Expert: Tom Whiting - 1/28/2008

Question
Which of the following wavelength regions cannot be studied with telescopes on the ground?  

A.  radio waves
B.  ultraviolet
C.  X rays
D.  both B and C
E.  both A and C  

Answer
Hi Andrea,
You will only find radio, visible light, and infrared (heat) telescopes on the surface of the Earth, and even
then, infrared scopes work best up on mountain tops. All the other wavelengths on the electromagnetic spectrum have to be above the atmosphere, because the atmosphere blocks (absorbs) these wavelengths.  These include Ultraviolet, X-ray, and gamma ray telescopes.  I know ultraviolet can cause a sunburn, but compared to the total incoming amount, that is a very small amount that reaches the surface of the Earth.  And it's really even better to put infrared (IR) scopes in orbit too. And visible light scopes actually work much better above the atmosphere too because they give much higher resolution, thus we have the Hubble Space Telescope up in orbit.
So D, both B and C is the best answer.

Realize all these different forms of electromagnetic
radiation.....radio, IR, visible light, UV, X-rays and Gamma Rays,  are all the same....all massless photons moving at light speed, but just different wavelengths, and that's all.  Otherwise, they are all identical photons.
Clear Skies,
Tom Whiting
Erie, PA
PS...Cosmic rays (which really aren't rays at all, but extremely high energy particles accelerated to near-light
speed - mainly protons)...are not part of the eletromagnetic spectrum, since they are a particle with
some rest mass.  They also don't make it down
to the surface, so Cosmic Ray telescopes also have to be
placed up in orbit, out of our atmosphere too.