The speed of light in a vacuum is approximately 299,792,458 meters per second, which is rounded to about 300,000 kilometers per second or 186,000 miles per second. This is an incredibly fast speed and serves as the cosmic speed limit according to our current understanding of physics.
To calculate the time it would take to travel between Earth and Mars or the Moon at the speed of light, we need to know the average distances to these celestial bodies.
The average distance between Earth and Mars varies due to the elliptical nature of their orbits. At their closest approach (opposition), the average distance is about 54.6 million kilometers (33.9 million miles). At their farthest, it can reach around 401 million kilometers (249 million miles). Taking the average distance of 225.3 million kilometers (140 million miles) between Earth and Mars, and assuming constant speed, it would take approximately 12 minutes and 30 seconds for light to travel from Earth to Mars.
On the other hand, the average distance between Earth and the Moon is about 384,400 kilometers (238,900 miles). At the speed of light, it would take approximately 1.28 seconds for light to travel from Earth to the Moon.
It's important to note that these calculations assume a direct, unobstructed path and constant speed, which are not currently achievable with our current technology. Additionally, human-made spacecraft do not travel at the speed of light, so the actual travel times to Mars or the Moon are much longer using conventional space travel methods.