# How sure can we be of the distances in the solar system?

• Warp10
In summary, there are multiple methods for measuring the speed of light, including using lasers and interferometry-based experiments. These methods have been improving in accuracy over time and provide a baseline for the meter. The fact that we have been able to accurately land probes on various planets in our solar system further supports the accuracy of our distance estimates based on the speed of light.
Warp10
And directly related to that: How can we be sure of the speed of light? I've been searching for a good answer as to how we measure the SOL and am yet to have someone give me a solid explanation. Today we shine a laser at a mirror on the moon and time how long it takes to get back. What it sounds like to me is: we use the SOL to measure a distance that we use to measure the SOL.

I've also heard that we have a device that measures how many times light bounces between 2 points within 1 meter. If I am not mistaken that's 3x10^8 times in 1 sec.

This to me seems like a pretty important thing to know considering our science is pretty well based on the SOL.

Physicists have been measuring the speed of light with ever-improving accuracy for quite some time now. Interferometry-based experiments provided incredibly accurate measurements. Nowadays, with the speed of light defined as 299,792,458 m/s (exactly), those same interferometry-based experiments provide ever-refined means to establish a baseline for the meter.

Having landed probes on, or put them in orbit around, most of the planets in the solar system is compelling evidence our distance estimates are pretty accurate.

## 1. How do scientists measure the distances in the solar system?

Scientists use a variety of methods to measure distances in the solar system, including radar, parallax, and triangulation. Radar is used to measure distances to objects within our own solar system, while parallax and triangulation are used to measure distances to stars and other objects outside of our solar system.

## 2. Can we be certain of the distances in the solar system?

While scientists have developed accurate methods for measuring distances in the solar system, there is always a margin of error in any measurement. However, with advancements in technology and the use of multiple methods, we can be reasonably certain of the distances in the solar system.

## 3. How do scientists know the distance from Earth to the Sun?

The distance from Earth to the Sun, also known as an astronomical unit (AU), is measured using the method of parallax. This involves observing the apparent shift of a nearby star against the background of distant stars as the Earth orbits the Sun. By measuring this shift and using trigonometry, scientists can calculate the distance to the Sun.

## 4. How do scientists measure the distances between planets?

Scientists use a combination of radar and triangulation to measure the distances between planets in our solar system. Radar is used to measure the distance to objects within our solar system, while triangulation involves measuring the angles and distances between two points to calculate the distance to a third point, such as a planet.

## 5. Have the distances in the solar system changed over time?

The distances in our solar system are constantly changing due to the gravitational pull of the planets and other celestial bodies. However, these changes are relatively small and do not significantly affect our understanding of the distances in the solar system. Scientists continue to monitor and study these changes to improve our understanding of our solar system.

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