If light always travels at the speed of light, how does it slow down when passing through air or water? Does it matter is light is made of particles or waves? What’s the difference between phase velocity and group velocity, and how does that all play into this?
Just as sound can echo off distant objects, light can echo too. And the echoes of light bouncing off stellar remnants, black hole accretion disks, and clouds of gas and dust provide astronomers with another method of probing the distant cosmos.
Light can be absorbed, reflected, and re-emitted by gas and dust, giving us a second look. They’re called light echoes, and allow astronomers another way to understand the Universe around us.
What does ‘time’ mean for light? What is the real lesson of the twin paradox? How can we all agree on the true age of the universe? Why is it all so technical?
Today, we understand gravity much better than we did in Galileo’s day, thanks to Albert Einstein. Over 100 years ago, Einstein came up with a theory of gravity that has so far passed all tests, in laboratories and out in space.
How hot was the cosmic microwave background? Do gravitational waves travel at the speed of light? How do we understand cosmological redshift?
The Milky Way is getting largeerrrrrr. Wait… how com? Check it out. And more about light in the void.
A Light in the Void, a live concert experience that will tell the story of science through live music, scientists’ live presentations, video, animations, and more.
We see the Universe in visible light with our photon detecting eyes. But there’s a whole spectrum of photons out there, from radio waves to gamma rays that astronomers use to understand the Universe. It’s time to see the whole picture.
Podcaster: Chris Impey