4 ms·
This very parallax effect. We know how far the Sun is from the Earth, and the Earth has moved twice this distance from January 1 to July 1. This in turn allows
by DavidSJ 4y ago
This very parallax effect. We know how far the Sun is from the Earth, and the Earth has moved twice this distance from January 1 to July 1. This in turn allows us to extrapolate distance to some of the nearest stars by their apparent motion relative to the other, "fixed" stars.
https://en.wikipedia.org/wiki/Cosmic_distance_ladder https://en.wikipedia.org/wiki/Cosmic_distance_ladder
https://www.youtube.com/watch?v=7ne0GArfeMs https://www.youtube.com/watch?v=7ne0GArfeMs
- avn2109 4y agoOK but then how do we know how far the sun is from the earth? Is it like "bounce a signal off it and count time of flight?" (Another serious question.)
- bombcar 4y ago> The first rigorous and accurate scientific measurement of the Earth-Sun distance was made by Cassini in 1672 by parallax measurements of Mars. He and another astronomer observed Mars from two places simultaneously. A century later, a series of observations of transits of Venus provided an even better estimate. http://curious.astro.cornell.edu/about-us/41-our-solar-system/the-earth/orbit/87-how-do-you-measure-the-distance-between-earth-and-the-sun-intermediate http://curious.astro.cornell.edu/about-us/41-our-solar-syste...
- BurningFrog 4y agoWe can't bounce signals off the sun, but we can do "interplanetary radar" bouncing signals off at least the nearby planets. Knowing those distances, the distance to the sun becomes a trigonometry problem.
- DavidSJ 4y agoThe video of Terence Tao I linked addresses that and many other questions about climbing the cosmic distance ladder.