What is the current axial tilt of the earth?
A) 24 degrees B) 45 degrees C) 21.5 degrees D) 23.5 degrees
Question 2
The Kurgans, identified as the first Proto-Indo-European speakers by archaeologist Marija Gimbutas
A) conquered much of East Asia several thousand years ago.
B) were a Germanic tribe that invaded England.
C) were herders from the steppes of today's Russia and Kazakhstan.
D) preserved Basque in present-day Spain.
E) were the earliest speakers of Sino-Caucasian, which they diffused through conquest.
The greenhouse effect: heat trapping by earth's atmosphere.
Possible Earth 5 billion years from now
Comparative sizes of the Earth and the Moon
Co-current flow in a concentric tube heat exchanger
Earth’s Spheres
Earth 600 Million Years Ago