how do we know?
Learning from Light
The Sun as seen from space.(click to enlarge) ©NASA, ESA, SOHO
Most objects in the universe emit light (
electromagnetic radiation), which contains all kinds of information. Almost everything we know about objects in the universe — from their chemical composition and temperature to how old they are and how fast they're moving — comes from studying this light, only a fraction of which is visible to the human eye. Sophisticated telescopes capture different wavelengths of light, like X-rays and microwaves, enabling astronomers to learn about celestial objects they'll never be able to visit or touch. On Earth and in orbit, these telescopes are our eyes to the universe.
Observations, Models & Simulations
A model of the planetary orbits in our Solar System.(click to enlarge) ©AMNH
Telescopes can provide snapshots of the cosmos in different stages of development. However the time scales are just too long to see cosmic collisions in action. So, to help them understand these observations, astronomers create mathematical models that are based on the laws of physics to describe how nature will behave. They use powerful computers to make the vast number of complex calculations involved in computing the models. Astronomers compare the results of these models to observational data for verification. The visualizations in
Cosmic Collisions are partly based on numerical models like these.
