A photon emitted from a star a billion light-years away arrives at a telescope having experienced no time whatsoever. Not ...

A team of scientists have demonstrated how to “weigh” galaxy clusters using light from the earliest moments of the universe—a new method that could help shed light on dark matter, dark energy and ...

In my recent post about calculating the speed of light, I mentioned Ole Roemer's calculation in 1676. The basic idea uses the orbit of one of Jupiter's moons. The orbital period is constant, but there ...

Determining the light levels in your shop is an important part of ensuring that your customers have a pleasant shopping experience. If you have limited natural light or operate at night, you can ...