apart and pulled together by the acceleration of the universe (link) and gravity (link) respectively. In 2011, Saul Perlmutter, Brian Schmidt and Adam Riess (link) were awarded the Nobel Prize in Physics for their discovery of the accelerating universe. As Royal Swedish Academy’s Olga Botner described, “This discovery is fundamental and a milestone for cosmology.Before their discovery, cosmologists made the assumption that the universe was static, non-moving, and all the galaxies were at a fixed position in space. We normally associate moving objects to be blurry in pictures as they are in motion; however, if we look at the Hubble Deep Space image, we are able to see that the image is very clear and most of the galaxies are distinguishable. Therefore, the assumption that the universe was static made sense at the time because our knowledge of the universe was based on the images and visuals that were available to us at the time. However, we are now aware that the universe is in fact not static, but is expanding and accelerating. (link)How do we know that the universe is accelerating? Adam Riess et al. were one of two research teams that started using the technique of calibrating type Ia supernovae to measure distances. They needed to measure two things to confirm the acceleration of the universe (Appendix 1):- The distance of type Ia supernovae from the Milky Way.- The rate at which the space between supernovae and the Milky Way is expanding; this was done by measuring the redshift of light being emitted by the supernovae. Measuring DistanceIn order to measure the expansion of space, Adam Riess et al. had to measure how far galaxies in our local group were from the Milky Way, then this was done over a period of time so that they could measure the rate at which the galaxies are moving away from us. In a lecture presented at Loyola University Maryland (link), Adam Riess used the analogy:”A ship captain at night wants to figure out how far away the rocky shore is, so they look for a lighthouse. They use the knowledge that a lighthouse is very luminous, so if the lighthouse looks very faint they know they’re very far from shore they’re very safe.”Much like a captain, astrophysicists can measure distances using the light emitted from an exploding star in a galaxy; otherwise known as a supernova. Astrophysicists know how luminous these supernovae are; therefore they are able to use the Inverse Square Law of brightness and distance to determine how far away the supernova is by simply measuring the faintness of the supernova.The inverse square law, tells us that the brightness decreases as the inverse of the distance squared increases (1/D2). This is because the same magnitude of light is required to fill the surface of a larger sphere of distance. Therefore, if the supernova is twice as faint, it’ll be four times as far.)Riess et al. created a chart that is similar to the one above; the magnitude of the type Ia supernovae was compared to the redshift from our perspective from Earth. In 1998, Riess et al. announced their results, the values they had measures were closely aligned to the model they had created of the accelerating universe – they had found that the universe was expanding.What Causes Acceleration of the Universe? (cite book)The acceleration of the universe can be explained by the idea that the expansion of the universe is speeding up (as it is not a constant expansion); therefore, there must be an unknown force of repulsion that counteracts the force of gravity.What Is a Supercluster?If the universe was viewed under a microscope, we would see a network of many fibres, extending out and clumping together. These are galaxies. Due to the nature of chaos in the universe, galaxies naturally form clusters (link), that are more concentrated in some parts and less so in others. These clusters of galaxies further clump together to form superclusters of galaxies.